Any good dirtbike mechanics in here? (I need help)

[4u2nv]

I have a Rm125 Suzuki dirtbike, and am having some issues. So I was wondering if there was anyone in here with some knowledge of them. I am getting boggy spots in 1st and 2nd gear. 3rd it seems to clear out but still coughs a little bit in the 6th gear.. I just put in a new top end (Needed it) with a wiseco piston, put in new active reeds, and still have the probs. I've cleaned the carb a good dozen times (a mukuni carb) and its seems clean.. All the lines are have pressure, and good vacume... Anyone have any ideas what to check next?

 

[Nathan_454]

try to get ahold of scottm... he knows his way around bikes, my roomate works on bikes too ill ask him.

 

[Nathan_454]

my roomate says it could be that your jetting is wrong for the oil mixture you are running, or maybe its too rich of an oil mixture. hope this helps.

 

[Got Nitro?]

I would have to agree with Nathan on the jetting,you may be too lean,richen it up,play with it a little,try not to run it lean,did you just have the top end redone?or did you mod it,call your local suzuki dealer,see if you can find the jetting settings for your model,they should have them,whatever you do,don't run it like a bad outta hell,you could fry the top end,take it easy and feel your powerband,you could be too lean,but I'm not sure,richen it up slightlly,then take it for a short ride,if it's still doing it,play with the jetting,if your hesitating through all gears after you richen it up,your too rich,then you should set it to where it was,then slightlly change the settings down,just remeber,How cold it is outside and the humidity can play a huge role in tuning,just remeber to keep it a little to be on the safe side,if it's cold outside you'll probablly want to re tune after it warms up,but that's a suggestion,try that out and lmk how it goes,i have a ton of buddys that can help you out too,everybody i know race's or drag races so lmk.

 

[4u2nv]

Ok Ill try that out. That was what my next thing was going to be. It seems to be running rich. the bike manual says 20:1 but the dealership said that can be adjusted all the way to 50:1. So I run 35:1 most the time. Yeah I just redid the top end. I didnt have to bore it or anything. The cylinder was fine, I just had it acid washed and honed.. But Ill try jetting id different and keep ya posted. Thanks!

 

[dodgeman]

You might wanna check the needle in the slide of the carb. There are usually 4 or 5 settings on that needle, most come from the factory in the center position. If you think it's to rich you can raise the clip one position and that will lean it out a bit but don't go too many at a time before testing it out. Try that and let us know how it works.

 

[scottm]

OK, this will be fun. First you have eliminate the obvious stuff - make sure it has a new plug, clean filter, fresh fuel and oil. Then you have to figure out if it is a lean bog or a rich bog. A rich bog is easy to ID - it runs like the choke is on, all blubbery and with a ton of smoke. If it is rich, the choke may be stuck on, or more likely the fuel level in the carb bowl is too high. Does it leak gas out the carb overflow when you rock the bike back and forth? If so the float/needle/seat is not shutting off fuel flow properly. Dirt will also hold the needle open and cause flooding. This is not the same needle as the jeedle jet on the slide, which controls fuel mixture from 1/4 to 3/4 throttle.

A lean bog is usually from old gas or clogged jets. It can also be from a bad reed valve or low compression. Fuel will leave deposits in the jets which are hard to see, but will make it run lean. The pilot jet affects running from idle to about 1/4 throttle. It is small and it doesn't take much to plug up. I use barryman's carb spray and a thin sliver of wood to clean out jets. Don't use a piece of wire.

 

[Got Nitro?]

OK, this will be fun. First you have eliminate the obvious stuff - make sure it has a new plug, clean filter, fresh fuel and oil. Then you have to figure out if it is a lean bog or a rich bog. A rich bog is easy to ID - it runs like the choke is on, all blubbery and with a ton of smoke. If it is rich, the choke may be stuck on, or more likely the fuel level in the carb bowl is too high. Does it leak gas out the carb overflow when you rock the bike back and forth? If so the float/needle/seat is not shutting off fuel flow properly. Dirt will also hold the needle open and cause flooding. This is not the same needle as the jeedle jet on the slide, which controls fuel mixture from 1/4 to 3/4 throttle.

A lean bog is usually from old gas or clogged jets. It can also be from a bad reed valve or low compression. Fuel will leave deposits in the jets which are hard to see, but will make it run lean. The pilot jet affects running from idle to about 1/4 throttle. It is small and it doesn't take much to plug up. I use barryman's carb spray and a thin sliver of wood to clean out jets. Don't use a piece of wire.

Damn,scottm you must know a lot about 2 stroke engines,4u2nv lets us know man.


Since you redid the top end,did you break the bike in correctlly?

 

[4u2nv]

Yeah the 1st two gears are realy boggy and puff out the bluish white smoke. Its definatly running to lean. but doesn't seem to drip any gas at all whatsoever.. A couple days ago I adjusted the clip on the main needle and put it up one, and it seemed more peppier but the first 2 gears are still boggy. And alos in 6th it still burps a bit. Tomorrow I'm going to rip apart the carb (For liek the 30th time) and see what the jet screw is, and get a smaller jetted one, and see what that does. Thats what everyone has been telling em to do.

I did just redo the top end, and did the break in how wiseco recomended.I also put in new reeds (Aktives) about 2 months ago. I still drive it, so the gas tank has been refilled a good 5-6 times this year already. And I also just put on a new filter, new plugs and cleaned the cap, and still have the probs..ugh..

 

[dodgeman]

Do you know what kind of mukuni is on that suzuki. There some of them that come with the flat side carb and a round slide.Alot of the mukuni's have the idle screw and a air screw, if it's the type with a air screw you can richen and lean the mixture also.The way i check my 2 strokes if there lean or rich is do a couple high speed runs then stop right away and pull the plug, if your plug starts to turn light gray to white then your to lean if it's still black then she's to rich.A good mixture should turn the plug a nice tan,light brown colour.

 

[Got Nitro?]

You don't want white smoke dude,you want blue smoke,but not too much blue,check your plug.

 

[dodgeman]

Yes like got nitro said white smoke is not good. Is that RM liquid cooled, if it is it could be burning prestone. Had a 1990 250 quadracer and it started smoking white and found out it had a crack in the cylinder and was letting prestone in to cause the white smoke. Ran like crap too.

 

[4u2nv]

I just had the top end done and theres nothing worng with that. Its in pefect shape and I'm getting 120psi on that. The smoke out the rear is a blueish smoke. Its not my plug..I have SOME experiance in engines so Id dont all the inor checks and stuff like that. I know its a carb/jetting issue, so I was wondering what people would think the next step would be after new reeds, new top end (Which needed it anyway) new plug, wire, and cap, Adjusted the needle, etc. The only thin left I think is to jet it different. So I'm going to try that and see what happens then. If it doesn't fix it, I'm dropping it off at the dealership and will have to take the hit to the wallet and just get it done..

 

[.21Rc10GT]

You never know, you cylinder gasket could be bad, or have a slight tear and be letting water in or something. Good Luck man.

 

[dodgeman]

if none of them things you tried didn't work the only thing left would be the jetting. Hope you get it running right, some dealers try to put it to ya, anyway if ya get it figured out let us know what the problem was.

 

[AD2Freak]

just keep the mill at near WOT and you will have no problems!!!!

 

[Got Nitro?]

They also could be right about your gasket's,my dad has a 87 LT-500 he's siezed that motor over 4 times in the past couple years,we redid the top end on it because it needed it and she went to hell,we even rejetted,We took it out a couple months back,we richend her way up,used more oil and still seized it,long story short,his engine has bad crank seals,wich will cause the engine to run lean,when you rebuild your engine,make sure to check all the seals and gasket's,they could be bad,are's was.

 

[joey]

that happened to me on my blaster..i went up a size on the main jet and moved the needle and it fixed the prob for me..