I got a LT250r, I use Bellray HR1 mixed 32:1 with a ratio-rite. Plug is NGK BR8EG & B8ES Both plugs was new and foul out within a few hours. But if i take em out and hit them with a steel brush and gas pop em in and bam fires right up. If i turn the ATV off well it might or might not fire up. I does seem ok when it warms up but does not idle long few secs them dies. What does this problem sound like? what action to correct? Thanks!!!

PS. The plug looks just solid black, until i clean it, no white marks ect. just black.

 

You could be real rich with the fuel mixture. The richer you are on fuel the more oil the plug sees. I personally don't like 32 to 1. I have used 40 or 50 to one in every two stroke I have ever owned and have never stuck a piston. Be it a weed wacker or a 500 cc twin it gets 40 to 1 on real hot days and 50 to 1 on normal days.
You might do a compression and see what you come up with. If it is down on compression it will foul plugs also.

 

Thank you for the reply i will do a compression test, but this is a fresh built motor 1 1/2 tanks in it.

 

z3us I reread your post and have another thought. When the plug is out, see how good of a spark you have. A poor ign spark will also give you the problems you are having.
Let me know what you find out so everybody can learn.

 

I did a compression test, i kicked it over 3 times and it tops out @ 178PSI With my kick start, first kick was around 40PSI @2nd goes to 100ish and it tops in the 3rd kick @178PSI.

The plugs will not spark at all until i clean it up. then i get a good spark every time, and the thing fires right up.

 

Sounds like you need a smaller jet. But if your gonna go with the leaner mixture, do that first. Then try adjusting the needle then move on to the jet. If you've got aftermarket reeds (which you most likely do) you'll need to run leaner. My lt has been doing the same thing. I've been scratching my head wondering. I replaced the top end after I tore it down because even though it was supposedely on first size over, it was on last. And the shop that put it together must have been morons because whenever it blew up, it made gouges in the sleeve that were still there after boring to last size and they put it together like that. Anyways I thought that the problem would be cleared up upon re-assembly. Nope. I put my brother's carb on, with my smaller jet and it was a lot better. After first ride, same problem. After talking to some other people I think that the mechanical seal in the water pump is bad. I really haven't messed with it because I bought an 06 z400.

 

sounds like your jetting is off to me

 

So, should i drop down on my mixture? from 32:1 to maybe 40:1?
Or rejet it?
Or Get a Keihin PWK 36, or 35 Air stryker

 

z3us did this thing ever have clean plugs come out of it........ever? If the answer is no, then you are going to have to jet down like these guys are telling you. A new carb won't help a jetting problem. You are just going to have to jet it to your conditions.
32 to 1 is not a bad mix. A lot of people run it with no problems. This tells me that you are probably fouling with gas instead of oil. Again, if this is the case, you are going to have to jet down like Sparky8370 and mucky have told you.
Oil fouled looks like it has boogers on the plug. Big clumps of black carbon. A gas fouled plug will just be black with no boogers on it. Like someone sprayed it with a paint can.
If it is as black as you are saying, you should pick up some power when you jet down.

 

Yea, I probably should have mentioned that I only changed the carb because I suspected that before I bought it somebody changed the...uh....brain fart here...anyways the other jet ( not the main)LOL I can't remember the name of the other jet I'm talking about!!! My problem may be more involved than jetting as I've tried a number of different mains, needle settings and air screw settings. Well this was all before I put the new top end on, but right after I did I bought a 4 stroke so it may just be jetting.
Finding the proper jetting can be a real pain in the @ss Your definetely going to need some patience here and if you have any other issues compounding the problem it's going to be a nightmare. You'll never be able to get it right if there's other problems. ie: airleak, leak between comb. chamber and water jacket, bad reeds, weak spark, stator timing off, broken keyway, or about a thousand other things.