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andy_g2k7

yamaha wr 400 help for newbie

3 posts in this topic

hi, first off id like to say i have flicked threw this forum many times before and have to say its great so finally decided to join and get some help from the people who know (and hopefully be able to give some help out).

right the bike

its a 1998 yamaha wr 400 with 10,000 miles on the clock. it was spitting white oil so naturally i went straight for the head gasket and changed it, was no obvious marks on gasket or cylinder but hey better safe then sorry. then read this forum and probable reason was that pesky breather on the cam cover sucking water in when i was hitting deepish water.

new problem

bike seems to lack power, used to pop the front up in second easily but now just revs. naturally new clutch plates (both sets) were fitted with new springs (friction plates soaked 18 hours before) problem still there although clutch bite has moved far out. i dont no alot about these bikes as im pretty new to the off road scene and dont no if the carb could be to big a task for me to undertake as looks complex from what i have heard (had a gpz 500 before and cleaned, rebuilt and balanced them easily)

the bike is running the yz timing (1 tooth out) and an r & g pipe? has bog off the line and pops out the exhaust on deceloration.

any help would be very much apreciated as i love the bike to bits

thanks for reading, great forum and sorry for the spelling.

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Bog off the line is usually Blocked or poorly set up accelerator pump.

Popping on decel is usually lean idle circuit conditions , turn fuel screw out 1/2 a turn.

I am no expert so feel free to correct me ;)

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Sounds like you need to tackle that carb jetting like Thommo said. Have you checked the valve clearances? How about a leak-down test on the engine? I think you've got the needed knowledge to tackle the carb, and besides, we will help walk you thru it!!

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