(DIR) Return Create A Forum - Home
---------------------------------------------------------
Chainsaw Repair
(HTM) https://chainsawrepair.createaforum.com
---------------------------------------------------------
*****************************************************
(DIR) Return to: Modified Ported Work or Race saws
*****************************************************
#Post#: 75135--------------------------------------------------
HolmenTree Bikesaw Resurrection
By: HolmenTree Date: December 29, 2016, 10:19 pm
---------------------------------------------------------
Well here we go. :)
I pulled my old relic from out of the attic, a 1982 Yamaha
YZ125J bike saw I built 33 years in my garden shed when I was a
young 25 year old timber faller.
Thanks to inspiration from saw restorer Ken Steeves I've
decided it's time to completely redesign and rebuild the old
YZ125. Which as a matter of fact put out more horse power then
all the other factory 125's during that era. Only trouble was
...left hand drive.
As I go through this rebuild project thread I'll show pics and
explain how I originally built it right hand drive through
inspiration from former Hot saw legend Gary Walrath with his
Yamaha 292 Thunder Jet snowmobile engine saw . But our saws were
different.... the chain turned backwards. :o
Threw rooster tail chips like crazy on the down cuts and pulled
in nice on the up cuts. But was a handful to hang onto ;D
I rebuilt it to left hand drive and worked well for me over the
years with our central region 10"×10"- 12"×12" three cuts all
down modified events.
But since retiring from competing for 25 years and since only
sponsoring and running my own little yearly saw cutting
competitions. I want to take one last stab at it and for fun get
out the Hytest axes, Mercier bow saw and crosscut along with the
YZ and maybe a quick little 272XP.
#Post#: 75136--------------------------------------------------
Re: HolmenTree Bikesaw Resurrection
By: HolmenTree Date: December 29, 2016, 11:39 pm
---------------------------------------------------------
Now you're probably wondering why I didn't build a 250 moto
cross engine saw.
Well way back in 1983 my intention was to compete exclusively in
the Canadian PNW. Canlog rules out there maintained 140cc
maximum displacement for hot saw.
So I went 125 ...with over 30 horsepower factory they were
competition for the Kart saws.
So here I am wanting to redesign my Yamaha 125 with massive
weight reduction and compactness. Already the powerhead only
weighs 32 lbs with lots of room to get it into the 20's.
So with my plans to go right hand drive I had several
decisions....rotate cylinder and piston and ignition then run
engine backwards, or....rotate crank and ignition, or....Lay
engine on back with carb up to right hand drive and run engine
rotation backwards with ignition reversed 180 degree .
Well I concluded after pulling the rewind housing and the
starter cup off the rotor. Why not run the drive sprocket off
the rotor.
From looking at the Jack Stewart/Sven Johnson 250 CanAm Rotax
bike saw rebuild that Ken Steeves did...the drive sprocket was
driving off a single long shaft held to the crank with 8 small
screws.
This shaft held the ignition, clutch, rim sprocket and rewind
starter. And that powerfull saw won Hayward, Wisconsin 7 years
in a row. 8) Best time 8.03 seconds in 3 cuts of 20" pine with
cold start.
So as my pics show with the starter cup removed what I'll do is
re-thread the rotor puller threads in the rotor to left hand
thread.
Build a 2 piece shaft with both pieces left hand thread. The
piece threaded into the rotor will be locked with a internal nut
on the crank. Supported by a sealed bearing and seal in a
aluminum side cover sealing the ignition. The 2nd piece external
shaft will left hand thread into the base shaft with a standard
7 spline welded to it, holding the 11-13 tooth Danzco rim
sprocket. With a washer and C clip on the end. Different size
rims can be easily swapped for different wood.
B/C will still be very close to crankcase centerline.
A new aluminium rewind rope spool will be mounted on the left
side crank end replacing the old 11 tooth spur sprocket.
Left hand rewind rope position will be a natural fit for a quick
cold start as the saw is lifted and started at the same time.
#Post#: 75138--------------------------------------------------
Re: HolmenTree Bikesaw Resurrection
By: adam32 Date: December 30, 2016, 9:36 am
---------------------------------------------------------
Ken Steeves did an awesome job on the Rotax! I sold that saw to
him. Great guy too!
I'll be watching this thread, should be really cool!!!
#Post#: 75139--------------------------------------------------
Re: HolmenTree Bikesaw Resurrection
By: HolmenTree Date: December 30, 2016, 9:58 am
---------------------------------------------------------
Thanks Adam.
Yes I meant to mention you owned that "original Rotax hotsaw" .
Very cool engine with the dual HR's on a rotary valve. With a
little redesign that saw could still be competitive today.
#Post#: 75141--------------------------------------------------
Re: HolmenTree Bikesaw Resurrection
By: adam32 Date: December 30, 2016, 10:49 am
---------------------------------------------------------
[quote author=HolmenTree link=topic=6238.msg75139#msg75139
date=1483113521]
Thanks Adam.
Yes I meant to mention you owned that "original Rotax hotsaw" .
Very cool engine with the dual HR's on a rotary valve. With a
little redesign that saw could still be competitive today.
[/quote]
I agree.
I thought it was 330cc? I never measured it though.
#Post#: 75156--------------------------------------------------
Re: HolmenTree Bikesaw Resurrection
By: aclarke Date: December 30, 2016, 4:44 pm
---------------------------------------------------------
Super cool, really like the lightweight bar!
How does the big tillotson (HR/HD?) work?
Adam
#Post#: 75165--------------------------------------------------
Re: HolmenTree Bikesaw Resurrection
By: HolmenTree Date: December 30, 2016, 9:19 pm
---------------------------------------------------------
[quote author=aclarke link=topic=6238.msg75156#msg75156
date=1483137879]
Super cool, really like the lightweight bar!
How does the big tillotson (HR/HD?) work?
Adam
[/quote]
Big Tillotson HD 42 mm works really good Adam. It's got H and L
screws which makes it super easy to tune. Very reliable carb,
there's a return line that cycles unused fuel back to the fuel
tank.
I had a smaller 34mm HR on it when I originally built the saw
with the engine laying horizontal with the chain cutting
backwards on right hand drive.
Here's some pics of the original setup. Plus some pics of Gary
Walrath's world record time setter 292 Yamaha Thunder Jet hotsaw
back in 1984 in Estacada, Oregon. Also cuts backwards while
throwing wood chip rooster tails 70 feet.
#Post#: 75167--------------------------------------------------
Re: HolmenTree Bikesaw Resurrection
By: sharkey Date: December 30, 2016, 9:23 pm
---------------------------------------------------------
Really cool project! I kike that Newspaper clipping too.
#Post#: 75171--------------------------------------------------
Re: HolmenTree Bikesaw Resurrection
By: HolmenTree Date: December 30, 2016, 9:43 pm
---------------------------------------------------------
[quote author=sharkey link=topic=6238.msg75167#msg75167
date=1483154635]
Really cool project! I kike that Newspaper clipping too.
[/quote]
I remember that event like it was yesterday. Thompson Manitoba
Winter Festival. We qualified outdoors Saturday the day before
when it was around 40 below .
Sunday afternoon we did the finals inside a hockey rink with
2000 people jammed to the rafters cheering us on. Rick McIvor
ran a 600 Polaris Indy snowmobile engine saw with triple tune
pipes..
We made lots of noise in there lol.
#Post#: 75173--------------------------------------------------
Re: HolmenTree Bikesaw Resurrection
By: HolmenTree Date: December 30, 2016, 9:52 pm
---------------------------------------------------------
I made some noise with my ole 090 before the YZ. Had it setup on
alcohol with a nice 34mm Mikuni alky kart carb. Direct drive
with no clutch, fan wheel and oil tank.
090 couldn't beat my older brother Dennis's Mac 101 kart saw
though. The Mac also ran a 34mm but on gas.
*****************************************************
(DIR) Next Page