MS 200T - Another Carb and Idle Question

[jpan]

Working on getting a 200T running for my buddy. I haven't vac tested it yet and just did a few quick things on the bench to see how it would initially run. His symptoms before were that it would bog down when under load. The fuel line was rotted, so I replaced that, filter, plug, air filter, and put fresh mix in it. I rebuilt the carburetor since the gaskets were hard and the screen had a bunch of crud in it. Cleaned it out with brake cleaner and light compressed air. The meter was set back to slightly above the base of the carb since that's where the original one was set when I removed it.

The issue......The saw started on full choke on the 3rd pull and ran up to full throttle no problem after taking it off choke. Throttle response is excellent and it revs up with no issue at all. The problem is that it won't idle at all and to restart it, I have to hold the throttle wide open. It will start on the first pull doing this. When running if I hold the throttle partially open, it does seem to sputter slighly, but any revving is instant with no hesitation but again it won't idle. Also, when I tilt the saw up, fuel pours out somewhere from the carb. I can't tell where it appears to be coming from, but it fills the bench with mix. All screws are tight on the carb and all gaskets installed correctly. Low needle set to 1 turn out - high needle set to 3/4 turn out

Any thoughts on what's going on? Is this an accelerator pump symptom, or perhaps the metering needle not set correctly?

 

[CR888]

Did you clean the metering seat? Sometimes a little crud can prevent it from sealing, a Q-tip works well. Impulse connected properly? I'd put a new carb kit in but it sounds like metering inlet is not sealing.

 

[jpan]

Did you clean the metering seat? Sometimes a little crud can prevent it from sealing, a Q-tip works well. Impulse connected properly? I'd put a new carb kit in but it sounds like metering inlet is not sealing.

I did clean it all out and used a new kit when i put it back together. I haven't checked the impulse yet, but that's next on the list. Was thinking maybe some kind of a carb issue since it pours gas from somewhere in or around the carb when turned on its side or vertical.

 

[SteveSr]

I did clean it all out and used a new kit when i put it back together. I haven't checked the impulse yet, but that's next on the list. Was thinking maybe some kind of a carb issue since it pours gas from somewhere in or around the carb when turned on its side or vertical.

Metering needle in the carb is not sealing letting gas from the pressurized tank through the carb and into the engine. Left to its own you'll soon have a crankcase full of fuel! The carb should hold 10-15 PSI at the fuel inlet indefinitely. Anything else is a leak!

 

[jpan]

Metering needle in the carb is not sealing letting gas from the pressurized tank through the carb and into the engine. Left to its own you'll soon have a crankcase full of fuel! The carb should hold 10-15 PSI at the fuel inlet indefinitely. Anything else is a leak!

I’ll pressure test the carb tonight. Thanks for the heads up on the crankcase...I didn’t even think of that overnight. If the needle lever is set too high is there a chance the diaphragm is pressing on it and not letting it seat? Should it be set flush to the base of the carb? I just did an 034 build and that one was set flush.

 

[SteveSr]

If the needle lever is set too high is there a chance the diaphragm is pressing on it and not letting it seat? Should it be set flush to the base of the carb?

Metering lever should be set to the carb masnufacturer's spec. Both Walbro and Zama make gauges for this. A lot (but not all) of them are set flush with the carb casting. It depends on the carb model. Post the carb manuf/model and someone can help you out.

 

[jpan]

Metering lever should be set to the carb masnufacturer's spec. Both Walbro and Zama make gauges for this. A lot (but not all) of them are set flush with the carb casting. It depends on the carb model. Post the carb manuf/model and someone can help you out.

looks like it’s a zama c1q other side says s61a

 

[SteveSr]

looks like it’s a zama c1q other side says s61a

That is a Zama C1Q-S61A. C1Q should be flush or slightly below the casting. I usually just reuse the factory metering lever as it is already set but I also check it.

Also make sure that the gasket and diaphragm are in the correct order. The gasket goes first next to the casting and then the metering diaphragm on top. If you reverse this order you may end up with the problem that you are experiencing!

 

[jpan]

That is a Zama C1Q-S61A. C1Q should be flush or slightly below the casting. I usually just reuse the factory metering lever as it is already set but I also check it.

Also make sure that the gasket and diaphragm are in the correct order. The gasket goes first next to the casting and then the metering diaphragm on top. If you reverse this order you may end up with the problem that you are experiencing!

thanks! Just bent the lever to where it should be. Carb holds 10psi. Gaskets are in correct order. Will try to fire in a bit

 

[jpan]

That is a Zama C1Q-S61A. C1Q should be flush or slightly below the casting. I usually just reuse the factory metering lever as it is already set but I also check it.

Also make sure that the gasket and diaphragm are in the correct order. The gasket goes first next to the casting and then the metering diaphragm on top. If you reverse this order you may end up with the problem that you are experiencing!

well just set the needle lever flush and fired it. It idles no problem now. With low set at 1 turn out and high at 3/4 it wanted to die when I throttled it but would rev slow. (Spark arrestor is removed) I richened it up and adjusted the idle screw until low was 3 turns out and idle was just under chain engaging. Starts first pull and isles fine. Seems to accelerate okay as well. Haven’t hooked my tach up yet.

Is this in the ballpark of how rich these carbs like to be? I’m assuming this is an earlier model. Not sure I’d it has the accelerator pump or not. There’s a plastic plug with a roll pin. Not a brass one like I’ve seen on other videos.

just wondering If the tune is in the ballpark or if it sounds crazy rich

Also tank vent is leaking. Looks like it’s weeping through the cloth. Guess it needs a new one.

 

[SteveSr]

@lone wolf ?

 

[lone wolf]

well just set the needle lever flush and fired it. It idles no problem now. With low set at 1 turn out and high at 3/4 it wanted to die when I throttled it but would rev slow. (Spark arrestor is removed) I richened it up and adjusted the idle screw until low was 3 turns out and idle was just under chain engaging. Starts first pull and isles fine. Seems to accelerate okay as well. Haven’t hooked my tach up yet.

Is this in the ballpark of how rich these carbs like to be? I’m assuming this is an earlier model. Not sure I’d it has the accelerator pump or not. There’s a plastic plug with a roll pin. Not a brass one like I’ve seen on other videos.

just wondering If the tune is in the ballpark or if it sounds crazy rich

Also tank vent is leaking. Looks like it’s weeping through the cloth. Guess it needs a new one.

It is supposed to be 1 turn out on both the H and L if it dont run right there it is malfunctioning unless you are in a very high altitude. Also take a good look at the impulse line that could be off or loose.

 

[SteveSr]

It is supposed to be 1 turn out on both the H and L if it dont run right there it is malfunctioning unless you are in a very high altitude. Also take a good look at the impulse line that could be off or loose.

3T out on the "L" sounds like an air leak somewhere. Are these Zama's known for main nozzle check valve leaks? This could be a source if everything else checks out.

 

[lone wolf]

3T out on the "L" sounds like an air leak somewhere. Are these Zama's known for main nozzle check valve leaks? This could be a source if everything else checks out.

It does sound like an air leak, M N don't go bad too often but always suspect as a last resort when all else fails. I always put a working carb on first then if it still wont run right vac test it. Saves hours of trouble. The impulse or seals are certainly suspect at this point.

 

[jpan]

It does sound like an air leak, M N don't go bad too often but always suspect as a last resort when all else fails. I always put a working carb on first then if it still wont run right vac test it. Saves hours of trouble. The impulse or seals are certainly suspect at this point.

thanks Lone Wolf. I don’t have another carb so should I do a vac n pressure test? Local dealer has new carbs for $75 but hate to throw money at it if it’s an air leak since my buddy is footing the bill as it’s his saw. I’m just the wrencher .

pressure test I did on an 034 was super easy but this saw definitely looks more difficult to get to everything.

 

[lone wolf]

thanks Lone Wolf. I don’t have another carb so should I do a vac n pressure test? Local dealer has new carbs for $75 but hate to throw money at it if it’s an air leak since my buddy is footing the bill as it’s his saw. I’m just the wrencher .

pressure test I did on an 034 was super easy but this saw definitely looks more difficult to get to everything.

look at the impulse yet? Yes vac and pres test it next.

 

[jpan]

look at the impulse yet? Yes vac and pres test it next.

not yet. Hope to get to it tonight possibly. Whole handle comes off to get to impulse line on this one?

 

[lone wolf]

not yet. Hope to get to it tonight possibly. Whole handle comes off to get to impulse line on this one?

Well to look at the end that usually pops off you look under the handle airbox on the left side rear. But for you to do a vac test whole handle,carb, tank then muffler off. See pic in my next post for location of impulse line.

 

[lone wolf]

 

[lone wolf]

Afterthought, before you rip it all apart set the H and L to 1 turn out and tell me how it runs?