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Hi Crash,
I suggest you read the Shop manual about Carb synchronization. This requires a special tool.

Just remember that prior to even attempt carb adjustment, your engine must pass compression testing, otherwise your time and money may just be invested in vain. Compression test requires... a compression tester (60$).

My suggestion to limit your carb maintenance to change float needles and possibly jets is based on the fact I don't think I can fix more than that, even if I understand more than the basics . If you think you can fix or refurbish a carb without a shop manual or experience, I wish you good luck.

I can tell you where to find some answers, but I'm not able to help you troubleshoot your carb. You will have to do your homework.

Have fun !

Martin

Hi again,
Unless you get a least 100psi pretty evenly on both cylinders on compression testing (preferably 125-180) your engine head, pistons or both need refurbishing. If so, remember than a spare engine is more than twice cheaper: Just finding oversize pistons and rings plus cylinder head refurbishing (must be done by a machine shop) will cost you over 400$, not including labor to put it back together and adjust it.

One hidden weakness of CM400 twin engine is the balancer chain: Once it is past the wear indicator (see Service manual) you must split the crankcase and remove the connecting rod bolts because balancer chain wraps over the crankshaft. Connecting rod bolts are discontinued and very hard to find. They can't be reused. I found a set in Germany and one in England, nothing in the US.

Another hidden danger of engine refurbishing is the poor quality of most engine gaskets sets, which are very brittle and often far from OEM quality.

A complete spare engine will often cost you 400$ and will come with at least a 30 days warranty.

Hmmm, neat Thread Necromancy from a spammer.