Hi there
I am trying to get to the bottom of what I think is a jetting issue.
I bought a set of standard CB750 carbs a few years ago that had been rebuilt for a "race engine" I told the bloke rebuilding them that the carbs would be used on a engine bigger than standard specs.
When the carbs arrived I couldn't help but bolt them on to my K2 to see what would happen although they were not intended for this engine. It ran fine above idle, it even seemed to go better mid range, but at idle it ran rough and if you blip the throttle it pumped out black smoke.
Fast forward to now and I have fitted the "race engine" to my bike and thought great I can try these carbs on the engine they were built for. Well it does the same thing. Idle is lumpy and as soon as you twist the throttle it pumps out black smoke.
I pulled them from the bike to check jet sizes the slow jet is #40 the main jet is #108 and the needle is 27201 with clip 2nd from bottom.
I checked this against my old carbs which have the same slow jet, the same needle with the clip in the same position, but the main jet in the old carbs is #110
I guess after work today I will bolt on the old carbs to the new engine to see what happens, but for now I would like to know how much difference there is in a 108 (new carbs) to a 110 (old carbs)
I have always had the air box in play when testing either set of carbs.
Thanks for any thoughts on this.
Scott