Two Problems; Fast idle and Pulse at idle... Any Ideas?

[brendonv]

My 4 year old MS460 has started developing a fast idle, really no matter how far I turn it down. Air leak? Where should I check? Clean air filter, although never replaced.

My two year old BR600 just started to pulse at idle. I heard your supposed to check the valves, and I still need to get that two pickup fuel filter deal. Cleaned air filter. Anyone have the part number for that?

 

[MasterBlaster]

If the thread titles would more accurately state the nature of the thread, it would show up much better in searches.

See the diff?

 

[brendonv]

Hey, look at that!

 

[SkwerI]

What are you 'turning down' on the 460? The idle adjustment or the low speed jet? The idle adjustment is nothing more than a stop bar for the throttle lever. The low speed jet adjusts the fuel mixture at idle. I would start by turning the L screw out (counterclockwise) about an 8th of a turn or so and see if that makes a difference. If it needs more than a quarter turn out from the current setting than it's time to start looking for an air leak.

 

[Cobleskill]

Could be a carb problem. It is nice if you can find a loaner to swap. Takes guessing out of the game. Some carbs are problematic.

 

[brendonv]

Thanks Brian. Did as you said, didn't take much on the 460. Cut some wood and seems to be good.

feel dumb

 

[SkwerI]

Cool. Probably related to the temperature changes, seems to take a bit more gas in the colder temps.

As far as the blower, it may be due for valve adjustment. That's the 4-mix type motor, right? My HT101 has valves but I haven't put enough hours on it for them to need servicing yet. If it does then I'll probably just drop it off at the dealer and let them do it. I'm not yet willing to learn the new technology and they can do it in a half hour.

 

[brendonv]

Yep, the 4 mix.

I've read somewhere that there was some kind of recall with the early models, not sure how old mine is, or where the cut off is.

I was just reading madsens about the tuning again. They mentioned pulsing if the low speed jet is out of wack. Check it out tomorrow I guess.

 

[Al Smith]

Cool. Probably related to the temperature changes, seems to take a bit more gas in the colder temps.

--but run they do in that cold dry winter temps if it's tuned right .

 

[sawinredneck]

Yep, the 4 mix.

I've read somewhere that there was some kind of recall with the early models, not sure how old mine is, or where the cut off is.

I was just reading madsens about the tuning again. They mentioned pulsing if the low speed jet is out of wack. Check it out tomorrow I guess.

Take that with a grain of salt, this is a 4mix, not a true 2 stroke, different animals!
Usually you have problems at high RPM or it's hard to start if the valves are out of adjustment. They aren't hard to adjust, just need to know the specs to set them and which valve is which. The exhaust needs more clearance than the intake normally, but a lot of them are set the same anymore.
It takes an allen wrench and an open or box end wrench and a feeler gauge. Most of the valve covers have O-rings on these so you don't need to replace them.
I'd look more at the carb though, sounds like a fuel issue to me, without hearing it.

 

[brendonv]

I wanted to get these on the site.

Stihl 4mix info.

First link is valve adjustment.

Second link is trouble shooting 4 mix engines.

Sweet!

http://www.cdcstihl.net/techtips/tips_v1n2_sm07.pdf

http://golftechs.us/Reference/4.pdf

 

[SkwerI]

Thanks for those, Brendon. Both are saved to my hard drive (with the titles changed so I know what they are).

 

[CurSedVoyce]

Thanks Brendon..
Ditto what Brian said.