yz 250 problems!!!! please help

[triadracer]

Hey everyone!! Im new to this site but i have been riding for years.

Lets get started!!

I bought a bike before the winter time, Its a 1992 yz 250. When i test road it the bike was hesitating and would not hit the power band. The guy i bought it from said i need to get some reeds for it. I belived him and purchused the bike.

During the winter i have replaced the following -

- Reeds (bought stock ones)

- FMF fatty pipe with a power core silencer

- cleaned the carb

- replaced the jets with the ones fmf specified me too

- 370 - main
- 45 - pilot

-airscrew - 1 1/2 out

- changed the airfilter

- changed the transmission fluid

- changed the gas to supreme 20:1

I started the bike tonight and it starts on first kick (would not do that before) when starting the bike cold before parts were purchased u had to dump some fuel into the cylinder.

I took it for a ride today and still hesitated in at low speed then once you get to open throttle it starts to pick up! In first and second it will not hit the power band, In all the other gears it does..

Can someone please tell me where to look next? I have checked the compression and it is to what the manual calls for!!!

thanks in advance

Sean

[JonAmaral]

Have you checked the float settings in the carb, also check the slide on the carb, My son's yz125 went through the same thing, turns out there was a 1/4 inch gap gouged in the slide, which you think would cause it to run lean, but it was running rich as the air speed through the carb was slow. are you fouling plugs?

[twostrokestevick]

i have the same bike, 2 years newer. sounds to me like the oil mixture is way too rich. is the smoke white more than blue? i was running 32:1 with castor 927 and i have similar mods and it'd be a b*tch to start, then would hesitste/ "stutter" to get up in gears, the weep hole on the side of the engine thats designed to let out the unburnt crap out spewed out oil and once she got hot it would cut off on me. but now i leaned her out and am running 40:1 with the same oil and now using purple urkel (cam2 bc the purple dye) and it runs 200% better; hope some of this helps you

[matt bristol]

i would concur witht he too much oil theory, when I used to race we ran our bikes at 40:1 using semi or fully synthetic and never had any bikes seize or do anything nasty. My brother in law races a kart with a honda 250 at 20:1 but that runs flat out (and beyond what it was designed to rev too) for over 90% of the time its running so a motocross engine will need a whole lot less oil.

Failing that if you have to put petrol down the bore its aloss of compression from either worn barrel or sticking rings