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81 Honda CM400 Issue. Help me out!

Posted: Sun Jul 14, 2013 9:57 am
by Bizmal
I Purchased an 81 Honda CM400 for cheap. It didn't run at the time however I took the carbs out cleaned them and replaced every part or seal that was damaged. I also blew out all the jets with compressed air so I can see light through every jet or hole or feel compressed air rushing through. Everything seems to be in working order. After every thing was done it started right up. I tuned the carbs to the Bike manuals specs and there was no delay when I hit the throttle.

The thing is that it idles right but every time I ride it more than a few blocks it dies on me and won't start up or idle with out the choke on max and it does not stay running for long. After that it will not turn over for 15 or 20 min. Both carbs seem to be getting fuel just fine. If I try and ride it now, giving it any throttle kills the bike. Since then I've taken out the carbs again. It looks fine....

Any ideas? :starwars: <------- Vader is the CM400 and I'm the yellow guy in this situation..

Re: 81 Honda CM400 Issue. Help me out!

Posted: Sun Jul 14, 2013 11:20 am
by GS_in_CO
If you cleaned the carbs but didn't attend to the condition of the gas in the tank you missed an important step.

Gas goes bad fairly quickly (< 1 year, a few months if stored in the heat). Putting bad gas in your newly cleaned carbs means you have to re-clean them.

Other issues can be that your idle jets actually didn't get cleaned. They have to be pretty small to do their jobs and gas varnish can plug them so that no carb cleaner can open them again. Sometimes the fix has to be new idle jets.

(This is all theory and secondhand observation for me as I've never experienced the problem myself. )

Re: 81 Honda CM400 Issue. Help me out!

Posted: Sun Jul 14, 2013 6:37 pm
by Johnj
Try riding around with your gas cap loose. Your gas tank vent may be plugged up.

Re: 81 Honda CM400 Issue. Help me out!

Posted: Mon Jul 15, 2013 10:59 am
by BRUMBEAR
yeah sounds a bit like airlock to me

Re: 81 Honda CM400 Issue. Help me out!

Posted: Wed Jul 17, 2013 6:37 pm
by Bizmal
Solved. The peacock was'nt letting enough gas through. Thanks for your help.