High revs

Dave M · Scooby Slapper Joined: 03 May 2013 Karma :

Hi all,

I just bought a cheap Hyosung gt125 comet 2010 as a bit of a project. Having a slight problem with idling as in it's idling at about 8000 rpm. I had carbs out to give them a clean. They were bad but not the worst I've seen. I sprayed wd40 on all rubber manifolds and revs get even higher. I've noticed a ring clamp missing from the air box to carb manifold. Could this be the problem or could it also be something else? I am going to fit a new clamp tomorrow. Also when I blip the throttle it is very unresponsive and cuts out. It's a v2 engine. Thanks.

Dave M · Scooby Slapper Joined: 03 May 2013 Karma :

Update.

Managed to get it to idle now but it won't rev past 3000 rpm without it wanting to die. Had a ride and got going only for it to bog down and die after about 5 seconds on road. At my wits end now. Please help!!!

Rogerborg · nimbA Joined: 26 Oct 2010 Karma :

Sounds like you have a leak in the carb -> inlet rubbers.

I'd assume that the last owner got as far as undoing the air box to carb rubbers, then thought better of it and decided to punt it on to some other mug instead of putting more time into it. Whistle

[UPDATE]
Whoa, what did you do to get it to idle?

All you've really said is "engine busted how fix?". Details, chap.

Also, if you put a location in your profile, ~~Paddy~~ someone might be minded to swing by and hold your hair back while you throw up.
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Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

Dave M · Scooby Slapper Joined: 03 May 2013 Karma :

Dave M · Scooby Slapper Joined: 03 May 2013 Karma :

I reset both mixture screws and it idles ok now. Throttle response is a bit better. I put my helmet on to go for a ride and it wouldn't rev past 3k rpm and cut out. That's all I can tell you? It will not rev past 3k. It just bogs down.

Rogerborg · nimbA Joined: 26 Oct 2010 Karma :

How's the air filter?

Done a plug chop? Rev as long as you can, killswitch and clutch in, stop, plugs out and have a look. It's either running rich or lean, you'll have to find out which.
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

bladerunner · World Chat Champion Joined: 09 Sep 2006 Karma :

Another option is the last owner dicked about with the carb trying to get it to idle by adjusting float height. Jets ...needle position etc....get it set to spec first and take it from there
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Current bikes...cbr929, KDX200's, Rd125lc mk2, RGV250's

Rogerborg · nimbA Joined: 26 Oct 2010 Karma :

That's why I'd suggest diagnosing what the issue is before "dicking with the carb". Wink

____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

Dave M · Scooby Slapper Joined: 03 May 2013 Karma :

Rogerborg · nimbA Joined: 26 Oct 2010 Karma :

It's not my fault that your bike is shagged, and I'm not minded to be a whipping boy for the queue of chimps who designed, built, shipped, sold and fiddled with it.

Best of luck.
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

An awful lot of presumed carburettor faults eminate in the exhaust.
I seem to recall, that the Hyasungs have rivited on headers, something to do with anti-tamper measures in some durastictions.
If any-one has tried removing the exhaust for any reason... this might have been a problem! could be blowing from the flange.
Worth a check.
Also worth checking for pin-holing in the pipe and rust in the low-point of the system / collector where two pipes join, as well as any dicking to de-baffle the silencer.
Any and all can screw carburation; so always should be first thing to investigate/eliminate when carb probs are encountered.

Next? Plugs. Tell you more about what carbs doing than anything. Run it up with clean plugs and then check colours against comparison photo's in pretty much any Haynes.

Remember to kill the ignition under circumstances giving grief, though, or you only ever get indication of how engine is running at idle when you turn ignition off.
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Dave M · Scooby Slapper Joined: 03 May 2013 Karma :

Az · World Chat Champion Joined: 16 Apr 2013 Karma :

Dave M · Scooby Slapper Joined: 03 May 2013 Karma :

Dave M · Scooby Slapper Joined: 03 May 2013 Karma :

Just found out from seller that carbs are replacement ones he put in himself but didn't have time to set up Rolling Eyes

Not sure if exhaust is stock or not? Went to have another look. Fired her up and first time on the button without choke although idling very low at around 1k. Started to piss down so tomorrow I will take pics of carbs, exhaust and fuel lines (that's another story)