Tuesday, August 18, 2020

Small part, big confusion…the 250-305 kickstarter pawl

 There are three little parts on the end of the kickstarter shafts of ALL 250-305cc twins from the 1960s. They are:

SPRING, PAWL product number: 28228-250-010

PAWL, SPINDLE product number: 28255-250-020

PIN, PAWL product number: 28256-250-000

Notice that the center codes of these parts is 250, which comes from the first generation dry-sump engines, which were built in 1957-60.

       Kickstarter shaft with kickstarter pawl and pin shown in correct installation order.

These parts are responsible for the kickstarter arm engaging the transmission’s low gear, which is connected to the crankshaft via the primary chain. While the kickstarter shaft only moves when the kickstarter lever is depressed, the kickstarter pawl/spring/pin parts are all actively engaged when the engine is running. The pawl is pressed into the inside features of the transmission low gear by the spring and pin, which stabilizes the spring as the assembly rides up and down inside the transmission gear.

For the kickstarter function to occur properly, several things have to be properly aligned and in good condition.

1. The low gear is supported on the kickstarter shaft by a stepped bronze bushing, commonly called the “low gear bushing.” This bushing is supporting two gears with a step in the middle to separate the two gears on the shaft. Over time, the bushing wears down, causing the low gear to wobble on the bushing. Also, the little step ridge on the center of the bushing gets worn down laterally, eventually wearing the ridge completely off of the center of the bushing surface. When this happens, the low gear is both wobbling on the bushing’s exterior and is also allowed to move laterally towards the adjacent gear and away from the kickstarter pawl.

2. The kickstarter pawl has a bit of “float” in the end of the kickstarter shaft, but needs to be fairly squared up inside the low gear’s inner engagement features. If the low gear gets too cockeyed and wobbly on the bushing and kickstarter shaft end, then the kickstarter pawl can’t fully engage the inside of the low gear and the whole mechanism “slips,” instead of engaging the engine properly.

3. Because the kickstarter pawl is always engaged, operating basically as a one-way clutch, the edges of the hardened steel pawl eventually wear down, causing another reason to create slippage when you try to kickstart the engine. The little pawl pin pushes up on the back side of the pawl to keep it engaged with the low gear teeth. The pin is spring-loaded by a tiny coil spring that drops down into the hole in the end of the kickstarter shaft. After many millions of cycles of up and down for all three parts, they eventually wear out. The sides of the spring can wear flat and begin to grab the outside of the pawl pin and the two begin to accelerate wear together, as they do their best to support the pawl itself. The tip of the rounded pin begins to flatten out, as well. In high-miles engines, the “teeth” that engage the kickstarter pawl on the inside of the gear also wear down, so they can’t hold the pawl end properly.

4. When maintenance is left undone, due to lack of oil changes, poor engine tuning and other factors that put additional stress on the kickstarter pawl system, eventually it fails completely. Because these parts are part of the transmission, the engine cases have to be split in order to replace the worn and damaged components. In some cases, either the end of the kickstarter spindle that supports the pawl will break off and/or the roller bearings that support the transmission gear on the opposite end of the shaft will wear through the hardness of the shaft surface and begin to dig into the shaft. 

Instead of rolling smoothly, the transmission gears start to engage the shaft during on-off throttle conditions. What happens is that the kickstarter shaft begins to swing back and forth, while the bike is being ridden. On a CB72-77, the kickstarter arm can come into contact with the rider’s shins on the right side, in a surprising display of force, as the kickstarter arm goes forward on its own, then whips backward towards your leg.

5. Another wear point in the transmission, being affected by the kickstarter pawl is the 14mm end spindle bushing surface face. The continuous movement of the pawl pushes up against the edges of the 14mm bushing causing the pawl to dig a trench into the bushing face. This adds more end play to the already sloppy transmission gears/shafts and can cause the gear dogs to lose their engagement contact surfaces. When this happens, the transmission jumps out of gear and when this repeatedly happens, the transmission gear dogs get rounded off causing even more shifting difficulties and damage to the transmission components.

In more than a few cases, while doing repairs on used 250-305 transmissions, has lead me to discover that a previous repair attempt has left the kickstarter pawl improperly installed. On a recent CL77 transmission repair, the bottom end, which had been apart twice, had the pawl installed backwards, so that the sharp edges were engaging low gear, just barely. It was “working” to a degree, but obviously it wouldn’t have lasted for a lot longer. The owner reports that the transmission repairs, including offset cotters, now shifts very smoothly and the kickstarter works perfectly.

                                             Incorrectly installed kickstarter pawl!

Bill “MrHonda” Silver


Image credits to cmsnl.com and Cappellini Moto (spindle bushing), eBay sellers and MrHonda.

Friday, August 14, 2020

Adjusting to the modern world…. Re-jetting vintage Honda carburetors

 For those of us who were alive and involved with 1960-80s Honda motorcycles before the advent of “unleaded gas” and “10% alcohol gasoline,” we remember that Honda motorcycles were carefully jetted for maximum power, economy and reliability, right out of the crate.

                                            Honda CB72 carburetor with "power jet" function.

Reviving those 40-60 year-old motorcycles generally requires fuel system cleaning and a careful inspection of the carburetors. Before the introduction of CV (constant velocity) carburetors on the DOHC CB/CL450 twins, the vast majority of Honda’s carburetors were made by Keihin and were simple throttle-valve units, consisting of a float valve, float, main jet, idle jet, carburetor slide and tapered slide needle. Changing the fuel calibration of the basic designs to accommodate various versions of each application was generally required when the exhaust systems were changed from CB=Street to CL=Scrambler. With mostly identical engine specifications between two series of machines, the change from a low-mount to high-mount exhaust causes the carburetors to act differently and so Honda’s engineers carefully made appropriate changes to needle taper, main jet and sometimes the idle jets to bring a smooth fuel delivery to each application.

For the most part, Honda offered many sizes of main jets, idle jets and needles to re-calibrate the carburetors, as needed. In the early 1960s, Honda changed the basic shape of the float bowl from a rounded shape to one that was more squared-off on all sides. There was no need to change the calibrations as the body shapes changed. When owners began to alter either the intake or exhaust system for more “performance” the original calibrations are no longer valid. Changes to the intake or exhaust systems often require a change in the jetting of the carburetors due to an increase in airflow or alterations in the intake or exhaust tract length. Changing the tract lengths changes the resonant frequencies of the systems which can enhance or detract performance from the original settings.

For example, the difference between the 305 Honda Super Hawks and Scramblers lie in both the exhaust header pipe lengths, muffler lengths and the length of the intake to air cleaner runners. The engines have the same pistons, cam timing, valve sizes and carburetor bodies, but the standard main jet of a CB77 is #135 while a CL77 runs jets down around #130. Even the pilot jet sizes change from #38 to #42 between the two models. 

The Scrambler’s long, long, header pipes have a much different resonance frequency that bounces a pressure wave back to the exhaust port that can affect the incoming intake charge in the cylinder. The longer intake and exhaust tracts of the Scrambler enhances some of the mid-range torque, while the shorter CB intake and exhaust lengths enhance higher rpm performance on the road or race-track. Scramblers are geared shorter than CBs, so feel “more powerful” than Super Hawks, but the CB77s will hit nearly 100 mph vs about 85 mph max on a Scrambler. While 305 carburetors with 26mm slides have 2.0mm cutaways, the CL72s have a 3.0mm cutaway but the CB72, with the same-sized carburetor has a 2.0mm cutaway. You have to look over each item carefully, if you are tempted to start mixing and matching Keihin carburetor parts from similar models.

Be aware that prior to 1967 all of the Honda carburetor jets were JIS thread pitch and thus not interchangeable with later ones. Main jets in ISO dimensions have a ring marked around the outside edge of the jet, whereas the JIS threaded jets were left plain. This can cause great confusion when you have a model like the 1965-69 S90, CL90, SL90 models. which bridged the 1967 changeover gap. When people start trying to mix-match a box of loose parts from models like these, problems will arise.

Fast-forward to the 21st Century and most all markets have succumbed to at least 10% alcohol-infused gasoline which is fairly unstable in long-term storage and has less fuel energy that pure gasoline. In order to compensate for the loss of fuel energy (and a slightly different fuel viscosity), the rule has become that bumping the carburetor main jets up at least one size (5 to 10%) will equalize the air-fuel ratios that these old engines were used to seeing. After setting up stock CB77 Super Hawks to original stock settings of #42/135, I found the bikes to having flat spots and seemed to be struggling at highway speeds. Swapping the #135 main jet for a #140 pretty much cured the mid-range/top end power problems and even helped the normally cold-blooded Super Hawks to warm up quicker and have better overall throttle control.

Similarly, I have had to re-jet a number of CB400F Super Sport fours from #75 to #80 main jets, in order to overcome the same lean conditions. I made that change to a bike that I sold to a young man from NY. He flew in to San Diego and drove the newly rebuilt machine all the way back to NYC in 4 days, running it at 70-80 mph for most of the trip. When I first drove the bike, after a careful check over (and it had an electronic ignition), the bike struggled at freeway speeds, feeling flat and struggling. A simple step up in the main jets solved the problem and allowed a successful cross-country journey, which I think might have suffered a melt-down due to the original lean jetting coupled with alcohol gasoline.

Bear in mind that by the mid-1970s, the EPA was beginning to lean on motorcycle manufacturers for their part in the increases of carbon monoxide and hydrocarbon that the world was experiencing. Motorcycles were carefully calibrated for emissions during start-up, idling, off-idle performance and at full throttle, just enough to keep them from seizing their air-cooled pistons during extended riding conditions. I think we have all seen the idle mixture screw limiters that were required to keep owner’s from destabilizing the factory settings. Lean mixtures due to slide needle taper designs were another part of the equation and soon owners were putting little thin shims beneath the needle heads to raise them up slightly to enrichen the fuel ratio mixtures at part-throttle.

1980s Kawasaki motorcycles were famous for requiring 5-minute warm-ups, just to get the bikes down the driveway due to lean idle/part throttle calibrations required to keep the engines clean enough to pass the EPA regulations. Kawasaki was always pushing the envelope on performance machines, but the more power they make, generally, the more pollution is created in the process.

In order to enhance engine performance, companies like “Dyna-Jet” began to develop “Stage” kits to help owners get a handle on carburetor calibration issues with either bone-stock machines or for ones that had a 4:1 aftermarket exhaust or replacement air cleaner element or full system. These were sold under the guise of being a “racing” product that was not to be installed in production street bikes, especially in strict-California emissions zones. Dyno tests generally showed some improvements to horsepower, throttle response, torque readings and overall drive-ability with installation of the kits, but obviously the previous emission calibrations were out the window and any measured emissions were substantially higher than those that were create at the factories.

The days of carburetors are numbered due to the introduction of efficient fuel-injection systems and computer-controlled ignition advance curves. But in the meantime, we have to do our best to work with what we were dealt with from the factories dating back sixty years. So, to begin with, we have to clean, clean, clean the carburetor bodies and all associated components, then start to make educated guesses about what the engine will need in the way of corrected fuel-air ratios at all engine speeds and conditions.

Just assume that the use of alcohol-gas is going to make the engine run lean with stock OEM jetting settings. Once the fuel passages are all clean (ultra-sonic cleaners are great!), then a careful look at each internal component is next and then consider obtaining some slightly larger sized main jets to begin the calibration experimentation. Multiple test rides will give you a “seat of your pants” feel of what the bike is trying to do and what it wants in the way of fuel needs. When you feel the flat-spot or performance plateau/misfire, try to pull the choke up slightly to see if the problem gets better or worse. If it improves, you need to richen up the mixture. If it gets worse, lean it out again.

Reading spark plugs is somewhat of a black art, as well, but an initial look at the overall appearance of the plug tip will tell you if it is running lean (all white tip), rich (black and sooty), fuel/oil-fouling (wet end) or has a nice tan insulator without a lot of build-up of carbon or oil.

The bike should start up with sometimes full choke for just a moment until it is running, then reduce choke to around 1/2-3/4 while the engine warms up. Backfiring back through the carburetors/air filters is a sign of a too-lean fuel condition. If the bike fires up with no choke, it is generally running too rich at idle and off-throttle. The engine should idle down normally after about 4-5 minutes of operation time and the air-mixture screws should cause the engine to change idle speed and quality when they are turned in and out within a quarter-turn of normal. Always make the final idle mixture adjustments when the engine is at full operating temperature.

If the idle mixture screws are not responsive, then you have issues with jet sizes, blocked air/fuel passages inside the carburetor body, air leaks at the intake manifolds or warped carburetor bodies at the flanges. Ensure that the suggested float levels are use without fudging more than a millimeter or so. If you have fuel running out of the bowl’s overflow tube, you either have a float valve not sealing, a float level that is too high or a crack in the brass tubing of the bowl overflow tube.

While Honda bolted carburetors directly onto the cylinder heads in the early years, they began to recognize the high-frequency engine vibrations could cause fuel frothing and inaccurate metering at various engine speeds. The new-generation 350s and 450s used rubber-fused manifolds to secure the carburetors to the engines with both damping qualities of the rubber, as well as some heat insulation features which helps to stabilize metering in both hot and cold driving conditions.

As an example: The little 1960s Honda 160-175 twins had solid-mounted carburetors, bolted to aluminum intake runners, which were then insulated from the head with phonolic blocks and o-rings. But, when Honda revised the 175 twin engine up to 200cc in the early 1970s, they created rubber intake manifolds to improve fuel metering and vibration dampening of the carburetor bodies.

Some of the most confusing carburetor sets are featured on Honda CB/CL350 twins. There were several different carburetor body styles and 4-5 different calibrations suggested for the bikes, depending upon whether they were CB or CL versions (and the early SL350s, too). In the case of the 350s, there were different camshaft timing periods between CB and CLs, so that, alone, is enough to cause changes in calibration settings. These early CV carburetors featured both a primary and secondary main jet to help with the transitions from part throttle to full throttle conditions. Sometimes, all the changes needed were to bump up the primary main jet to the next size in order to smooth out the throttle response. One of the problems with 350 twins is that they vibrate quite a lot and the original mufflers for both CB and CLs tended to either break or rot out prematurely. Replacing the damaged components with OEM items (of which there were several types) was often costly and the parts were hard to find due to demand. Owners resorted to use of other slip-on muffler systems which had different lengths and back pressure features, all of which caused metering problems back at the carburetors.

Many of us “old-timers” know that the carburetors are the LAST thing to blame/adjust when engine performance is suffering. Setting up carburetors to operate correctly requires a sound foundation in several aspects of the engine’s systems. Go back to the beginning: Compression test, valve adjustment, camchain adjustment, ignition timing settings, spark advancer function, coil/condenser/point conditions, spark plug caps and even the correct spark plugs are all to be checked and confirmed before diving into the carburetors.

If you have a low-compression engine that is using oil and fouling spark plugs, the carburetors probably are not the root cause of your engine performance issues. If the point contact faces are all pitted due to age/miles or a bad condenser, you will have erratic ignition output at the coils. If the coil leads are crispy and cracked, the sparks might be jumping to somewhere else than the gaps of the spark plugs. Spark plug caps should have no more than 5k ohm resistance measurements and should be screwed onto the spark plug wire ends which have been trimmed back to bare wire.

Aged condensers cause points to arc randomly or excessively which adversely affects ignition coil output. Make sure that you are using a fully-charged, load-tested battery and that the charging system output is keeping the battery charged during operation. Engine vibrations can cause loose connections in the wiring harness and individual connectors to loosen or disconnect altogether. When Honda started putting ignition switches up in the center of the fork bridge, the pull on the switch connector often causes the switch connection to come apart, partially or completely. Bikes with KILL switches need to have the switch contacts checked and the wire connections secured so the coils get a steady feed of voltage.

All of these aspects of motorcycle function and maintenance can come into play causing performance issues that are first attributed to “the carburetors.” Obviously, if the carburetors have been sitting for months/years with old fuels in the bowls, then they need careful cleaning and scrutiny for normal function. Carburetor work is made more difficult with the alcohol in the fuel, which attacks most rubber parts, especially float bowl gaskets! If you drop the bowl off of a carburetor and the gasket is not the original glued-on version, chances are that the gasket will swell up and will NOT fit back into the carburetor body grooves. Cleaning with soap and water then drying in the sun or gently with a heat gun will generally allow them to reclaim their original shape and size. If you are doing a lot of jetting or carb work, plan on getting several sets of bowl gaskets to have on hand for quicker service procedures. 

To review:

Test drive evaluation…

First, start the engine and listen to it to hear if it is going to need a prolonged period of “warm-up” or if it will take enough throttle to drive off after a minute or two of running. Run the bike up gently with slowly increasing throttle openings. Listen and feel if the engine is taking throttle cleanly or if there is a hesitation or misfire occurring at certain throttle openings. While driving, if it is safe and easily accessible, pull up the choke lever or knob slightly during the time when the misfire or roughness is occurring. If you feel a surge of power or increased smoothness in the engine performance, then you will need to enrichen the fuel mixture at that point.

Off-idle hesitations can be resolved with either an increase in the size of the idle mixture jet and/or raising the needle slightly with shims. If the hesitation is more in the ¼ to ½ throttle settings, then you can raise the needle a little bit more and/or increase the main jet size slightly, one step at a time. Remember that if you increase the main jet size, you have enriched the whole fuel ratio from around ¼ throttle all the way up to WOT. If you get a good full-throttle response, but the mid-range is sagging and the plugs start looking dark and sooty, start to lower the needle back down one step at a time.

It’s a balancing act, but one well worth pursuing in order to maximize the engine’s performance over a wide rpm band and to conserve fuel that might be wasted in an engine that is running excessively rich. Pull a spark plug or two and look at the tip to see if they are getting a nice color on the ends which indicates proper jetting.

Excessive rich conditions can wash down the oil on the cylinder walls, leading to ring wear or even piston seizures in extreme cases. Excess fuel will contaminate the engine oil, as well, leading to lubrication breakdown. There is a whole chain of events that happen when you start to “adjust” the carburetor settings, so think it through first, before you begin wholesale changes. On many bikes, just removing the carburetors is a huge pain, so you don’t want to be in the position of having to do it more than once or twice, at the most.

Take time to understand each stage/function of a carburetor, so any changes you make are done with caution and thoughtfulness about what you are trying to achieve. Carburetor wizards are getting harder and harder to find these days, now that fuel injection is becoming more and more common. Take time to learn the craft for yourself and to help your friends who are in need of timely and educated repairs.

Bill “MrHonda” Silver


Friday, August 7, 2020

1964 CL72… ornery and out of the ordinary

Lately, I have been nursing a somewhat one-off 1964 CL72 250cc Scrambler, for a new customer who has owned it for many years. His family owned a Honda shop in the Mid-West and this bike has stayed in the family for a long time.

I had been contacted by the owner to “get it running” after it had been stored for a long time. It seemed like a fairly simple request, but I haven’t worked on a 250 Scrambler for quite a while and had forgotten how difficult they are to do simple maintenance on without having to disassemble half of the bike every time you need to service the carburetors.

What’s special about this bike is that it had been built with Akront alloy rims, over-sized tires and a CB72-77 cylinder head, featuring a tach drive. A later model CB77 speedometer and headlight shell were installed in place of the usual single meter setup. Additionally, the bike had been fitted with a YL72 alloy fuel tank, which was a factory-issued “racing part.” These tanks are very rare and made of an easily damage alloy, so finding ones in good condition is a rare event, 56 years after production.

I gingerly removed the fuel tank after working off the old fuel lines and set it aside for petcock repairs. Also, the original gas cap latch for the “flip cap” filler had broken and somewhere along the line the owner’s father had contacted me about some billet ones that I have made available for the past 10 years. The problem was that the retainer pin had been removed/lost and so a beach-ball inflator had been inserted into the cap latch pin hole, as a temporary fix. Additionally, the caps had a cork gasket installed to seal the opening and the cork had broken up so a 329 code Honda gas cap gasket was installed around the central holder. The OD of the gasket was too small, so the cap leaked during driving.

When the tappet covers were removed for a valve clearance check, I was greeted with the look of alloy valve spring retainers, so I could only imagine what had been done to the engine beyond that. The clearances were close to stock .004” so I just reset them all to that, hoping that the camshaft was still a stock unit. The carburetors and air filters were removed for cleaning (filters replaced) and that gave easy access to the camchain tensioner adjustment nut/bolt. The adjuster moved in about an eighth of an inch, so you can either assume damage to the roller or just a lack of maintenance of the tensioner.

The clutch pull effort was very heavy, leading me to think that there was some kind of heavy-duty clutch installed, perhaps with the 275-810 clutch springs from the CB77s. After draining the dirty oil and removing the clutch cover, the clutch pack was removed. It was apparent that the clutch was a Barnett performance unit, including the springs. The clutch plates were stuck together and the wire retainers for the clutch hub were missing. Fortunately, the clutch plates were of the correct thickness so that the wire retainers could be installed, making for a clean clutch release action for city driving.

With the clutch cover removed, the oil filter was accessed, which proved to be packed with an eighth inch of dirt/crud. The filter was cleaned and reinstalled. This bike had the “small hole” clutch cover, which barely clears the OD of the filter, so doing a filter service with the clutch cover in place is impossible. Overall, the insides looked fairly clean, so the cover was replaced. In order to minimize the clutch pull effort, the kickstarter cover was removed for replacement of the clutch adjuster. The clutch adjusters are made of a soft material and wear down quickly, especially if not kept lubed up and when asked to work against heavy-duty clutch springs.

The carburetors were removed, disassembled and cleaned in a sonic cleaner, then reassembled with new bowl gaskets and o-rings; the rest of the parts were reused. The petcock was rebuilt with an aftermarket kit and all was put back on the bike for an initial fire-up. Well… The petcock fuel lever was pitted on the back side, so it was dressed up with a file, which took out most of the imperfections. Even after a couple of rechecks, it continued to slowly drip, drip, drip… When the carburetor fuel lines were attached, the float bowls began to weep around the forward straight edges of the bowls. This has become quite a problem for me lately. Part of the problem is that the non-OEM gaskets are a little too wide where they encounter the locating posts. The gasket channel is about 3.25mm and the gaskets are 3.5mm wide. When installed the gasket tips up against the posts and doesn’t lay flat into the channel. Installing the bowl should, theoretically, just clamp down on the gasket and flatten it into the channel.

Most of the aftermarket gaskets are layered instead of solid material and it may be that the gasoline is bleeding through the material. Even rechecking the float levels several times, the bowls continued to weep a bit. I dug out a solid rubber gasket from an old kit and installed it in the left side carburetor, which seemed to have solved the problem, but I only had one to use. The bike came with a box of odd spares including a set of 1967 CB77 carb bodies. I took the bowl clip off of one of the spares and tried it on the CL72 carburetor after I had notched the gasket with a small paper punch. That seemed to work, but overnight there were signs of fuel leaking and it turned out to have a tiny crack in the overflow tube. A spare bowl was installed and that seemed to be the cure.

With everything installed, it was time for a road test. Initially, the bike fired up loudly (straight pipes with no baffles) and it seemed more or less okay. When I took off, in gear, the engine bogged down, then cleared itself after about 3k rpms. Above those engine speeds it seemed to run strong, but cracking the throttle in low gear at slow speeds repeated the bogging down feeling. Because it was jetted for 1964 fuel (no alcohol and lead added), I have generally found that the carburetors need to be jetted up to compensate for the 10% alcohol in the gas. Removing the float bowls, in order to change the main jets, set up another challenge… the float bowl gaskets fall down and absorb the alcohol in the gasoline, causing them to swell up and then they don’t fit back into the carburetor bodies!

I have found that taking the gaskets out and laying them in the direct sun for an hour generally dries out the gasoline and the gaskets shrink back to size again. I reinstalled the new main jets, after I had raised the needles one notch and put it back together again. Now it wouldn’t even run on the right side cylinder! At first, there was no power to the points on that side. Removing the seat and then the tank bolt gave enough room to access the wiring connectors to the coils. One connector was snapped in, but you could feel that it was dancing around inside the connector. A squeeze with some pliers and a good push in remedied the power problem to the points. I dropped the tank back down on the mounts and tried to start the engine again… STILL not running, but on the left side now. I raised the fuel tank back up and got the bowl off from below the carbs. There is VERY LITTLE room to do carburetor work on the left side with the carbs still mounted on the engine. The float valve needle turned out to be rubber-tipped, and it jammed itself into the float valve seat, shutting off the fuel supply to the carburetor bowl.

I dug out an all-metal float needle and installed it while the carb was still attached and shrouded by the exhaust pipes and the dipstick tube. This really takes watchmaker skills to do and it doesn’t go easy if you are successful. Of course, the float bowl gasket had dropped out of the body, so that was the second step to accomplish. Eventually, everything was back in place with larger main jets and needles raised up. The result was pretty much the same as before. It still has a big bog off-idle, then clears up and runs well at high rpms. Pulling the choke on when it was struggling just made it worse, so apparently, we have to go the other way with the needles and see if that helps, even though it is counter-intuitive to what is generally found when jetting vintage Hondas.

Potential factors in why it is running the way that it does are: Straight pipes with no baffles installed. The pressure waves from the long pipes may be out of synch with the carburetor calibrations causing an over-rich condition. Secondly, if the cam was changed, along with the valve springs/retainers, the cam timing may be causing low-speed running issues and/or both factors could be at play.

The throttle cable on the bike was very old and coming apart at the ends. I decided to stop playing with it until a new cable comes in and then I can drop the needles back down at the same time. Other tasks done on the bike included painting the aftermarket chain guard and making repairs to the gas cap.

The bike barely stood on its centerstand because there as an ancient 4.00x19” tire mounted on the back and a 3.50x19 tire on the front wheel. Several hundred dollars later, a stock-sized set of Metzler tires were mounted up, but the bike is still a little unstable on the centerstand because the aftermarket rear shocks are about 1/4” longer than stock.

Much of the wiring harness was replaced, previously. The neutral light bulb was broken when inspected, but a new one didn’t light up apparently due to a neutral switch malfunction, which is located beneath the kickstarter cover. In order to remove the clutch cover or kickstarter cover, the footpegs must be unbolted from the bottom of the frame. There are few straightforward repairs or adjustments that can be made on a 250-305 Scrambler, without having to remove 3-4 associated parts in order to gain access to what you wanted to do in the first place.

Of all the 250-305 models, I have found the Scramblers to be the hardest to work on and the least satisfying to ride once you finally get them going properly. Because of the closed-loop frame and the exhaust system bolted to the side of the chassis, the amount of vibration becomes excessive and fatiguing, at least to me. For the die-hards who think that Scramblers look cool and sound cool, they can have their say, but they will not sway my opinion of them in the least. Give me a nice Super Hawk any day!

Bill "MrHonda" Silver 07/2020