Sup Y'all

[wildbob]

How's it been folks? Been busy with military stuff and looking forward to getting the buggy running. It's pretty much been sitting since I put the mikuni VM26 on it last year. Now that I have some time I'll be able to do some diagnostic runs with it to see if I can get the carb tuned. I've got the smallest pilot I can buy and it still seems to run rich, bogs when you gas it, etc.. Also seems to work better with the air screw only turned out about 1/2 a turn, but that's what testing is all about..

[x-bird]

Could be a few areas.
i'd start with seeing if you can drop the needle down a notch or two, that would lean the bottom out.
Which side of the slide is the screw on? filter side is air, intake side is fuel, gotta think in those terms. If the screw adjustment doesn't affect the idle or isn't in the 2 to 3 turn range, it's showing you which way you need to go with the tune. You need to get it in that range and have it affect the idle with only a little screw turn or you'll be fighting issues in one rpm spot or another depending on what's amiss.

Might be too big of a main as well ....
Are you set up with gravity feed? might be overflowing the float needle spring. Ran into that issue with a VM that was originally vacuum that i set up as gravity. Couldn't get a needle/seat that was rated for the gravity setup. solved it by going with a vacuum pump and pressure regulator.

[wildbob]

Yeah, I think I have the clip at the top of the needle. VM26-606 doesn't look like it uses vacuum. The screw is on filter side and affects the idle, but it's super boggy 2+ turns out. Starts right up, but not choked. revs with gentle throttle input, but if you give it a handful of gas it bogs right down. I had a 30mm pumper on it before, which was a bit much, but worked pretty good. I'd heard people rave about the mikuni's, but haven't gotten mine work well yet.

[jmansracerocket]

glad to see your back wildbob

[x-bird]

adjustment screw is an airscrew then, and it's showing it's getting too much fuel. needle is in the hole all the way, which is the leanest. so it's saying it wants a smaller pilot or there's something else dumping in too much fuel. While running with the TM 24 flatslide, my vacuum through the carb was so strong since the bore was so small, that i ran into the need for an ultra tiny pilot that i had to make myself because of the way it would pull fuel up around the main, even at idle. just too small of a carb. you may be at that stage where a 28mm bore is what the engine really wants.


open your petcock and let it sit a few hours in a "safe" area. then check to see if it's flooding out the needle. if the fuel flow coming in is a mismatch to the needle and seat setup, it can make it rich no matter what the jetting. ran into that with the Suzuki's oem VM 26. check and eliminate that idea ... I had to go from gravity to a regulated fuel pump to get that situation under control. carb doesn't car how it's fed, just as long as the float needle and seat match the feed rate. Speaking of which, did you check the float height? may be too high.

[wildbob]

I'm pretty sure I've got the smallest pilot they make for it, but I'll check the float height. How do you determine if it's "flooding out the needle?"

[wildbob]

OK 15 pilot, 140 main, clip one down from top on the needle. bent the tab down a bit on the float, and it seems to run pretty good idle - 1/2 or so throttle, past that it bogs again, but popping, crackling now past 1/2 throttle. Definitely better idle to 1/2 throttle. I went so small on the jets trying to fix it, I may have to jet back up on the main now that the float has been adjusted

[jmansracerocket]

Originally Posted by wildbob

OK 15 pilot, 140 main, clip one down from top on the needle. bent the tab down a bit on the float, and it seems to run pretty good idle - 1/2 or so throttle, past that it bogs again, but popping, crackling now past 1/2 throttle. Definitely better idle to 1/2 throttle. I went so small on the jets trying to fix it, I may have to jet back up on the main now that the float has been adjusted

sounds like the main is to big

[x-bird]

to test if the gravity feed is stronger than the float needle and lifting it, just leave the fuel petcock in the on position and let it sit. check inside the carb throat to see if it's wet around the main. if so, you've got an issue with it. if not, good to go. behaves just like a float needle with debris stuck on the seat. you'll end up with gas in your oil and too much fuel during idle/part throttle....

[wildbob]

So, I think the float was the issue. After adjusting it, it was popping and sputtering over 1/2 throttle, so I went bigger on the main (140-->145) and it rips around pretty good. Now it's running well enough that I can do a plug check, and get it dialed in!! WhoooHoooo!!!

[jmansracerocket]

Originally Posted by wildbob

So, I think the float was the issue. After adjusting it, it was popping and sputtering over 1/2 throttle, so I went bigger on the main (140-->145) and it rips around pretty good. Now it's running well enough that I can do a plug check, and get it dialed in!! WhoooHoooo!!!

good to hear, im surprised its running well with a 145 main that's a pretty big jet for your mods at least that's just my 2 cents.

[wildbob]

We'll see. It wasn't running enough to drive at all before, now at least I can see where I'm at. I've got the air screw out 2 turns now as well. I'll put a new plug in it to do some testing next weekend.

[timmzzy]

please guys i wanna know how fast i can go with a buggy weighing 210kgs 26hp 25 inch tires gear ratio 3:1 and 4000rpms and 800cc

[wildbob]

Originally Posted by timmzzy

please guys i wanna know how fast i can go with a buggy weighing 210kgs 26hp 25 inch tires gear ratio 3:1 and 4000rpms and 800cc

Best bet would be starting a new thread with the buggy's info (brand, motor, etc) There's plenty of folks on here that either bought or built something similar, I'd imagine.