KDXRIDER.NET

ok, so this is my first post. bought my first kdx a few months ago. bike had skirt knock pretty bad but i had to have this bike. did the top end a few days after i bought it as the noise was pretty loud. it has about 12 hours now. I was riding yesterday and put about another hour or so on it. cruising about third gear half throttle and the bike just bogged and shut off. bike fired back up 3rd kick. started heading back to the truck, boggs down again about a half mile later. very reluctant to start. finally does after about a bajillion kicks. make it another half mile or so and it peters out again. will not restart. send friend for truck. wait for about 20 minutes and try to kick it over. fires first kick. wtf???? tonight i pulled the pipe and looked up the exhaust port and see scarring on piston. coolant was full, clean filter, and i run castor 927 @ 32:1. could this be caused by the crank bearings? could not reallyfeel any play on the flywheel. any help would be awesome.

plug fouling?

what's your jetting, what mods do u have.
have u changed oil mix recently?

Pull the flywheel and check that the woodruff key did not shear. I have had that happen on two bikes and had similar experience as you describe.

scheckaet wrote:plug fouling?

Agreed, did you change it?

when i did the top end is when i went to maxima castor 927. as for the plug, doesnt seem to be any fouling. havent checked the woodruff key yet. will try to check it tonight.

did you happen to mix oil from your new castor batch with whatever was left in your tank with the old oil?
if not that could be it.

jrmumford527 wrote: i pulled the pipe and looked up the exhaust port and see scarring on piston

Pull the top, inspect for scarring in the jug and broken pieces of piston ring....

If you have a broken ring (or piece off the side of your piston) pull the engine and flip it upside down and get all the piece(s) out, you'll need to be careful to account for all broken pieces - otherwise you've got a date with a case splitter, or pray that any chunks settle to the bottom and just flow out with the oil.

Good luck, take your time with it.

as far as the fuel thing, the tank was completely drained then topped off with the good stuff...this may be a crazy question, BUT i am pretty sure that the bottom has never been done. having said that, dou you think i should bite the bullet(or crank) and just do a full rebuild...please, no facepalms. lol.

Might as well.

A little premature to just split the case already, for all we know it's just something simple.
Dirty carb/plugged up jet...
Time to trouble shoot.

JohnPainter wrote:

jrmumford527 wrote: i pulled the pipe and looked up the exhaust port and see scarring on piston

Pull the top, inspect for scarring in the jug and broken pieces of piston ring....

If you have a broken ring (or piece off the side of your piston) pull the engine and flip it upside down and get all the piece(s) out, you'll need to be careful to account for all broken pieces - otherwise you've got a date with a case splitter, or pray that any chunks settle to the bottom and just flow out with the oil.

Good luck, take your time with it.

There is no oil to "flow" out the bottom of the crank case. 2 stroke crank case is sealed, and does not contain tranny oil. If the piston is broken or there are chunks in the bottom, definitely need to split.

Hopefully that is not the case. I'd try a brand new plug just in case. Hard to look at one and tell if it's fouled...

juliend wrote:

JohnPainter wrote:

jrmumford527 wrote: i pulled the pipe and looked up the exhaust port and see scarring on piston

Pull the top, inspect for scarring in the jug and broken pieces of piston ring....

If you have a broken ring (or piece off the side of your piston) pull the engine and flip it upside down and get all the piece(s) out, you'll need to be careful to account for all broken pieces - otherwise you've got a date with a case splitter, or pray that any chunks settle to the bottom and just flow out with the oil.

Good luck, take your time with it.

There is no oil to "flow" out the bottom of the crank case. 2 stroke crank case is sealed, and does not contain tranny oil. If the piston is broken or there are chunks in the bottom, definitely need to split.

Hopefully that is not the case. I'd try a brand new plug just in case. Hard to look at one and tell if it's fouled...

CHANGE THE PLUG !!! rule out the simple stuff first, I had a similar problem once and it turned out to be a plug...
the intermitence of the starting makes me think a plug is the culprit.

Wait awhile & it fires right back up?
Sounds like the gas cap vent's clogged, starving the motor of fuel.
Remove the cap and hose, you should be able to blow through it with little resistance.
The scored piston could be from lack of lubrication due to an extremely lean condition cause by lack of fuel.

I agree - look for the simple stuff first. Change the plug, fire it up and see if it stalls again.

If it does, loosen the gas cap and listen for air hissing in, or try with a loose cap (with a low gas level).

If it is still intermittent, get the piston to the top of the bore and check the timing mark on the flywheel to see if it lines up with the mark on the case.

Could be a weak coil, losing spark when it gets hot. If it stalls, pull out the plug right away and check for spark. Or keep a spare in your pocket for testing.

Also, check your kill switch wire. It may be shorting out.

alright. i changed the plug. i let it run for about 15 minutes. no bog.still skirt knock, but no bog. i may have to wait to take it out this weekend so i can get more than a few minutes on it.

i hate to make iether one of us sound like we dont know what we are talking about but...can you tell me the difference between skirt knock and KIPS rattle ?

(the kips seem rather perculiar and since you've only had the KDX for a little while you may not recognize it as part of the regular noise)

i

hate to make iether one of us sound like we dont know what we are talking about but...can you tell me the difference between skirt knock and KIPS rattle ?

Yeah, My KDX motors have always been pretty noisy.
I got used to it.

Let your bike idle in neutral. Apply and release the clutch while engine is running. If the sound goes away with clutch pulled, thats a normal KDX knocking noise.