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· Registered
1 Posts
Discussion Starter · #1 ·

I got a CM400T from -81 which have been standing still for several years.
I've made it my mission to get it running again.

I've so far changed oil and gasoline in the bike, want the bike to run well with the engine first, before changing the rest of the stuff.
When I emptied the carbs the gas was green, very very green. So I took the decision to clean the carbs, which was a good choice, the carbs looked really bad inside.

I cleaned them a bit and assembled them again, only to find out that the bike ran bad and was leaking gas from the carbs overflowing.

With the help of this forum, ebay and a ultrasonic cleaner I think I've made the carbs clean enough.
Changed some gaskets and took the carbs apart as much as I could.
When I assembled them to the bike again, it was a success, the bike ran better and no leakage.

Now to the current problem.
The bike has a high idle RPM, around 3000RPM and when accelerating the bike seems to drench itself. If I try to rev the engine to fast it almost dies and then comes back to life.
If I rev the engine slow it runs alright.

I believe that I have some tuning of the carbs to do, but this is the part I need help with.
Where should I start?

I've checked the idle screw, and it isn't even laying against the idle funktions, so it isn't the idle screw. Also, the choke is untouched.

All response would be of assistance!

· Registered
9,708 Posts
Welcome to the forum. Great to see another 400 series here. Got any pics of the bike to share?
It sounds like your linkage is not together correctly, or , if you had your throttle plates out, one or both are not centered.

I would take the carbs off again and go through Jim's tutorial on these carbs.

Here's some good reading as well....

You'll also need a proper manual.

PM sent.

· Premium Member
23,965 Posts
Does the accelerator pump work? small squirt from each of the nozzles when the throttle is twisted.
Is the linkage free and moves easily on the left carb body?
Are the carbs sync'd? Are you trying to run it without the airbox boots in place?
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