stock carb fuel adjustment screw

GoldenMotor.com
GoreWound

GoreWound

New Member
Dec 1, 2014
480
2
0
Canada
So, my fuel adjustment screw fell out, and my engine immediately started running better. but, I'm positive that running with a hole in the side of my carb is a recipe for a headache.
The question is, how do I plug the hole but retain this benefit?
I am not one hundred per-cent sure but if I just sawed the pin off the spare screw I have and put it in almost tight would it be the same as not even having one, or would I need to drill a hole through the screw as well?

or should I get some threaded tube and sandwich a filter between two bits of it inside the hole?

just throw some ideas at me here guys, I don't believe any idea can be too crazy!

It's worth mentioning that I am already shopping around for a delorto clone, but in the meantime I would like to get on with breaking it in.
 
maniac57

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
22
0
memphis Tn
That's an idle adjustment, not a fuel adjustment. It requires a special blunt nosed screw. You can easily make your own if you have the right size screw and a dremel. Also has a spring supposed to stop it falling out....
Search for image to go by.
 
GoreWound

GoreWound

New Member
Dec 1, 2014
480
2
0
Canada
idle adjustment? the thing does less than I thought, the only way I can manage to adjust the idle is with throttle cable tension.
seriously though, I did have a spare, which I put on the carb, and then I figured a way to put the air filter directly onto the carb without the "Vader head" airbox thing at all. (I also cut a coke can in half and stabbed a bunch of holes in it but that didn't fit) hopefully it will breathe a little better like this, I optimistically put the choke back on.
gotta wait till tomorrow to try it though, middle of the night right now.
 
maniac57

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
22
0
memphis Tn
Yeah it's simply a stop screw that hits a groove on the carb slide to set idle. If you are using throttle cable adjustment to set idle, your cable is too tight.
 
GoreWound

GoreWound

New Member
Dec 1, 2014
480
2
0
Canada
two-strokes are weird, without the air-box on she runs quieter, but with half power.
choke still does nothing, also the idle adjustment screw seems to have no effect regardless of which direction I turn it, throttle cable remains the only way to adjust idle speed.

seems like every time I take her out I spend half my time messing with the carb!
I think I will continue considering the carb a temporary solution.
 
2door

2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
If closing the choke "does nothing" it's a good bet you have an air (vacuum) leak somewhere downstream of the carburetor. The choke should actually kill the engine.
This would also explain why your idle speed screw doesn't adjust idle speed and why the cable adjustment will. You're really just shutting down the inlet of the carb so the engine is barely running.

Start checking how the carb is attached to the intake manifold and then the gasket between the manifold and the cylinder. These are the two most common places for excess air to enter. The kit gaskets are notorious for early failure especially when using the steel manifold which usually doesn't seal well due to a warped flange. The flange warps during the welding process and won't allow the manifold to fit flush against the cylinder mating surface.

Contrary to popular belief the kit air filter is not a restriction. The engine will breath just as well with it as with any aftermarket, so-called, "high performance" air filters. A stock engine can only take in so much air and the stock filter will provide that. Drilling holes in it will not give you any measurable performance increase.

Tom
 
Last edited:
GoreWound

GoreWound

New Member
Dec 1, 2014
480
2
0
Canada
when i said "nothing" what i should have said is "prevent engine from running at all"

I have an aluminum intake manifold and it appears to be very nicely sealed to the engine. the idle adjustment screw seems to be for show, when running turning it in either direction has no discernible effect until it comes right out, then the engine runs better. before I finished building the bike I was messing around with the carb and was initially confused by that screw, I couldn't tell what it was supposed to be doing at all, when tight and touching the slide inside the barrel there seemed to be no change in slide movement compared to when the screw was loose.

the clamp that holds the carb on is tight, but that took a bunch of work to do, worst clamp ever.

and my experiment without the air box seems to suggest that too much air in is a problem, engine ran quieter but with more vibration and less power.
as far as I can tell the issues I am having with the stock carburetor are best addressed by replacing it.
 
You must log in or register to reply here.
Top Bottom