Yamaha kt100 homemade chainsaw hot-ish saw

Wesspur
Rugged made
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Yeah, thats the type. If I tapped right off the exhaust tho, I wouldnt necessarily need the pump. The exhaust pressure would be just enough to pressurize the oil tank.

Main reasoning behind the pump is that it'd be metered, and not possibly purge the entire tank too fast.
 
McCleach said:
Yeah, thats the type. If I tapped right off the exhaust tho, I wouldnt necessarily need the pump. The exhaust pressure would be just enough to pressurize the oil tank.

Main reasoning behind the pump is that it'd be metered, and not possibly purge the entire tank too fast.
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Another way you could do it is just with a check valve right off the crank case. A lot of small vintage saws used this style as it was cheap and easy. So when the piston is on the way down there is positive pressure in the crankcase. Use that to pressure up the oil tank. Then you simply need a valve on the output to adjust the flow Just food for thought
 
Bill G said:
Something that I have always found interesting about the KT 100 and the Comer K80 kart engines is their physical size and the cooling fins. Take a look at them compared to a Mac 101 or West Bend 820. The Yamaha and Comer are smaller in displacement but much larger in physical size. They should run a lot cooler.
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That’s because they are free air. No fan
 
McCleach said:
Looks like mcculloch actually used a pulse pump oiler, on like a 610 and 650.
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Yes many macs used a diaphragm pump. My pm605 is like this, with a manual bypass oiler as well. If I'm being honest, my older manual oil saws didn't wear bars out and I doubt it would be a big issue for you with a manual oiler either.
 
Decided to try out exhaust pressure to the oil tank as a bar oiler to start with. Thats what they do on hot saws, and its very simple. If its not all its cracked up to be I'll switch a pulse pump.

My main worry is if the tubing will pick up too much heat off that copper line. Only one way to find out. Its all thick pulse tube that came with the motor.

Once I get the other guide bar in the mail, I'll be able to locate and rout the oil line and valve through the mounting plate.

Im going to make my own fuel clunk/filter. I just dont like the general garbage thats out there.
 

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McLeach said:
Decided to try out exhaust pressure to the oil tank as a bar oiler to start with. Thats what they do on hot saws, and its very simple. If its not all its cracked up to be I'll switch a pulse pump.

My main worry is if the tubing will pick up too much heat off that copper line. Only one way to find out. Its all thick pulse tube that came with the motor.

Once I get the other guide bar in the mail, I'll be able to locate and rout the oil line and valve through the mounting plate.

Im going to make my own fuel clunk/filter. I just dont like the general garbage thats out there.
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The standard walbro clunks are actually very well designed and quite simple. May be a tad small for 100cc, but it is what I've ran on 98cc alx full port engines in large scale rc. Never had a fuel supply issue. Not quite the load that a saw should be under though.
 
I'd been waiting for the second guide bar so I could use it to match the oil ports for the homemade elliptical bar. Damn thing had been sitting at the post office for two weeks! The seller never gave me a tracking number, and the post office never gave me any slips saying they wouldn't deliver it. I guess they can't drive in the snow. There was a rather large line of people at the counter that also simply quit getting their mail with no notice.

Anyway, it's a stihl 3002 pattern. I put the oil journal n stuff in there and sealed the tank up. Almost ready to fire the engine up! Last thing is to finish the kill switch and thermal shutoff switch. It will automatically kill the motor if the head goes over 450 degrees. Waiting on the thermal glue tho...
 

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Alright, I fired up the engine today. It started real easy and runs great. Doesn't have that brash throaty sound of the old 125 mcculoch, but boy is it responsive. Def sounds like a yamaha.

I ran out of daylight, and it got pretty cold out. Spent some time inside to make the 117 DL chain and put the cannon bar on it. Everything is ready.

The homemade eliptical bar will have to wait tho. I screwed up the taper at the nose leading to the roller. It's to narrow and there's a gap. I guess I wasn't paying attention. 😑 I can fix it, but its gonna take some machining time.

The bar oiler does technically work, but not much was coming out. I wasn't going to rev it hard without load tho, so I know it can do better. We'll see. Not sure if I'll get around to trying it in a cut tomorrow.
 

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Very nice thought through design, I used to do contract tree felling in the early seventies using the Mc SP125 family of saws. One of them was the 101b kart powered saw which was just slightly disappointing because of the power fall off at full throttle. IMHO, kart engines are made for acceleration out of the turns and onto the straights and I don't think this is what makes them a formidable powerhead. Again IMHO, I think a chainsaw needs to run at a steady near full throttle where its design demands max hp & torque? Using identical chains & rims, I would race my leaned out 125C with the 101b and the 125C most of the time would whip the kart powered saw.

Hey, good luck with your cool invention, it should be a ripper!!
 
McLeach said:
Hopefully the 16000 rpm makes the difference.
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Wow! I am totally out of touch with the modern kart & hot saw world, do they make chains that actually cut at that wild chain ipm? 16k rpm is nearly twice the speed of the old McC's I used to run.
 
Not sure if the chain will make it that far, but I'll find out 😬. Thats why I only did a 10 tooth sprocket. Real hot saws with dirtbike engines have something like 20 tooth on them, to get that high of chain speed.

There's a video of a kt100 saw out there from years ago. Just google kt100 chainsaw.

I couldn't believe the rpm's. It just keeps going higher and higher.
 
Sweet build! Can't wait to see it cut.

Can you please link the bar thread? I couldn't find it via search.
 

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