Is the bigger the number on your main jet mean better flow? cuz i got a dynojet kit 4 my XR250L and the stock main jet was a 130 the dynojet main jet was a 124. I would tthink aftermarket jets would provide more flow. Also my bike makes a very loud knocking noise. i have tried special oil addatives, and high octane gas(i used to run regular) etc. It still knocks especially when it is cold. Is there anything else I can do or should i get it checked out?

 

Altho these so called jet kits use the same size numbers as Keihin & mikuni. the actual sizes of the kit jets don't correlate with OEM jets.
As for the knocking, I would certainly take it to a qualified mechanic for his opinion before operating the quad again

 

Knocking: You probably got about twice as much valve clearence as the spec. says. Jerk that valve cover off, get the right clearence for your machine, get a good feeler blade, put the crank on index (TDC) and see what you got. Drain the oil (to get the NASTY additives out of there), and get a hold of some quality ATV oil.

 

Last time I changed the oil I used golden spectro 20-50. The bike was burning quite a bit of that oil so I put stp oil treatment in it and almost immiediatly it stopped burning oil. I'm prolly gonna change it pretty soon again and don't feel like spending 6 bux a quart so i was thinkin of used castrol gtx at about 2 bux a quart.

 

I hope you didn't run it too long with STP in there, or you might run a good chance of frying the clutch. If it stopped burning oil with that thick stuff in there, you probably have worn rings,or the jug is getting worn, and the knock you are hearing could be piston slap,from all the slop between the piston and the cylinder walls,which could also be the source of your oil burning. Take a compression check,if you are under 115 psi, it is time for a bore out and bigger piston. You didn't mention the type of quad, or how old it is,but from what you describe, that's what it sounds like to me.

 

Its a 1993 honda XR250L. So are you saying that it needs to get a knew piston and sleeve? Someone else said the knocking was just the valves out of adjustment. The bike has 4000 miles so the piston shouldn't be that warn. If so what kind of piston would you recommend and would it be okay to just run Castrol GTX oil or is that bad 4 it?

 

Valves don't knock, they make a metallic ticking or tapping sound when loose. 4000 miles doesn't sound like a lot, but depends on how hard it was ridden. My quad needed a piston after 6 years of hard running, and it was getting piston slap, making a knocking noise,especially under load. Like I said, a compression check will tell if the rings are shot, which would explain your oil burning. Oil like Castrol GTX would be ok, just go 10-40 or more, look at the label, and stay away from 'energy conserving' oils, they have friction additives that will make your clutch slip after a little while. Best bet is motorcycle type oil rated for wet clutches. If you are due for a rebuild, Wiseco makes a good piston, as well as Pro-X,or you can go with factory replacement in the next size up.But first do the compression check to see what kind of shape the piston/rings are in.