HolmenTree bikesaw projects.

[HolmenTree]

What's the difference between a "practice" bar and a "production" bar in a race scenario? What's the practice bar lacking?

lxskllr,
These harvester bar/chain are .404 .080 rated for 25hp min/65hp max.
When you're testing and constantly practicing this heavy duty setup is a must when you're saw is pushing over 50 hp.
The expensive. 063 46RST high tooth race chain would be stretched and ripped to shreds.

[teakwood]

That is some serious sprocket!! will give chain speed,wow

[HolmenTree]

That is some serious sprocket!! will give chain speed,wow

That's just a small 14T .404 teakwood.
I have a 16T coming in the mail next week.

[HolmenTree]

Anyone out there having experience speed bucking the 22" Douglas fir at Squamish  B.C. and other areas. 
Please send me a PM if you have any info on sprocket size etc.
I've never cut competition wood that big before.
Thanks. 

[HolmenTree]

My local machinist here in the photo is making bolt on  starter rope pulleys for the Honda and Yamaha.
He has a well equipped shop and been in it for over 40 years.
Last pic is my work bench.


 

[HolmenTree]

Pulleys are on my work bench.


  

[Magicman]

   That sprocket looks like it could go on a combine.  8)

[HolmenTree]

 That sprocket looks like it could go on a combine.  8)

Indeed :D and it's just a medium sized one!
Speaking of farm equipment I remember wrapping a rope around the starter pulley on a Wisconsin powering my Dad's swather.
Not such a big deal like flywheel hand starting a John Deere D with the petcocks open but makes one appreciate electric starters.   ;D

[HolmenTree]

I will have the little YZ125 in the wood soon, the Honda CR250 will be saved for last.

My machinist did a great job on the drive sprocket and rewind pulley. 
I got the PTO side dust seal perfectly centered to the crankshaft on my own.


 

 

[HolmenTree]

My construction journey is slowly coming to an end. 
Saw's profile foundation is done. 
Now to cutting the top handle sideplates to balance and start bolting on pieces.


 

 

 

[HolmenTree]

Another mockup profile pic, this time the YZ125. 
My welder tig welded the pipe back together . I'm now making the mount brackets for him to weld on, plus he'll bend the stinger pipe away to the side  from the rear handle.


 

 

[HolmenTree]

It's official guys, I now have a third hot saw project.
I just won an auction on Ebay for a 1984 Honda CR500 cylinder, piston and complete intake assembly.  A friend is shipping me a crankcase set from Oregon. Just need to find a head and crankshaft.
Research tells me this 1984 engine was the most powerful CR engine Honda ever built.
It's the last air cooled model (I'm removing 2/3 of the cooling fins)
What made it so powerful was its short 139mm connecting rod and very strong port numbers,  so strong HRC detuned the porting in 1985 onwards to make the bike more rideable .
This was the only CR500 ever to have the large oval open exhaust port. All the other years the CR500 had the restricted bridged exhaust port with a lower duration degree #.

Got it all covered now 125cc 261cc 500cc.

[Air Lad]

Honda has become an icon for qualityt machinery worldwide
The "Red devil" motocross bikes were something special

[SpaceBus]

500cc two stroke chainsaw sounds insane. That engine in the right hands could make close to triple digit horsepower. 

[HolmenTree]

500cc two stroke chainsaw sounds insane. That engine in the right hands could make close to triple digit horsepower.

Naturally aspirated  with a big bore P/C and the right pipe  ignition,  squish and carburetion you may get 90hp maybe.
With nitrous yes 3 digits about you won't find me on the operating end of that saw.  :D
Stihl Timbersports event hotsaws are running in the neighborhood of 60 to 70  hp max at the crank.
The old high revving short stroke Rotaxs were getting more but not as nimble and now since Stihl Timbersports are running smaller diameter wood the lower powered and lighter saws are winning.

The new Wankels are putting out incredible horse power.

[realzed]

Why "removal of 2/3 of the cooling fins" Willard?  
Do you really save very much weight for actually doing this and is that  the real reason - or is there other logic at play here, like clearance issues or ? to make it worth the effort?
I would imagine the more cooling effect the better as the horsepower gets pushed up..  

[SpaceBus]

500cc two stroke chainsaw sounds insane. That engine in the right hands could make close to triple digit horsepower.

Naturally aspirated  with a big bore P/C and the right pipe  ignition,  squish and carburetion you may get 90hp maybe.
With nitrous yes 3 digits. But then you'd need 3/4" pitch harvester chain to keep up with that kind of power.
You won't find me on the operating end of that saw. Hahaha.
Stihl Timbersports event hotsaws are running in the neighborhood of 60 to 75  hp max at the crank.
The old high revving short stroke Rotaxs were getting more but not as nimble and now since Stihl Timbersports are running smaller diameter wood the lower powered and lighter saws are winning.

The new Wankels are putting out incredible horse power.

Even 75 Horse is out of control for a chainsaw! What's the fuel consumption per minute on something like that? 

[HolmenTree]

realzed and SpaceBus,

Maybe I posted a little too much information. My projects are for race use only. They will only run wide open throttle for 5 to 10 seconds in a competition . No cooling is needed.

Rules are 1 minute warmup allowed up on the stage , that's warming it up then shutting it off , putting hands on log and waiting for the starting command.
These saws need to warm up fast hence the reduction in cooling fins.
They must be in the peak state of tune to start on the first pull of the rope and be at WOT into the 1st of 3 cuts.

Now you think that is hard, now look at the fact you must make 3 complete cuts with all that hp within 6 inches of wood. If you don't your disqualified  :D

[Mad Professor]

Great thread!

Brings back memories of my dirt bike days of the 70s-80s.

I had a friend who put one of the air cooled CR500 motors in a Husqvarna WR frame, he called it a Hondavarna.

[thecfarm]

Now you think that is hard, now look at the fact you must make 3 complete cuts with all that hp within 6 inches of wood. If you don't your disqualified  :D

And in how many seconds?  ;)

[HolmenTree]

Guys, nothing to show besides a pile of parts of the two saws.
Presently glass bead blasting the cylinders, heads and crankcases.
Then rebuilding both engines with NOS OEM parts from bottom up.

As I said earlier seeing the Covid 19 may outlast my two hotsaw projects I'm starting to gather Honda CR500R engine parts for the third hotsaw project.
I got this freshly bored and honed 1984 CR500R cylinder and brand new piston from out of Newfoundland, Canada.  It's a 91mm bigbore displacing 514cc.

This first year CR500 with it's big oval exhaust port with very aggressive port numbers along with a short rod crank was the most powerful CR500 that ever came out of the factory.
Removing the majority of cooling fins will reduce a lot of weight for its 5 to 10 second runs at WOT.

I have a matched set of crankcases coming out of Oregon as I speak.


 

[Tacotodd]

Willard, that's a big piston for a lot of automobiles!

[HolmenTree]

Willard, that's a big piston for a lot of automobiles!

Tacotodd, it sure is big alright.  I can put my hand inside the cylinder with no problems.  Easy to work on .

[mike_belben]

In my teens i rode a CR500 once, and a quadzilla 500 once.  Both bikes that you didnt beat on... They beat on you.  You had to look for spots to crack the throttle just to hear what the top end was like because in the northeast woods there was nowhere with room enough to open them up for more than a few seconds.  So it was a blip here and blip there to stay on a 125 or 250. If you were out front and doing more than blips, you were going too fast for the trail pretty much instantly.  


Where i could keep my 250 to maybe 70% output, a 125 to 80% and a 80cc to 95 or 100% output most of the time,  the 500cc stuff was the bike putting out 40% and me at 105.  Injury speed in an instant, just twist and the front comes up.  

[HolmenTree]

Mike, I've never ridden a 500 or 250 but from YouTube videos of the guys on a CR500 some didn't even use 1st or 2nd gear. ;D
Bikes are tractors from how they pull the front wheel up with a rooster tail of dirt off the back wheel.
One video of a CR500 hotsaw the operator didn't rev it to WOT before hitting the log, it just opened up in the wood.