ms880 MS880 Rumbling noise

[KMWilliamsWoodcraft]

hey guys, i recently put a new meteor piston kit in my ms880 as the previous piston put in by the PO was a cheap Chinese golf brand and it was scored up and actually had a crack in it...it was running ok however was low on compression hence why i put a new piston in.  While i was doing this i also put in two new crank seals, exhaust and base cylinder gasket. Saw is now at 165 PSI compression HOWEVER there's now a strange rumbling noise ive not heard before and it wasn't there before, nor is it present on my other ms880. 

The saw seems to be running lean and doesn't want to idle if the screw is set low and it cuts out sometimes and bogs out. When it cuts out it can be hard to start again but will fire up easily if the choke is on... prior to the new piston it was actually running pretty well. I didn't remove the carb. In this very poorly taken video you can hear the low rumbling noise and it seems like its coming from the flywheel side. I swapped over the entire clutch side from my other 880 to this one and the noise didn't go away so i can clarify its nothing to do with that side. There is also 0 play in the crankshaft either side, no up down no left right its all tight so im assuming that means the bearings are good? but it sounds like a bearing rumble...

Has anyone experienced this before? Im going to try and get a vacuum/pressure tester and test for air leaks as i feel its running lean and then move on to the carb and check the impulse line, does this sound like a good plan of action?

cheers everyone!

 

and heres the old piston i pulled out...cylinder wasnt bad at all, came up good after a little scrub up.

 

 

[Stubby]

47 minutes ago, KMWilliamsWoodcraft said:

hey guys, i recently put a new meteor piston kit in my ms880 as the previous piston put in by the PO was a cheap Chinese golf brand and it was scored up and actually had a crack in it...it was running ok however was low on compression hence why i put a new piston in.  While i was doing this i also put in two new crank seals, exhaust and base cylinder gasket. Saw is now at 165 PSI compression HOWEVER there's now a strange rumbling noise ive not heard before and it wasn't there before, nor is it present on my other ms880. 

The saw seems to be running lean and doesn't want to idle if the screw is set low and it cuts out sometimes and bogs out. When it cuts out it can be hard to start again but will fire up easily if the choke is on... prior to the new piston it was actually running pretty well. I didn't remove the carb. In this very poorly taken video you can hear the low rumbling noise and it seems like its coming from the flywheel side. I swapped over the entire clutch side from my other 880 to this one and the noise didn't go away so i can clarify its nothing to do with that side. There is also 0 play in the crankshaft either side, no up down no left right its all tight so im assuming that means the bearings are good? but it sounds like a bearing rumble...

Has anyone experienced this before? Im going to try and get a vacuum/pressure tester and test for air leaks as i feel its running lean and then move on to the carb and check the impulse line, does this sound like a good plan of action?

cheers everyone!

and heres the old piston i pulled out...cylinder wasnt bad at all, came up good after a little scrub up.

 

Just a stab ( and I read that you have had it apart , new crank seals etc etc ) but maybe you have not found the original cause , probably an air leak and you are back to square one . Rumbling could be mains . 

[Muddy42]

I can’t say I can hear the rumbling noise, but maybe that’s the audio. I think I can hear the high pitched rattle sound of worn clutch springs though?

Edited 20 hours ago by Muddy42

[KMWilliamsWoodcraft]

15 minutes ago, Stubby said:

Just a stab ( and I read that you have had it apart , new crank seals etc etc ) but maybe you have not found the original cause , probably an air leak and you are back to square one . Rumbling could be mains . 

Yes perhaps your right, thats why i did the gaskets and crank seals, i guess a vacuum pressure test will tell me if theres still a leak.

do you mean main bearings?

cheers bud!

[KMWilliamsWoodcraft]

13 minutes ago, Muddy42 said:

I can’t say I can hear the rumbling noise, but maybe that’s the audio. I think I can hear the high pitched rattle sound of worn clutch springs though?

Yeah the clutch is known but not urgent at the moment. ill upload a video of my other 880 for comparison (ignore the chain break noises thats all fixed now) 

Edited 20 hours ago by KMWilliamsWoodcraft

[Muddy42]

2 hours ago, KMWilliamsWoodcraft said:

Yes perhaps your right, thats why i did the gaskets and crank seals, i guess a vacuum pressure test will tell me if theres still a leak.

do you mean main bearings?

cheers bud!

Agreed. Always pressure and vac test.

[spudulike]

Probably main bearings. The noise of bad main bearings resembles leaving the saw running on a concrete hard standing, a heavy rumble from the bottom end. 

With the top end off, the crank spinning should be super smooth when you rotate it holding on to the con rod with the piston not fitted.

Possibly debris has made their way in to the main bearings and won't show as play in the crank....if you do fit new, ensure you "de-stress" the bearings by whacking the crank on both ends after putting the cases back together again.

 

[spudulike]

In addition to my earlier post, a repaired seized saw should be pressure and vac tested, the carb overhauled and then tach tuned. You need to ensure that the reasons for the seize are eliminated otherwise it is likely to go pop again.

These tests will also ensure the new seals are sealing well.

On the running lean issue, are you seeing the idle racing, light plug colour, flat out revs too high?

[KMWilliamsWoodcraft]

46 minutes ago, spudulike said:

Probably main bearings. The noise of bad main bearings resembles leaving the saw running on a concrete hard standing, a heavy rumble from the bottom end. 

With the top end off, the crank spinning should be super smooth when you rotate it holding on to the con rod with the piston not fitted.

Possibly debris has made their way in to the main bearings and won't show as play in the crank....if you do fit new, ensure you "de-stress" the bearings by whacking the crank on both ends after putting the cases back together again.

 

Ok, ill take the cylinder off tomorrow and check all that.

38 minutes ago, spudulike said:

In addition to my earlier post, a repaired seized saw should be pressure and vac tested, the carb overhauled and then tach tuned. You need to ensure that the reasons for the seize are eliminated otherwise it is likely to go pop again.

These tests will also ensure the new seals are sealing well.

On the running lean issue, are you seeing the idle racing, light plug colour, flat out revs too high?

It never seized, it was just low on compression and i thought id repair before it went pop. I think it could have been overheated. 

the spark plug has a light grey colour and the saw wont idle low like my other one, it either has to be idling high or it dies.

thanks for your insights my man! cheers

[Stubby]

8 hours ago, KMWilliamsWoodcraft said:

do you mean main bearings?

cheers bud!

Yep .