Just got a 84 atc 250r

[ricmonro4]

I just picked this up for 300 bucks as a parts bike. Mainly for the motor cus i blew out the top end on my original motor on my 83.

I'm wondering what is that canister on top of the head of the motor. It runs a line in between the carb and the intake?? What is it and what does it do ?

[ricmonro4]

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[manbearpig]

Boost bottle. and i see its grafted into an OEM intake boot. get rid of that... its one big air leak. leaks = blown motors. carb is a big aftermarket flat slide mikuni. likely around 38mm. a bit overkill for a stock motor, unless its heavily ported. even then, id think the stock exhaust would be somewhat restrictive. the carb and bottle were bolt ons available from almost any distributor back in the day. pictured in lots of ads in old mags

consensus is that boost bottles on singles are gimmicks. its a semi neat aftermarket piece and has some value to someone.. hell i'll give you $20 for it. PM me if interested. shipping to SD from LA should be a couple bux