Farmertec/Huztl MS200T - Idle problem

[Axotopia]

I am new to the forum but been lurking for a few months. I got interested in repairing chainsaws recently and decided to build a MS200T from AM & used OEM parts as part of my education. Completed the "MS200T" finally except that it will not idle. Easy start, lots of power and acceleration, but have to keep throttle slightly depressed to keep running, made all the adjustments with maximum Idle and Low setting on the curb, all parts are new and clean. Any suggestions will be greatly appreciated.

 

[s sidewall]

Did you vacuum and pressure test for leaks while you where building it?

Steve

 

[kenton.a.frank]

Also I’ve bought an aftermarket carb that the L must have been plugged. Same symptoms. Also stupid thing but make sure your impulse line is plugged in... done that before as well and had similar issues...


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[67L36Driver]

A: Aftermarket carbs can be crap or work fine out of the box.

B: Crankcase assemblies put together by eight year old Chinese children can have ‘efft up seals.

 

[s sidewall]

A: Aftermarket carbs can be crap or work fine out of the box.

B: Crankcase assemblies put together by eight year old Chinese children can have ‘efft up seals.

I've seen that before, had to pull the lower clamshell off the fix the cockeyed crank seal.

Steve

 

[lone wolf]

Pressure and vac test it and we can take it from there. Otherwise this could take a while.

 

[Axotopia]

Thanks for the suggestions.

I pressure and vacuum tested the crankcase and both tanks (vents plugged) during assembly, all held pressure at 8-10psi.

Crankcase gasket are in place, so is the cylinder gasket.

Actually purchased (2) carburetors when i started this project. Carb#1 had problem starting and holding idle, so ended up replacing it with Carb#2. Carb#2 actually was able to marginally idle during break-in with 3 tanks before it would not idle any more.

Turning the carburetor L screw clockwise till it locks did not slow or kill the engine when it did idle on the initial few tanks. Turning anticlockwise slowed and stall the engine.

The exhaust port seems wet with fuel/oil residue, the piston viewed from the exhaust port also looked quite wet. Could be the higher oil 1:32 mix I am using for break-in or it may just be running too rich.

As noted, power at high was stout and acceleration was quick. No bogging down. Just cannot get it to idle.

 

[Axotopia]

Just curious if the somebody can confirm if the throttle valve gap looks normal for the MS200T. Seems a little tight for air flow and inducing fuel suction.
Photo shows at maximum idle setting with idle screw fully screwed in (clockwise)
The gap at top of disc looks like 0.25mm (like the gap setting between on coil and flywheel),
Bottom disc gap is slightly bigger, maybe 0.45mm (slight smaller than the spark plug gap)

 

[lone wolf]

Thanks for the suggestions.

I pressure and vacuum tested the crankcase and both tanks (vents plugged) during assembly, all held pressure at 8-10psi.

Crankcase gasket are in place, so is the cylinder gasket.

Actually purchased (2) carburetors when i started this project. Carb#1 had problem starting and holding idle, so ended up replacing it with Carb#2. Carb#2 actually was able to marginally idle during break-in with 3 tanks before it would not idle any more.

Turning the carburetor L screw clockwise till it locks did not slow or kill the engine when it did idle on the initial few tanks. Turning anticlockwise slowed and stall the engine.

The exhaust port seems wet with fuel/oil residue, the piston viewed from the exhaust port also looked quite wet. Could be the higher oil 1:32 mix I am using for break-in or it may just be running too rich.

As noted, power at high was stout and acceleration was quick. No bogging down. Just cannot get it to idle.

Thanks for the suggestions.

I pressure and vacuum tested the crankcase and both tanks (vents plugged) during assembly, all held pressure at 8-10psi.

Crankcase gasket are in place, so is the cylinder gasket.

Actually purchased (2) carburetors when i started this project. Carb#1 had problem starting and holding idle, so ended up replacing it with Carb#2. Carb#2 actually was able to marginally idle during break-in with 3 tanks before it would not idle any more.

Turning the carburetor L screw clockwise till it locks did not slow or kill the engine when it did idle on the initial few tanks. Turning anticlockwise slowed and stall the engine.

The exhaust port seems wet with fuel/oil residue, the piston viewed from the exhaust port also looked quite wet. Could be the higher oil 1:32 mix I am using for break-in or it may just be running too rich.

As noted, power at high was stout and acceleration was quick. No bogging down. Just cannot get it to idle.

Pressure and vac test it and we can take it from there. Otherwise this could take a while.

Thanks for the suggestions.

I pressure and vacuum tested the crankcase and both tanks (vents plugged) during assembly, all held pressure at 8-10psi.

Crankcase gasket are in place, so is the cylinder gasket.

Actually purchased (2) carburetors when i started this project. Carb#1 had problem starting and holding idle, so ended up replacing it with Carb#2. Carb#2 actually was able to marginally idle during break-in with 3 tanks before it would not idle any more.

Turning the carburetor L screw clockwise till it locks did not slow or kill the engine when it did idle on the initial few tanks. Turning anticlockwise slowed and stall the engine.

The exhaust port seems wet with fuel/oil residue, the piston viewed from the exhaust port also looked quite wet. Could be the higher oil 1:32 mix I am using for break-in or it may just be running too rich.

As noted, power at high was stout and acceleration was quick. No bogging down. Just cannot get it to idle.

Thanks for the suggestions.

I pressure and vacuum tested the crankcase and both tanks (vents plugged) during assembly, all held pressure at 8-10psi.

Crankcase gasket are in place, so is the cylinder gasket.

Actually purchased (2) carburetors when i started this project. Carb#1 had problem starting and holding idle, so ended up replacing it with Carb#2. Carb#2 actually was able to marginally idle during break-in with 3 tanks before it would not idle any more.

Turning the carburetor L screw clockwise till it locks did not slow or kill the engine when it did idle on the initial few tanks. Turning anticlockwise slowed and stall the engine.

The exhaust port seems wet with fuel/oil residue, the piston viewed from the exhaust port also looked quite wet. Could be the higher oil 1:32 mix I am using for break-in or it may just be running too rich.

As noted, power at high was stout and acceleration was quick. No bogging down. Just cannot get it to idle.

Try a carb from a Known runner those aftermarket carbs rarely work I only know of one in particular that does and they are sold out.

 

[jr27236]

Since you have the carb off did you ever go through it and check it out? Maybe they put the diaphragms in backwards or out of order?

 

[Axotopia]

Wonder if there are other thoughts of potential causes of the idle problem besides the carburetor ... low compression, spark plugs, etc.
I will be doing a tear down of one of the carbs as suggested, and looking for some other makes in the mean time.
Thanks.

 

[Axotopia]

Try a carb from a Known runner those aftermarket carbs rarely work I only know of one in particular that does and they are sold out.

Lone wolf. Can you PM me (if it is not appropriate to post) the AM carb that is sold out. I would greatly appreciate your help.

 

[lone wolf]

Wonder if there are other thoughts of potential causes of the idle problem besides the carburetor ... low compression, spark plugs, etc.
I will be doing a tear down of one of the carbs as suggested, and looking for some other makes in the mean time.
Thanks.

What is the compression reading?

 

[kenton.a.frank]

I’ve had one come in my shop with idling issues. Turns out the handle was aftermarket. And the carb stud bottoms were too long and caused the OEM metal band thing “official term” to not seat correctly behind the carb. I had to tap the studs out and grind the circumference down to allow the band thing to seat and the carb to have good contact on the intake boot.


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[lone wolf]

I’ve had one come in my shop with idling issues. Turns out the handle was aftermarket. And the carb stud bottoms were too long and caused the OEM metal band thing “official term” to not seat correctly behind the carb. I had to tap the studs out and grind the circumference down to allow the band thing to seat and the carb to have good contact on the intake boot.


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Damn Chinese can not get the same precision. I have seen that problem also among many others now the studs are too short!

 

[Axotopia]

Did a temporary fix to get the saw to idle:
1. Blasted the 3 tiny ports inside the carburetor metering reservoir with carburetor cleaner. Also removed the L screw and jetted carb cleaner into that cavity. Thought was to remove any debris from the manufacturing or assembly process. Not sure if this step did anything. did anything,
2. Placed a tubing on the carburetor throttle shaft where the throttle screw meets (image below).
The saw now idles, but is I can the idle speed is inconsistent. The return to idle seems to run at slightly different idle speed. Also, the engine runs slightly erratic at idle as well. L screw still doesn't affect RPM when screwed all the way (clockwise).

I will be purchasing a couple of other carburetors, an AM part and maybe a used OEM from and rebuild it. The Famertec carb does not appear to work out of the box for the two that was sent to me. The tear-down of the metering reservoir revealed that internally, they may be designed a little different from the OEM. The 'primer' vacuum port is not drill but slotted. The Low speed ports are even a little different between the two Famertec carbs that were shipped at the same time. Thought I would post the photos.

Anyway, I will get the compression tested in a week of two. My current gauge is broken and I am shopping for a new replacement.

Just curious, is there anything else that could be causing the idle issue? Just want to make sure I am not obsessing over the carburetor if that the problem could be something else.

Thanks.

--------------
Farmertec carburetor with piece of tubing at idle screw.


Farmertec carburetor (#2) for those who want to spot the difference between OEM and AM.


Famertec Carburetor (#1) slight variation at the L needle port

 

[lone wolf]

Vac leak or carb providing the compression is good. If you are so inclined vac test it again very very carefully and make sure it it 100 percent not leaking if not buy a OEM or Huayi carb dont buy anything else its a waste of money.

 

[diezelsmoke]

Not sure I am following, but to adjust idle you are talking about the L needle, to adjust idle higher you adjust the screw I have circled.

 

[lone wolf]

OP are you aware some aftermarket carbs do not have the same amount of adjustment out on the H and L needle as the standard OEM carb? And I cant tell what it should be on yours only OEM or Huayi.

 

[lone wolf]

Not sure I am following, but to adjust idle you are talking about the L needle, to adjust idle higher you adjust the screw I have circled.

I think he said turning the L needle all the way in had no effect = bad carb. Once he puts a OEM on there I would think it will run great unless the piston is scored.