Ms150 high jet.

[Gerbutt]

Hello

 

My 150 is running as if it’s a little rich so thought I’d give the high jet a tweek, but when I have it on full revs and wind the high jet in and out it barely makes a difference. I’m used to saws racing when it’s wound in but if anything this one got a bit more groggy! Any ideas?

[The Technician]

Check your fuel filter in the tank. It may be blocking up. So it's leaning out the fuel. You will need a new fuel filter if you can't blow into it easy. Part number is 0000 350 3500

[Gerbutt]

Cheers bud. Wouldn’t that make the saw race though? This one is acting as if it’s got too much fuel, but doesn’t make hardly and difference turning the h jet in. The air filter isn’t blocked.

[Gerbutt]

Also, I put a new car kit in to no avail.

[spudulike]

The 150 and 201 are a bit weird like that. They don't tend to react like a typical carb! It may be a dirty air filter or dirt in the check valve holding it open!

 

[Gerbutt]

Hiya spud, I took the air filter off and nothing changed. Where is the check valve?

[spudulike]

It is in the carb and is where the high speed fuel enters the carb throat before entering the manifold - usually brass!

[spudulike]

If you have been using a poor oil, it could be the muffler hole is blocked - easy one to check if it is a later model with a removable outlet cowl. 

[Gerbutt]

No always good oil bud. The exhaust is ported so I can see that it’s clear. I’ll take it off though and check it’s not blocked cylinder side. I’ll also have a gander for the check valve. Is there a chance the high jet could be broken?

[spudulike]

If the muffler has been drilled then it won't be blocked. It is worth looking at the piston through the exhaust port and seeing if it is scored - you should be able to see the horizontal turning marks still on the piston and there should be no build up of carbon encroaching on the port and closing it off.

The check valve is a one way valve that stops fuel being pulled from between the main diaphragm and carb body when the saw is on idle. The fault is that this valve either stops flow in both directions causing no high speed running or flows in both directions that can cause the saw to load up at idle and get smoky and not run well at all. The valve should only allow fuel to be dragged from it by the vacuum in the carb throat causing a venture effect on it.

This valve is the device that shuts the high speed fuel system off when the throttle valve is closed and allows the low speed system to work alone.

I recently had a MS200T with a dodgy open check valve - symptoms were very a poor/rich idle but would rev out OK.

Is your choke valve opening fully - I know it is a very simple lever. A dirty air filter would cause this issue but you have checked this. Is the plug black or tan?

It is possible that the kill wire is shorting out which will cause interesting running. Have you tried a new plug as these 10mm ones can give some dodgy running issues CMR6A from memory!