Okay all....

Here it goes again.
I thought I had my stock carb spot on.... but maybe not.

Here's my setup;
PPD airbox (no lid with a K&N), stock carb and motor, RW pipe.....

Jetting; 45 starter, 47.5 pilot, 3 turns out, 190 main (mikuni), and Alba needle clip at 5th position (out of 6), spring cut.

When I'm running the quad through the dunes it seems great. Cruising around... still, great. HOWEVER.... when I'm all out on a sand flat area... and I mean pinned. Not letting off. Wide friggin' open..... it starts to cut out. I get a bobble after holding her wide open. The sand's pretty smooth.... I mean the quads running pretty smooth (my teeth aren't falling out or anything).

Could it be the fuel bowl isn't holding enough fuel?!
What do ya all think I'm experiencing???

 

Have you checked your floats?

 

yup.

They're set at a point where I need to turn fuel off when my bikes sitting still... there's a tad of spillage overnight. Like a 8" puddle on the garage floor. So I know they're set a little high with fuel in the bowl.

Next idea.... [img]i/expressions/face-icon-small-happy.gif[/img]

 

Try a 180 main.. Sounds like it's too rich on top end.

 

Could it be the dreaded rev lmiter?? You didnt mention you had an aftermarket CDI. And you also said " I get a bobble after holding her wide open" This could be your problem...next time it happens try and look at your tach....you might be surprised.

 

Yep, it sounds like your bumping the rev limiter.....

 

johnny, i had the 190 main jet in mine also and had similar problems, went to a 175, runs much better[img]i/expressions/face-icon-small-smile.gif[/img]

 

Hmmm....

I don't think it's the rev limiter....
I've hit that a few times in the dunes... but not on the flats. On the flats, in 5th gear wide open I can't always pull top end. Like at 7900RPM I mean. Usually it's head wind or too tall of gearing for the paddles... and that day it was pretty windy.

I also noticed that jetting on this thing is SUUUUUPER critical. When I jet my other bikes... it's not so picky. This stock carb is pretty picky. I mean... If jetting is off, you can't even get the bike to hit the rev limiter sitting still. Ya know, by blipping the throttle. If I jet it correct, it'll nail the rev limiter. Weird. I guess it's the whole vacuum carb thing. Something I'm totally new to.

I'll take a few jets with me next trip. And try leaner.
The more I think about it.... it didnt' do it the first few days I was in Glamis. Remember... I was there 12 days or so. And towards the last of those days is when it was having the issue. SO I'm sure the K&N wasn't breathing as easily..... making it too rich. Or richer. A tad leaner may just do the trick.

Also...
Anyone running aftermarket carbs that aren't vacuum??? I know there's tons of you that are on this site.... but I don't want clearance issues (with my IMS tank) or any other problems. If you are, can you give me an idea of which carb your running and why it's better than stock?! I'd like to not have a "vacuum" operated carb... it just seems like I'm not too familiar with it. And I'm beginning to think I don't like the way it performs.

 

Do you have a vented gas cap?
Mine does what you described every once in a while and if I crack the cap open a little it runs normal.

I have a 190 (or 195??) in mine, maybe I should try going a little leaner!

 

After holding wot for a time, pull in the clutch and immediately shut the motor down. Pull the plug and see what color it is. That will tell you whether you are rich or lean. Mabye a plug change will help you out also. I wonder if one of your plugs is not firing and at wot, too much fuel is coming in for just one to ignite?