Hello,

I'm having some problems when running at low RPMs. The mixture is too rich. I have tried to adjust it with the mixture screw with a partial success, and it also has helped to check the level of the carburetor floats, but I do not want to lower more the level to prevent fuel lack at high RPMs.

Now I think it could be usefull to drill the airbox in order to facilitate the air intake. I think that this should make the mixture less rich at low RPMs.

Do you think that this would be usefull?

I'm using the stock air filter.

Thank you for your support.

Best regards.

 

No! Drilling out the airbox is not the proper way to tune the carburetor.
First, I'd check the easy-fix: are the fuel-enricheners opening and closing smoothly? If there's a problem with the linkage or if either one is not opening and closing smoothly, that could cause the richness, and a fix would be as easy as a quick squirt of WD40 and a pass with a rag.

Did you buy this bike used, have you installed a jet-kit, or have you done any diddling with the pilot screws? The latter is most likely the culprit for low-rpm richness.
What makes you think that setting the pilot mixture screws at the stock settings will cause fuel lack at higher rpm? The main jets allow plenty of fuel at higher RPM, as long as they're not gummed up with varnish or rust from your tank.

Has the bike ever been sitting for a long time without being winterized? It seems like half of all carburetor problems originate from someone throwing in a jet (without knowing what they're doing), and the other half are from getting gunked up after sitting for a few months.

Are you certain both carbs are too rich? If it's one or the other, there is a decent chance that your pilot jets are gunky or damaged. If the pilot needle isn't sealing properly, that would also cause richness.

Good luck and let us know how it goes!
-CCinC

 

I bought the bike to a guy that hadn't used it in 5 years. the first thing I did was to send the bike to my mechanic to clean the engine and to tune it up.

Everithing was working fine. but a few months ago I changed the exhaust line. the bike is running propperly, but it is too rich at low RPMs, and the mixture screws does not seem to be the problem. I have tried set ups between 2 1/2 turns and 1/2 turn and the problem does not seem to be solved. The bike seems to run better on 1 3/4 turns on the mixture sceews.

Another important detail is that the engine has lost it's 'kick' effect at the 7K RPMs, and now this effect appears at 4K RPMs. I think that it could also be a question of needle, springs, and jets set up. I'm thinking about installing a Jet Kit, but I'm not sure about the effect.

Any idea?

thanks for your support.

 

Oh, I dunno... put your stock exhausts back on? Mr. Kawasaki knows a hell of a lot more about making an engine run stronger, longer than Mr. K & Mr. N do.
When we riders tinker with the delicate balance of compressible-fluid dynamics, we're rarely as good at it as the engineers who built the bike.
The traditional answer to a lean condition after the installation of an aftermarket exhaust is to get a jet kit, (and if you've got the bucks, an afternoon with the dyno-tuner.) But it's my unpaid opinion that most jet kits solve a variety of problems by simply throwing more fuel at them. The bike usually feels smoother to the rider, so the only downside is a decrease in fuel efficiency, right?
BUT, I've seen several bikes with chronically darker plugs after a jet-kit. Carbon build-up will kill an engine more quickly than the most squiddly malicious throttle hand.

Of course, another option that didn't occur to me before is that if the bike sat for a long time and the carbs were rebuilt, a bent float arm might be causing your rich condition. But given the sudden appearance of a problem upon the installation of an aftermarket exhaust, maybe not...
Good luck.
-CCinC

 

OK, then I'll try first to check again the floats level.

My plugs are getting very dark,thats the reason why I'm so interested in getting a smooth running at low RPMs.

best regards

 

low rpms like 0-3k? What was the plug chop like if you did one? And how did you do it?
sorry guys, just trying to follow this post.

 

yes, what I refer for low RPMs is from 0 to 3,5K, above that range of RPMs the carburetor seems to change from the low needle to the high one, and the problem disapears. At this point 3,5-4k the engine has it's kick effect.

The plugs are very dark and the engine losses all its power when reaching the 3,5k RPMs. after this value the engine works very smooth.

best regards

 

yeh, low end=emulsion tubes, mixture screws, idle screw and choke settings.