MS 440 compression

[Rusty-880]

And my stock strong ms361 only made 85psi....
Different testers different readings

 

[kenneth davidson]

What should the compression be on the Stihl MS 440? Is 135 too low?
thanks

Just bought a used 440 off ebay. Needed bearings a seals. The saw wont run so I checked the compression. 90 psi cold. I will try new rings before buying a new piston and jug.

 

[lone wolf]

Just bought a used 440 off ebay. Needed bearings a seals. The saw wont run so I checked the compression. 90 psi cold. I will try new rings before buying a new piston and jug.

Pull it apart and inspect.

 

[Rockjock]

170 PSI @ 35 F no lube

 

[Brianlol]

If ur pulling apart to put bearings and seals and new rings won't do it to get the compression up might as well put a big bore kit on it. 90 psi is real low. Is it scored a little. I hope u got it at a good price bud. I know 160 to 170 is much
Desired but u can get away with 150 to 155 but if ur going through all the trouble I would want 160 to 170


Sent from my iPhone using Tapatalk

 

[cgraham1]

If ur pulling apart to put bearings and seals and new rings won't do it to get the compression up might as well put a big bore kit on it. 90 psi is real low. Is it scored a little. I hope u got it at a good price bud. I know 160 to 170 is much
Desired but u can get away with 150 to 155 but if ur going through all the trouble I would want 160 to 170.

I know it's already been said, but... If the cylinder is in good shape, there is no good reason to install an AM big bore kit. I would recommend a Meteor piston kit, or just replace the rings with new ones if the piston is still in good condition. There may be a few exceptions, but the OEM cylinder is almost always a better option than aftermarket cylinder kits. A meteor piston is usually around $40.

 

[Brianlol]

In a way I agree but it's all what one wants. I've put the big bore kit in many and in my own saw and it's not a huge difference but it is noticeable. Basically it turns an 440 to a 460 but if the cylinder is not scored, yes put a piston in it but if u have to get the jug, why not put the 52 mm in it . For the cost there it's not much.


Sent from my iPhone using Tapatalk

 

[kenneth davidson]

If ur pulling apart to put bearings and seals and new rings won't do it to get the compression up might as well put a big bore kit on it. 90 psi is real low. Is it scored a little. I hope u got it at a good price bud. I know 160 to 170 is much
Desired but u can get away with 150 to 155 but if ur going through all the trouble I would want 160 to 170


Sent from my iPhone using Tapatalk

surprisingly there was little to no scoring. there is an area where the nikasil is worn down to the aluminum so that could be the culprit. i dont get my rings for a week or so, so i wont know until then

 

[kenneth davidson]

If ur pulling apart to put bearings and seals and new rings won't do it to get the compression up might as well put a big bore kit on it. 90 psi is real low. Is it scored a little. I hope u got it at a good price bud. I know 160 to 170 is much
Desired but u can get away with 150 to 155 but if ur going through all the trouble I would want 160 to 170


Sent from my iPhone using Tapatalk

I was thinking the same for the big bore kit. This thing was 300 bucks, got maybe another 100 into it for seals, bearings, oil pump.

 

[kenneth davidson]

I know it's already been said, but... If the cylinder is in good shape, there is no good reason to install an AM big bore kit. I would recommend a Meteor piston kit, or just replace the rings with new ones if the piston is still in good condition. There may be a few exceptions, but the OEM cylinder is almost always a better option than aftermarket cylinder kits. A meteor piston is usually around $40.

the OE piston looks really good so I will see if the new rings work out. I will let you all know what the compression comes up to .

 

[Brianlol]

Good deal . Have fun and don't be afraid to figure things out for ur self. Take all the advice u can get and move forward. It sounds like u got it handled . I converted a 064 case to an 066 case by machining out the seating for the fly wheel seal so it could adapt to the 660 crank lolol soo many stihl dealers mechanics said to me I'm crazy and it can't be done but I did it anyhow and it's cutting like a mad dog. So every one is different but u decide what u can do with the saw . Remember to have fun with it


Sent from my iPhone using Tapatalk

 

[kenneth davidson]

So happy. My Caber rings came in from the guy that sells them on ebay. The guys is in Athens, Greece so they took about 3 weeks to get here. My old rings measured about 0.070 in and the new ones measure about 0.090 in across, so that seems like pretty good wear on the old piston rings. After fighting and fighting to get it to fire off a couple of weeks ago, I followed some of your comments about taking the cylinder gasket out. It would run for a second or two and the compression went up to 125 psi without the gasket from 90 psi. I tried the aluminum can gasket method, but it was so sticky with the copper spray gasket sealant. I just used permatex and sealed the jug right to the case. With the new rings installed today the saw fired off in about two pulls and seems to run nice. I was worried my porting job on the cylinder messed something up, but apparently it was just worn rings.

 

[Philip Wheelock]

The saw is for sale, and was told the compression reading was 135. And the claim was it was in the normal range...

More like 160 psi. My '05 MS440:

 

[kenneth davidson]

Hello All. I ran a couple of tanks through the new 440, running it easy, not full throttle. Yesterday, I decided to have some fun with it. I do not have a tach, but the saw seems to really take off after about 3/4 throttle. If you have any experience with dirt bikes, its how the YZ250 is tuned. We used to call it "being on the pipe". Does the 440 normally do this? All I can say is, its not like a linear rpm curve that I experience with my 391. Its like the rpm curve is linear, then it goes exponential. It is really an exhilirating feeling.

 

[gary courtney]

Hello All. I ran a couple of tanks through the new 440, running it easy, not full throttle. Yesterday, I decided to have some fun with it. I do not have a tach, but the saw seems to really take off after about 3/4 throttle. If you have any experience with dirt bikes, its how the YZ250 is tuned. We used to call it "being on the pipe". Does the 440 normally do this? All I can say is, its not like a linear rpm curve that I experience with my 391. Its like the rpm curve is linear, then it goes exponential. It is really an exhilirating feeling.

make sure it is not lean at that point, recommend tach

 

[kenneth davidson]

make sure it is not lean at that point, recommend tach

good idea. i was worried about that. thanks for the recommendation.

 

[AKDoug]

It should be pretty linear in the throttle, not "pipey" like a dirt bike at all. You have an issue of some sort if the revs just take off.

 

[kenneth davidson]

It should be pretty linear in the throttle, not "pipey" like a dirt bike at all. You have an issue of some sort if the revs just take off.

Thanks. I am glad you knew what I was referring to. I did port and polish the cylinder and port the muffler so I didn't know if that had something to do with it. I never ran a 440 so I wasnt sure if
they did that stock.

 

[lone wolf]

surprisingly there was little to no scoring. there is an area where the nikasil is worn down to the aluminum so that could be the culprit. i dont get my rings for a week or so, so i wont know until then

Anyone catch this?

 

[blsnelling]

You should not be consistently running any saw at part throttle.