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Discussion Starter #1
My 340 colt has no carb filters.
I have the air screw at 1 turn out.

If I give it full throttle from idle, it bogs for a second like its getting too much air then finally goes.
This is with the engine at idle and the track off the ground.

If I fully close the air screw this doesn't happen and it's responsive right away. No bogging whatsoever.

Is it ok to have the air screw turned all the way in?
 

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Peter,

First, your sled should have an air box (without filters). If it's missing, that would cause your sled to run a little lean.

Despite this, the air screws shouldn't need to be turned all the way in for it to rev up.

I don't know if it's okay to run with the airscrews turned in fully, but that leaves you no more room to enrich your mixture.

My Formula Plus had similar issues last year, although they were at the other end of the spectrum (WAY too rich, ran like sh*t). It turned out to be just dirty, out-of-adjustment carbs. The guys here convinced me to try cleaning them.... problem solved. It was crap blocking some of the air passages. You may have the same problem with fuel passages.

If it were my sled, I'd try cleaning and setting the carbs to factory specs; then see how it behaves.

If you're not familiar with how to do it, there's a link on how to clean your Mikuni carbs at the head of this forum. It was a lifesaver for me!

Hope this is some help.

-Strato-
 

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If when you turn the air screws all the way in it runs better, that indicates that the chokes are likely in need of adjustment/replacement as they are not closing/sealing properly.

A through cleaning of the carbs is in order.

Most of the Colt series never had an air box on them at all, they just had a carb screen to prevent sucking in any debris (weed seeds and such) because the front of that hood had such a large opening in it.
 

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Most of the Colt series never had an air box on them at all, they just had a carb screen to prevent sucking in any debris (weed seeds and such) because the front of that hood had such a large opening in it.
I stand corrected. My carbs came from a 295cc Colt and had an airbox, so I assumed they all used them.

YES, I do know what "assume" means! :eek:

RJ, you raised an important point.... the chokes on my VM26SS carbs (zinc) have pretty beat up choke plungers. The brass barrel themselves are pretty worn, more importantly the neoprene bottoms have a permanent impression in them- they probably won't seal the inlet passage properly.

Is it possible to buy the plunger only? Everything else is in decent shape, and I'd rather not pop for an entire choke kit at ten bucks apiece.

Thanks,

-Strato-
 

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Discussion Starter #6
I cleaned the carbs, synced them and adjusted the chokes.
The sled starts fine and with the air screw at 1 turn out has a slight bog when you give it full throttle.
With the air screw turned all the way in there is no bog.
I,m going to adjust the idle.
Right now its at 3000 rpm which is a little high. I think it should be around 2500 rpm.
Then I will adjust the air screw and see what happens.
 

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Idle should be < 2000 rpm.
Set the air screw at 1 turn out, adjust idle speed to 2000, turn air screw in or out 1/8 turn at a time until rpm's start to rise and then reset idle speed.

Are the slide needles on the middle notch?
 

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Discussion Starter #8
I have everything running fine and took it for ride.
Everything was ok until the sled became sluggish.
I opened the engine cover and noticed fuel was leaking out of a hole in the side of one carb.
I attached a picture showing the hole where the fuel is leaking from.
Anyone know why it leaks from here?

 

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Discussion Starter #10
I'm setting up the carbs now but I think my slides are going to high at full throttle.
Does anyone know if the slides are to go all the way to the top or just stop as soon as they pass the top of the venturi?
 

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Discussion Starter #12
RJ Gleason,
in order to get the slides to stop at the top of the bore, I have to turn in the throttle cable adjuster all the way in until the lock nut and adjuster nut are touching each other.
I then have about 3/8" of play at the throttle lever at idle and doesn't run right. I get a bog at full throttle that feels like it's running on one cylinder and is about to stall.

I'm not sure if I synced the carbs correctly. I can't find a clear explanation on how to do this but this is what I did:

Unscrewed the idle screws until the slides were at the bottom of the carb.
Loosened the throttle cable adjuster lock nuts.
Turned in the throttle cable adjuster until the slides were all the way down and had about 1/16" of play in the throttle lever.
Press the throttle and watch if the slides reach the top at the same time and adjust accordingly (they go further up the bore about 1/4").
Turn the idle screws in until they just touch the slides then 3 more turns in.
Air screw 1 1/2 turns out.

Is this the correct way?

Before I started I cleaned everything up, adjusted float levels to spec and after syncing I do not get a bog at full throttle.
What happens now is when at idle and I give it full throttle it bogs for a second then catches and goes. If I feather the throttle it goes ok.

I cant get the idle past 2000 rpm no matter if the idle screw is turned all the way in.
It does however come down if I unscrew them out.
 
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