1984 atc250r woes

[xr650r]

Well just blew my top end think either was jetted to lean or forgot to put oil,doubt that.Bike will now have cylinder bored .60 over Wiseco,34mm pj carb, stock air filter.I need to know what size jets to use,needle position,air screw adjust.Or should i use stock carb?This is the first time I blew a bike up tuning it,please help thanks.Also I hear conflicting things about boring cylinder and jetting

[Mudbug20]

I have a mikuni VM38 carb that needs a cleaning, I took it off my 250r but I'll sell it cheaper then a stock carb and they are super easy to change jets on and it's 38mm which i hear does
wonders on the 250r's?

[SiiCHo]

I just ordered a pj34 myself, along with a bunch of jets for my 84 250r. Ill let you know how my tuning goes, but i am at 5000 ft above sea level, so my tune will likely be different from yours. Read the factory service manual, it tells you how to set your air screw and idle.

http://www.kb0nly.info/ATC/index.php

[SiiCHo]

Read this http://www.thumpertalk.com/topic/347305-is-your-two-stroke-running-rich-read-here/ this is the best write-up on tuning a 2stroke ive come across

[barnett468]

Hello


PISTON/CYLINDER CLEARANCE

I typically just use the spec suggested by the piston mfg however when a cylinder is bored more than .040” over I add .00025” to the clearance because the engine is going to run a bit hotter due to a thinner cylinder wall.



CARB JETTING

If you use the stock carb I would run a 145 main jet up to 5000 ft on a stock engine and a 148 on a modified engine to begin with plus a 1 size larger pilot if available.

Std idle mix screw setting is 1 1/2 out from full in.

STOCK CARB

PE 30
MJ 130 up to 5000 ft elevation
MJ 128 from 6000-6500

[xr650r]

Thanks guys how are you jetting the pj 34?Will the over bore affect jetting?Do i need to check connecting rod?

[Mudbug20]

Read this http://www.thumpertalk.com/topic/347305-is-your-two-stroke-running-rich-read-here/ this is the best write-up on tuning a 2stroke ive come across

that is a really informitive article i have ran across more then once. Every time I do I take something else away from it! Thanks for posting it.

[red_russian1]

I just picked up a carb off eBay for my '83R. The guy says its a 34 that came off an '86 R. It says PE 37AAYC on the side. Supposedly all I have to do is heat the carb boot and it'll slip on. My question is: what jetting should I start with? I just bored it out to 71.5 mm, installed Boyesen Pro reeds and it has the "gold DG" head.