Problem with 02 suzuki Rm125

[hoytproshooter]

i am having some big trouble with my bike......and was wondering if anyone and that has a solution could help........i bought a 02 suzuki Rm 125 from a buddy he said the bike was just redone top and bottem........when i got it from him he had a FMF sst pipe on it and told me that the bike was not jetted correctly but he had rode it and the bike was fine the way it was.....so i continued riding as the bike was....then i had about 3 hours on the bike and i notice the bike getting more sluggish and hard to start so I checked the piston and it had burnt it up bad front and in the middle really bad.......so i figured i would replace the piston and gaskets and all that good stuff.........and after about 2.5 hours on the brand new piston the bike blew up again this time just a nice sized burn mark in the top of the piston head............and after that happened I was think of all the possible reasons the bike would be doing this and i figured it was the jetting so i took out the stock 460 jet and put in the 430 jet what FMF calls for and placing the clip on the needle on the 2nd notch and the air screw 1.5 turns out...........i was running 40:1 Maxmia super M premix oil ..............so now that i have the bike jetted correctly should the bike run right ....or what are some other possible problems that could be happing with the bike to make it burn up the pistons so bad.............PLEASE ANYONE WHO CAN HELP.....IT IS GREATLY APPRECIATED...........THANKS ALOT....JOSH BYERLY

[hoytproshooter]

does anyone have any idea of what could be wrong.......

[the_privateer]

sounds like a lean condition. could be an air leak, search the knowledge base forum for finding air leaks.

Leaning out the jetting is going to make it worse.

are you using the correct sparkplugs? a plug that is too hot can burn up pistons.

are you breaking in the engine or just ripping on it right away?

[Rotorranch]

[ossagp]

Rotor is right. When you say the middle, I am guessing that you mean the middle of the top of the piston. That usually indicates preignition. That can be caused by a plug that is too hot among other things. If you are tuned on the edge as they say, then go to a hotter plug it may do it in a big hurry, like seconds of hard running.

If you are running fuel which is too low in octane for your setup it can do it. All of those things get aggravated further by an air leak.

Since the bike is new to you, I would start by changing out the igntion side crank seal at the very least. You can change it about as fast as you can test it. You just need a flywheel puller, a seal, and something to remove the seal with. A bent ice pick or a 3 dollar curved awl works just fine for me. I dont have anything that has a 6 year old crank seal in it, for the reasons you just described. Seasonally changing them makes a difference in how they run.

As was mentioned, the leaning out of the jetting will only hasten the next meltdown if you don't find out why it did that in the first place.

[hoytproshooter]

the sparkplug i was using was nkg Br8es plug......and the bike had fried that plug to so the getting to hot thing could be it.....what kind of spark plug should i be running in it........Thanks alot....josh..

[ossagp]

that is warmer than what the book calls for, a 9 heat range would be better. I think you will be shooting yourself in the foot if that is the only remedy you try though. on stock jetting that 8 would not normally have the result it did unless you are just winding it to hard. I would still do the seal change. 6 years is too long. Check for leaks when you get it back together and changing the seal would be a good place to start.

[hoytproshooter]

ok thank you..........i will try the new plug also.....and may be a dumb question but how do u check for leaks i am really not to sure how to.....and also when i changed the jet to a 430 and i leand it out more should i change it back to the 460 ..........and what type of piston would u recommend......THANKS A BUNCH.....JOSH...

[Fireman87]

$17 Leak Tester (2-Stroke)

Theres a link to an easy way and explination to mke your own leak tester instead of paying upwards of $150 for one.

And i'm not near as knowledgable as Ossa and Rotor but what i would do is change all of your stuff (plug, jet ect) back to stock specs and than try the leak tester and go from there, if everything is at factory specs you can eliminate problems a lot easier (atleast i think so).

But hey thats just what i would do


Good luck.

-Dan

[hoytproshooter]

fireman.....when u say u would put everything back to stock would u put a stock piston head in it or would it not matter.........and i also have the fmf pipe on the bike would u change it back to stock to......thanks ...josh

[yamarider4life]

hey josh i talked to my uncle....and he said it prolly was an air leak or the plug just like everyone else has been sayin......thought i would let u know.......tim

[Fireman87]

Originally Posted by hoytproshooter

fireman.....when u say u would put everything back to stock would u put a stock piston head in it or would it not matter.........and i also have the fmf pipe on the bike would u change it back to stock to......thanks ...josh

No not stuff like that, i'm talking your jet settings and float level stuff like that internally. Your pipe and piston isn't a factor.


-Dan

[hoytproshooter]

ok thanks alot guys....i appreciate all the help.........JOSH

[hoytproshooter]

hey guys got some more questions.........i went to the NGK website and gave them my information on the bike....they said that the best spark plug for my bike would be a R6918B-8..............what i have in it now is a BR8ES.......so my question is whitch one would be hotter .....and if anyone has tryed these specific plugs what do u think of them?????......THANKS ALOT.....JOSH BYERLY

[markmarino]

Did you check to see if you have the right plug in?

[Spikester]

Originally Posted by hoytproshooter

hey guys got some more questions.........i went to the NGK website and gave them my information on the bike....they said that the best spark plug for my bike would be a R6918B-8..............what i have in it now is a BR8ES.......so my question is whitch one would be hotter .....and if anyone has tryed these specific plugs what do u think of them?????......THANKS ALOT.....JOSH BYERLY

The reason people run BRBES plugs is because that plug costs something like $27, I run a BR8EV in my '97 RM250 for the same reason. What condition is your cylinder in after all these melt downs? Water pump pumping? Ignition set to stock setting?