3rd gen lumpy low rev

Hi

I’m experiencing the bike a bit lumpy in the low rev range.. Like if I’m almost down to a stop in 2nd gear and around 1800-2000 rpm, then accelerating, it jumps a bit until it reached +3000 rpm

The bike pulls well, it’s just that low rev range that bothers me.. Almost kangaroo-ing.
Is it suppose to be like that?

The bike has fresh filters, plugs, oil, clutch springs, slave clutch and carb synchronised.

Any suggestions or is it the way these old bikes are??

Kangarooing around when doing towns and so on?

 

I can't speak specifically to the bike but carb or FI I periodically run seafoam through to keep them running great. today's gas is terrible and doesn't last

 

clean the carbs paying special attention to idle jets and mixture screw passages.

 

I was thinking of doing this myself when the season comes to an end..
Buying a carb kit and replacing all of the jets and so on...

Is it a straight forward job?

 

you don't need any kits to clean carbs, just make sure things are free of any sticky residue and that you can see light through the idle jets.

easy job? not exactly !!!!

 

I get the impression you’ve not had this bike long. Maybe you’re used to an in-line 4. Sea foam probably wouldn't hurt, but I’m wondering how often you are going down to 1800-2000 rpm in second gear. That’s pretty low considering that idle is 1100 rpm. These bikes from my experience are somewhat lumpy below 3000 rpm and ideally like to be above 4000, and pull strongly from there. Although a v4 they’re a bit like a v twin and like to be above 3000 rpm.

 

I overhauled the carbs on my 93 a couple of weeks ago, and changed all the o-rings while I had the carbs apart. I then bench synchronized the carbs with drill bits. I did not replace any jets or diaphragms. You want to check that the diaphragm rubbers are in good shape while you have the carbs apart, though.

The jets were full of gunk and there were deposits in the passages, but they cleaned up very well. I agree with squirrelman that there's no reason to replace the jets if you aren't planning on fiddling with the fueling and induction/exhaust (I wouldn't, TBH).

The motor pulls cleanly from idle, but you can feel the thumps of each cylinder below 2k rpm, so it will feel lumpy. It certainly doesn't help, if the carbs are out of sync.

As far as taking the carbs apart, the first hurdle will be removing the carb assy from the intake boots. Loosen the bands up (very loose) and pop the two rearmost carbs out first with the help of two pry bars - wedge them between the lifting points on the carbs and the edge of the rear valve cover; after you've popped out the rear carbs, the front carbs should lift out from the boots quite easily. It helps if you warm the boots up with a heat gun to make them more pliable.

After you have the assembly out, it's a fiddly job to get the enrichment arm lever, throttle arm and fuel/air pipes and tubes off, but it's not impossible. I wouldn't try doing it all in one night on your kitchen table, though. It will take a couple of days and some patience, I found.