Monday, March 15, 2021

When logic fails…. Vintage and not so vintage Honda problems.

 It was a challenging couple of weeks dealing with some unusual Honda problems that defied normal logic in order to solve the issues.

First, an enthusiastic Honda 305 Dream owner was having problems with keeping the bike running. He had rebuilt the petcock and the spark plugs looked clean, but it would die in just a few miles down the road. He noticed that when the fuel line was removed from the petcock, fuel flowed out very slowly. The petcock lever was difficult to turn as well, so I assumed that the petcock kit parts were not installed properly, as they were OEM Honda parts, not one of the aftermarket kits that have undersized holes for the bottom gasket. The gasket has to lay flat down on the petcock body, otherwise, it jams the lever up tight when everything is tightened down.

I looked at the gas cap which was a brand new, new-generation OEM cap, which helps prevent leaks when the tank is full and gas is sloshing around inside. That’s all you can buy for gas caps from Honda these days, anyway. His old one was leaking around the cap, so he bought a new one from Honda.

He had drained the fuel tank, mostly, but there is always a bit of fuel floating round in the bottom of the tank. Rather than pull the tank off, I dismantled the petcock lying upside down on the ground and removed the assembly. Surprisingly, the petcock seemed to have been assembled properly with the little metal tab on the upper fuel gasket located in the slot for it. I pried out the old parts and we installed all new ones. The new bottom cork gasket wasn’t sitting down on the body properly, so I reamed out the holes just a little bit. Reassembling the petcock body to the fuel tank is a challenge when it isn’t on the workbench, but I got lucky enough to push the body up in place and get the three screws started and tightened up. The lever pull effort was now “normal” to me and I finished up the installation.

We refilled the tank and started the engine up. It started pretty quickly and settled down to an idle after a few moments. I took it out around the block and down the street for a total of about ½ mile of driving, but when I returned to the driveway, the bike stalled at idle. Well now…??? Logic would lead you to remove the carburetor and make sure all the air bleed passages were open, the jets were correct, etc and to replace the o-rings in the flange and insulator. Carb removal on a Dream is a PIA and you wind up wrestling with the air filter tube ends and that usually winds up requiring battery removal to get to the rear clamp and end of the tube where it fits onto the air filter.

With the carburetor off, I noticed that the choke arm function was very sloppy, so I un-staked the washer and made some turns on the retainer nut so there was more friction on the lever. The next discovery was that the main jet was a #110 instead of a #120. The bike had come from Colorado and had been re-jetted to high-altitude specs. The pilot jet was correct and the air bleeds were cleared out with brake cleaner spray can straws. The flange was warped and o-rings flattened out, so that was the next task to sort out. The high spots on the flange were knocked down and the o-rings replaced. We wrestled the carb back onto the back of the motor after fitting the throttle cable and slide to it. Then we tussled with the air filter tube until it was properly fitted back in place and clamps tightened up on both ends.

The bike started back up, seemed to be happier, and was still idling when I came back from the same short test ride. Success, I thought and we wrapped up the afternoon’s work. Earlier, on the first test ride there was a noticeable clunk in the front end that felt like looks steering head bearings or a warped brake drum. Jacking up the front wheel, there was a clunk when the fork was moved fore and aft, which seemed like steering head bearings. We covered the fuel tank with a towel and removed the handlebar clamp bolts and upper holder, to access the bit square nut that holds the top of the fork plate to the stem. It was kind of loose, but I took the first look at snugging the steering bearing upper nut down on to the top bearing race to remove any excess play. It didn’t move very far, but the clunking was still present. Finally I realized that the lack of the top nut was allowing the mounting plate to shift back and forth on the end of the steering stem! I have one of the cool giant square special tools for the top nut and when I cranked it down firmly, the noise and play were gone completely. The following test runs showed a nice quiet front end and the brakes pulled evenly with no sense of being out of round.

It was all looking good, after 3 hours of tinkering and adjusting things. I offered to let the owner take it out for a run, but he refused and we loaded the bike back up for his trip up the freeway on that Saturday afternoon.

I was out with my riding buddies on Sunday morning where we stop for breakfast up in the mountains each week when I checked my messages on the phone. The report was that the bike had gotten about less than a mile from home and was stalling out again. I recalled that there wasn’t a lot of gas in the tank when we refilled it, so figured that it needed to be left on RESERVE until he could get to a gas station. More messages back and forth indicating that the petcock was on RESERVE and it was still stalling out. All that was left to suggest was to remove the gas cap to see if it was causing a vapor lock condition inside the tank, which was not uncommon with the old caps when the bikes sat up for many years. The evaporating gasoline eventually plugs up the tiny vent hole on the gas cap and it causes a fuel stoppage. Honda even put out a TSB to suggest drilling a second 1/16” hole opposite the original one to prevent this kind of problem from happening. Knowing that the gas cap was a new OEM replacement would normally cause you to dismiss it as being a potential problem to cause fuel stoppage. The next message I received was “I loosened the gas cap and the bike ran fine afterwards.”

Logically, that should never have happened, but it did…

The second brain-teaser was my friend’s 2013 Honda PCX150 scooter. The bike was one of two that my friend and I purchased together a couple of years ago. Both bikes had less than 500 original miles showing and were in perfect condition. I rode mine a few hundred miles doing local errands, where it was getting close to 100 mpg each tank. My friend rode his on the freeway to and from dental appointments just across the border into Mexico. Technically, the bikes are “freeway legal” but the top speeds are in the low-mid 60 mph range, so it’s pretty sketchy to be riding them on SoCal freeways these days.

Well, my friend keep making those repeated trips back and forth and didn’t keep an eye on the oil level. Suddenly, on the freeway, the bike started to slow down and stalled. It would start up and then shut down repeatedly. He got it towed home and discovered the lack of oil in the engine, which caused the piston to seize and ruin the cylinder bore. So, he tore down the bike, removed the engine, replaced the top-end parts (which are quite inexpensive on these models) and eventually got it all back together again. In the meantime, he had no scooter to drive, so I sold mine to him as a replacement.

Eventually, the first bike was successfully revived and sold. The second one did several thousand more miles until it suddenly stalled and quit on the freeway. This time the crankshaft big end went south, so it was going to take a full tear-down and rebuild to get it back to running condition again. With shop manual in hand, he pulled the motor out and disassembled the top end. Unfortunately, he didn’t have the correct flywheel puller tool to remove the rotor, so he improvised with a three-jaw puller and ultimately damaged the outer rotor bolt holes that mount the little plastic fan and the screws had dug into a few of the coils on the stator. He brought the engine to me and I had the rotor off in a few minutes using the correct Honda tool. I noted the damaged parts and suggested that he replace the stator and rotor, but he declined as the damage seemed minimal to him.

Over a period of several months after he finally got the engine reassembled with a new crankshaft and seals and gaskets, he got the engine started, but it ran poorly and was throwing MIL error codes on the dash lights. He took to a friend’s motorcycle shop for a look-over and to diagnose the error messages. One of them was for the TPS sensor, which also incorporates a couple of other sensors. He replaced the part, but it did not solve the problems he was encountering. The bike would only run to about 55 mph, then would just die out completely, until you stopped and restarted it again. No matter what he tried, the bike continued to be stubbornly uncooperative in returning to its normal functions. After much pleading with me to help him sort it out, I relented and let him drop the scooter off at the house here.

The Shop manual is helpful, but there are a lot of troubleshooting steps that end with “Replace with a new part” to see if that fixes the issues. My first move was to remove the old stator and track down a good used one on eBay. This is about a $125-150 part when new, but I found what looked like a good one for $80 delivered. It came in within a few days and I labored to reinstall it in the bike. There are many, many little fasteners and clips that keep all the bodywork on these chassis and it all shrink-wraps around the chassis, requiring a lot of disassembly just to get to do some service items.

Once I finished installing the stator and checked wiring connections, I started the bike up, but it struggled to turn over even with a good battery installed. There were some leftover trouble codes in the computer, but I cleared them with a paperclip into the diagnostic connector. I charged the battery and did a lot of thinking and reading about how the starter/alternator functions from the shop manual. These engines have a starter/alternator magnetic set up so that there is not a separate starter motor to turn the engine over! When I would check the engine, by watching the rotor, the engine would initially turn backward before going forwards to start it up! This can’t be a good thing! I pulled more bodywork off in order to access the onboard computer to ensure that the connectors and wiring were not damaged. Every little step takes 10-15-20 minutes in order to get to the part that you are trying to test or inspect.

At this point, the engine would start up and immediately die as soon as you turned the throttle open just a little bit. Then, it would set a code for the alternator/starter system. Finally, I went back to eBay and found a rotor, which apparently is the same part for several years of production. The seller offered a stator for only $40 and based upon the part number he listed, should have worked on this bike. Well, it didn’t…

Honda changed the part number in 2015 and the harness lead was a good two feet shorter than what I was working on. In the meantime, I put the first replacement stator back on the engine with the nice-looking rotor that came with it. Fortunately, the rotor did still work with either stator combination, so it fit right onto the engine. BAM! It started immediately, sounding crisp and took throttle with ease! I pieced the rest of the bike back together enough to take it for a test run and it hit 68 mph going downhill without any struggle or stalling. FINALLY, it was FIXED!

Logically, following the trouble codes that were repeatedly showing up would have indicated issues with the stator or the connections to the computer. There is no trouble codes for a damaged rotor, so you have to just trust that everything else was good enough and go with the leftover damaged parts that you might think were not bad enough to cause the problem. That was a wrong logical assumption!

As the saying goes: "You live and learn" and so I have learned not to rely completely upon logical assumptions in cases like these.

Bill “MrHonda” Silver


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