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03 rm125 wont idle.

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hi my name is zach. i have a 03 rm125 that wont idle. i know that it shouldnt be the top end because i put a new 1 in myself at the beginning of winter. it has a wiesco piston, v force reeds, hot rod crank, and a alumnium cylinder head. it supposidly has a "over sized carb" but i have never heard of that. i just got it before the winter and it wouldnt idle when it was hot. it soon had low compression and wouldnt start so i took off the cylinder head to find the piston being eaten away. i put a new top end in it and it started 4th kick. it allways starts 1st kick now. i think that it has some sort of powervalve modd. it has amazind top end bugt absolutely no low end before like 8 thousand rpms. my friends race 450s and they say that it has more than normal power. it aalso has full fmf. the guy i bought it from said that it was a 144. this kid was not informed with motocross. when i put the new piston it was stock or at least i think it was. anyways it wont idle right. it will start easy and idle really high when it is cold but when it heats up it keeps wanting to stall out. help. maybe old coolant it isnt working as efficantly.

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Set the air screw at 1-1/2 to 1-3/4 and I would really pay attention to the jetting on this bike. First you said the old piston was being eaten away which tells me one of four things. 1st, jetting is real lean in the mid or top range. 2nd, someone has jacked with the stator plate and got the timing off. 3rd, fuel detention from low octane (has your head been shaved) or from the lean jetting, which would cause more heat. 4th, air leak around the reed gasket or base gasket. I would think that when you replaced the top end, you would have solved any air leak.

I am almost positive you need to really work on the jetting. Every thing I listed above will cause over heating or running hot. Good luck.

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it definately runs hot. if i ride it for a hr and shut it off it will not start again. but if i leave it for 10 mins then try it it will start again. the air screw does make some sense of it running lean. it has no high end bod tho, i do think that the powerband is a lot higher than most 2 strokes. oh ya i need to know what screw is the idle on this bike. im pretty sure i have the right 1 but i came from a 250f thaat just had a knob that you turn. the one i am adjusting is a phillips head with a nut around it to stop it from mooving. i think it is the 1 all the way to the right.

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oh what i mean by it wont idle is that the idle gets lower. ill ride for 5 mins and it is lower. then sooon it will sound so low that it might cut out. that is when i stopped riding it

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Your adjusting the idle screw. The air adjustment screw takes a flat tip screw driver and is located just before the air box boot that clamps to the carb.

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First of all, why do you care if it idles? Most 2 stroke dirt bikes are not set up to idle, as there is no reason for them to do so. It's not like you have to wait at stop lights to make a left turn or sit in traffic on your dirt bike. As for the jetting, you need to be looking at your plug, which should ideally be tan. If the bikes runs good and does not foul plugs, and the plug is tan or black, or jetting is probably OK. If your plug is white, or black and fouling, then you likely have jetting issues.

To get started, make sure your airfilter is clean, and mix up some 32:1 premix. Buy yourself some cheap NGK BR8ES plugs from any autoparts store (about $2 a plug). Read up on jetting, and give it a go, making incremental changes from what you have now. Only change one thing at a time, and test the bike after each change. The RM 125 manual is pretty good at explaining jetting, and you should have the bike running well very quickly, and you can fine tune things later.

As an example, my 04 RM is used for woods racing and riding. It does not idle (and I have never tried to make it idle), but it runs extremely well. I am about 1K above sea level and I usually run a stock main, stock needle and clip position, 1 step smaller pilot, and the air screw is adjusted per the temperature. It sounds like your bike has a fair amount of mods, so your jetting needs will be different, but I doubt you will need to go far from stock (although that "oversize carb" thing sounds weird).

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Having your bike idle , comes in handy when you are riding technical terrain.

I guess it might if the terrain is so "technical" that you frequently come to a complete stop. But if you are moving at all I don't really see the purpose. My bikes are normally used on very rocky and rooty single track with steep inclines and declines here in the mountains of North Georgia. My KTM does happen to idle (it came that way from the factory), but my CR and RM do not. I've never felt the need to make the RM and CR idle, even when riding the KTM and other bikes back-to-back on technical trails.

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well i need it to idle cuz im gonna be racing harescrambles. even if it doesnt idle still it drops lower and lower to a point where if i dont keep giving it gas it will stall and be increadabily hard to start. if it is cold it starts first kick every time. the plug is black and it hasnt fouled one. i hae been riding it for around six to eight hours now. when the bike is cold it has smoke like a regular 2 stroke, but when it is hot and doesnt want to idle it doesnt have any smoke at all. i dont want to continue riding it if it is not smoking cuz im afraid im gonna screw up the engine

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There is no need for an idle in harescramble or any other form of racing. HS racing is all I do these days, and as I noted above, only one of my bikes idles, and it is totally irrelevant to racing. An RM 125 does not normally idle, and making it do so may well interfere with other aspects of tuning.

If your bike has a black plug, I doubt that any of the circuits is too lean. It is totally normal for your bike to smoke at startup, and then smoke much less once it is warmed up. A lean condition will result in loss of power as the motor gets hot, and various unpleasant noises. If you have a clean air filter and are running a good ratio (e.g., 32:1), you should be fine. Why don't you just have somebody experienced take the bike for a spin. They can tell you in a minute if it's lean.

Good luck racing. You have made an excellent choice for a bike. Few bikes can fly through the tight woods like an RM 125.

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Yea, I guess it does give the impression that I'm focused on the idle, but what I was trying to do was to get him to focus on more relevant issues beyond the lack of idle. From his initial description, it sounds like he may have some pre-ignition going on.

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Mechanically every two stroke or four should sit and purr like a kitten. Then you know every part is working as designed. If a bike does not idle smooth, then its a problem with compression, jetting, float height or flooding, weak electrical, problem with the reeds and I can think of many more combinations that can cause pour motor performance. Many times its just a worn float needle or low compression. I work on my two strokes and make sure that they have a smooth idle on the stand while I put my last tidbit of gear on. Just my preference I guess. I also know riders that could care less if their bike idle. Too each his own.

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mine idles like a dream. i didnt make it idle. it just dose. my bike smokes like a bastard too.

i run her a little rich for reinsurance purposes.

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well i think it might be flooding or the float height is a little high. the bike has to be almost exactly straight up or the over flow will start to very slowly drip. ill try to make it a little lower i think that might solve it.

also im restoring a 1966 yamaha catalina yds-3 any suggestions on what i shoul do next before trying to start it. i looked at the engine, carbs, got new spark plugs , changed the oil, and even mixed some pre mix instead of the oil injected to make sure that it gets oil\

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k now i was riding it and it got hot and wouldnt idle. it stalled and wouldnt start for a half hour.... i dont know whats up with it. i have yet to adjust the carb becase i had a house fire in january and we have mooved out of where my bike is stored. so now i dont have any tools there so if i want to use some i have to bring them with me. and when it is hot it has low compression. like it used to before i rebuilt the engine. i dont know i may just sell it and get a different bike. this is the lat thing that i really need right now is more money to spend

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