Drowning Carburetor?

Mighty_Max

New Member
Nov 20, 2013
18
0
0
Wisconsin
I recently switched from a CNS carb to an NT carb and although my overall performance has improved greatly, i still have a few issues. New ones.
Firstly, when i first start up the bike and let it idle, all seams well, it idles at the right speed, and aside from a few missed power strokes, it seams ok. When it heats up to about its middle range, everything seams to go pretty well also, accept for a bit of intermittent four stroking at wide open throttle. When it heats up to full operating temperature, all four-stroking goes away, i get a little more power and all seams well accept that when i let go of the throttle and clutch its idling at something ridiculously high and loud. This last part kinda sucks. (no, my cable is not sticking, and yes i let go of the throttle completely)
Item #2: shortly after finishing a ride where i have this idle problem, i can see that there is gas running down the side of my bike and engine underneath the carb and the air filter is soaked.

Specs: Grubee Skyhawk GT5, NT carb with SBP High Airflow filter
 

Dave31

Moderator
Staff member
Mar 1, 2008
11,204
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Aztlán, Arizona
Sounds like to me you have a vacuum leak and your float is sticking most likely from junk causing a overflow of fuel.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
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memphis Tn
I agree. Stuck float causes the flooding.
As far as the high idle once fully hot, I'd be looking for intake leaks or possibly crank seals.
(New seals are cheap insurance anyway)
 

Rump Rocket

New Member
May 21, 2014
26
1
1
Michigan
I was told years ago the best way to check for leaks is to spray a little starting fluid around the suspected area, if the engine accelerates you have a leak.
 

Mighty_Max

New Member
Nov 20, 2013
18
0
0
Wisconsin
How could it have gotten junk in it? I only just put it on a week ago and its been doing this since my first ride with it.

I will try that starting fluid trick and see what happens. I was told that NT carbs were pretty bad for leaking air on the manifold side of things.
 

2door

Moderator
Staff member
Sep 15, 2008
16,326
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Littleton, Colorado
Did you clean the fuel tank before installing it? They come from the factory with rust, scale, dirt and who knows what. No extra charge either.

Every kit tank I've ever seen needed to be cleaned before putting the first drop of fuel in them.
You should also use a good in-line fuel filter. It only takes a spec of crud to block the float valve open resulting in the problem you have.

The high idle is a sure sign of an air (vacuum) leak somewhere downstream of the carburetor inlet. The kit intake manifold gaskets are notorious for early failure and can leak bad. Make a new one from good quality gasket material and while you're at it check the intake manifold flange for flatness. They're usually warped from the welding process and that can also contribute to gasket leaks.

Tom
 

TakeiT

New Member
Apr 17, 2014
127
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Oshawa, Ontario
I check for vacuum leaks by covering the engine with baby power, then firing it up. If it coughs out white gold, then you have a leak!
 

2door

Moderator
Staff member
Sep 15, 2008
16,326
124
63
Littleton, Colorado
I check for vacuum leaks by covering the engine with baby power, then firing it up. If it coughs out white gold, then you have a leak!
The only problem with that method is if you have a vacuum leak it will suck the baby powder in, not "cough" it out.

Tom