Fin loss on cylinder, how much is too much?

[fearofpavement]

Im running a 390xp that I crushed several days ago and rebuilt from the crankshaft up basically. It has 4 or 5 of the top fins broke off but since its my saw, I crushed it, I fixed it back, so I decided to run it and see what happens. Ive cut somewhere around 30,000 ft with it in the last few days since the rebuild and its doing fine. If it ends up frying the top end, I will replace it then. The way I look at it is that every dollar it makes me between now and meltdown is free money.

Keep us posted in this thread how it lasts. Lots of "opinions" on how much fin loss is acceptable but it would be nice to collect some actual field experience.

 

[Huntaholic]

Keep us posted in this thread how it lasts. Lots of "opinions" on how much fin loss is acceptable but it would be nice to collect some actual field experience.

I cut another 20K or so with it this week so that brings it up to over 50K bd ft Ive cut since the rebuild. My cable puller has nicknamed this saw Lazarus since its been brought back from the dead twice now.

 

[Fish]

Keep us posted in this thread how it lasts. Lots of "opinions" on how much fin loss is acceptable but it would be nice to collect some actual field experience.

Brad is the final authority on acceptable fin loss!!!

 

[MustangMike]

I'm wondering, since you seemed to have all the broken fins, if JB Weld would have held them.

With the AM tank handles, lube the control levers (I use Fluid Film) and I mod the end of the control lever to get the choke to work. The angle of the choke lever on the AM carbs is slightly different than most OEM. I've drilled a hole and inserted a piece of wire at the correct angle and had it work. I would then glue it in place (JB Weld or PL Premium, etc). Part of the PITA of working with AM stuff.

On the plus side, I like the translucent fuel tanks, and the AM flippy caps don't leak (like most of the AM screw in ones).

 

[Stump Shot]

I'm wondering, since you seemed to have all the broken fins, if JB Weld would have held them.

With the AM tank handles, lube the control levers (I use Fluid Film) and I mod the end of the control lever to get the choke to work. The angle of the choke lever on the AM carbs is slightly different than most OEM. I've drilled a hole and inserted a piece of wire at the correct angle and had it work. I would then glue it in place (JB Weld or PL Premium, etc). Part of the PITA of working with AM stuff.

On the plus side, I like the translucent fuel tanks, and the AM flippy caps don't leak (like most of the AM screw in ones).

I'm not an engineer, but I do not believe that epoxy will transfer heat like aluminum does. So there would be no point other than looks. Welding would transfer heat normally if the welds are 100%.
Otherwise on the subject I have used broken fin cylinders on my saws and saved the good ones for others. While I'm not worried about my saw as I can fix it if it does go haywire, I wouldn't do that to someone else.

 

[Huntaholic]

Another 40K ft or so and its still running fine.

 

[M2theB]

Checking into this thread to see if there any updates?
I came across this 272 and couldn’t pass on it.
It looks to have a bad seal on the FW side and has a tiny amount of xfr
I’m leaning towards running it and see how it goes, after some soft goods make over.
The breaks look old and hours on them already.

 

[MustangMike]

I'd run it.

 

[Mastermind]

I'd run it.

Me too.

 

[Wonkydonkey]

Me three

 

[fearofpavement]

So I thought I would make an update on this pair of MS460's. Turns out I decided to put them back together with the existing engine and thought I would run them thoroughly before I returned them to the customer. Long story short, the customer never picked them up when I informed him they were ready. So while I was waiting for him to get around to it, I ran the snot out of them. We had a major tornado near here (in Newnan, GA) and I ran a lot of hours on these two saws. I had previously done some extensive tree jobs with them. Neither of them exhibited any detrimental signs due to the fin damage. These saws were all OEM engines but all the plastic and handles were aftermarket.
Flash forward to recently. I sold one of the saws to a customer that has purchased other saws from me in the past. That recouped the significant investment in parts. It's been a few years and the original owner never got in touch with me. I still use the other one. (The saws are so similar, I'm not even sure which one he picked out of my row of available saws.) So anyway, even though the fin loss on these two MS660s was significant I've run lots of hours on both of them and they seem fine.

 

[jakethesnake]

I think it would take an unreasonably hot run time for that to make any difference. I’ve ran some saws with greased up fins which would likely insulate the saws and keep heat in with no problems.

if it was 103 degrees out and I was cutting stumps flush with a dull chain. Well yeah maybe the. It would matter

keep cylinder clean and it should exchange heat just fine.

I’ve got a couple air cooled 4 stroke motors that lived around dry fertilizer. The fins have all grown together. Still never experienced overheat issues

my opinion which is worth just one cent. I’d just about run any cylinder with several broken fins. Just keep the grime blown off. Especially after reading this thread