top end or bottom end problem?

[redneckshredder]

ok i just bought a 98 kx125 that the guy said had Carbon Fiber Reed Valves, Wisco Piston, Hot Rod Connection Rod, Moose Main Bearings, Cylinder is renickel coated and that it ran great and he would ride it anywhere. when i brought it home, it ran great for about two hours,lots of power and then while riding about mid rpm, i accidently hit the kill switch and the bike bogged down and died, wouldnt start and has no compression at all in the kickstarter. also i changed the spark plug and the old one had a broken tip on the part the goes in the cylinder. any ideas is this just a top end problem? i can still shift through all gears thanks

also how much would a typical shop charge to do either a top end or bottom end on this bike?

 

[whenfoxforks-ruled]

What kind of plug?

 

[redneckshredder]

its an ngk but i dont know if it broke off in the cylinder or what because its really corroded but it could have been like that

 

[AV8R]

That corrosion sounds a lot like detonation. Detonation will eat the tip off the plug. Detonation can cause severe piston damage. Maybe there is now a hole in the top of the piston. You will need to take the head off and see what the damage may be. Detonation is caused by too lean jetting or too low of an octane on the fuel usually.
You should be using 91 or higher for pump fuel.
Plug should be NGK BR9EG or ES.

 

[redneckshredder]

could it cause any bottom end damage? or could i just rebuild the top end and be done? also what does the bottom end consist of

 

[_JOE_]

You won't know until you get it apart. I suggest picking up a service manual and going into it yourself, at least the top end. Once you get the top end off, take the entire engine to a good service shop. They will be able to tell you if the bottom end will be re-usable, and they can measure the tolerances in all the components (good idea when buying a used bike). Just removing the engine from the bike yourself will save you quite a bit. You will want to get aquainted with replacing the piston. Good luck.

 

[redneckshredder]

the problem is i am really limited on money atm and im gonna attemp to rebuild it myself. how much will a shop charge just to figure out whats wrong with it?

 

[redneckshredder]

also , is it possible it could just be the kickstarter,like some kind of clip or spring in there? because it ran great until this just randomly happened. thats why i am a little hesitant to rebuild the top end right now.

 

[IndyMX]

also , is it possible it could just be the kickstarter,like some kind of clip or spring in there? because it ran great until this just randomly happened. thats why i am a little hesitant to rebuild the top end right now.

not very likely.

 

[redneckshredder]

can anyone tell me what the bottom end of this bike consist of?

 

[IndyMX]

Crank, Rod, Bearings, Seals

 

[redneckshredder]

thanks i was just curious. so how likely is it that my bottom end is messed up?

 

[Shaw520]

From the info your giving us,.... its anyones guess.
Start off with a compression check, should be between 130 -150 psi, that'll tell you if you need to take the head/cylinder off.

 

[CarnageZ28]

The plug definatly makes it sound like it was detonating ... Thats when the air-fuel mixture ignites BEFORE the spark, due to the heat of the compression. And as said earlier, lean jetting or insuficiant octane can cause this. It ignites before the spark, and results in a "explosion" inside the cylinder rather than the controlled burn you get from spark plug ignition.

As said earlier, compression test it, and go from there. If it has adequate compression, try catching it in gear? But DEFINATLY will want to check your jetting specs out.

You said it has a V-Force reed valve on it right? With a full exhaust. These mods pretty much require rejetting the carbureator. I am betting the bike is running lean cause someone just threw "go-fast" parts at the bike...

If it is blown up, rebuild it, and as soon as it is running again, jet it properly ...

 

[justalonewolf007]

Check for water in the gas/tank?

My bike died 5 minutes after my first ride on it, because of water in the gas from the previous owner. It had sputtered and died as I was trying it out.

We had to rebuild both the top and bottom end, due to it throwing little metal pieces that scored the piston badly.

By the time we figured things out, after "forcing" the bike to run, the crank finally froze.