Ducati Monster Forum

Need some help with a 97 Ducati Monster 900 that has a 99 engine in it. The original engine was replaced due to burning up oil and not wanting to get involved with engine internals and machine work. The bike was purchased to be converted to a café racer. This involved relocating a few things and the elimination of the charcoal canister. The original 97 engine had ‘W’ heads and the new 99 engine that came from a running bike has ‘V’ heads.

Since the build was complete, we have been experiencing inconsistent issues. The bike continues to run excessively rich and at times it pops and runs very rough and even goes down to 1 cylinder firing. We have changed all the ignition components and had no success so then began to look at the carbs wondering if the change in cylinder heads could be the cause of our issues but the inconsistencies do not add up. We bought another set of good condition OEM carbs to test the bike with and have had no success with them. Even altering the floats and turning the mixture screws seem to have little to no effect.

Could the change in cylinder heads be making the carbs behave erratically? We capped the vacuum ports on the intakes where the charcoal canister used to connect to and tried to leave them open to ‘lean’ out the mixture, but the bike just continues to run poorly. Any suggestions to what could be causing this inconsistent issue? Any advice or direction would be much appreciated. Thank you 

Not sure if this helps, but I had an idle issue with my 750 a few years ago. Used a temp gun on the headers to see which cylinder was the culprit. Horizontal was 750° and vertical was 350. Turned out to be a bad vacuum diaphragm on the carb. It popped sometimes and felt rough at idle cause it was so lean.