Idle surging

PCD · 10-16-2009, 10:35 PM

I hate to ask for help when I havent exhausted every possibilty I can think of, but its -1 Celcius in the garage and I'm wiped from 60+ hours this week.

200cc Gio Beast
Mikuni Upgrade
Fresh fuel with stab.

I took this carb apart before installation. It was perfect. needle on the fat side, but not sure thats relevant here. Bowl was clean, everything looked OK.

If warm, bike fires instantly, less than 2 seconds. If cold, needs to be choked but runs fine.

Take it for a spin and throttle response is darn near instant. Zero hesitation or bog. VERY, VERY, snappy.

Also have CDI & Pipe installed.

If I adjust the idle screw to a rather high rev, it will sit there and rev high for 30 seconds or so, than ALMOST die..then a few seconds later rev back up to where I set it.

Throttle cable adjuster is at beginning of adjustment, no fooling with that.

Does this sound like a gas cap issue, and if so, why will it run great when riding?

Any quick and dirty things to check?

Thanks very much.

phil · 10-16-2009, 11:00 PM

i can give 2 easy tips but i am condemed a lot for this
1. run av gas its 100 lo-lead. wont hurt a thing, no corn,dirt or water just costs more but then how much do you really burn? it also stores much longer
2 take off the air filter rev the motor kindly, but hard. then take the palm of your hand and seal off the inlet of the carb, this makes the full vaccum of the engine pull through the jet circuits and lets it eat anything you may have missed or couldnt see. dont foul it, just choke it till its eyes pop 8O do this a few times it sometimes works wonders....sometimes it dont do anything. but its free

Weldangrind · 10-17-2009, 01:49 AM

The fat setting on the needle is in play once off idle, so I'd suspect the air / fuel screw setting. Tweak the screw under the carb a bit and see if that helps.

PCD · 10-17-2009, 05:27 AM

Phil & WG...thanks for the replies. I will try the choke with hand deal as soon as its light out....I love free, trust me.

WG...I'm confused as usual...off idle the bike runs like a 340 six pak...darn near instant response.

If i fool with the A/F screw at the bottom of the Mik I could screw this up right?

its almost like an intermittant vacuum leak...putt putt putt...roar for 20 seconds then putt putt putt again. rinse and repeat. Like an invisible hand is screwing the (green marked) idle screw in and out on me.

As per your other advice I backed up the throttle cable adjustment to the beginning of its range and did the idle with the carb instead.

Air breather maybe? But then it would do it all the time (no UNI yet running on coarse filter pad only atm for testing).

Fuel line not pinched (petcock and new line going in Sunday when C/T puts out thier new stock) btw.

Cant be the crappy little in line filter or it would starve at riding speeds right?

Engine has about 2 hours on it by now...maybe i need to go run the snot out of it up and down the road a few times.

WG, I am not ignoring your advice (good way to never get help again) but the A/F screw worries me a bit.

Pete

10-16-2009, 10:35 PM	#1
PCD Join Date: Oct 2009 Location: Newmarket On Canada Posts: 382	Idle surging I hate to ask for help when I havent exhausted every possibilty I can think of, but its -1 Celcius in the garage and I'm wiped from 60+ hours this week. 200cc Gio Beast Mikuni Upgrade Fresh fuel with stab. I took this carb apart before installation. It was perfect. needle on the fat side, but not sure thats relevant here. Bowl was clean, everything looked OK. If warm, bike fires instantly, less than 2 seconds. If cold, needs to be choked but runs fine. Take it for a spin and throttle response is darn near instant. Zero hesitation or bog. VERY, VERY, snappy. Also have CDI & Pipe installed. If I adjust the idle screw to a rather high rev, it will sit there and rev high for 30 seconds or so, than ALMOST die..then a few seconds later rev back up to where I set it. Throttle cable adjuster is at beginning of adjustment, no fooling with that. Does this sound like a gas cap issue, and if so, why will it run great when riding? Any quick and dirty things to check? Thanks very much. __________________ Good, Fast, or Cheap....Pick Two.
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10-16-2009, 11:00 PM	#2
phil Join Date: Jun 2008 Location: wise va Posts: 636	i can give 2 easy tips but i am condemed a lot for this 1. run av gas its 100 lo-lead. wont hurt a thing, no corn,dirt or water just costs more but then how much do you really burn? it also stores much longer 2 take off the air filter rev the motor kindly, but hard. then take the palm of your hand and seal off the inlet of the carb, this makes the full vaccum of the engine pull through the jet circuits and lets it eat anything you may have missed or couldnt see. dont foul it, just choke it till its eyes pop 8O do this a few times it sometimes works wonders....sometimes it dont do anything. but its free __________________ halls auto l coolster, modcycles, yanmar & zongshen, dealer fired roketa,lifan and jet moto and apollo quit me who's next
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10-17-2009, 01:49 AM	#3
Weldangrind Join Date: Mar 2009 Location: Sardis, BC, Canada Posts: 25,977	The fat setting on the needle is in play once off idle, so I'd suspect the air / fuel screw setting. Tweak the screw under the carb a bit and see if that helps. __________________ Weldangrind "I figure I'm well-prepared for coping with a bike that comes from the factory with unresolved issues and that rewards the self-reliant owner." - Buccaneer
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10-17-2009, 05:27 AM	#4
PCD Join Date: Oct 2009 Location: Newmarket On Canada Posts: 382	Phil & WG...thanks for the replies. I will try the choke with hand deal as soon as its light out....I love free, trust me. WG...I'm confused as usual...off idle the bike runs like a 340 six pak...darn near instant response. If i fool with the A/F screw at the bottom of the Mik I could screw this up right? its almost like an intermittant vacuum leak...putt putt putt...roar for 20 seconds then putt putt putt again. rinse and repeat. Like an invisible hand is screwing the (green marked) idle screw in and out on me. As per your other advice I backed up the throttle cable adjustment to the beginning of its range and did the idle with the carb instead. Air breather maybe? But then it would do it all the time (no UNI yet running on coarse filter pad only atm for testing). Fuel line not pinched (petcock and new line going in Sunday when C/T puts out thier new stock) btw. Cant be the crappy little in line filter or it would starve at riding speeds right? Engine has about 2 hours on it by now...maybe i need to go run the snot out of it up and down the road a few times. WG, I am not ignoring your advice (good way to never get help again) but the A/F screw worries me a bit. Pete __________________ Good, Fast, or Cheap....Pick Two.
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