Hi guy's my cousins fzr 400 1wg has starting issues and won't idle steady it will idle high in the 4k-5k range and after a while just shut of by itself if left alone throttle response is shit! i have cleaned the carb's 1000 times tried air/fuel adjustment screw but nothing again and it will start up with a little difficulty but with the choke on or just by giving it a bit throttle what could it be? By the way it rides OK has power in all rev ranges but sluggish throttle response! plus it backfires huge flames when he closes the throttle!

I'd suspect an air leak somewheres, either a rotted vacuum line or a failing carb boot.

It does sound like an air leak or it's very lean at idle, it could be a leak around the air screw are the o rings all in place and in good condition?.
The screws should be about 2 .5 to 2.75 turns out from just seated. Balance the carbs too as that can have an affect if they are out your idle will be rough.
At the age our bikes are now things are starting to wear out so it may be worth getting one of the carb rebuild kits from
Lite Tec, the o rings get compressed and leak air / fuel and you can't get a setting when they are like that.
It sounds like the Fzr' s are starting to have that "gsxr" problem with knackered o rings.

clean the carbs again taking all jets out and blowing then thru.

take floats out and blow thru all holes.

I would guess carb boots, if you have cleaned the carbs. Fuel level in these things is very fussy too. I have had my carbs off about 20 times and its pretty good now, but i have all new boots for both sides of the carbs new mixture screws/o-rings as well.

Which 1WG do you have? I have the early non exup Genesis which has the following as stock:

15 pilots
87.5 mains
3.5 turns out on mixture screw.

kirbster wrote:I would guess carb boots, if you have cleaned the carbs. Fuel level in these things is very fussy too. I have had my carbs off about 20 times and its pretty good now, but i have all new boots for both sides of the carbs new mixture screws/o-rings as well.

Which 1WG do you have? I have the early non exup Genesis which has the following as stock:

15 pilots
87.5 mains
3.5 turns out on mixture screw.

My cousins fzr 1wg is the exup model,i was also thinking that he need to replace his carb boots and i have searched eBay for car rebuild kits for he's bike with no success

Have you chacked the valve clearances? Just a thought.
Cheers
Ian

The huge flames are unburnt fuel in the exhaust pipes - they hit the pipes and the heat from them causes detonation.
Have you balanced the carbs, that would help wth rough running and starting.
Replace the spark plugs ? Sometimes a plug will spark on the head but then break down under load.
Does the exup work ? you need to hear the weep, weep sound when you turn the ignition on. Take off the chrome cover and look for the cables moving the pulley. Have a look at the two little tongues they should return and be over the hole in the back plate.
But I'd say to check the vale clearances.

Evilchicken0 wrote:The huge flames are unburnt fuel in the exhaust pipes - they hit the pipes and the heat from them causes detonation.
Have you balanced the carbs, that would help wth rough running and starting.
Replace the spark plugs ? Sometimes a plug will spark on the head but then break down under load.
Does the exup work ? you need to hear the weep, weep sound when you turn the ignition on. Take off the chrome cover and look for the cables moving the pulley. Have a look at the two little tongues they should return and be over the hole in the back plate.
But I'd say to check the vale clearances.

I have changed the plugs and the exup setup we disconected it because the valve in the exhaust wouldent open but you can see it work where the cables ate connected,do you happen to know the valve clearences for the bike?

If the exup valve is stuck then that's your problem. If it's shut the bike wont fuel above 8000rpm. If it's open then the exhaust is to big for the engine at low revs - below 8000 and it will be a bit gutless.

I'd do the valves too - look in the document library (the links at the top of the page) and it should be in the setup library (use the 3TJ SP doc) alternatively there's usually a cd around on ebay, it's a rough scan of the workshop manual.