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RM 250 Surging idle

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so heres the deal: idle surging, pull the plug and it doesnt look lean...

sprayed wd 40 and ether all around looking for leaks including the left side crank seal and no noticeable change in rpm. i cleaned the carb and set everything stock with stock jets.

when idling if i pull the choke up it will begin to run mint which i think means an air leak but i cant seem to find one.

also have fresh high test with an octane booster and 32:1 as the manual says...

should i try to do the homemade leak down test?

also the head and cylinder bolts are all tight with no sign of leaking... does not leak oil from the cases either...

if it was the clutch side seal wouldn't it burn tranny oil??:thumbsup:

any help appreciated, thanks in advance

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I would try richening the pilot jet.

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i will try that and get back tomorrow...

shouldnt it run properly with stock jetting though?

also how much does the choke change the air fuel mixture? how much will i have to change the pilot jet to make it run like it does with the choke on full...??

also the kill switch seems to not want to work sometimes (could be unrelated)

to get it to stall with the air screw at idle it is more than 3 turns out....

does all this point to an air leak?

Edited by Batman11585
add info

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What year is the bike?

I just fought this major battle my self, i actually heard from many people that I am lean and I have an air leak and all that. I tried all those and it turns out I actually was rich on the bottom. I put a leaner jet in and it went a away. go figure. :thumbsup:

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its a 2000...

i let it idle and pulled the plug and looked rich... not very experienced with jetting though...

i would think with the choke making it run properly that i am currently too lean though... that way the choke richens it up and runs properly... not sure tho because this could also be air leak... i am going to build Faded's leak down tester tomorrow and post back...

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its a 2000...

i let it idle and pulled the plug and looked rich... not very experienced with jetting though...

i would think with the choke making it run properly that i am currently too lean though... that way the choke richens it up and runs properly... not sure tho because this could also be air leak... i am going to build Faded's leak down tester tomorrow and post back...

Where do you have the air screw set IE how many turns out and and how many clicks do your have the Choke Idle assembly turned out?

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air screw was 2 turns out and choke was also 2 turns(or 12 clicks).. i put all to stock..when it is running i have to turn the air screw out prob 4 turns before it dies...

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air screw was 2 turns out and choke was also 2 turns(or 12 clicks).. i put all to stock..when it is running i have to turn the air screw out prob 4 turns before it dies...

Are you referring to turning 4 turns out? if you turn it all the way in, does it say running?

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sorry yes 4 turns out will make it stall. at 2 turns out it will idle but the idle surges and hiccups... sounds like crap.. sounds like somebody knocking on a dry piece of wood as well.... best i can describe it lol..

with choke on sounds like it should

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sorry yes 4 turns out will make it stall. at 2 turns out it will idle but the idle surges and hiccups... sounds like crap.. sounds like somebody knocking on a dry piece of wood as well.... best i can describe it lol..

with choke on sounds like it should

Ok, what happens when you turn the air screw all the way in cause you know turning it out gives it more air leaning it and turning it in cuts out the air richening it, same as pulling the choke does. I would suggest turning it in and see how it reacts maybe not all the way in but at least only 1/2 turn out. If this helps then your way too lean on the pilot.

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I just went thru this on my 2000 and fixed a ton of problems, some were contributers and other were not. But the item that helped the most was replacing the exhaust. Take your pipe off and see if you have restictions due to carbon build up.

Also, just as some added information, the manual actually calls the choke

"The Enricher". What is says is that pulling the choke adds fuel to the pilot circuit for cold starts so the bike does not run lean due to cold running.

If pulling the really makes it run better and you are hearing the pinging of a leaned out piston. You need to riched your pilot jet.

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i think i already tried all they way in and didnt make much of a difference... i will try again tonight to be sure.

Thanks

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I just went thru this on my 2000 and fixed a ton of problems, some were contributers and other were not. But the item that helped the most was replacing the exhaust. Take your pipe off and see if you have restictions due to carbon build up.

Also, just as some added information, the manual actually calls the choke

"The Enricher". What is says is that pulling the choke adds fuel to the pilot circuit for cold starts so the bike does not run lean due to cold running.

If pulling the really makes it run better and you are hearing the pinging of a leaned out piston. You need to riched your pilot jet.

ok i will pick up a couple richer pilot jets tonight and try that too.. il post tomorrow how it went

thanks

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i will print that forsure thanks... how many jets larger than stock should i get... i think there is a 35 in there now(stock)???

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i will print that forsure thanks... how many jets larger than stock should i get... i think there is a 35 in there now(stock)???

I would only say two to begin with. If you have to go more than two sizes up from stock to get it right, then I would look into other factors like a weak top end or your packing is burnt out, but you may have mentioned you had fresh top end and new packing I don't remember. Don't forget you have a needle clip you can adjust to that effects throttle response. Get that pilot sorted out first by reading that article.

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sounds good.. top end 190 psi.. not sure when it was last done..

muffler packing could be suspect.. bike was bought used.. probably never changed

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sounds good.. top end 190 psi.. not sure when it was last done..

muffler packing could be suspect.. bike was bought used.. probably never changed

Top end sounds tight at 190 but if your dealing with burnt out packing it could hender you getting your jetting dialed in. I wouldn't hesitate to repack that silencer. Its only about 10bucks and then you will know :smirk:

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ya sounds good. i will give that a try too, i never thought that would have much of an effect but i guess if its all gummed up it will restrict flow...

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i have exactly the same problem and started a new thread so maybe i will continue in here. I tried all the different pilot jets starting with 48 then to 50,52 and 55. all made it slightly better but they all started to idle up over time. Upping the pilot caused the bike to run noticibly worse as i went up to the next pilot size. Eg richer and richer to the point the bike was horrible to ride. I took a while to try it but the air screw was 1 1/2 turns out i played around with it and found that running the air screw around 1/2 turn out the idle issue went away. Now the funny thing was between a 48 and a 52 pilot i had to have the air screw in exactly the same spot or it would idle up meaning the pilot was not the issue. So i would definetely try that first, and also check reads. Now i just have to find out why i need it only 1/2 out for it to idle

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