zzr250 engine not right

[Trev zzr250]

Hi Guys/Girls

Thought i would ask this here.....

my zzr250 i have had for about 4 months love it...
its done about 22k on the Speedo and it is starting to do some weird things..

when i am riding the bike it seems to surge at under load and has a bit of a louder humming noise out of the muffler (like the motor is struggling).. This happens at any rev and also backing off as well....
BUT
when the bike is sitting still in neutral I can rev it and nothing is wrong... also idles fine. no sounds or engine struggling..
I first thought it was spark or fuel problem..... not that.. (mechanic looking at it now)..

the mechanic is thinking its the big end bearing......
what symptoms should I get if big end...?
Please help..!!

I was hoping that it was maybe the clutch slipping or something like that, or the carbie had a bad jet… but I don’t know enough about engines….

[BladeBoy]

Crap fuel my friend, if your mechanic thinks it is the big ends I would be looking for a new mechanic.

[moto_O]

maybe water/crap in the carby bowls, its fiddly but draining the bowls should help. same thing happened to mine when i had one

[Trev zzr250]

So you recon do a carbie clean and drain fuel and put new fuel in might fix the problem....

I felt that the mechanic might be pulling my leg as i have heard big end bearings noises in lawnmower engines and in my old Subaru and the bike seemed fine noise compared to them....

the problem really only happened after i transported it on a trailer up north on holidays......

[Plaz]

Just to throw a spanner in ......hows your clutch???

[Trev zzr250]

I never had anything wrong with the clutch..
it has never slipped and engages well, not jurky...

the bike is still at mechanic will ring in the morning and have a talk with him.

why do you ask about the clutch?

[krusty]

If you drain the bowls put a rag or connect a tube to the bottom of them so fuel doesn't go everywhere. From memory you use an allen key to open the screw.

[SocialSecurity]

definately sounds like dodgy carbs to me

[Stereo]

Yeah, humming is usually the cylinders getting too much fuel... have you noticed a petrol smell to go with it?

Could be a couple of things....

carby dirty
spark plugs dirty (this is what I suspect)
crappy fuel

[SocialSecurity]

i find that a humming or burbling kinda noise from the intake or exhaust generally means lean.... like think of when the bike runs outta fuel and your rolling to a stop with the engine still turning

[Trev zzr250]

guys thanks for all this......


Stereo: i have replaced the spake plugs (no change)... the old ones seemed ok but one was a bit white though

i think white spark plugs means lean mix.....

[mike-s]

Yup, should be a faint tan brown colour

[kellz]

have you checked the jets and needles in the carby,
1 they could be clogged from bad fuel or
2 they may need re aligning and setting..

jsut when mine was doin soemthing similar( gpx250) the carbies were dirty, jets were uneven and teh float was set wrong, think it was to low frm memory.

maybe drain teh carbies, strip them down give me a good clean and the set the abck as per teh manual, remember the manuel is never wrong.......unless your trying to make your bike run better......


also another part which could be playin up is teh fuel filter, very easy to check and change, sometimes with the poor quality fuel that is circulating at the moment you could of picked up some water or dirt and it is clogged.....


just tryin to think of teh cheaps solutions for ya

[Trev zzr250]

Has anyone got a electronic copy of a service manual on the carbie for a zzr250??

I do have a electronic manaul of a gpx250... i hope same carbies and i will be ok...

[kellz]

they wodulnt be to different. the zzr is dual carbie aswell yeh

have you tryed googling for a manual

try that if taht doenst work, go to teh kwakka site sometimes you can find manuals on there if you look hard enougha nd long enough.....