Why do bike motors make so much more power?

[1Alpha1]

These pretzels are making me thirsty.

 

[cuttinties]

Don't forget the muffler design - the design of chainsaw mufflers likely is the most limiting factor. It is limited how much a larger carb and more transfer capasity helps, with chainsaw style box mufflers.

Even with a tuned pipe there's only so much room in a piston ported,short stroke crank case

 

[SawTroll]

Even with a tuned pipe there's only so much room in a piston ported,short stroke crank case

Yes - but it is the mufflers (space and practicality) that that dictated that basic design - and retrofitting a piped muffler can of course not reverse that.

 

[spencerpaving]

Bret, you need to get to KY in Sept.

You'd have a blast.......and I'd get to meet you.

I would love to...but with a 2 year old and a 4 month old my traveling is gonna be limited to day trips to gtgs for a while....the pa gtg is pushing it for me down and back makes for a long day

 

[spencerpaving]

This a pipe I just did on a 088 gas race saw for a competitor. ..it runs very very well...but won't hang with a good 125 bikesaw...like others have said two diff design motors

 

[Nitroman]

Well which engine would rev more short stroke.

Short stroke.

 

[wyk]

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[jar944]

That is a very strange port layout.

 

[Nitroman]

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Bingo!

Too bad most of you guys a real young and don't mess with snowmachines, then you'd have a good idea of what is going on. Some here do, some don't.

I remember Startingline Products, back when they made a big name for themselves taking the Polaris Indy 650 engine, a piston ported, 3-into-one pipe engine making about 90 horsepower, and welding manifolds on the case for reeds, and building individual pipes to take it up to 130 horsepower at over 10k rpm. After Polaris started making the case reed motors, the 580 XLT would only make around 100 hp with the 3-into-one pipe. SLP's pipes and tuning recommendations would get you 145 hp.
Even with the saw motors choked down, you have to have a carb to get air in, and the supercharger (the pipe), to help it out. There is only so much you could do with the design, but a bigger carb and pipe would be the biggest bang for the buck. But could you imagine Mikuni flatslides and big-assed curly pipes and big gastanks on a saw? Kewl to run for a little while, but all day?

If you really want to wring out all the changes that can be had to a motor, you need a way to measure the changes. Like the following:

And

Both those little monsters (35cc), are making around 12hp at 18k rpm. But you need a set-up to carefully and accurately measure subtle changes like the length and diameter of the stinger on your pipe.
Have fun.

 

[wyk]

That is a very strange port layout.

Bike engines allow much more creativity than saw engines. Which is one reason why race saw engines are often bike engines.

 

[treesmith]

Looks cool, can't see me using that near a chipper though

 

[jar944]

Similarities and differences. BTW its a 7900 on the left.

 

[jar944]

Bike engines allow much more creativity than saw engines. Which is one reason why race saw engines are often bike engines.

I meant that's a very strange layout for a bike

 

[wyk]

I think that's an old 250 ktm.

I meant that's a very strange layout for a bike

 

[wyk]

Looks cool, can't see me using that near a chipper though

You could power the chipper with that.

 

[cuttinties]

Boost ports, auxiliary exhaust ports, primary and secondary transfers paired with case volume, full circle cranks and carburetors that are capable of keeping up there's very little you can't do.

 

[wyk]

Boost ports, auxiliary exhaust ports, primary and secondary transfers paired with case volume, full circle cranks and carburetors that are capable of keeping up there's very little you can't do.

The stroke also tends to be longer as well. For the same RPM as a saw, you get more piston speed and more potential flow/port timing.

 

[cuttinties]

The stroke also tends to me longer as well. For the same RPM as a saw, you get more piston speed and more potential flow/port timing.

I've mentioned that a few times already. I didn't want to sound like a broken record. Lol

 

[STIHLTHEDEERE]

I like turtles.

i like the phrase ""I have a potty mouth""

 

[superw6]

Can't compare a race bike with 0 warranty and short piston life to a Tool aka chainsaw that can have multiple. Years warranty .


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