QuestionQUESTION: Bill
My problem is that when I adjust the carbs to a satisfactory idle speed and gun the engine it just races like the throttle is wide-open. I have cleaned the carbs, checked the throttle cable,checked for air leaks, etc. I have tried so many different things that I believe the carbs just need to be rebuilt at this point. I think this problem is beyond my basic skills and available tools. Can you recommend someone that works on these older bikes? I live in Orange County,Ca. Thanks
ANSWER: Robert, High idle speed conditions as you describe are generally due to a number of factors.
1. Throttle cable routing ia;ncorrect, cable is kinked and/or the cable is hanging up internally due to rust or broken wire strands. Lube throttle cable drum at the handlebars, so it rotates easily on the bars.
2. Carb slides are in backwards. They are left and right side specific. Install them with the cutaway edges facing the air filters.
3. Sticking spark advancer. They can seize up on the pivot shaft, causing the spark advance to "hang" in advanced mode due to the centrifugal weights. Remove the points plate, remove the spark advancer, check if for looseness of the springs and freedom to advance/retard easily.
Check those items, before you throw in the towel....
Bill Silver
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QUESTION: The towel is thrown! I have checked the 3 items you suggested and they do not appear to be the problem. I am not familiar with the spark advancer but I did as you instructed and to my untrained evaluation that does not seem to be the problem. I think someone with more motorcycle savy may need to look at the problem. Any suggestions?
ANSWER: Illustration: http://www.cmsnl.com/honda-cl160-scrambler-160-usa_model1040/partslist/E++09.htm
#6, just so we are on the same page. With the points plate removed, twist the end of the spark advancer cam and watch the weights as they swing out and then the springs will snap them back into place when you let go. If you have a lot of slop in the cam, where it wants to move a little without engaging the weights, you can crimp the ends of the return springs down with needle nose pliers. You want it to be advancing and returning easily and quickly. Sticking spark advancers are usually the cause of this problem, but of course not the only one.
Pull the carb slides off the ends of the cables and push them down into each carburetor body to see if they are moving freely. Sometimes the carb bodies get warped/corroded and the slides will hang in the carb bores, even against spring pressure.
I don't have any good recommendations for people in OC. I have a friend Richard Bowers in Torrance who is pretty good.
I'm just finishing up a CB160 today, after a whole rebuild. It wouldn't run on the right side until I cleaned out the idle jet. Your carb settings should be about a turn and an eighth out on the idle mixture screws. Make sure that you are setting your ignition timing so that the points just OPEN at the F mark alignment on the end of the rotor. Set gap so it is about .014" maximum, then adjust the point plate around until the points open at F mark.
Bill Silver
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QUESTION: I will give it a try this weekend.I have contacted Richard and he walked me thru several tests like those you have mentioned with no success. His suggestion was to rebuild the carbs(I ordered 2 rebuild kits but lack the expertise). He was going to do the rebuild for me but he has a hand injury and cannot work on bikes for 5 or 6 months. I should add this bike had been stored for 15 years and with Richards help it was running very strong but I tried to do some idle adjustments when started idling rough and very rich. That is when this problem started. The carbs have never been rebuilt and Richard felt this was the root of the problem. I am really looking for someone with expertise to make sure the bike is safe and hopefully reliable. Do you do repairs?
AnswerRobert, I would agree if the carbs have never been cleaned and kitted in 45 years, then they would need a thorough cleaning and adjustment.
http://www.oldmanhonda.com/MC/Rcarbs.html
http://www.dansmc.com/carbs.htm
It is important to identify your carb set. They are usually stamped on the intake manifold flanges, either C or LD models. C models have a 19.5mm float level and LD carbs are set at 21mm.
#92 main jets for C carbs and #98 for LD carb sets. Idle jets are #38 (C) and #35 (LD) clip in the middle of the five little notches on the needle.
Running rich symptoms can come from pinholes in the floats, causing them to sink and not shut off the fuel, which causes either a high float level or carb overflowing. I suspect that the air bleed passages in the carburetor throats are probably blocked. One is for the main jet and the other is for idle mixture air.
I have a friend in TX who can clean and adjust them for you, pretty quickly. I am buried in work, at the moment, with about 7-8 bikes waiting for me, plus I am in San Diego area. If you pay attention and remove everything slowly and carefully, you can clean them with a couple of cans of carb spray and replace each part, one at a time.
I had a Classic Honda Carburetor Repairs story just printed in the VJMC newsletter last month. I can email a copy to you, if you contact me through my website: www.vintagehonda.com
Bill Silver
