Fzr400 dies when you throttle off

[tazwars991]

So after a engine rebuild...new piston rings and valves, she is back together. She starts and revs perfect. Only problem is I basically have to ride the clutch to keep it going. If I close the throttle to quick the engine stalls.
On initial start up and putting in gear there was a bang and it stalled....guessed the clutch plate was sticking as it didn't do it again.
Only other thing is the 3rd of the exhaust down pipes doesn't really get hot?
Driving me crazy now please help.


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[DonTZ125]

I don't suppose you cleaned the tank and carbs while you had it all apart? Sounds like your pilot jets are full of crap, to the point your #3 cyl isn't working and has probably fouled the plug.

[venari]

Does having the fuel tank full make any difference? If so it could be your fuel pump not priming the carbs properly.

Like Don says - it could easily be just blocked jets. You can get get carbs ultrasonically cleaned pretty cheaply and it's very effective! Although you can do nearly as good a job if you buy an aerosol carb cleaner (wear glasses!!!) and a toothbrush.

Also check the carb / airbox seal boots, look for holes in exhaust and check plugs are tightened down.

This is probably going to be a case of eliminating possible problems rather than fast-forwarding straight to an answer.

Looks like a nice clean bike which should make the process much more enjoyable!!!

Good luck

[tazwars991]

Carbs have been ultra sonic cleaned twice and rebuilt the tank is amazingly clean as I had to get a second hand one. Fuel level is pretty low mind you! It's going back to the garage where the engine and carbs were rebuilt. I have my own ultrasonic cleaner now aswell due to my many projects. They are brilliant!!

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[willandrip]

Does having the fuel tank full make any difference? If so it could be your fuel pump not priming the carbs properly.

Harrumph

[willandrip]

Only other thing is the 3rd of the exhaust down pipes doesn't really get hot?
Driving me crazy now please help.

No. 3 cylinder carb pilot circuit....or perhaps ignition HT lead to that cylinder defective.

[venari]

Does having the fuel tank full make any difference? If so it could be your fuel pump not priming the carbs properly.

Harrumph

Sorry Will.....

[willandrip]

Lol.

[Evilchicken0]

It sounds like either a plug is fouling / HT lead is breaking down (clip 5mm off the end open the lead up and rescrew the ht lead onto the cap) / the carb jet is blocked.

Clean the jets in No3 - probably the slow running jet. It doesn't matter if they have been cleaned you can still get crap in them. Make sure the fuel filter is new.
Balance the carbs and take it to a dyno - The bad part of a dyno is the expense (and finding one) the good bit is the bike should be fixed, it will run and be proven to run and lastly you won't be left wondering if it could be this or that .... or something your mate said down the pub

[willandrip]

Throw the pilot jets away and replace with new units...the slightest distortion internally will restrict flow.

They cost $5.
http://www.partzilla.com/parts/detail/y ... 32-A0.html

Ultrasonic does not always clean interior passageways.

If you cannot afford $5 ...swap the jets from another cylinder and see if problem follows the jets !

You can also extend one lead temporarily from the coil that supplies the suspect cylinder so that it reaches the "wrong" cylinder of the pair ..swap the leads from that coil to the offending cylinder.
That eliminates ignition components.

[willandrip]

It's going back to the garage where the engine and carbs were rebuilt.

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This should have been sorted before the bill was paid !

Also : If you have not rebuilt the carbs yourself and have not verified the fuel/air mixture setting AND the state of the airscrew and O ring you may find the problem lies there.
If the needle end of the screw is flattened/distorted from overtightening then the bike will never return to a stable idle.
(This can also be checked by swapping between cylinders.)

The worse thing on a four cylinder bike with four sets of carbs is that there are four carbs to go wrong.
The best thing is that there are four sets of every part that give problems that may easily be interchanged for diagnostics...you already have them at hand.

It is only with very small jets or O rings that ALL four become suspect. (Disregard the last comment when referring to the Suzuki GK76A....ALL the O rings are ALWAYS suspect) .

[tazwars991]

The garage was given a rolling chassis and a engine so could not be test riden in any way. Hence why the bill was payed. They are having it back now it is all built and can do a proper test ride and sort the issue. They have been great. I am sure he will find the problem just wanted to know if there was any of the normal fzr problems it could be.

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[willandrip]

The garage was given a rolling chassis and a engine so could not be test riden in any way. Hence why the bill was payed. They are having it back now it is all built and can do a proper test ride and sort the issue. They have been great. I am sure he will find the problem just wanted to know if there was any of the normal fzr problems it could be.

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Well if you had used the search facility you would have found that in excess of 90% of problems are carb orientated.
Of that 90%...over 95% of problems are from the idle/pilot circuit. !

"Driving me crazy now please help."

Contributors/members help others daily on this or any other forum.
The process usually involves pry bar tactics to gain the full history of the offending problem before the subject is diagnosed correctly.
This topic and the subsequent answers to questions has not proved to the contary..

[Evilchicken0]

As a general thing - Be careful when you ask a garage to do something, if you say you think it's XYZ they sometimes just sort that out because you've given them a diagnosis of a problem. If the bike still has the original problem they can say they've done what you've asked.

It sounds like you've got a better relationship with this garage though, a good garage is something to hang onto.