Too lean?

Spagina

Spagina

PR Elite
I recently purchased a nearly new 2002 cr 250... it still had stock chain and sprocets, plastics and graphics. the previous owner said he had replaced the top end 5 hours ago. i rode the bike 3 or 4 times but i dont trust what people say so i just tore the bike down and am rebuilding it this winter.

i have always ran a 16 oz bottle of oil to 5 gallons. is this too lean?
the reason i am asking is because when i tore it apart everything looked GREAT. cylinder still had all the cross hatching with zero vertical marks, pison looked good, etc.
the only thing is, there is next to ZERO carbon in the head or on top of the piston. there is a little bit of brown on the exhaust side of the dome of the head, and also some blow by that actually goes 1/16 of an inch below the 2nd ring on the exhaust side of the piston that is brown. but no real carbon

i just dont wanna fry anything and usually i feel like there is a little more oil buildup than that.. am i wrong?
 
I run 4oz of yamalube per gallon. That is 32:1. Been raised up to run 2 strokes like that. But other guys in here run 40:1 and 50:1 even.

Personally I would mix 4 more oz in your 5 gallon can to keep it light brown. But the way you're doing it is probably good all the same.
 
im the same, always was told 32:1 growing up so ive stuck with it.

it blows my mind and makes me so nervous in my stand up ski when i run it 50:1 lol...
 
i had an 02 CR250 and ran it at 32:1 with no problems! but make sure you have that pro seal air box gasket in it as the filter cages did'nt tighten properly in the airbox letting dirt in the engine!!!
 
Thanks half pint... ive only even cleaned the filter once and i havent noticed. I have it down to the frame right now, going over everything over the winter, ill have to add that to the list.
 
+2 on Halfpint's comment. Stock, the air filter was little more than a decoration. FWIW, switching to a Keihen 38mm "PWK' series carb is a good investment. I would recommend that before pipe / reeds. The stock Mikuni can be tempermental.

32:1 is OK, as is 40:1. Pick one ratio, one oil and stick with it.
 
baxterj787 said:
+2 on Halfpint's comment. Stock, the air filter was little more than a decoration. FWIW, switching to a Keihen 38mm "PWK' series carb is a good investment. I would recommend that before pipe / reeds. The stock Mikuni can be tempermental.

32:1 is OK, as is 40:1. Pick one ratio, one oil and stick with it.
Click to expand...

I agree 100% i got a year out of the same top end and never pulled the motoer runnin a 38mm pwk carb.. mine was bored to 40. Couple that (38mm) with V forces, pipe and silencer, reed spacer, powervalve cover spacer, and exhaust spacer that bike will be pretty intense.

I also ran techniplate at 32:1. Thats what I run in my 07 KX 250. I'll run nothing but klotz. It's a dirty oil so you gotta clean your powervalves every so often but it lubricates very well and doesnt run from heat near as fast as, amsoil, yamalube and 2 others I cant remember. We tested this on several seperate aluminum plates with a torch to keep each test consitant it had to be seperate plates due to them holding heat.
 
You can get Pro Seals off of Ebay for starters. Or you could take the airboot / airbox junction apart and use a liberal amount of weatherstrip cement and do it yourself. Doing it yourself, you save money but might get your hands dirty.

From what I recall, the screw posts sicking out of the airbox were too tall. When you tightened up the screws holding the boot to the box, the screws would bottom out but would still leave clearance around the sealing face of the boot. As you might imagine, this proved less than ideal. American Honda had a product update campaign that basically had dealers trim the posts down and apply Hondabond to the entire sealing surface to solve the problem.

Another shining example of Honda designing a product and letting their janitors finish the job...
 
While everybody posted their ratios nobody asked you the most important question before answering yours. What oil are you running? Most premium synthetics can easily run at 50:1 or even higher. I've run 50:1 for years and years with premium racing oils (MC1 and now Blue Marble) in everything from my rides to my chainsaw and weedwhacker, but if you're running off the shelf conventional two cycle oil I wouldnt run any leaner than 32:1.

If your top has only 5 hours on it, Id be more concerned if it DID have carbon buildup.
 
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