Maximum "safe" RPM?

[SawGecko]

Hello alll, first post of a fellow saw nerd and long time lurker, so I apologize in advance as I'm nearly certain I've already done something wrong. Anyway, I've seen a few similar threads, but nothing that quite answers my question.

Has anyone ever centrifugally exploded a flywheel? I've seen some modded saws turning 16k and I know that Stihl's lawyers say 12k max. I understand that higher speed equals faster wear, but I'm not really concerned about that. Rev limited coils notwithstanding, what is the typical failure mode of overspeeding? Obviously a melted piston is most common, but whats the next weak point? Broken Connecting rod or crank? Bearings? Or an exploded flywheel?

 

[jr27236]

I have never heard of an exploding flywheel due to over revving and would be quite fearful if that happened, because im sure it would cause some serious injury. I would think the connecting rod would be the next to go before anything else. But to Rev at an rpm to cause these failures would be intentionally crazy in my opinion.
Did your flywheel break?

 

[SawGecko]

I've not seen a chainsaw flywheel blow, but I did see a POS WeedEater branded trimmer blow one. It was fine, normal speed, and then the flywheel was no longer in one piece or attached. After looking over the pieces, it looked like a casting flaw allowed a crack to form. But that trimmer was obliterated. The coil mounts broke off at the cylinder and knocked a hole all the way throught the cylinder wall. Pretty well toast. I got luck that the peices flew away from me. Sounded like a 20 gauge.

I guess I'm just paranoid now about ignoring the lawyer recommend speed. Just wondering if anyone had seen anything like that before. Especially on bigger engines than the little 20 something cc weedwacker

 

[jr27236]

What saw or machine are you worried about tuning to such high rpms?

 

[Ryan'smilling]

12k is slow. Maybe that'd be the max for some older stihls or maybe an ms880 (just speculating), but just about every modern saw maxes out higher than that. My stock ms 460 four strokes pretty hard at 13.7k. Tuning most any stock saw at 12k would really limit the performance.

 

[ironman_gq]

I've got a modded 044/046 hybrid that is perfectly happy at 15,500, pulls 12-13k or so in the wood. My mostly stock 026 will pull 15k with just a touch of 4-stroking, factory spec was 14k. It's perfectly normal for small 2-stroke motors to spin this fast and as long as they're designed for it it's safe, they do build in a pretty healthy safety margin in components that can come apart at high speed.

 

[bikemike]

12k hmm slow il run my oh26 in the lower to mid 17k with the old felt air filter more with the mesh. flywheel stiHL intact

 

[SawGecko]

Yeah, it seems I'm just being overly paranoid.

 

[sawfun]

346 Husky's are supposed to go over 14,000 stock. I have a Dolmar 5100 that even says "Speed" 14,500 on the top in big characters from the factory. Those are only 50cc machines, several larger ones are rated well over 12,000.

 

[82F100SWB]

242 Husky was 15,500 stock.

 

[bikemike]

346 Husky's are supposed to go over 14,000 stock. I have a Dolmar 5100 that even says "Speed" 14,500 on the top in big characters from the factory. Those are only 50cc machines, several larger ones are rated well over 12,000.

The oh26 pro was stock tune no load 14,500.

 

[trappermike]

Look at factory reccomendations-they really know since they designed the thing.Guys who say they rev them to 15,000 or more are wrong,and I test race saws in the cut and they don't turn as high in the cut as they(********) claim. These BS'rs blow up saw after saw and have NEVER won one single race in an international Loggers Sports competition
Ridiculous rpm claims and a bunch of hot air!

 

[bikemike]

Look at factory reccomendations-they really know since they designed the thing.Guys who say they rev them to 15,000 or more are wrong,and I test race saws in the cut and they don't turn as high in the cut as they(********) claim. These BS'rs blow up saw after saw and have NEVER won one single race in an international Loggers Sports competition
Ridiculous rpm claims and a bunch of hot air!

What size logger race saws are you talking about. Next time ur test running them please make some vids cause we all like vids

 

[82F100SWB]

Rpm does not magically make power, I run into it in the snowmobile side of things all the time. Clutch so it spins to the moon and wonder why they cant keep the bottom end together. Porting determines where power is made. Spinning past it is just making noise and reducing reliability. Without significant changes in port timing, significant changes in rpm are not required.

 

[bikemike]

Look at factory reccomendations-they really know since they designed the thing.Guys who say they rev them to 15,000 or more are wrong,and I test race saws in the cut and they don't turn as high in the cut as they(********) claim. These BS'rs blow up saw after saw and have NEVER won one single race in an international Loggers Sports competition
Ridiculous rpm claims and a bunch of hot air!

 

[sawfun]

Rpm does not magically make power, I run into it in the snowmobile side of things all the time. Clutch so it spins to the moon and wonder why they cant keep the bottom end together. Porting determines where power is made. Spinning past it is just making noise and reducing reliability. Without significant changes in port timing, significant changes in rpm are not required.

I dunno, maybe it was the funny fuel, but I'm pretty sure the nitro 088 I ran was at 17k rpm and heading north in a hurry. That saw just kept pulling harder like it HAD no power curve. Then again, as I recall from cars, nitro kinda tends to bend the rules that way. Those things pull until they go nunclear. Works saws, hopefully not.

 

[bikemike]

I dunno, maybe it was the funny fuel, but I'm pretty sure the nitro 088 I ran was at 17k rpm and heading north in a hurry. That saw just kept pulling harder like it HAD no power curve. Then again, as I recall from cars, nitro kinda tends to bend the rules that way. Those things pull until they go nunclear. Works saws, hopefully not.

Yeah I was wondering if you would jump in on this.

 

[82F100SWB]

Funny fuel does all sorts of fun stuff due to its different burn characteristics.

Sent from my NABI2-NV7A using Tapatalk

 

[82F100SWB]

Don't get me wrong, my dad always has the story of when he burnt up his 254 and all his dealer had was a 238. Story goes in 3 weeks time when he went to get another 254 and the husky rep happened to be present; dad had done his muff mod and tuned the hell out of it, no 4 stroking in his tuning plam , that's for sure. The rep heard the 238 being run for a trade check, requested the shop owner(1 man show) tach it. Dad had it set on the firey edge of meltdown for limbing speed, spinning 19,800. Trade in never happened, rep bought the 238 on the spot, Dad's new 254 was purcased, a and the 238 made its way to a lumberjack competition and didn't last the weekend.

 

[trappermike]

Normal high quality ball bearings(let alone rod big end bearings)were never designed for 14,000 t0 15.000 plus!Anyone claiming more I dont believe and wanna see tach results after extended rpms.
First of all a moodeed work saw has a toque and horsepower peak around 10,000,hotsaw max cutting rpm around 11,500. These are saws that win international competitions. For someone to tell me their saw revs 13 to 19 thousand under load is proposterous.Go to an i9nternational competition,mount a tack and show me this happening,and winning a race.This increasing rpm ******** claims have proved no worth.
Mainly the bearings will disintegrate,check manaufacturers specs on those bearings,-they dont go anywhere NEAR thoae highs-they fail according to factory.
Yeah my 066 still turns 20,000 rpm and 18,000 in the cut....yea...