Following on from my "3tj cdi post" such terrible running!!

[MarkT]

i am assuming that the cdi is at fault but is it? Bike mint condition for a 1990 model when running at a standstill the engine sounds really nice and healthy was has been done by the previous owner is:-

!. Valve clearances
2.carbs cleaned 3 times
3. compression test
4. spark plugs
5.oil filter

The problem is that although it starts first time and you can rev it ok, when you go to pull away it has no power and the engine misses really badly. If you manage to get to the road and open her up come 6,000 revs it tears up the road like a good un with no probs! sometimes when going slow it will come to a stop and with full throttle the engine is not going over about a tickover speed and close the throttle and the engine dies? I has had new fuel filters and the previous owner who has had these for years (Not a jap one) says the olny thing left is the the cd1 and the bike has been derestricted.

Would you all argree? I know nothing about fzr 400's buat am ok with spanner, i really can afford to spend much money on it and if I cant fix it with a cdi which I am having terrible trouble finding I may have to sell it as a non runner which seems such a shame as it is moted and taxed for the year.

Would apprieciate any imput as at the moment I am a very worried man but what cdi's will fit. I am told a 3tj, 40x and that is all. Do any of the ones at e-bay that start withe the number 1 fit or can they be made to fit?

Really any help would be great and locating a CDI would be marvalous!

Thanks for reading
Mark

[CRM]

well i dont have a 3TJ, but from what you described would say to me carbs. blocked pilot yets perhaps.
if it rides fine after 6k then that when its on main jet. so the low speed running would be at fault.
if it was a plug or coil, again i would expect the opposite, as it gets warmer to get worse, ok low down and poor up top when it starts to break down under load.
CDI's in my exp, are either working or not, no middle ground.
wait for evilchicken and the gang, these guys are spot on and know the yamaha's inside out.

[MarkT]

Thanks that's what I would have thoght! Bjut the carbs have been cleaned really well 3 times and are ok, the problem seems to affect all cylinders but as I say standing stil the bike runs lovely and revs happily until you get on it where on letting the clutch out the engine misfires like crazy just stutters along like crazy!

[laminator]

Have you checked the EXUP valve is working correctly? Can you hear the EXUP servo open and close when you switch the ignition on? You could also take the cover off on the exhaust side to see that the valve is opening and closing. It could be the valve is either stuck or motoring too slowly.

Does it have an aftermarket exhaust or the stock (with the EXUP)?

[MarkT]

aftermarket exhaust but will have a look at the exup
thanks

[Evilchicken0]

The carbs, idle jets are either blocked or the wrong size - probably the latter. Take the bike to a dyno and get a power run it might not have been tunned for the new pipes.

The FZR will run with not exup or they can be wired open, you get a bit more top end (good for racers) but the bottom end suffers and it becomes a bit all or nothing. The best thing would be to find a set of exup downpipes.

[MarkT]

exup valve taken out, just a bolt in place of the valve.
THANKS
Mark

[Evilchicken0]

So it's an EXUP system .... ?

Put the EXUP back in.
The FZR's were made to rev high and so make good power. That robbed them of low end torque so to try and get that back Yam made a variable exhaust. So put it back in and you won't have to rev the t!ts off it to get anywhere. When you turn the ignition do you here a "weep, weep" noise ??? if so the servo is still there and connected, have a look down there for the cables too. Find the parts you need depending on what you've got (obviously).


Oh - there's a rule .... we need pics of the bike

[MarkT]

Yamaha still make the parts from japan, a tasty £475 and I need all of it!
Spoke to a few dealers and they say it's ok as it is just make the bike a bit slower on lower range.
It would not shudder and misfire. Going into workshop wed for diagnostics. Fitting a cdi tues so everything is crossed.

[Evilchicken0]

Not sure I follow .... you say you have the exup taken out, just replaced with a bolt ???
If you ask around on here for the exup gubbins then refit it you should be ok.

From what you say I don't think it's the cdi, I think it's the carbs / pipe combination not being tunned for each other.