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1996 rm250 pilot jet vs needle clip position

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Hello, I have a 1996 RM250 that I recently did a complete rebuild on and now i am working on getting the carb tuned. It has the original PJ carb. I install a new vforce 3 reed cage during the rebuild and the carb had been clean thoroughly and the float level has been set and rechecked every time I remove it to make adjustments. Now for the issue I'm having, I have nearly got it dialed in with a 55 pilot jet and 170 main with the stock needle at the second clip position from the top. Air screw around 1.5 turns.

 

With the bike at operating temperature it will idle ok but if I just give it a small amount of throttle, like less that 1/8, it sputters bad to the

point that it wants to stall out. If I give more throttle it clears up. And while riding it does the same things and runs really well on the main jet circuit. The air screw likes about 1.25-1.5 turns out. I have tried turning it out more but then it gets a pretty bad hanging idle.

 

It will be a few days before I can work on it again so I'm just trying to get some info to maybe keep from pulling the carb so many times. Is it possible that if I move the needle clip up it could clear this up? I'm reluctant to change the pilot jet because the air screw seems to be in the correct position. I'm fairly new to tuning carbs so I'm no pro at it. Also mods are vforce reeds, pro circuit pipe and FMF turbine core silencer and elevation is around 1100".

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It sputters,not stalls?

If so its rich?

U can rotate carb while installed enough to remove slide.

I'd start by changing the clip, 1 leaner, top grove.

If worse. Go the other way?

Ps-main jet and float, gotta be right first?

Tune main first.

Then needle.

Then screw.

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Yeah it's rich. It will sputters to the point that it will stall if I let it. I will try the needle clip before changing pilot. Thanks

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That's a lot of sputter? Might have to lean pilot? But be sure main is not rich, it changes all other settings.

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Ok so I put the 52 Main jet in and it seemed to lean. Had the tune the air screw way in, and I still had the issue when opening the throttle. So I put the 55 back in and tried a few different needles and different clip positions. The engine responded to the changes, however none of them corrected the issue. Can anyone help steer me in the right direction? I'm wondering if I should try a different slide. That's the only thing that I haven't tried.

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Awesome thanks. So you think a leaner needle will fix my issue? I'll get on there and order 3 or 4 different sizes. And maybe a leaner slide.

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So with the 52, u richened the clip, and no better?

What bout the needle brass, is it not replaceable?

Have u tried stock settings across the board?

I've tuned over 100 carbs, never had to order a needle to get it close?

Is the carb stock, or has someone before u monkeyed with?

U sure your main ant tooo big?

 

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It is the stock carb. I put the 52 in and it just seemed lean overall. I did richen the clip but it just didn't seem right. Right now I have the 55 pilot in and a 1469 needle and I likes that alot, however I still have the light throttle issue. Someone in another forum mentioned that the power valve might not have enough tension causing the exhaust valve to open to soon. Thoughts? I did remove the pv assembly to send the cylinder off for replate. I put it back together per the manual and I may try to adjust it a bit.

 

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9 hours ago, Del1650 said:

Awesome thanks. So you think a leaner needle will fix my issue? I'll get on there and order 3 or 4 different sizes. And maybe a leaner slide.

I do. Not necessarily overall leaner, but leaner in starting diameter. I had a 96 that I racked up tons of hours on, so I can relate to the 1/8 throttle stutter... It’s fine if your racing MX and never use 1/8 throttle, but for trail riding it sucks. :)

Another thing to check is your jet block gasket. Those don’t last forever, and depending on how/where it’s deteriorating, could be pulling in extra un-metered fuel. Might be hard to find for the PJ. Not a common carb anymore. Will have to check aftermarket. Keihin considers jet block a non-serviceable part, so you’ll need security torx bits to replace gasket.

Simple way to check is remove bowl, float, etc. have carb upside down, prop breather hoses up, and fill with fuel above the jet block mating surface. Come back 1/2 hour later and see if it has leaked fuel into carb bore. It’s not a complete check, but you’ll at least know if raw fuel is leaking by...

If that checks out ok, then order a couple needles. Throttle slides typically cost a lot more, so let’s see if we can get it fixed with just some 6$ needles first...

 

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OK I'll order up a few needles. It's running good overall, so I think I'll see what that does and then maybe switch to a pwk. Through research I've read that the pwk is more desirable carb.

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So I have acquired a PwK air strike carb that I have installed. I’m still in the process of getting it jetting right, it’s too rich right now but I have had a chance to mess with it too much. Can anyone steer me in the right direction as far as what needle to use? It hard to find info on this subject since the carb it’s not original to the machine. If I look up specs for the 1997 Rm250 (which uses the PwK), it uses a triple taper needle. I’m wondering if I should mimic the jetting specs from a 1997. I know I can figure this out with trial and error, just seeing if someone with more expertise can steer me in the right direction.

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Oh forgot to mention the carb came with a ddj needle. But I’m curious if I should use a triple taper needle

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