Dirt Bike Modifications Forum

i just rebuilt my 98 cr125 with bored out top end and reeds and intake system and clutch and etc. it ran great at first but now, only when the bike gets hot and i ride it for a little while does it sound very rattly and smokes everywhere and bogs.. WHATS WRONG!!??  

Are you sure that it isnt jetting? by changing inernal dimensions of your bore and stroke and cc's and doing other mods, I would think that it would throw your jetting off. If your main jet too fat? Or do you think it is a rebuld error?

my main jet is a 175 stock. i first went down to a 172 and it was still too rich and now im at a 170. i might need to go leaner still but i have to make sure not to go too lean so i dont fry my engine  

The richer it is, the more you bike will smoke.

Not always true. Your bike could be running rich and still not smoke when you are riding. Maybe when you first start it up though and its cold. I would rather be rich than lean any day.

Considering it ran great at first..have you taken it aprat to check the internals? My guess is that maybe you spited up a ring. Aslo, you may want to bleed your cooling system and make sure you have proper cooling fluids in there filled to the correct levels.

haha id just buy a new bike... that suckers OLD(no offense)..... and i have no clue whats up with your bike dude sry

Its not that old. If you take care of your bike, it will last for a long time. Why are you hacking on other people?

yea...i agree with CR. Anybike will last forever if you take care of it. There is no old bike, a bike is a bike.

ok do you knbow how i can delte this?? cause i dont even know what you guys are taking about me and MOTOCROSSCHICK are sistas!! and were being stupid... so can we delete our names ?

Just quit posting stuff, you dont have to delete your name...

Hey i build these engine often for my buddys bike and other people to i ahve seen this problem if the smoke is a dark blue that is a sign that you are way hot anther way to know of your hot is to feel around you radiator to see if iis like blistering hot and do a compression cheak to seee if is low then when it cools it is back up it is running to hot and also run premum in it and sum nice oil let the bike warm up to prevent seiz. then you need to pull the plug what does it look like if it has like an orange color to it is very hot and you need to mix you gas with more oil. in the turms of jetting it is not going to be affected by boring in let you running an achol motor so don't worry about that and when you in stalled your piston it should one go in one4 way with the little whole to the pipe, let me know how it turn out thanks jake.  

hey i couldnt really understand some of the stuff you were saying because of your grammar but the piston is installed correctly and yes the bike does get very very hot when i ride it.. the coolant level is fine and i bled the system out too. the compression is alright also. i didnt perform a compression check but i can tell by the feel of the kick (i have had this bike for a while and can tell the feel of proper compression)  

add more oil to your gas to richin it up and cool her down that should do it.  

I dont think that trying to compensate for poor jetting by messing with the oil in your fuel is the best way. I think that the best way to fix the problem is to fix it right and jet it correctly.