Engine bogs down at low RPMs

My '81 Maxim 650 bogs down when taking off from a stop. It has great pickup once I'm moving, but coming from a dead stop it seems to drag. The air box was replaced by a PO with K&N cone-style filters and he says it was re-jetted for that modification. I'm wondering if it really was... Also trying to figure out if I should do something with the crankcase breather tube, right now its clamped off with a piece of foam filter.

Looking for suggestions, should I just re-jet the carbs to be sure? Exhaust is stock, so is everything else as far as I know.

 

That is the biggest problem with K&N filters, no throttle response. If you keep playing with jets you may get it right. Lots have tried, they say their bike runs great but when compared to a stock setup it does not run so good. I have had bikes with pods running well but I have never seen one run like the stock setup. I favor the stock airbox with a K&N filter, they are much easier to tune. The engine breather tube should have some kind of filter on it, what kind is up to you. Normally that tube connects to the airbox.

 

i would pull the carbs (with pods it takes 2 minutes tops) and clean the pilot circuit (also check jet sizes and compare to stock). more than likely the pilot jets are clogged and/or the sync is a little off. a small E guitar string is perfect for poking through the pilot jet btw.

cheers,

Trev

 

the crankcase breather tube is there to vent the pressure from inside the motor. it's connected to the air filter box so that the crankcase vapors get recirculated into the engine through the air filter system instead of venting and polluting the atmosphere. i'd hate to see what could happen if that hose is blocked from venting.

while the idea is nice to run a k & n setup over the stock box. it be nice if they developed a system to keep that breather tube hooked up some way.

i'm sure we'd all love to have cleaner air.

 

I just ordered a stock airbox and a new air filter to replace the K&Ns. I'd rather keep it stock, and I'm not looking to boost performance, just get the best I can out of the bike.

 

Rebel51,
If it's jetted for the cone filters, you may need to go back to stock jetting once you make the switch back to the stock filter. YMMV.

A reputable cycle shop told me recently that (assuming zestfully clean carbs, as Chacal likes to say) the low-end lag can be reduced by raising the main slide needle height. Not knowing your carbs, they may have clip positions on the needles. If not, it would be a matter of shimming the needle(s) higher with a washer(s).