QuestionI have a 1982 Honda CB900c. It's idiling really high around 3500 or so the idle adjustment screw has no effect whatso ever, which leads me to belive I have a vaccuum leak in the intake boots between the carbs and the block. They appear to be the originals that came on the bike so i want to replace them, but can't seem to find them anywhere. Any ideas on where to look?
AnswerTrey, before you go tearing into the manifolds, spray some WD40 or carb cleaner/starting fluid around the manifold junctions while the motor is running. If there is no change in the rpms, then I would suggest that either a vacuum line to the carbs is loose/broken or quite likely the automatic fuel control valve diaphragm has failed, which causes a vacuum leak, as well as a reduction in the fuel flow to the carbs, resulting in lowered float levels/leaned out mixtures. That will also result in a high idle.
http://www.cmsnl.com/honda-cb900c-900-custom-82-us_model7250/partslist/E++21.htm... $$$$$ only one left over there.
If you are thoughtful about it, you can plumb around the automatic fuel valve, plugging off the vacuum line and running the fuel hoses direct to the carbs from the petcock. Just remember to shut off the fuel supply every time you park the bike.
If you loosen the clamps and can move the manifolds around the connections, then they are too loose.
http://www.cmsnl.com/honda-cb900c-900-custom-82-us_model7250/partslist/ shows all photos of parts.
http://www.cmsnl.com/honda-cb900c-900-custom-82-us_model7250/partslist/E++02.htm... see 11,12,13,14.. They all have different part numbers!
http://www.bikebandit.com/houseofmotorcycles/honda-motorcycle-cb900f-1982/o/m957... for US sales. Still available at $20.80 each!
Looks like they fit all 900 and 1100cc bikes of that era.
The mechanical spark advancer runs in oil on the left end of the crankshaft and seldom has problems. However, if the springs were to stretch or break, the spark advance would start early and also cause high idling speeds.
Bill Silver
