Daydreaming about tuned pipes

[hal9000]

Morning all,
Right off the bat, this is more of a "what if" thread than anything. I don't have the time for another project (but I always have time to think about silly stuff like this)

So, I work at a University, and there are a handful of those DIY motorized bikes around the campus running small (50-80cc I believe) 2 stroke engines. The other day, I noticed the physical similarity between those motors and the motor in my MS390. Of course that got me wondering....

I know that there are tuned pipes available for those conversions, and the similarity got me wondering if there's any chance that the pipe from one of those bikes would be even close to appropriately sized for a similar displacement chainsaw. I had the chance to handle a broken one a while back and holding it up against my saw, it was even configured pretty well in terms of shape.

I know that pipes are designed around a specific rpm range and displacement. I don't know enough about the math to evaluate the performance potential of one of those pipes, but I figured that since every piped chainsaw I've seen looks like a custom job somebody around here might know how far off center this idea is likely to be. I wouldn't expect an off the shelf fit, but if it could be made to work with slight modifications (IE, mounts, changing the flange or headpipe, maybe a little sectioning), it might make a fun weekend project for someone's knockabout saw (Plus I'd love to see someone give it a try!)

Thanks guys.

 

[Homelitexl903]

Check out a thread by bikemike. It was called Project pipe the echo.

 

[Chris-PA]

@bikemike

 

[hal9000]

Thanks for the link. At least it's not an original thought. I'll have to reach out and ask if he got anything other than a cool sound out of it....

Correct me if I'm wrong here, but aren't smaller pipes (relative to the engine of course) biased towards higher rpm? Bikemike's pipe is way bigger than the broken one I looked at. Maybe a matter of a torque pipe vs a high end pipe...? If I can find that one (the headpipe flange was broken off) again, maybe I'll bring it home and throw it on the shelf.

 

[blsnelling]

 

[hal9000]

Did you build that yourself? If so did you use one of the pipe design programs?

 

[blsnelling]

No. A former AS member, Gink, built it for me.

 

[Chris-PA]

"Daydreaming about tuned pipes"

A pipe dream then....

 

[RedneckChainsawRepair]

There are some good pipe makers out there. Dont know if any of them left here or not.

 

[RedneckChainsawRepair]

Few I was shown for Helsel saws.

 

[mountainlake]

Hows this Steve

 

[Blokhead]

I built these pipes myself;

 

[hedge hog]

What motor?
250's were the only 2 cylinders I remember.
The seat tells me you might want to get your chin close to the handle bars


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[jeepyfz450]

@spencerpaving builds tuned pipes. I have a few of them that are really nice. I have modded a dirtbikes expansion pipe before with decent results. The tuned pipes he builds are much better performers.

 

[hal9000]

I have modded a dirtbikes expansion pipe before with decent results.

Details please.... If it came down to it I wouldn't be interested in "maximizing performance" in the sense that my say is still just for firewood cutting anyway. So the custom built competition pipes that stick 2 ft off the side of the saw wouldn't be practical. But something that hugs the side and adds a bit of hp or rpm vs a stock box muffler... Well one can always dream.

I spent last night doing a bit of reading/research on pipe design last night. I'm pretty sure that broken pipe is still around and if I can find it I'll grab it and a) take a few photos to show why it had me thinking along these lines, and b) make a few measurements to see if there's even a chance it might work out.

 

[jeepyfz450]

I have some pics somewhere. It was a kx80 pipe just built a header and cut it to wrap around the saw. It's mocked up for a 440 460 Stihl. What are you looking to build one for?

 

[hal9000]

Honestly, it's more just an interesting line of conversation at this point (hence the title of the thread). I was intrigued by the close physical fit of the one pipe I looked at when held against my stihl ms390. With a different header, and one strategic cut and 90* twist in the belly, it would nestle very nicely against the side of the saw. I started the thread b/c I was curious if anyone had modified pipes from other small engines, what they've done (those questions have been answered), and what the results were in terms of performance.

I don't currently have any car projects to work on, so my thoughts along those lines are aimed at my saw for the moment. When I rebuilt the saw earlier this year I warmed it up a little with a mild port/polish job, and a little timing advance. So if I have a free weekend sometime and have a free pipe lying around that would warm it up a little more without making it unwieldy in the woods, it might be a fun thing to put on my list of "someday projects"

 

[jeepyfz450]

Ohh ok I see. With mild port work it will be a little faster but incredibly louder...

 

[hal9000]

Mine has a muff mod anyway so it's a bit louder than stock, but your comment brings up another question.... Does anybody know how much a silencer/spark arrestor affects the way a pipe works vs. just an open stinger? From my motorcycle days, I'm assuming a minor negative impact, but it's dry out here and our USFS folks are serious about spark arrestor requirements.

 

[jeepyfz450]

Kx pipe is on the bottom

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