part throttle miss

[fatboy ron]

howdy, i have a 97 evo that cuts out at 3200 rpm (sputters), but only does it at part throtte. checkd the intake gaskets they seem ok, have cleaned the carb and installd a dynojet kit, helpd a bit but prob is still there. any help would br greatly apprecatiated.

[Dr.Hess]

I dunno what a dynojet kit is or what carb you have, but it sounds to me like you are too lean in the middle. I'd guess your mid range jet or circuit is gunked up.

[fatboy ron]

runnin a cv carb, dynojet is a carb tuning kit. i cleand the carb out the best i could, where exactley inside the carb is the mid range circut? thank you for the reply.

[Dr.Hess]

I'm not a CV carb guy. My suggestion of a midrange circuit issue was from my experience with conventional carbs. Hopefully one of the CV guys will chime in. However, my understanding is that the CV carb's needle sort of acts across the whole range, unlike more conventional carbs like my S&S or a Weber, for instance. You could also have issues with the slide thingie. Is it smooth/no binding? A vacuum leak or problem with the vacuum slide system could affect things greatly with those.

[Fartnokker]

K know that I'm late in chiming in, but just in case you're still having the issue, the midrange circuit is your needle jet, the one that goes right thru the middle of the carb slide. The DynoJet kit comes with an adjustable needle, where you can move a little "c" clip into different notches machined into the top of the needle.

After removing the needle, hold it with the pointy side down & the clip side up. What you'll want to do in order to richen up the mid circuit is to carefully move the clip down one or two notches towards the pointed end of the needle. This'll raise the needle up in its seat & allow more fuel to flow past.

Give it a try, & be careful with the slide diaphragm. An easy way to reassemble it without pinching the diaphragm is to put the slide/diaphragm in a ziplock bag, then put it in the freezer for a couple of hours. This'll cause the diaphragm to temporarily shrink a bit. Don't pull it out until you're ready to reassemble the carb. It should seat nice & easy.

Hope this helps somewhat. CV carbs really aren't that difficult, when you get the different circuits sorted out. Pretty easy to tune.

[ironheadbuck]

good advice ----also read plugs at missing rpm

[Fartnokker]

ALso good advice!

[90Harley]

I once had a cracked intake clamp that allowed it to spread and not seal in that area when torqued. didn't find it after a couple gasket sets until someone pointed me in that direction.