Cleaned decompression valve - still sticks...

[DeanBrown3D]

Hello all, I cleaned the decompression valve on an MS460 today. It was quite blackened inside. I cleaned it with carburettor cleaner and the pin hole was clear. However, putting it back again, it still pops out on every starter pull. It was stiff, pushing in or pulling out.

Any tips here? Should I have lubricated the valve?

Dean

 

[Lakeside53]

Hello all, I cleaned the decompression valve on an MS460 today. It was quite blackened inside. I cleaned it with carburettor cleaner and the pin hole was clear. However, putting it back again, it still pops out on every starter pull. It was stiff, pushing in or pulling out.

Any tips here? Should I have lubricated the valve?

Dean

No lube...
Throw it out and fit a new one. If you ever have one break off and drop inside your cyinder, you'll wish you had. About $20 or so from the dealer.

 

[timberwolf]

Before you toss it, try drilling it out to 1/64. I had the exact experience on my 066, like I said before, once it was drilled out it never kicks, as opposed to sometimes kicked right from the day when it was new.

 

[Lakeside53]

The valve should not be "stiff" pulling or pushing by hand - it should be easy to move but with a distinct lock/unlock postion. Try a new one at the store and compare with yours.

 

[04ultra]

An ms-460 is an expensive saw is it worth the gamble. It's under $30 for new and about half of new to rebuild it if breaks off.. If it were my money I would just replace it like Lakeside53 said. just my 2 cents..

 

[timberwolf]

I suppose it is possible for the inside end of the valve to shear off and drop into the cyl, but I have neaver heard of it. But as the potential for dammage is high if it ever did sear off, it could be worth the 20-30$ to replace.

I would not put any lube that could cake on into it, but a bit of carb cleaner to break up the carbon, and a little mixed gas, can't see why not to give it a shot. the decomp valve sees gas and 2 stroke oil all the time.

If it is dammaged and thats whats bunging it up, there is no question, get a new one.

 

[DeanBrown3D]

Thanks all for the help .Timberwolf I did not ignore your earlier thread to drill it out - I just dont have a 1/64 drill that will fit in my press (little buggers are too skinny!) I will try the dremmel and also compare with a new one.

Cheers all,

Dean

 

[THALL10326]

That Decompression Valve

If Its Popping Up On Every Pull Then Its Time To Replace It Or Just Not Use It At All. The Ms460 Has A 16:1 Compression So Its No Surprise With That Much Compression Those Valves Tend To Pop Up. I Always Skip The Valve And Crank The Saw Without Using The Decomp Valve..

 

[Freakingstang]

I have a question.... I am not familar with the stihl's as I have never had any apart. The huskies are threaded into a boss into the cylinder, (out side, where the cooling fins are. Then inside the threaded hole, there is a cavity that has about an 1/8" hole that goes into the top of the cyl assy. The end of the valve is about 1/4-3/8" and wouldn't fit into the cylinder directly, but if it were sheared, then it could fall into one of the transfer ports, but the way it is designed, I don't think that is too likely.

I gues my question here is: Does the end of the decomp valve on the stihl's actually enter into the cylinder where if it would shear off, if it would fall onto the piston?

 

[DeanBrown3D]

THALL10326

Doing that would put my shoulder out - it really kicks

 

[THALL10326]

Welp I won't argu with you that a 460 is tuff to crank without a decompression valve. The elasco handle cushions the pulls abit but yes, your correct, the shoulder still takes a beating. Best thing to do is merely put in a new valve, not very costly. Part number is 1128-020-9400. Cost $21.80 list price.

 

[Lakeside53]

I gues my question here is: Does the end of the decomp valve on the stihl's actually enter into the cylinder where if it would shear off, if it would fall onto the piston?

Yes. They almost never fail, but if they do.....

 

[Lakeside53]

If Its Popping Up On Every Pull Then Its Time To Replace It Or Just Not Use It At All. The Ms460 Has A 16:1 Compression So Its No Surprise With That Much Compression Those Valves Tend To Pop Up. I Always Skip The Valve And Crank The Saw Without Using The Decomp Valve..

It's about 10.5:1, not 16:1

I always start them with the decomp to save my hands, and it works fine for me...

 

[DeanBrown3D]

Before you toss it, try drilling it out to 1/64. I had the exact experience on my 066, like I said before, once it was drilled out it never kicks, as opposed to sometimes kicked right from the day when it was new.

Timberwolf,

Do you remember if it was 1/64 or 1/32? I can't find 1/64, and that would seem exceedingly thin to me! Were you using a dremmel or something to do this?

-Dean

 

[davefr]

My 046 did the same thing. I used a #67 drill bit to open up the bleed orifice. Then I connected a piece of hose to the threaded end and hooked the other end to an air gun and gave it a blast of air from both ends.

Works fine now.

 

[Lakeside53]

Just a thought for you guys that are opening up the bleed holes with drills - make sure you aren't just compensating for a worn out sloppy decomp valve, Sure it might "fix" the problem, but... If you don't know how it feels worn or not, then head to your local stihl dealer and play with one on display.

Just FYI, the 044, 46 and 66 (and the MSxxx) use the same decomp valve. If there were problems with decomp bleed, I'd expect it on the 066 more than the 046 etc.

 

[timberwolf]

066 decomp valve is # 67 .032 to start with, I drilled it out to .052 # 55.

100% right 50% of the time or 50% right 100% of the time, sorry bout that, for some reson I had 1/64 in my head.

Left valve is .32, right one is .52 after it was drilled out.

Cant remember if it was drilled in the drill press, or by hand, but it was done at slow speed.

 

[1953greg]

hey guys, just fyi

i can vouch for the fact that the decomp valves do break. 2 broke for me last summer. the original (4-5 yr old) and the replacement (10 minutes old). the story can be read with search for "066 decomp woes". really wierd occourence. my assesment is as one of the top cover screws was missing allowing the plastic cover to viberate against the button and snap it off where the detent is cut in the stem. anyhow, it hasnt happened since i replaced the screw. luckly no critical damage to the saw although the piston n cylinder was pinged a little.

good day 1953greg

 

[DeanBrown3D]

TimberW -

0.052 is 1/19.2"

What do you think - I have several 1/16 bits, too big?

BTW - many thanks for taking the pic. Never seen such a small set of drills in my life!

 

[timberwolf]

I would think it ok, you should be able to spin the drill bit down a bit by running it with the side againts some sand paper.

my 066 has more displacement and higher comp so maybe the stock 46 would be best with a tad smaller hole. if the hole was too big it cold drop the compression too much and make it hard starting.

Drill bit set is only 5$ from Lee Valley, I have made a lot of use of that set.