BIG BORE POPPING AT HI REVS UNDER NO LOAD

[Phill Cresswell]

Hi there, hoping a clever few might be able to answer a technical question, I have recently put a big bore pot a nd top end on a MS 441, THE SAW STARTS GREAT TICKS OVER FINE AND GENTLY CUTS AT A STEADY TONE THROUGH BIG TRUNKS, MY QUESTION RELATES TO WHEN THE SAW IS REVED TO HI REVS WHILE NOT ACTUALY IN A LOG , IE UNDER NO LOAD, THE ENGINE SEEMS TO POP AT HI REVS LIKE A RACING ENGINE , CAN SOMEONE CONFIRM THAT A BB KIT CAN CAUSE THIS COMPARED TO A STANDARD CYLINDER.

 

[HarleyT]

Did you mess with the cam lobes?

 

[Phill Cresswell]

NO NOT AT ALL BUDDY.

 

[danimal]

Timing is retarded...
Or the coil is to far from da flywheel or its bad.

 

[blsnelling]

Most are rev limited.

 

[danimal]

Cutting out and backfiring are two different situations.

 

[JimMorrison]

Would not the one cause the other?

 

[alexcagle]

If your saw hits a rev limiter, it fires every other revolution to limit the rpm. This leaves unburnt fuel in the muffler, and can ignite inside the muffler from overlap flame burn from combustion.

 

[crabby cooter]

did you try a new spark plug?

 

[HarleyT]

Just out of curiosity, where does one get a "big bore" piston and cylinder for this model?

 

[alexcagle]

China....

 

[HarleyT]

Found this one on E-Bay........

http://www.ebay.com/itm/FORESTER-52...S411-MS-411-/371077574147?hash=item5665f26e03

It doesn't fill me with confidence in quality........

 

[Phill Cresswell]

Having checked the coil resistance today , all wiires disconnected, the two windings are giving a reading of 1.84 killo ohms, my other saws tend to be around 12, can someone confirm that this will cause week spark and saw to be lacking power.

 

[Definitive Dave]

Brad and Alex hit it on the head, that is the way the saw is supposed to act.
The rev limiting coil makes a distinctive sound like a pop.
ignore my language but you can clearly hear the limiter in this video

 

[trboxman]

So is that measurement scale from small furry kitten at 0 to coitus with one's mother at 10?

 

[ELECT6845]

WOW Dave the thing oils like a MF'ER LMAO

 

[Definitive Dave]

I had purchased a couple of nice used 3120s and had never started them up, so I took one up to Shawn that he was interested in.
We didnt have large mount husky bar that was really big enough, but he just wanted to try it out ot make sure everything was in good working order.
We pulled the muffler and the piston and cylinder looked pristine and it popped on choke easily.
Shawn fired it up for the first time ever as I was standing a good ways off and had just started the video.
As he piss revved it I got showered with drops of bar oil.
I was pretty surprised

When I tested the other one back at my shop a few days later I only had a large mount 16" bar for it and even with an aggressive square chain it was on the limiter even buried in the test log completely.
Those saws are no joke