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Need to pick your brains!
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Sorry, not a TTR, but my bro has been having trouble with his early Yam FJ1200 and it falls to me to solve it so I'm after some ideas before I delve in. As this is the only bike forum I'm active on, it's you lot I'm turning to first in my hour of need!

Starts fine from cold, runs for about 4 miles then starts to run rough then dies. Let it cool and off you go again. (for another 4 miles or so!)

My thoughts so far:

Blocked fuel tank breather

Coil breaking down with heat

Any reason a blockage in the carb might give these symptoms?

As I say, haven't started digging in yet, but if anyone has a lightbulb moment please let me know.

Answers on a postcard...

Cheers,

Simon.



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It may be that the carburetor needs re jetted/adjusted. It's probably running very ritch. For example carbureted bikes if you warm them up then you turn the choke on the bike will shut off. That's because a ritch mixture is great for starting cold bikes but once thy warm up(3 to 4 minutes) they can't run with the choke on. Try watching a video on adjusting carburetors. Try to make it run lean but not to lean. Then the bike will run hot. Adjust the carb and let me know if that works.


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It's run fine for 4 years! Wondered if they had gone out of balance somehow?

Thanks for the rapid 911 responsesmile



-- Edited by mossproof on Tuesday 13th of February 2018 07:15:03 PM

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Any chance that the choke is stuck on?

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if it is caused by heat look at the coils / CDI / pick coils..

go for a ride with the fuel cap off or lose...
dose it have a vacume fuel tap?

but you did say cooling down.. the fuel system is not effected
by heat as such..

but may be it's not cooling down but more the time it takes to cool letting
any vacume locks disapate giving the impression heat is the issue..

blocked carb fuel bowl breather...


.





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Just two more posts and you will be promoted to Guru status Simon biggrin



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On more thing I thought of is bad gas. I don't think it would matter but why not eliminate it.

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All good suggestions thanks. Will keep you informed as I go.
When I say "cool" I mean "let it rest for a while". Don't know if it's a heat thing, slow release of pressure/vacuum or whatever.
Guru? I'm asking for help here not dispensing sage wisdom

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I had the same symptoms with a jap four and it was valve clearances so needed shimming then all was good again. I would imagine it has two coils?

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