QuestionHi, I bought my CB900 this summer from a friend, he had the problem too...
When cold, engine is hard to start, the battery is full, starter works and it take alot of time, and drain alot of power before finally make it run, sometime I even have to take my car's powerpack to supply more juice, but finally it always start.
Once started, run perfectly, I let it warm up, and after, I can turn it off, and will start easily. I only get this problem when starting cold engine. I did some long run, never had any problem while running.
my friend told me, that 2 summers ago, he took the bike to the garage for compression test, batteries test, everything s fine.
Since I got it, I change the spark plugs and wires, make sure there was fire, check air filter,air filter booth.
I cleaned every parts, every corners of the carburetor with a q-tips, thinking that was finaly it because of the varnish, but didn't solve the problem...
I check, with the carbu drain screws, to make sure there was fuel in every carb. everything good....
I've been told to redo the carb thing, that maybe I mist something.
any idea what should be my next step??
Dave
AnswerYou didn't say whether the starter turned the engine over at a normal speed or very slowly. If it is very slow you might need to service the starter motor - after 27 years the grease is probably hard & contaminated.
I'm not sure of the details of cleaning that particular starter motor, but the ones I have done were held together by 2 long bolts that run from one end cap to the other. Once you have them out, carefully take the ends off, making sure that you don't damage the brushes or their holders. Be careful not to loose any thrust washers that might be in there either.
Once it is apart, flush everything out with electrical contact cleaner. NOTE: WD-40 is not contact cleaner and will contaminate the contacts if it gets on them.
When all of the old grease is cleaned out of the bearing surfaces and the electrical parts are free of debris from tbe brushes wearing &c, apply some new grease that is suitable for electric motors (mine was sold by Black & Decker for use in poewer tools) to any bearings & gears (be careful not to get any on the brushes, their holders or the parts they make conact with) and put it all back together.
If that doesn't fix the problem it could be in the ignition - possibly a coil that is getting ready to fail or spark plug wires that need replacing, or maybe the timing.
You didn't say how long the bike sits idle before you have this problem. If it is only happening after it sits for 2 or 3 weeks, the problem could be that enough fuel is evaporating from the carbs' float bowls that it can't start until you crank it long enough to fill the bowls again. Most Hondas of that era have vaacuum petcocks that automatically shut off the fuel when the engine is off and there is no vacuum. Cranking the engine will not produce enough vacuum to open the valve fully so it can take quite a while to fill the bowls. The best solution to this is to take the bike to work every day. If that isn't possible, try blowing gently into the petcock drain tube for 5-10 seconds before trying to start it.
If none of that helps, I recommend asking the folks at the Honda DOHC Customs forum http://www.cb750c.com/index.php
It would probably be worth your while to join anyway. There is no cost to join the forum and if anything can be done with a Honda 4 someone there has probably done it or knows why it can't be done.
Tell them Sidecar Bob sent you. I'm sure they won't hold it against you ;-)
