The cast of characters:
Owner from N. Cal (600 miles away)
Bike: 1966 CL160, bought from Craigslist with unknown history
Referral: Tim McDowell (MD)
Stated problem: Won’t idle down properly.
Troubleshooter: MrHonda, Spring Valley, CA
So, I get this call from Tim saying that he referred a caller to me about a CL160 with carb problems. Okay, I don’t work on 160s as a regular thing, but how hard could it be????
The owner, named Pete, drops off the bike from the back of his pickup and wants to hang out as I try to figure out just what the issues are with his machine. All he knows is that when it starts it up, it revs to the moon and he can’t control it even with idle screws all the way out.
First, the tank and seat come off and compression checks are made. Cylinders are showing 180/165 psi. The spark plugs are fuel/oil-fouled black. The spark advancer was replaced previously, but the ignition timing is about 10 degrees retarded. Timing reset and a separate fuel bottle is hooked to the carbs. Carb bowls were already pulled off for inspection and gunky gasoline discarded. Fuel bottle connected to carbs, engine kicked over, but won’t start. Check spark and clean plugs with brake cleaner. Spark to both plugs, but still won’t start up. Check right side bowl and it is empty. Check float valve, but it is clean and we determine that the fuel bottle isn’t high enough to feed the carbs. Reposition fuel bottle and engine starts up and immediately revs to a million rpms.
We know that spark timing is okay, carbs are getting fuel and slides are now backed off enough to allow an uneven idle, but the exhaust is pumping out blue smoke worse than any Kawasaki Triple on pre-mix. Holding the idle up to medium revs to clear the exhaust system of un-burned fuel sand carbon for a few minutes doesn’t help clear the smoke. It’s obvious that pistons/rings are not doing their job and the engine will have to come out for repairs. On top of that, there is an irregular knocking noise coming from somewhere deep inside the engine.
Pete watches for a while and then heads back up to LA where he’s staying with family for a few days. Engine removal continues and once it drops onto the dolly, I wheel it back to the workshop for a quick tear-down of the top end. Nine fasteners hold the head down to the cylinders and the top cover is off. Cam and rockers all seem okay, so camchain master link is found and disconnected. I put pieces of 22 gaelectrical wire through the ends of the chain with a knot tied in one end of the wire to keep track of the camchain.
The head then comes off and I am surprised to see one shiny new piston installed in one side and a used one in the other. ????? I remove the pistons from the rods and check piston clearances and end gaps on the rings, all of which seem to be in specs. The cylinder bores are glazed and looking at each piston ring, I find that several are installed upside down, including the scraper ring which pulls oil off the cylinder walls and sheds it into the crankcase. The rings are tiny and markings barely seen without magnification aides. The top one just has a T mark, while the second one is marked with a T2 (or R2) as they are Riken ring sets. The one-piece oil ring does have a T mark as well.
I hone the cylinders, reset the rings and reassemble the engine once again. Fortunately, I had a full engine gasket kit on hand to do all of this work on the spot. My floor jack is leaking oil when I jack the engine back into the chassis, so everything is getting messy. Finally all the bolts are installed and once the carbs and exhaust are mounted up, the bike is fired up again. The engine smokes again for a few minutes but it is much reduced and begins to clear fairly quickly. I can hear the engine is running rich off-idle and had noted that Keyster kit parts were installed in the carbs. These kits are notorious for being out of tolerances for correct jetting and cause all kinds of tuning problems. Despite the engine running much better already, I drop the needles all the way down to clear the rich condition and the engine responds as desired. Still the knocking sounds continue, so the next step is to pull the clutch cover and check for something loose or broken inside.
The oil is drained and is clouded with tiny metallic specks but no big chunks so far. I removed the first drain plug I see and only a few spoonfuls of oil come out. ???? Then I remember that these engines have two drain plugs! The forward one is 19mm not 17mm and turns out to be a self-tapping plug. Lots of oil pours out of that drain plug, but is laced with metal flakes.
The clutch comes apart only after removing the crankshaft mounted oil filter outer cover, then the inner locking nut. Then one of the two off-set drive gears comes off. The clutch pack comes out as a block after the springs are removed. The clutch is stuck solidly, so obviously this engine has not run or run well for a long time. I pry the plates apart and then bend back the locking tabs on the oil pump which comes off with the clutch outer hub as the pump is driven off an eccentric on the back of the clutch outer.
The pump screen has two little support feet which are all bent backwards because someone installed the screen in reverse of normal. There is a little backlash on the clutch basket even with offset gears that are supposed to neutralize the play. The whole clutch basket has some end play that could cause some of the knocking sounds, but nothing is conclusive. With the clutch plates untangled from each other, the whole assembly is reinstalled and a new cover gasket placed in between the cover and crankcase. 1.2 liters of Honda GN4 10-30 oil fills the crankcase up to the fill mark on the dipstick and the engine is fired up again. Now the clutch is working, but the knocking sounds continue unabated. I’m running out of ideas… I go to the rotor side of the crankshaft and remove the bolt and use my 16mm rotor bolt tool to pop the rotor off the crankshaft end. I put the dyno cover back on and start the engine… same noise.
I pull the cover back off and grab the end of the crankshaft and pull/push. There is noticeable end play in the crankshaft assembly, which must be the source of the noises. As the engine is revved up into the middle ranges, the sounds subside and the engine sounds normal until you drop it back to idle again.
It is what it is, so I button it all up and install the air filters, side covers, tank and seat for a test ride down the street. About the time I am putting it back together, I look through a box of spare bits and find a container with all of the OEM carb parts, including the correct needles! Swap in the needles and the bike is running sweetly now. The idle adjustments continued to be very touchy and I swapped in a set of shorter idle speed screws, so they catch more threads to stay in place and are more adjustable.
The bike is starting with one kick and idles down normally, but one hundred yards down the street and a new noise comes to my attention. The growling sounds of the speedometer bushings are making themselves known and the needle is showing 70 mph while I am trolling along in 2nd gear at mid-throttle. One more issue to present to the owner. I suggest that either he finds a really good crankshaft, but he realizes that replacing it is a full engine tear-down that will take a good 6 hours to perform. Or maybe someone has a low-miles engine that can be swapped into the chassis instead.
While Pete was back in LA, he was following up on a CL77 bike for sale and winds up buying it. The bike has not run for many years, but is a complete 1967 Candy Orange model with chrome fenders. The serial numbers are above 68,000 so it must have been one of the last ones to come off the line.
So, guess what? Pete comes down with the CL77, drops it off, picks up the CL160 and heads back to LA, then home to N. Cal. He plans on returning in a month and in the meantime I am gathering up parts and scheduling in work to get the bike running, change the tires and make it ready to ride once again.
At the moment, I have 7 motorcycles on the property. Three CB77s which are mine, the CL77, a SS175 Harley AMF 2-stroke street bike with dead ignition, a CB500 in for carb work and oil leaks and finally my 2020 Royal Enfield, which I ride on Sundays with the Jamuligans (my buddy’s name for our little group). So, again, no good deed goes unpunished. I keep trying to clear my backlog of parts and repair jobs, but the volume is continuing to grow instead of shrinking. This is going to have to stop one of these days…