After sitting a year added new carb, idles, revs but cuts out under load acceleration

[stacyc72110]

Lifan Hi-Bird QH250GY

I let motorcycle sit for a year, gas went bad in fuel bowl and ruined carb. I replaced the carb with one from eBay for $23, it had imperfections in the throat mainly a sunk in place with some swirls, looks like not enough metal in the mold or took out of mold before it cooled. The carb seems fine, the bike will idle kinda rough with hesitation sounding pops. It will rev and seems fine but will not take gas under load. It hesitate and won't run very good at all, and it you kinda rev it up there by being easy giving it gas and kinda give it a lot of gas it pops and even backfired. I tried to adjust the fuel/air screw and it didn't really affect the idle at all. Need help with this. Thanks

[pete]

dose the new carb have the same jet sizes as the old carb ?
is it the same type of carb ?

I see these adds for chinese carbs...
fits 50cc to 150cc.... as if a 50 & 150 use the same
size jets...
But I think the real story is told in the prise....

get a good carb & jet it....




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[stacyc72110]

This is the same exact looking carb as the one that came off it. It just ain't got a name on it. 30mm and everything looks the same. The plug has black soot all over the exposed end in the cylinder, it looks kinda like powder and it's covered. Like if you'd hold it over candle flame.

[Adjuster]

Very rich. Verify the position of the choke and turn the choke off.



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[stacyc72110]

Carburetor came out of the box like that, but no adjustments needed to get bike to start. I did try to adjust fuel/air mixture screw but it did nothing in both directions. Made it stumble at idle once or was just carburetor, tried both directions till screw almost fell out. It never raised the rpm.

[Adjuster]

Air filter installed? The filter needs to be installed for the carb to work correctly.


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[pete]

Ok yer had it on... starts but dosn't run .. turned the screw..
no luck..
I know yer after a bolt on fix..but yer now past that stage..
Pull both the new & old carb apart check the jet sizes are the same
thats really the next step.... no amount playing is going to make it
run if the jetting is way out....

This may be the way to go...
I use a OKO on my 77 Montesa Cota 348.... goes like Mr Montesa
never dreamed they could... Also have one to go on my TTR250
when I ever get around to it.....

http://www.aliexpress.com/item/32mm-...227603941.html

http://www.aliexpress.com/item/10pcs...338882878.html


http://www.aliexpress.com/item/New-m...580288731.html



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[Adjuster]

That is a very cool carb. I don't understand all the inlets/nipples, it has like 5 of them???


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[pete]

Originally Posted by Adjuster

That is a very cool carb. I don't understand all the inlets/nipples, it has like 5 of them???


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1....Fuel in from tank....
2....Fuel bowl breather..
3....Fuel bowl over flow
4 & 5...The 2 with the connector tube... stay as they are..
"power jet" / accelerator pump... gives a small squirt of
fuel when you open the throttle quickly so the motor
responds to the throttle with out hesatation...
richen the mixture for a secound or so.....
When you snap the throttle open the air flows faster
than it can make enough vaccume to pick the fuel
up though the jets from the fuel bowl... giving a dead patch of
air with very little fuel in it "lean"... accelerator pumps helps to stop this...

Hope this helps....

heres a pre-jetted 30mm OKO/koso carb for a 250cc bike.... good start point..
http://www.aliexpress.com/store/prod...367847876.html







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[stacyc72110]

After thinking it over I decided to take the carb off and return it. While looking it over after I got it off, I turned it sideways and gas poured out a hole. I looked to see where it was coming out. It was a nipple looking thing that stuck out next to gas line connection. Suppose to have a brass plug or bb stuck in hole but was missing. It was getting unfiltered air through the hole. The fuel/air screw didn't work and I guess that's why, no vacum. Was a faulty carb, my guess. Carb had tool or hammer marks in throat as well, next to choke. I'll have new carb next week. Thanks for the replies.

[Weldangrind]

I've probably installed a dozen of these, all with excellent results: http://www.ebay.com/itm/Mikuni-Carbu...324a61&vxp=mtr

The castings are quite good, and jets are easy to find.