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A real puzzle... (I thought I knew it all... lol)

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Usually I can iron out jetting problems without too much trouble, but this one has got me.

300 kawi Lakota, fresh rebuild, wiseco piston, jug milled .050, new valves... Rod n crank bearings are perfect and whole engine is like new.

New Mikuni 32mm roundslide carb (TM32). Came with 35 pilot, 200 main, 6DP17 needle, 159 Q-6 needle jet (2.730mm bore primary type), 3.0 slide, and a 2.0 airjet.

The airbox is stock (dual airboxes really) with a uni foam filter. Its pretty restrictive.

I found it runs best with a 160 main... No questions there. The problem is I can never get the idle and the off idle response just right. Also, I can't get the thing to wheelie (it won't take throttle that fast).

So, I switched to a 2.0 slide, 25 pilot, 5L1 needle, 176 O-8 needle jet (2.640mm bleed type), and plugged the air jet and it runs great. Revs to the moon, chugs around fine, but won't wheelie. Plug looks good too.

So, I go back to the primary type (2.73mm) needle jet with the 6DP17 needle and 2.0 airjet, but this time with a 10 pilot. Now it will wheelie a little better, but the off-idle is way rich.... and the needle is at its leanest clip.

Is there something about these roundslides that I just don't know? Is it even possible to get it to take throttle without a fuel pump or less air restriction? Am I just chasing shadows? If I had a dollar for everytime I've yanked that tank to change something, I could buy a brand new fuel injected 450!

Or do I just need a different needle jet? I think if I could just get it to take throttle, the rest I can figure out.

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it wont wheelie becuase it wont take the the fast throttle input?

the simple answer is wiht out a accelerator pump you have to run the slide and needle so rich that it will run like poop doing anything but snapping the throttle open.

i would jet it for best overall driveability and revving.

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I was affraid you would say that.

Why do other engine/carb combos w/o accl pumps do ok with snapping the throttle and also regular driveability?

Is the carb too big in my situation (32mm)??? (The intake valve is 37mm and exhaust is 31mm).

Do you think less air restriction would help?

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I don't know why I never got a subscription update in my email for this thread, but I had some info I wanted to add anyway....

We just put a plain ole 38mm mikuni roundslide (no accel pump) on a warrior with an FMF glasspack and KN filter. It pulls the front up really easy. The jetting was surprisingly easy in this case. You can't hit the throttle too fast. I can play the drums with the thumb flipper, lol. I'd need a shotgun to hit it any faster! It has a 40mm intake valve.

I put a 28mm flatslide (no accel pump) on a 230 quadsport and its the same as the warrior. The intake is 32mm for this one.

So, how come I can't get the 32mm to work on a 290cc machine with a 37mm intake valve???? Could the stock muffler be the reason? That's about the only thing different between the 3 engines.

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has nothing to do with the valve size.

just go to a richer slide.but dont be suprised when it runs crappy when doing anything but wacking the throttle open.

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velocity through the carb has A LOT to do with response! As Eddie said, put a smaller carb on and you'd have great response but lack the top end.

And just because you may have a monster valve in the thing doesnt mean that it will flow the maximum amount the valve will allow... there are many other variables!!!

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has nothing to do with the valve size.

just go to a richer slide.but dont be suprised when it runs crappy when doing anything but wacking the throttle open.

I did that. I have a 2 and a 3 slide.

I valve size is irrelevant, then how do we choose the proper carb size for an engine?

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I valve size is irrelevant, then how do we choose the proper carb size for an engine?

is that supposed to be if?

Im not sure on how to choose the size other than talking to others or trial and error...

Also the higher the velocity the easier it is to tune, the less finicky with weather and better throttle response (w/o an a/p).

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velocity through the carb has A LOT to do with response! As Eddie said, put a smaller carb on and you'd have great response but lack the top end.

And just because you may have a monster valve in the thing doesnt mean that it will flow the maximum amount the valve will allow... there are many other variables!!!

The carb is the same size as stock. Its just not a cv carb.

The valves are stock as well. 37mm is not monster, lol. The Mojave has dual 29's.... That's monster for only a 250cc engine!

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is that supposed to be if?

Im not sure on how to choose the size other than talking to others or trial and error...

Also the higher the velocity the easier it is to tune, the less finicky with weather and better throttle response (w/o an a/p).

Yes, oops, should have been "if" (got a taco in one hand n pecking the keyboard with the other, lol).

I always figured the carb can't be bigger than the intake valves. That's about the only rule other than: small = lowend power and big = topend.

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Yes, oops, should have been "if" (got a taco in one hand n pecking the keyboard with the other, lol).

I always figured the carb can't be bigger than the intake valves. That's about the only rule other than: small = lowend power and big = topend.

pink taco?? 👍

WIth the larger valve did you have it ported as well? if so was the person a reputable/ trusting knowing builder?

EDIT: just read your other post... The CV (constant velocity) may have been a big part of it! With that carb, the carb will only open enough for what the engine can 'ingest'... meaning when you whack the throttle open, the vacuum operated (from engine vacuum) slide is opening much slower than the throttle plate (which is opened almost instantly by your hand!).

so with that the 32 stock carb may have worked good (enough), but only because there was a circuit that you had almost NO control over!

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pink taco?? 👍

WIth the larger valve did you have it ported as well? if so was the person a reputable/ trusting knowing builder?

LOL, no.... not at the moment. Had to try one of those Volcano Taco from the Bell. They are kind pink looking....

Anyway, I rebuilt it. The valve isn't larger. Its stock. I didn't do any porting (if I did, it would probably be some of motoman's velocity porting). I just milled the jug down .050 and used a wiseco piston with a polished top. Here's the piston:

pistonsshiney.jpg

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generally a straight slide carb needs to be at least 4mm smaller than cv.

Oh ok, I was wondering why the cv always seemed to be a bit bigger when manufacturers switched in newer models.

But, I still don't think 32 is too big for this engine, do you? Lots of guys have had success with that same 32mm on 230 quadsports.

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... looks pretty...

eddies post should sum it up.

Yeah, I was kinda proud of that. 👍 It was a lot of work!

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so with that the 32 stock carb may have worked good (enough), but only because there was a circuit that you had almost NO control over!

That's exactly why I hate cv carbs!

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ahhww man, I was helping you with a quad?!?!?!?!?! I hate them things!👍

Good luck with it... I dont have any more info for you!

(no, really! I dont know any more than what I told you... at least that may have relevance other than keep playing with, have the head ported or get a smaller carb.)

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I made this last night:

DCP_2934.jpg

DCP_2935.jpg

DCP_2938.jpg

DCP_2941.jpg

That's a 230 quadsport in the pic with the engine off.

Hopefully, it will help me get to the cause of the trouble. If a warrior will work with a 38mm, a lakota should work with a 32mm.

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