QuestionHi Bill,
My son has an old (1969?) Honda CL-90 Scrambler he bought at a garage sale for 45 dollars last fall. It is pretty beat up, leaked oil from a cracked clutch cover, had a broken off clutch lever but seemed like an interesting father-son project. And depite the James Bond Oil spray from the craked case, it ran fine. We are not looking to restore it, just get it running reliably for him to have fun with.
Clutch cover and control lever were no big deal, easy fix for us novices.
However, this spring, she just refused to run. She would start up after two or three kicks, run for two or three minutes and then suddenly shut down.
Thought it was either a fuel starvation issue or an intermittent electrical problem. The latter is always tough to find so, what the heck, I bought a carb rebuild kit and promptly removed the carburator and got busy.
Now I have never rebuilt a carb before. I took it all apart and found a substantial amount of "caked" rust on the bottom of the inside of the bowl. I used starting fluid and got it all as clean as I could.
I replaced the main jet, float valve, air mixture screw, etc..no problem. I turned in the replacement idle jet and encountered some resistance before it fully seated...Ah-Oh. Backed it out, compared it to the original ide jet...looked the same. OK, I thought I just needed to screw in the new one and if a little resistance is met, no problem. Bad decision. I screwed it in until the jet seated and decided to back it out to check...the little jet tube with the holes drilled in the sides had snapped off inside the channel.
Not good. I could not get that little tube out. I decided to screw what remained of the jet in anyway, put everything back together and even if idle was rough, see what would happen.
Well, it will now not start at all. I am thinking new "bolt on carb" at this point.
When removing the carb again to check p/n for re-order purposes, I noticed something funny. The fuel petcock on the underside of the tank was accidently still set to "Fuel" (as opposed to off) yet the output tube, disconnected from the carb, leaked no fuel!? Should the fuel not freely flow from gravity? Does it need vacuum from the carb to flow?
I removed the inlet tube from the pet cock, the one that runs to the tank. Fuel flowed like crazy.
Is it possible that my problem all along was a fouled petcock? The tank is rusty. I did find a lot of rust in the carb bowl.
What do you think?
mbarile@sprintmail.com
AnswerMichael.... You have to be careful when working with small carb parts about over torquing the jets. In some cases there were different thread pitches used in the 1960s and the threads will not be a perfect match, as you have discovered.
You really have to have a nice clean fuel system to ensure that the bike will run reliably. Clean the fuel tank, clean all the passages in the petcock. The fuel tube is for the ON position and when the fuel level drops below that, then the RESERVE position will drain the rest of the tank through the bottom of the petcock body passage. When you have rust in the tank, it all settles in the petcock, plugs up those passages and then you have no fuel flow when the level is low.
The carb is similar to S90s, so you may have to settle for that instead. NOS carbs are rare and over $120 each, if you can find them. The broken emulsion tube in the carb body is probably blocking the fuel mixture process for the idle circuit.
Two other concerns.... this is a battery operated ignition, so be sure that you have a fully charged battery in the circuit, otherwise the charging system will knock out all the light bulbs.
Check the fuel cap for blocked vent passages. When plugged, the fuel will get vacuum locked in the tank.
Finally, be sure that the valves are set to .002" cold on compression stroke and be sure that the ignition timing is set so the points open at the F mark on the rotor alignment. The mechanical advance should be checked too, which is behind the point plate.
Bill Silver
