Hi all. I have 3en1 which I recently purchased off ebay (have had it 3 days now) with a strange problem.

The bike starts but it wont rev past idle and needs to be at 1/3 throttle to keep it idling.
Shut it down and restart a few time (about 4 or 5) then it revsup and act normal. Go for a ride around the block a few time
with no problem. Jump on the bike again a few hours later and the problem returns.

I have removed, cleaned and reinstalled exup valve (adjusted)
Pulled out the carbies stripped down and cleaned.

Reinstalled the carbies and the bike fired up first go and idles much better and reves.
Went for a test around the block and the second time around it bogs and dies.
Once again the same problem (wont rev past idle and I have to have it at about 1/3 throttle to keep it going).
Try restarting it two time and then it revs up and goes well for like 400 yards, then dies again.

Managed to get back to the garage. shut her down and restart and all is normal again.

All suggestion are welcome.

Thank you

It could be a few different things as the bike isn't standard.
Does it still use the fuel pump ? so when you turn on the ignition and the kill switch is set to run you hear a clicking ? This should stop after a few seconds but just to check flick the kill switch to off and then run again.

Are the fuel filters clean - there should be two, one in the tank on the fuel tap and another inline.

Are the carb diaphams ok

Could you have accidentally altered the needle height

Have you checked the valves clearances.
As the valves get older they stretch and can dish in the head. This causes poor starting and the bike won't run well until warm when the tollerances clear up. This is a bit more "involed"

Check the air vent in the tank filler cap it could be blocked.

Hi guys,
I think I have diagnosed the problem. Have spend the last two days.
Putting back the original petrol tank (had the to remade the front support and fabricating the piece that was chopped of the sub frame.
So now I have the original tank and seats on. Anyway took it for a spin and the problem reoccurred. So I turned off the fuel and as the level dropped on the carbies it's revs returned then of course ran out of petrol. So it looks like its getting flooded. Tomorrow is the last day of my holidays, back to work on Monday. Hopefully I will have time tomorrow to pull out the carbies and have a look.

Its very hard (not many were imported to Australia) and expensive to get parts for the 400. Is there a list on alternative replacement parts from other Yamaha models
that fit the 400 ?

Thanks again guys for the help

Buzzawak (Michael)

Mainly FZR600 3HE parts .... but of course not all of them fit