Author Topic: Need Stock Carb Help. (Read 1531 times)

98TUNNER · « **on:** November 10, 2012, 06:50:47 pm »

Got all of the issues straigtened with the old 250 except one. Jetting is at 45 pilot 190 main. Runs strong piston wash and plug look good. Problem i'm having is it will not idle, can't screw idle screw in far enough to make it idle high enough. Haven't tried removing the spring to see if this helps yet. To get it to start I need to hold the throttle open just a hair, just about enough to take slack out of the cable. With the trottle at this possition it will sit there and per like a kitten. Need some thoughts please..

Deebo · « **Reply #1 on:** November 10, 2012, 06:57:44 pm »

Adjust your slide height to about 1-2 mm open.

Chevyvettezr1 · « **Reply #2 on:** November 10, 2012, 07:38:57 pm »

Like deebo said...set the slide height to 2mm open. Adjust pilot sizes till it idles correctly.

98TUNNER · « **Reply #3 on:** November 10, 2012, 10:45:46 pm »

Does the stock idle screw have a oring on it and only threaded part way? I dug threw my misc. drawer and found a idle screw that was threaded farther then what was in the carb and it idled great. When you set the carb 2mm open are you measuring air box side or engine side?

Rainman56 · « **Reply #4 on:** November 10, 2012, 11:48:47 pm »

I had to lean my pilot down quite a bit on my 250 when i had the stock carb on it.I,ll have to check but I think I started at a 30 and worked from there.Also make sure your slide not to badly worn as it can cause all kinds of tuning issues.

Deebo · « **Reply #5 on:** November 11, 2012, 07:03:37 am »

Quote from: 98TUNNER on November 10, 2012, 10:45:46 pm

Does the stock idle screw have a oring on it and only threaded part way? I dug threw my misc. drawer and found a idle screw that was threaded farther then what was in the carb and it idled great. When you set the carb 2mm open are you measuring air box side or engine side?

Set the slide height with cable adjustment.

98TUNNER · « **Reply #6 on:** November 11, 2012, 10:38:10 pm »

Deebo- Isnt that dangerous taking all the free play out of the cable??? Have seen people do this before and when they turn the rpms climb and usually crash.

Deebo · « **Reply #7 on:** November 12, 2012, 08:07:51 am »

There will still be some free play in the cable.

98TUNNER · « **Reply #8 on:** November 12, 2012, 03:05:44 pm »

Not to sound stupid but how can there be free play if you take the tension out to raise the idle?

JPW59165 · « **Reply #9 on:** November 12, 2012, 04:52:39 pm »

If you are running a 45 pilot and a 190 main jet, I assume you have a 1985/1986 model and somewhere above 3750' above sea level elevation.

If this is the case I would drop down to a 42 or 40 pilot and set your air screw for 1-5/8 turns out, then try to set your idle.

I had a 1988 Suzuki LT250R QuadRacer, I am at 4300' and my stock Mikuni 34mm was jetted/tuned as such:

air screw 1-5/8 turns out
pilot jet 37.5
needle 2nd clip from top
main jet 210

It would start right up and idle all day at 1500rpm, I remember the idle screw being right in the middle of it's allowable adjustment

98TUNNER · « **Reply #10 on:** November 12, 2012, 07:05:38 pm »

Correct on the year. Elevation is about 800

JPW59165 · « **Reply #11 on:** November 12, 2012, 07:13:39 pm »

you have any mods; pipe, silencer, air box?

have you tore it down, cleaned the carb, rebuilt it with a new kit?

at that elevation you should be somwhere in this ballpark:
- air screw 1-1/4 turns out
- pilot #45
- needle 3rd clip from top (middle)
- main jet 190 (stock) 200 (aftermarket silencer) 210 (exhaust and air box lid removed)

after that it should idle fine if all is clean and operating properly

98TUNNER · « **Reply #12 on:** November 13, 2012, 06:05:17 pm »

FMF silencer, every thing else is factory as far as I can tell. Pretty sure pipe is factory but can't swear to it. Cleaned carb several times thinking I missed something, new needle and seat. As far as your adjustments, what you sugested is where all are set. in exception to air screw mine is at 1 1/2 out. Thats were it seemed to be the most responsive.

JPW59165 · « **Reply #13 on:** November 13, 2012, 06:35:33 pm »

when you cleaned the carb did you take it completely apart and use a rebuild kit, or did you just reuse old components?

remove the idle screw, should be a screw, spring and maybe an o-ring, clean all components and orifice
remove the air screw, should be a screw, spring and o-ring, clean all components and orifice
remove the slide/needle, should be a needle, clip, spring, retainer, clean all components
remove the main jet, clean the jet and orifice
remove the float assembly, pull the retaining pin
remove the valve jet, should be a needle, clean the needle and orifice
clean the overflow tube
spray carb cleaner throughout the inside of the entire carb

if you really cleaned everything you should have gone through a whole can of carb cleaner

when you put it all back together, set the air screw to 1-1/2 turns out and turn the idle screw all the way in before you put the slide/needle assembly back in, throw it back on and update us. If that doesn't fix the problem, then you may need to look at a new carb

Q2W · « **Reply #14 on:** November 13, 2012, 06:51:36 pm »

adjust your idle with the air screw not the thumb screw. Do like everyone said and set the slide height (thumb screw) to about 2mm. Adjust your throttle cable so there is no play in the cable.

If your pilot size is close you'll be able to turn the air screw one way or another and the idle will change. Out=more air . In =less air. if you have to go beyond 2 turns out, you will need to drop your pilot 1 size and try again. If you have to under 1 turn you will need to increase your pilot one size. adjust till you get it to idle. If you get no change in idle no matter how many turns in or out on the air screw, your pilot is way off.

good luck

Nekrofilliak · « **Reply #15 on:** November 14, 2012, 01:38:35 pm »

i had hard time jetting a lt250r in the past it wont idle fine , jetting was alway too rich , i had to change the jet needle, the needle and the reed petal.

98TUNNER · « **Reply #16 on:** November 14, 2012, 05:52:44 pm »

Ya carb was completely disassembled, cleaned very maticulously. Not a rookie at this stuff just stumped on this one. Why does everyone say to remove all freeplay from cable??? 2mm are you measuring the air box side of the carb where the slide meets the body[ where the jet needle sticks out of body]? As far as the air screw it does change the throttle response but still will not idle.. 1 1/4 out bout as good as I could get it. Any leaner more turns out had a nastly lean bog, more turns in responded very slugish.

JPW59165 · « **Reply #17 on:** November 14, 2012, 06:55:53 pm »

I would not take any slack out of the throttle making it raise the slide personally, there needs to be a little slack at the thumb, maybe a 1/8th of an inch. You say you took it apart and cleaned it, but did you rebuuild it with a kit and measure the floats? It could be as simple as putting new components init. I orderred a rebuild kit for like $12 to $13, came with everything I needed for the carb.

98TUNNER · « **Reply #18 on:** November 14, 2012, 07:28:37 pm »

Agree on the cable, wasn't sure if there was somthing I didn't know. It goes against every thing that i've been taught to do that.. Thats why I wasn't sure why every one kept saying that. I did not put in a kit, I replaced needle and seat with oem suzuki, replaced pilot with oem mikuni, left main, jet needle and needle in that was in. I don't like aftermarket kits I had a bike burn down on me before because of aftermarket jets.

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Author Topic: Need Stock Carb Help. (Read 1531 times)

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