Bike dying at 10k revs

[nlpples]

so i bought this zxr 250c. and i love this thing with a passion
i fixed up some of the issues it had, changed spark plugs, cleaned the carburettors and so forth. however, since i bought it the bike is just losing power every time i hit about 10,000 revs regardless of what gear im in :(. i sat it on its stand and tried it without a load and i could redline it so i dont know whats going on there.

anyone got any ideas?

[quallman1234]

Get a manual. the problem is the airbox hose's aint connected up correctly. The airbox has to be at the same atmospherical pressure as the Carbs.

[Grasshopperus]

I had a similar problem with by zxr250a. Cleaning up the ignition coils helped. But the biggest thing was finding that the previous owner had put in oversized carby main jets.

Also, take a look in the engine/fuel section in the kiwibiker mechanics sections.

[nlpples]

alright, yeah my old man mentioned that there might not be enough air pressure getting into the carbs but i had only cleaned out the lower part of the carbs, i hadnt checked the hoses. ill go have a fiddle.

[glegge]

perhaps fuel supply, fuel tank vent blocked? fuel line pinched, filter dirty.. red line when sitting still is easy - under load requires more fuel.. worth a look.
cheers

[nlpples]

perhaps fuel supply, fuel tank vent blocked? fuel line pinched, filter dirty.. red line when sitting still is easy - under load requires more fuel.. worth a look.
cheers

nah mate it was one of the first things i checked. everything to do with fuel was fine. it turns out one of the hoses from the vacuum valve to the airbox had split. thanks for that grasshopperus. it bought the revs up to about 16thousand + , however it still chokes and hiccups if i accelerate too much which i can seem to remedy by either dropping a gear or releasing the throttle a little. might put more grease round the gasket seals between the airbox and carburettors because theyre a bit had it and i suspect there might be an air leak there.

[Grasshopperus]

I really recommend checking the size of your main jets on your carbs. As I mentioned, stuttering under heavy throttle in my zxr250 was due to a previous owner putting oversize jets on. From memory they should be #122 on cylinder 1&4 and #125 on cylinder 2&3. Any larger and your engine chokes under full throttle.

People increase the jet size when they've put a more free-flowing exhaust on. It may be that the old owner had a cool exhaust for your bike but put the standard one back on when he sold it.

[angelindisguise]

does it have a kill switch? they can cause a bit of grief if you've put a new one in/changed it...

[nlpples]

low and behold it turned out to be poor air pressure due to crappy gasket seals, fixed it up with a bit of grease and i got the bike to redline and got it up to 160km/h, i will eventually have to seal it properly with proper gasket sealant though . unfortunately on the flipside, today i thought it'd be kind to give my mate a tiny ride round the carpark in first gear on my bike..... this resulted in him hittting one of the curbs flat on and bending my front forks inwards. back to taking the bike apart.

[Grasshopperus]

Damn dude. Sux

[Mrs Shrek]

alright, yeah my old man mentioned that there might not be enough air pressure getting into the carbs but i had only cleaned out the lower part of the carbs, i hadnt checked the hoses. ill go have a fiddle.

Just goes to show you should listen to your olds first up eh :whistle: saves a heap of hassle

[j_redley]

And don't bother letting people ride your bike. In future, you could use a can of "start yah bastard" and spray it around joins and gaskets when the engine is running. When the rev's increase it indicates a leak where the stuff is getting in. You definatly don't want grease mixing with petrol or oil and gumming up the carbs.

[lone_slayer]

Had a similar problem On my GSXR250 once over 10k just lost all go.... Probably the easiest fix ever... My fuel had been in there for about 2 and a 1/2 months due to repairs so drained that out put in some new 98 and some carb cleaner and she was all good after about 5 mins of riding