My Bike Smokes????

[cclark1788]

I have a 1991 KDX 250 and i just got the cylinder replatted and put new piston rings and gaskets on it. When i start it up it smokes a little but after it gets warmed up it really smokes and i dont know why?? Can someone help me out? Also is it going to hurt it smoking that much????

 

[julien_d]

It's a 2 stroke, they do smoke. If it's smoking too much you could be burning tranny oil, coolant, or just jetted too rich. You'll have to figure out which it is. Is the smoke really white, or does it smell sweet like antifreeze?

 

[2strokerfun]

Try Chantix. It helped me quit smoking.

Seriously, how's it running other than the smoke?? Have you tried adjusting the air screw?? What effect does putting the choke on and off have while it is running? Does it gurgle, splutter or rev unexpectedly at any point in the throttle range when riding?? Is the filter clean? Have you tried a new plug? Fresh gas? What's your gas/oil ratio?? Did you measure the cylinder, piston clearance and ring gap when rebuilding??
Might need carburetor cleaning. Might need some jetting. Might be something else. If top end done right, I suspect carburetor, but there is a whole lot of variables here. And no, if everything is clean, done right and working right, you shouldn't be bellowing smoke.

 

[cclark1788]

no i haven't adjusted any scews because i dont know what they are supposed to be set at. i dont know much about 2 strokes. it just smokes blue. it doesn't smell sweet or anything. my gas is mixed 40-1 and the throttle is really touchy. it also dies if it idles. i havn't messed with the screws because i was told if i adjust them wrong i could scortch the piston? I'm not sure if thats true but thats what i was told.

 

[ellandoh]

heres a couple links that might help

http://www.dirtrider.net/forums3/showpost.php?p=1383626&postcount=7

http://www.dirtrider.net/forums3/showpost.php?p=944584&postcount=2

 

[Matt90GT]

what model is this? US or the SR version?

 

[dirt bike dave]

If it is the US model and it has stock jetting, it is overly rich. Kawasaki really missed the boat on the stock jetting.

Search the KDX forum for some good ideas on jetting.

 

[mxl]

Bad oil or your jet is too big...

Maybe you aren't fast enough? :-) Get him into more rpm..

 

[julien_d]

Cylinder re-plate and a fresh top end means re-jetting for sure. Make sure crank seals aren't leaking, and you aren't burning coolant, and then jet that puppy.

Spanky's jetting guide posted by ellandoh above should help you out immensely. I'm in the process of re-jetting, again.....

It's a constant process. Many times a small change you make to the bike will require some amount of re-jetting, so it's a good art to learn if you plan on turning your own wrenches.

 

[cclark1788]

:cool: Thanks guys it was my water pump seal and my crank seal that was leeking i replaced them and it runs like a champ again

 

[julien_d]

You replaced a crank seal? You know the cases have to be split to replace crank seals? So you did a bottom end rebuild, or what?

Just curious....

J.

 

[ellandoh]

i never had to split a case to change a seal?

 

[julien_d]

Then you never replaced the crank seals in a KDX. They are only accessible from the INSIDE. Poor design? Perhaps. IMO if you have to change the crank seals you should be changing the bearings as well, so maybe that was also KAW's thinking on it?

 

[cclark1788]

i did split the case and had someone help me put all of the seals in including the crank shaft seals i didn't put the berrings or anything in just the seals

 

[sr5bidder]

Then you never replaced the crank seals in a KDX. They are only accessible from the INSIDE. Poor design? Perhaps. IMO if you have to change the crank seals you should be changing the bearings as well, so maybe that was also KAW's thinking on it?

I agree if you have it right in front of you and the seals where being replaced the bearings should be replaced too

 

[julien_d]

Shame you didn't spend the few bucks to replace the bearings while you were in there. When I had my cases split, I replaced every bearing I could find!

Anyway, I'm really glad this did the trick for you, have fun with the bike!!!

J.

 

[zeerx]

My KDX220 smoked too. Found out the rings were stuck in the piston. Cleaned it up, new rings=no smoke (or verry little).

 

[mudpack]

Excessive smoke in a two-stroke can only be caused by too much oil being burned....that, and maybe burning coolant.