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Stopper Dan
22nd February 2006, 20:18
I have an 86 (i think) GPZ400R that i can't get to run on all four. I have checked the fuel and spark and compression, everything seems fine. The bike starts fine but fuel leaks out of the exhaust port where the pipe bolts to the head. Needless to say it runs like shit, no power no pickup, even when i thought it was running on four and was revving like a mutha f#$@er it then ran like crap on a test ride. Im stumped, everyone i talk to seems to think its electrical (the spark isn't the best on any cylinder) i think it maybe the carbs (the diaphram on the cylinder that won't run didn't sit in its grove quite right, ?? ) any help would be much appreciated.

skidMark
22nd February 2006, 20:23
if fuels coming out then it's definately getting gas id say you have a spark problem because even if you take the plug out and lay it on the head it may still have spark but once it's in the cylinder under compression it will have too vmuch on it to create enough spark to ignite the gas so try a new plug.

or better yet swap the plug with that of another cylinder

hope that helps

Cheers: MA

team cudby
22nd February 2006, 20:42
I have an 86 (i think) GPZ400R that i can't get to run on all four. I have checked the fuel and spark and compression, everything seems fine. The bike starts fine but fuel leaks out of the exhaust port where the pipe bolts to the head. Needless to say it runs like shit, no power no pickup, even when i thought it was running on four and was revving like a mutha f#$@er it then ran like crap on a test ride. Im stumped, everyone i talk to seems to think its electrical (the spark isn't the best on any cylinder) i think it maybe the carbs (the diaphram on the cylinder that won't run didn't sit in its grove quite right, ?? ) any help would be much appreciated.hi bud.Ive dealt with this prob before.It will either be your coil on the leeking side or your battery.Does the bike start of the battery or does it need help?Pm me if you wish

Stopper Dan
22nd February 2006, 21:36
I tried swapping the coils over still wouldn't fire on the number one cylinder

kro
22nd February 2006, 21:44
If fuel is pissing out the exhaust header, my guess is the exhaust valve is seized open, or has a shagged valve spring that hasn't got the oomph left to shut the exhaust valve tightly.

This is of course if thats what you meant when you said fuel was leaking out the pip where it joins the cylinder head (header pipe)

Bikes will shit valve springs, its not common, but it happens. Whip the rocker covers off the top end, and see if the exhaust side valves are returning to closed position.

EDIT... just re-read your post, and offer this advice also........................

Check the intake rubbers between the carbs and the block, if they are perished and cracked, its prolly getting shitloads too much air sucking into the mixture, and leaking fuel away. I quick test is to smear some chewing gum (rough, but works), or blu-tack, around any areas you suspect are leaking.

Stopper Dan
22nd February 2006, 21:53
the rubbers between the carbs and airbox are inefective at best. They won't sit on the carbs properly.

kro
22nd February 2006, 21:57
Those rubbers arent as critical as the ones between the carbs and the engine itself.

I'd suggest checking the valves out first, it really sounds like that to me. Most likely a case of removing seat and tank (2 min job), and un screwing the cam covers, and seeing if the exhaust pipe side valves on the cylinder thats leaking fuel, are shutting fully, also, physically push the two valves by hand, and see if the springs are strong.

Thats about all I can offer. Sounds similar to what happened to my 750 A3.

Stopper Dan
22nd February 2006, 22:00
cheers for your help!!

mini_me
22nd February 2006, 22:10
the rubbers between the carbs and airbox are inefective at best. They won't sit on the carbs properly.

I would say that is your problem
a fueling problem can seem to be a electrival problem

m/m

FROSTY
25th February 2006, 08:17
dude you need to sort out the air leaks and carb leaks . Itll never run in a million years till you do . I suspect you also have a leaky fuel tap.
Those lil bikes are getting a bit worn out so ya need tio give em every chance to run propperly.Those rubbers NEED to fit propperly for it to run well.

skidMark
25th February 2006, 17:31
not the coils :shit: thatll fuck up your firing...swap the plugs man :blink:

and yer if your carb aint on properly no way in hell shes gunna go

kawa
1st March 2006, 17:34
kro sounds the most logical, go with what he says and good luck