This 066 Grenaded........What The Hell Happened???????

[komatsuvarna]

Non of us are experts on the matter of detonation or piston erosion. However with experience and some knowledge we can make a guess. I've seen pistons look similar to both examples above.

Rogue's piston exhibits what I know to be classic detonation.

Komatsuvarns's saw I'm not sure about. To me it looks like the piston got too hot on the exhaust side, which means it was tuned too lean IMHO. Non of this has anything to do with the oil itself.

I've talked about this and have brought the subject up before. In a work saw, how much do you really gain pushing compression passed say 180 psi for an example. Yes you will make a bit more power, but at what cost? Most of the old school saw builders will tell you a true production saw with lots of compression will not last long. A firewood guy that knows how to tune a saw likely won't have any issues.

There's a big learning curve here and I myself, has a long way to go.

I agree Andre. I'm fairly sure I didn't have that saw tuned to lean. It has the rev limited coil and I always just tune it to about 14,000 and go cutting. That one day I remember in particular, It was hot out side, high humidity, I was probably running a little too much bar and chain and probably over working the saw a little in big. That combined with the extra power and compression I fell is what done that. I know the saw got hot.......maybe it was on the verge of too lean for the conditions I was in. My back was hurting like hell and I wasn't carrying around a big ass saw .

 

[Andyshine77]

I run the smallest saw I can, for as long as I can before grabbing something bigger myself.

In your pics it looks like I see a bit of a brown carbon like spot below the ring on the exhaust side of the piston. Am I seeing that correctly? If so this is a sign the saw was running on the edge. Sometimes in hotter ported saws that will happen even with proper tune, the engine simply can't dissipate heat fast enough.

 

[komatsuvarna]

Yes your seeing correctly.

HEY! I just thought of something else too! That saw had the factory Zama on it for awhile. On that same job it got to acting strange with the zama and I swapped it out for a HDA199 one evening after I got off work, and took it back the next day to work. It was acting like it was running out of fuel, wouldn't hold a tune, and wouldn't idle right, was out 2.25 rounds on the high side, so I put a new HDA199 on it and problem solved. That carb could have caused it to lean out in the cut I guess, and caused that..... That sounds more likely, I'm really not one to lean a saw out for all it's got.....not a work saw. I like'em fat!

I really need to put a black coil on it so I can hear the tune constantly I guess......

 

[Andyshine77]

Sounds like you found your answer.. I'd check the tank vent as well to be safe, the 346's had a run of tanks that had improperly drilled vent holes, they would go lean @ WOT. I like the black coil's on the 346, they seem to handle the rpm's just fine. Saws like the 390 do fine with a stock blue limited coil, or a blue coil from a higher revving saw like the 346.

 

[Mastermind]

I like to use the 372XT coil on the 390.....

13,500

 

[mdavlee]

On the 346s I messed with I drilled an extra small hole under the tank vent to let it vent more.

 

[Trx250r180]

don't some huskies have a vented fuel cap to resolve that problem ?

 

[Andyshine77]

don't some huskies have a vented fuel cap to resolve that problem ?

Not that I know of.

 

[Mastermind]

I've heard of a vented gas cap......but never found one.

 

[Trx250r180]

I think Simon posted the part # a while back in his thread

 

[Trx250r180]

372 Issues
If you don't mind spending a bit of money for a nice feature, buy a 503-8280-04 vented fuel cap.
Post by: Simonizer, Aug 24, 2012 in forum: Chainsaw


wow the search thing works fast now

 

[LegDeLimber]

That little spot on the skirt was on there the day I bought it. They tuned it at the dealer, I brought it home and gave it a muffler mod and it was there then. They's no transfer spots.

Ahh, Well it's not the first time jpeg compression
and monocular diplopia have bit me in the as.. er... uhm "opinion".

This damned vision glitch makes trying to guide a burr tough now.
had to give up vernier scales for all dials a few years ago too.

Just bare with me if ya can fellows!!

 

[Mastermind]

372 Issues
If you don't mind spending a bit of money for a nice feature, buy a 503-8280-04 vented fuel cap.
Post by: Simonizer, Aug 24, 2012 in forum: Chainsaw


wow the search thing works fast now

I did a Google search and found it at parts tree too.

 

[Cfaller]

any problems with the h1r seperating from the fuel in cold weather ? i had dirt bike oils in the past that would ,i think it was 927 maxima

H1R mixed at 32:1 at -18 F.

 

[albert]

87 octane is all I ever use.

If you use 87, with no additives, I suspect you've had or will be seeing detonation damage.

 

[Mastermind]

If you use 87, with no additives, I suspect you've had or will be seeing detonation damage.

Why?

 

[Andyshine77]

H1R mixed at 32:1 at -18 F.
View attachment 321380

Separation is normally associated with castor oils, or oils with castor in them. Maxima castor 927 being one of such oils. http://www.maximausa.com/shopping/index.php?main_page=product_info&cPath=2&products_id=13

 

[albert]

Why?

87 can cause damage on a stock saw under tough conditions. Add more compression, timing, heat, load and you increase the main things that cause it. Detonation harms more than piston tops. Do you spike your fuel or use it as it come from the pump?

 

[Mastermind]

I use Torco race fuel concentrate.

 

[mdavlee]

I've been using 87 with no additives in saws with 200 lbs of compression and none have shown any damage 5 gallons of mix later and one had at least 75 tanks thorugh it.