spark plugs for breakfast

[rutlandtrails]

ok i have a 2001 KX85 and it will run perfect for about 2 days but after that second day when you go out in the morning on the third day it will start and then die........so i take out the plug and its wet with oil.......the carb is tuning is stock and im mixing the gas at 32:1.........its not leaking bottom end oil or anything and my question is would going to 40:1 help my problem or not help and will it hurt my motor? sorry about the book any help would be greatly appreciated.

thanks rutland

 

[flattie]

dont change your premix ratio, change your carb jetting

 

[mattb348]

ok i have a 2001 KX85 and it will run perfect for about 2 days but after that second day when you go out in the morning on the third day it will start and then die........so i take out the plug and its wet with oil.......the carb is tuning is stock and im mixing the gas at 32:1.........its not leaking bottom end oil or anything and my question is would going to 40:1 help my problem or not help and will it hurt my motor? sorry about the book any help would be greatly appreciated.

thanks rutland

KX's seem to always seem to have a pilot jet that is to lean. This will definitely foul the plug when you first start it before it is warmed up; I know this becuase it used to happen all the time on my KX 250 before I rejetted it.

I would try bumping down the pilot (also know as slow jet) by a couple sizes (maybe even more). This should fix your fouling problem (along with make it run better).

If you don't know how to jet it yourself then you can always bring it to your local bike shop. Jetting is alot easier than you may think though; just find out what the stock pilot jet is (should tell you in your manual, or you can go to www.kawasaki.com and look it up), and then put one in thats atleast a couple sizes smaller, maybe even 3. I actually bumped down my 250 by 4 sizes on the pilot jet. I wouldn't jet yours down that far though.

 

[i_955]

KX's seem to always seem to have a pilot jet that is to lean. I would try bumping down the pilot (also know as slow jet) by a couple sizes (maybe even more). I actually bumped down my 250 by 4 sizes on the pilot jet. I wouldn't jet yours down that far though.

Mattb348 must have meant RICH, not LEAN.

I agree with the rest as I had to reduce (lean) my pilot size by two on my KX100, my needle by 1 and enlarge my main by 2.

I still have to increase my main by one or more now that the temps have fallen.

 

[mattb348]

Mattb348 must have meant RICH, not LEAN.

I agree with the rest as I had to reduce (lean) my pilot size by two on my KX100, my needle by 1 and enlarge my main by 2.

I still have to increase my main by one or more now that the temps have fallen.

Yea, I meant RICH, not lean. Thanks for catching that :)

 

[mini rider]

try leaning your carberator out it should be in the owners manual how to and your bike from the dealer is set up for racing so you dont blow the engine up

 

[nikki]

Are you running the stock R6252K-105 plug? If so, try a BR9ES (one step hotter than the stock 10) or BR8ES if you still foul the 9.

 

[mattb348]

Are you running the stock R6252K-105 plug? If so, try a BR9ES (one step hotter than the stock 10) or BR8ES if you still foul the 9.

Isn't going down 2 heat ranges a little hard on your engine though? I think it would be better to just rejet.

 

[flattie]

ya, not a good idea to change plug heat range. stick with stock unless you modify, eng then you actually can run a cooler plug.

 

[flattie]

changing spark plugs does not fix bad jetting

 

[rm_racer]

Im pretty sure the plug heat range is just the tempature the plug clears at? Im not sure tho. If that is the way it works I cant see any potential damage to the engine. This is just a quick fix tho, as rejetting would be the proper fix.

 

[mattb348]

Using a hotter plug can definitely damage the engine from what I understand :)

I'm never gonna test that theory either LOL!

 

[DLHamblin]

Isn't going down 2 heat ranges a little hard on your engine though? I think it would be better to just rejet.

Not necessarily. Depends on the bike (stock/modified), jetting, and rider ability.

While its correct to say you shouldn't use spark plug heat range to try and fix bad jetting; its also equally wrong to try and fix all spark plug issues with jetting as well. They kind of go hand in hand.

An example is my son's YZ-85 (2006). Stock they come with a BR10EG which lasts about 30 minutes even if jetted correctly (unless you are on a MX track where the throttle is never closed). Be on a slower track or trail riding and it fouls in 30 minutes (with proper jetting). Lean it to where it won't and the bike is too lean and runs like crap. Put a BR9EG in and it will run for weeks (for just trail riding we use a BR8EG). Bike runs well and neither plug looks like its running too hot.

Bottom line is don't randomly drop 2 ranges without doing some follow-up checking; but if the jetting and top end condition are good; don't be afraid to go one range at a time hotter plug. The bike will let you know its too hot by pre-ignition (which is what would burn the piston, not the plug itself).

 

[DLHamblin]

Im pretty sure the plug heat range is just the tempature the plug clears at? Im not sure tho. If that is the way it works I cant see any potential damage to the engine. This is just a quick fix tho, as rejetting would be the proper fix.

Each range hotter has the tip temperature increase by about 100 degrees centigrade. The purpose is to have the tip hot enough it clears by burning off deposits that cause it to foul.

If you got too hot for your jetting/style of riding the plug gets hot enough it causes pre-ignition (pinging or knocking are some other terms...) which can burn a hole in the piston.

After running a bit with a hotter plug pull it out and look at the tip. Besides looking very white (a sign of over heating) in extreme cases og pre-ignition you will see tiny specs of aluminum (blown off the piston by the pre-ignition) on the tip.

 

[mattb348]

Not necessarily. Depends on the bike (stock/modified), jetting, and rider ability.

While its correct to say you shouldn't use spark plug heat range to try and fix bad jetting; its also equally wrong to try and fix all spark plug issues with jetting as well. They kind of go hand in hand.

An example is my son's YZ-85 (2006). Stock they come with a BR10EG which lasts about 30 minutes even if jetted correctly (unless you are on a MX track where the throttle is never closed). Be on a slower track or trail riding and it fouls in 30 minutes (with proper jetting). Lean it to where it won't and the bike is too lean and runs like crap. Put a BR9EG in and it will run for weeks (for just trail riding we use a BR8EG). Bike runs well and neither plug looks like its running too hot.

Bottom line is don't randomly drop 2 ranges without doing some follow-up checking; but if the jetting and top end condition are good; don't be afraid to go one range at a time hotter plug. The bike will let you know its too hot by pre-ignition (which is what would burn the piston, not the plug itself).

Good post DLhamblin; thanks for the info. :)

 

[rutlandtrails]

thanks guys that night my dad came home with four BR9ES plugs and it hasnt fouled the first one yet so thanks again this site is pretty much the freakin best.........i LOVE it!!!!

 

[xr400xr50r]

Mattb348 must have meant RICH, not LEAN.

I agree with the rest as I had to reduce (lean) my pilot size by two on my KX100, my needle by 1 and enlarge my main by 2.

I still have to increase my main by one or more now that the temps have fallen.

I know this post is old but wanted to re-hash anyway...
In the owners manual the correction factor chart shows that if you have a correction factor at all that it would apply to both the slow jet and the main jet, or IOW if you have a .96 correction factor and go from 45 to 43 on the slow jet, that you'd also use that same factor and take your main from 140 to 134-135...is this correct? So would they both lower?
Thanks

 

[DLHamblin]

Isn't going down 2 heat ranges a little hard on your engine though? I think it would be better to just rejet.

I was typing areply but see this is an old post and I did already :whoa: