FZRSupport: the FZROnline Archive

Hey all,

I've got some serious issues with an FZR250 that im slowly starting to get through.
I started out with a bad earth problem, then an electrical short problem combined with some serious overheating followed by a broken air box!
Just when i thought I'd done ok when i fixed all these things, i ran into another major issue....

When i take it out, at about 10000rpm ( and its pretty much EXACTLY the rpm everytime ) the bike starts to jerk and won't rev through it ? It almost feels like some cylinders don't fire cause the jerking is at a consistent rate ?

If i pull the throttle to absolute max it struggles for a bit and somehow eventually manages to get through whatever the issue is and then revs off through the rest of the range ?

Can anyone help me out ? I can't seem to find what the issue is, if i rev it up when its in neutral on the driveway it revs up through that point fine ?

Appreciate anything help i can get !

This is one area that we are severly lacking in - the FZR250. There are very few people who own them and even fewer who are on the forums.

Did the bike sit for a while? The carbs may need a good cleaning.

garyhoons wrote:Hey all,

I've got some serious issues with an FZR250 that im slowly starting to get through.
I started out with a bad earth problem, then an electrical short problem combined with some serious overheating followed by a broken air box!
Just when i thought I'd done ok when i fixed all these things, i ran into another major issue....

When i take it out, at about 10000rpm ( and its pretty much EXACTLY the rpm everytime ) the bike starts to jerk and won't rev through it ? It almost feels like some cylinders don't fire cause the jerking is at a consistent rate ?

If i pull the throttle to absolute max it struggles for a bit and somehow eventually manages to get through whatever the issue is and then revs off through the rest of the range ?

Can anyone help me out ? I can't seem to find what the issue is, if i rev it up when its in neutral on the driveway it revs up through that point fine ?

Appreciate anything help i can get !

Hi,
it is one of two things
Spark or Gas.

change the plugs for a new set gapped correctly if the problem persits it is gas and the carbs are either dirty or more likely jetted incorrectly.

If you then pull the new plugs after a stuttering run at 10K they should be tan brown but most likely either sooty black (too rich at that RPM ) or very pale and the mixture is running lean at part throttle.
you will have to mark where the throttle is (in respect to fully closed) at 10K to see what jets you need to look at.

Hi,
The bike did sit in the garage for a while while I worked on the other things, I've sprayed a fair bit of carby cleaner down the throat but that doesn't seem to of helped, should it have or do I need a more thorough cleaning ? (how do i do that ? )

I just changed the plugs and gapped them, hasn't seemed to help either.

Thanks

On that note, what could be in these carbies that could be cleaned that would be rev specific ?

I've got the manual for an FZR400 and its extremely close to the 250....

garyhoons wrote:On that note, what could be in these carbies that could be cleaned that would be rev specific ?

I've got the manual for an FZR400 and its extremely close to the 250....

GH,
Like I said earlier until you work out where 10k is in response to the throttle it is a bit hard to tell you which bit of carb is the most likely suspect!

garyhoons wrote:Hi,
The bike did sit in the garage for a while while I worked on the other things, I've sprayed a fair bit of carby cleaner down the throat but that doesn't seem to of helped, should it have or do I need a more thorough cleaning ? (how do i do that ? )

I just changed the plugs and gapped them, hasn't seemed to help either.

Thanks

a lil seafoam in the gas tank could help

but it almost sounds like jetting, you didnt change anything did you?

dont those rev to like 6k?

haunter wrote:

garyhoons wrote:Hi,
The bike did sit in the garage for a while while I worked on the other things, I've sprayed a fair bit of carby cleaner down the throat but that doesn't seem to of helped, should it have or do I need a more thorough cleaning ? (how do i do that ? )

I just changed the plugs and gapped them, hasn't seemed to help either.

Thanks

a lil seafoam in the gas tank could help

but it almost sounds like jetting, you didnt change anything did you?

dont those rev to like 6k?

Beat me to it! Try some seafoam! like, $7 a pint, could just need a cheap fix like that!! Don't get discouraged with us though! We need to have a 250 guy around Although we might not be experts on the 250, there are a few of us who are considered experts with the 600's and bikes in general (not saying myself!) or combustion engines so we could still have good tips

oh and haunter, 250's rev to like, 14 or 16k. They're 4 bangers!
how bad do you want one NOW!?

I meant 16K, just a typo

zero9243 wrote:

haunter wrote:

garyhoons wrote:Hi,
The bike did sit in the garage for a while while I worked on the other things, I've sprayed a fair bit of carby cleaner down the throat but that doesn't seem to of helped, should it have or do I need a more thorough cleaning ? (how do i do that ? )

I just changed the plugs and gapped them, hasn't seemed to help either.

Thanks

a lil seafoam in the gas tank could help

but it almost sounds like jetting, you didnt change anything did you?

dont those rev to like 6k?

Beat me to it! Try some seafoam! like, $7 a pint, could just need a cheap fix like that!! Don't get discouraged with us though! We need to have a 250 guy around Although we might not be experts on the 250, there are a few of us who are considered experts with the 600's and bikes in general (not saying myself!) or combustion engines so we could still have good tips

oh and haunter, 250's rev to like, 14 or 16k. They're 4 bangers!
how bad do you want one NOW!?

Hi,
wether it is a 250 or a 1K they are the same basic 4 stroke motor and that means problems are either gas or electrical if it is running rough or not at all, the badge on the tank or side cover means nothing !

Hey Guys !

Firstly, thanks for all the info.

Secondly, its starts to red line at 17k.....absolutely howls.

I've got a service manual for an 1989 FZR400 and everything is so incredibly similar that its really rare i find anything different, so if you know about 400's, you almost know these inside out.

Anyways , i couldn't find any seafoam in the shops here. I was looked at like a dope when i asked for it. Saw an add for it on the net and it looks like good stuff.
Anyways, my curiosity abound what yamaha_george said about the throttle position got me searching and i turned up this link:

http://www.iwt.com.au/mikunicarb.htm

Awesome page on the brand carby that this has. So after a little confidence from this i took the carbies off and opened em up. Turns out they had a pea size of rusty sludge sitting in each which must of come from the fuel filter. I recently changed that and it was full of junk. I cut open the filter to take a look and thought i broke the filter paper off on the inside when i did that, but now i reconsider it, it looks like it might of been broken for a while and hence the junk was flowing straight into the carby. Not to mention the tube above the valve in the tank had come off so all the rust from the bottom of the tank was flowing straight in.
So i cleaned the carbies really well with petrol, carby clean and an air compressor on the jets. Put the bike back together and away she went ! Soaring past 10k.

So thanks a million, working well now !

Appreciate your help !

garyhoons wrote:Hey Guys !

Firstly, thanks for all the info.

Secondly, its starts to red line at 17k.....absolutely howls.

I've got a service manual for an 1989 FZR400 and everything is so incredibly similar that its really rare i find anything different, so if you know about 400's, you almost know these inside out.

Anyways , i couldn't find any seafoam in the shops here. I was looked at like a dope when i asked for it. Saw an add for it on the net and it looks like good stuff.
Anyways, my curiosity abound what yamaha_george said about the throttle position got me searching and i turned up this link:

http://www.iwt.com.au/mikunicarb.htm

Awesome page on the brand carby that this has. So after a little confidence from this i took the carbies off and opened em up. Turns out they had a pea size of rusty sludge sitting in each which must of come from the fuel filter. I recently changed that and it was full of junk. I cut open the filter to take a look and thought i broke the filter paper off on the inside when i did that, but now i reconsider it, it looks like it might of been broken for a while and hence the junk was flowing straight into the carby. Not to mention the tube above the valve in the tank had come off so all the rust from the bottom of the tank was flowing straight in.
So i cleaned the carbies really well with petrol, carby clean and an air compressor on the jets. Put the bike back together and away she went ! Soaring past 10k.

So thanks a million, working well now !

Appreciate your help !

RESULT good to see you found the MIKUNI page take a look at SUDCO as well for lots of carb related info.
Glad we could get you rolling

well.....it DID get me rolling..........I got the thing back inside and changed the coolant after it appeared to be running well.
However, adding coolant made it difficult to start. So i started investigating. I ended up finding where the coolant was slowly going......into cylinders 3 and 4.
This became obvious when after trying to start, balls of smoke were coming out of the radiator pipe, and even more obvious when i stuck my finger in the coolant, took it out and could smell all the fuel that's entering it.

So im back OFF the road again........

did you get everything tightened back up right? idk why it would do that if all you did was change the fluid hmmm

Its been doing that since I started working on it. I noticed the bubbling coolant a couple of weeks ago, but really didn't want to have to pull the engine apart so i searched out other problems and fixed them (selective ignorance). One of the issues this thing has had since we bought it, which is why i brought it in and started pulling it down in the first place, was that after 20 minutes or so the thing got red hot and ran out of coolant ! I checked the water pump and pipes and changed every o'ring and gasket in the thing, as well as the thermostatic valve and switch. Fixed some earth problems that were affecting the temperature gauge reading and changed the radiator cap. It still got hot though. I have found so many small problems with this thing and fixed them( stupid things like a short in the light switch that drained that much current that the blinker relay blinked at the speed of someone lighting a candle and blowing it out again), but it seems i won't get this coolant issue beat until i take the head off and see whats under there. I just have to deal with Australian suppliers in getting another head gasket now at an over inflated price !

But i'll keep soldiering on ! I've got another 250 ( zzr ) and my friends have hyosung gt250rs and none them come close to this in terms of acceleration. For a 250, its a rocket.