RPM's......How much is too much after muffler mod????

[RED WOOD]

I picked up a Trail Tech tach/hour meter and hooked it up to my MM'd MS 290. After I got it warmed up I held it WOT for a few seconds to see how many RPM's it was running and the tach read 13,950. Stock max. rpm is 12,500. It have been running it like this for a while and it seems to be 4-stroking at WOT but is this too many RPM's for this saw to take??

On a separate note I hooked the tach up to my stock Huskvarna 450 and checked it out and the top RPM is 12,480. Looked in the owners manual and it doesn't show a max rpm only max power RPM of 9000. Does anyone know what the max RPM should be for this saw????

 

[moody]

Tune it to 4 stroke at wot don't worry about rpm

 

[Jimmy in NC]

Don't worry about it as long as it's 4-stroking! Saw an 026 turning well over 16k last weekend and it's holding up fine.

 

[locofrog]

Was that some of the. Guys from down here jimmy? I know of a couple 26's down here with expansion chambers that throw wild numbers. And I ran a 046 like that a while back.

Loco

 

[RED WOOD]

Don't worry about it as long as it's 4-stroking! Saw an 026 turning well over 16k last weekend and it's holding up fine.

Thanks for the reply....anyone got any ideas on the Husky 450 max RPM?

 

[struggle]

14K on a MM MS290 is lean it would seem to me. It should be under 13K for sure.

 

[Adirondackstihl]

Make sure the saw 4-strokin and not bouncing off the rev limiter.

 

[RED WOOD]

Make sure the saw 4-strokin and not bouncing off the rev limiter.

Never heard of a MS 290 with a limited coil??

 

[RED WOOD]

14K on a MM MS290 is lean it would seem to me. It should be under 13K for sure.

I could fatten it up to 13K and see how it is in the cut. It is 4-stroking now, though.

 

[Stihlofadeal64]

One of the things the muffler mod is going to do is give you more grunt in the cut. It should still 4 stroke at the top end though. The tach is going to help you manage your numbers a little more efficiently. I'm not comfortable saying anything near "don't worry about the rpm's" --because the faster it turns the more heat it generates. If you removed the limiters on your carb you should be able to tweak the high side and readjust the low side to be ok. (Just for laffs and giggles have you took a look at the piston through the exhaust window since you have been running it like this. For peace of mind I believe I would remove the muffler and just make sure that the saw is not lightly scored.) Happy Sawing. :msp_thumbup:

 

[luckydozenfarm]

You want to know what I do on my modded muffler saws? I tune them to spec RPM or lower, then I get a decent sized log out and make a first pass listening to intermittent 4-stroking. Then I tune it a tad leaner and leaner until I don't hear it anymore. Usually works fine from there. I would say if you are 14K and above after this method I would be surprised. But it all depends on what you did to that muffler. LOL

 

[rmh3481]

12,500 no load w/bar and chain.

 

[B Harrison]

It sees odd, but specs I am looking at are 9600 for the max rpms on a 450. Last Baileys circular second page.

240 is also low at 9000
455R running 13k
460 13.5k
445 13k

So for some reason the 450 isn't a fast saw at all, I hope its got a lot of guts in that 50 cc engine to back up the non impressive rpms.

 

[Chris-PA]

It sees odd, but specs I am looking at are 9600 for the max rpms on a 450. Last Baileys circular second page.

240 is also low at 9000
455R running 13k
460 13.5k
445 13k

So for some reason the 450 isn't a fast saw at all, I hope its got a lot of guts in that 50 cc engine to back up the non impressive rpms.

The numbers you are talking about are no-load WOT - they don't mean anything about how fast the saw is under load. It is just a means of setting the fuel air mixture, nothing else. It is theoretically possible to lean out a saw and increase the no-load WOT rpms and actually slow it down under load in the cut (because the mixture is then too lean).

No-load WOT rpm numbers have one purpose and one purpose only - it is a way for the factory to specify the fuel mixture on a stock saw at lower rpms in the cut, because they have characterized the way that stock saw behaves. They know that if they tell you to set the no-load WOT rpm at X, then at much lower rpms under load the mixture will be correct. Once you modify the saw you change that relationship and the number means little - you have to tune in the cut.

 

[blsnelling]

It sees odd, but specs I am looking at are 9600 for the max rpms on a 450. Last Baileys circular second page.

240 is also low at 9000
455R running 13k
460 13.5k
445 13k

So for some reason the 450 isn't a fast saw at all, I hope its got a lot of guts in that 50 cc engine to back up the non impressive rpms.

That's the RPMs where it's HP rating is, not max RPMs.

 

[BloodOnTheIce]

Make it fat wide open no load, and then make sure it cleans up under load.
Most muffler mods I have running 12.8K-13.2K rpms.

 

[bplust]

It sees odd, but specs I am looking at are 9600 for the max rpms on a 450. Last Baileys circular second page.

240 is also low at 9000
455R running 13k
460 13.5k
445 13k

So for some reason the 450 isn't a fast saw at all, I hope its got a lot of guts in that 50 cc engine to back up the non impressive rpms.

The 240 and 450 specs you're quoting are what the should turn at IN the cut. The numbers you have for the others saws are for revving them with no load beyond a properly tensioned bar and chain.

 

[Chris-PA]

That's the RPMs where it's HP rating is, not max RPMs.

Exactly - WOT rpms should be neither impressive nor non-impressive - they are just a number used for tuning.

 

[luckydozenfarm]

This is also true for any mod to the saw. Big bore kit, high flow air filter, sprocket change, or even bar length change. Once the saw is under load in the cut things change. Once you know what to listen for, you can make changes. Just like a guitarist knows what each note sounds like and can tune by ear. I blew up a few saws before someone showed me.

 

[RED WOOD]

That's the RPMs where it's HP rating is, not max RPMs.

Exactly, 9000 rpm is where it makes its max hp, not the max rpm under no load. I am thinking the 450 is pretty close to where it should be at about 12,500 under no load. I have not modded the muffler and it is 4-stroking at WOT but not in the cut.