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Author Topic: HolmenTree bikesaw projects.  (Read 4181 times)

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Offline HolmenTree

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HolmenTree bikesaw projects.
« on: April 15, 2020, 12:19:07 PM »
Been away for a while, thought I'd check in with some pictures of my project that's been keeping me busy.
I thought Ed (ehp) would especially like this!

This is my little 1982 YZ125 which at the moment I'm building the oil tank to match up to the fuel tank. It's got a peaky 202/129.55 road race porting so I figure the 14T .404 sprocket will be lots enough of gearing.
Then it's on to adding the bar pad with Stihl 084 studs.

Last pic is my 1983 Honda CR250R waiting in the sidelines to get worked on.


 

 



Making a living with a saw since age 16.

Offline Evanguy

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Re: HolmenTree bikesaw projects.
« Reply #1 on: April 15, 2020, 12:33:22 PM »
Thats awesome, i have a 1984 cr250 motor im building a saw with. I built it up quite a bit, When it was in my bike it dynoed at 46whp. Yours looks like a 84 without the big power valve box by the exhaust port. Well not really a power valve but a little flap that opens a small chamber in the head to make a low pressure zone at low rpms.  Either way i removed it on mine.

If you use an oringed head you can use a 3mm over piston from the 250r three wheel motor ( same part number but not listed under cr250)  if you dont oring the head you need to find a multy layer steel headgasket like on the newer motors, (  composite with steel ring wont seal) boyesen radvalve also picked up good power. Also switching to an '88 cr250 flat face carb was nice (38mm pj) i ported it some, (mostly cleaned up the castings and raised exaust port), used an oem 2002 cr250 pipe on it with no silencer

I didnt cut the transmission off like you did. I stripped it of all its bearing, gears and shafts then used the 2 rear mounts to attach my handle too. My top tandle is attached to the cylinder head mount.

I was thinking about building a newer cr80 next ( 20hp in stock form and revs to 12k)

Online Hilltop366

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Re: HolmenTree bikesaw projects.
« Reply #2 on: April 15, 2020, 01:09:45 PM »
Cool projects guys, back in my bike dealer days I had a Yamaha rz350 for a while (twin cylinder 350cc two stroke) I always wondered how it would work as a race saw engine. I think the Banshee motor is very similar with out the YPVS.

Anyway the bike was super fun to ride and then I sold it so it matters not.

Offline HolmenTree

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Re: HolmenTree bikesaw projects.
« Reply #3 on: April 15, 2020, 01:22:37 PM »
Evan, awesome to hear of your '84 250. Your cylinder head is almost identical to my '83. The plug leans in opposite directions with both years.

I looked at the '84 250 but the exhaust port with no bridge kind of scared me off a bit.
I may in the future put in a wiseco 69mm 526 piston but I'd need to lower my cylinder 3mm for it to work.
I got a 68mm cylinder and a spare 66.75mm cylinder both in excellent condition.
The reason I picked the '83 CR250R is it matches my right hand ignition YZ125  with the PTO opposite your '84
I can do both builds with the same laid down horizontal design and reversed engine rotation with a bi directional PVL ignition.

Making a living with a saw since age 16.

Offline HolmenTree

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Re: HolmenTree bikesaw projects.
« Reply #4 on: April 15, 2020, 01:24:57 PM »
Cool projects guys, back in my bike dealer days I had a Yamaha rz350 for a while (twin cylinder 350cc two stroke) I always wondered how it would work as a race saw engine. I think the Banshee motor is very similar with out the YPVS.

Anyway the bike was super fun to ride and then I sold it so it matters not.
Those are strong motors alright.
But rules and regulations at the contests are standard with 1 cylinder only to keep things safe.
Honda CR500 is a wicked saw.
Making a living with a saw since age 16.

Online Hilltop366

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Re: HolmenTree bikesaw projects.
« Reply #5 on: April 15, 2020, 01:30:40 PM »
Honds CR500 is a wicked saw.


Yikes! It must it needs a large pulley on the pull chord?

Offline lxskllr

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Re: HolmenTree bikesaw projects.
« Reply #6 on: April 15, 2020, 01:49:13 PM »
Still on for May(is it?) Willard?

Offline HolmenTree

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Re: HolmenTree bikesaw projects.
« Reply #7 on: April 15, 2020, 02:43:25 PM »
Still on for May(is it?) Willard?
Unfortunately I hear all shows  everything cancelled.
So next year maybe??
Oh well this time off will give my lots of time to get them built right and tested in the wood.
Couldn't find a better excuse to spend more time in the shop haha!
Making a living with a saw since age 16.

Offline barbender

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Re: HolmenTree bikesaw projects.
« Reply #8 on: April 15, 2020, 02:56:11 PM »
Those things are just madness! I can't imagine a CR500 saw, those things were uncontrollable in a bike!
Too many irons in the fire

Offline HolmenTree

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Re: HolmenTree bikesaw projects.
« Reply #9 on: April 15, 2020, 03:03:17 PM »
Thats awesome, i have a 1984 cr250 motor im building a saw with. I built it up quite a bit, When it was in my bike it dynoed at 46whp. Yours looks like a 84 without the big power valve box by the exhaust port. Well not really a power valve but a little flap that opens a small chamber in the head to make a low pressure zone at low rpms.  Either way i removed it on mine.

If you use an oringed head you can use a 3mm over piston from the 250r three wheel motor ( same part number but not listed under cr250)  if you dont oring the head you need to find a multy layer steel headgasket like on the newer motors, (  composite with steel ring wont seal) boyesen radvalve also picked up good power. Also switching to an '88 cr250 flat face carb was nice (38mm pj) i ported it some, (mostly cleaned up the castings and raised exaust port), used an oem 2002 cr250 pipe on it with no silencer

I didnt cut the transmission off like you did. I stripped it of all its bearing, gears and shafts then used the 2 rear mounts to attach my handle too. My top tandle is attached to the cylinder head mount.

I was thinking about building a newer cr80 next ( 20hp in stock form and revs to 12k)
Evanguy, thanks for the tip about the cylinder head. I noticed lots of glue on my one cylinder deck where someone was trying to seal it down.
I haven't run my Ebay pieced motor yet and I noticed the squish band in the head is off center as my picture shows. Both cylinders have the same offset with the head.
So I got to send it away with 3 pieces of squished solder to get it machined to normal. Will have to cut the cylinder top deck clearance in the hole to zero first.
I may make my own head gasket out of some copper sheet which is easily available through a local retailer in different thicknesses.
Our cylinder heads are strong with their 7 stud design.  Only the 1983 and '84 CR250R had a 7 stud head.
Has to be strong as the CR500 has a 7 stud head.


 

Making a living with a saw since age 16.

Offline HolmenTree

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Re: HolmenTree bikesaw projects.
« Reply #10 on: April 15, 2020, 03:06:31 PM »
Those things are just madness! I can't imagine a CR500 saw, those things were uncontrollable in a bike!
Yep they are a real powerhouse alright.
I never saw anybody handle a CR500 hotsaw in anything smaller then a one cut hot start 27 inch diameter Douglas fir.
Making a living with a saw since age 16.

Offline ehp

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Re: HolmenTree bikesaw projects.
« Reply #11 on: April 15, 2020, 08:18:00 PM »
I hope you guys all got chain for those saws as no more high tooth being made is the word we re hearing , none has been made sense last June so hope you know someone with a roll or 2 .

Offline HolmenTree

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Re: HolmenTree bikesaw projects.
« Reply #12 on: April 15, 2020, 11:37:06 PM »
I hope you guys all got chain for those saws as no more high tooth being made is the word we re hearing , none has been made sense last June so hope you know someone with a roll or 2 .
Still some new HT for sale but expect to pay $500 plus for s loop.
One guy was asking CAD$1000 for a loop for a 28" bar, Lol.
I was talking to a rep in Virginia Beach last fall and he says the factory is not replacing the worn out dies.
But there "may" be a new .404 chain in the works in the very near future.
I got 30 feet of NOS Oregon 50AL .404 to run on the YZ125's 20" b/c.
May run it for now on the Honda too.
Making a living with a saw since age 16.

Offline Air Lad

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Re: HolmenTree bikesaw projects.
« Reply #13 on: April 16, 2020, 03:35:53 AM »
I owned a YZ125. C model around a 75 build I think
Yammy were first with monoshock system. That is suspension talk, nothing to do with cutting wood.
You're water cooled version is a country mile ahead of the old peaky, non user friendly power band thingy that I thought was the best thing since
sliced bread. Looks like yours has reeds .A later version had a valve that added low down torque and was controlled in unison with the throttle. Bike I had then was a trail only. About 89 model but the mx bikes might have had this valve mabye 85 ish. Dunno .
Hope she cuts great

Offline HolmenTree

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Re: HolmenTree bikesaw projects.
« Reply #14 on: April 16, 2020, 08:28:50 AM »
My 1982 YZ125 here was the second year of water cooling and the first year for the powervalve.
Japanese MX motorcycle development really turned on with the biggest changes from about 1981 to 1986. Then after that it was just yearly small improvements.

Honda pretty well got most things right from day one in the 1980's and the other big three  (Yamaha, Suzuki, Kawasaki) manufacturers followed.  
But Honda did back track to some of their early designs.
Interesting note the Honda CR250R had the same 72mm stroke since 1978. Yamaha YZ250 ran a square 68mm68mm B/S right up to the late 1990s then switched to Honda's 66.4072mm B/S.
The big four shared alot of the same exact engine parts like bearings etc.


Making a living with a saw since age 16.

Offline barbender

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Re: HolmenTree bikesaw projects.
« Reply #15 on: April 16, 2020, 10:06:45 AM »
Holman, how do you deal with the water cooling with no cooling system? Just fill the jacket with coolant since it won't run long?
Too many irons in the fire

Offline HolmenTree

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Re: HolmenTree bikesaw projects.
« Reply #16 on: April 16, 2020, 01:30:06 PM »
Holman, how do you deal with the water cooling with no cooling system? Just fill the jacket with coolant since it won't run long?
No coolant needed. I filled up the cylinder's water jacket with Devcon aluminium epoxy. Keeps the cylinder bore more stable after increased horse power mods reducing distortion.
In competition we're allowed a minute to warm the saw's motor up.
Then on the word "go" we start the saw and makes our cuts as short as 3 to 4 seconds at WOT.
No water cooling needed, a quick efficient warm up is needed in this situation.
Heat  gauges help keep an eye on engine heat. Usually above 160F these engines will start to lose power.
Making a living with a saw since age 16.

Offline Evanguy

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Re: HolmenTree bikesaw projects.
« Reply #17 on: April 16, 2020, 03:53:09 PM »
Thanks for making this thread, it got me re-excited about my build and I've since found all my parts and got back into it (sorry if im out of line talking about my build in your thread and posting pics, do let me know if i shouldn't be)

that's an interesting idea about cutting the case, then tipping the motor back and reversing the direction, saving on both wright and over all size. also getting the exhaust out of the way of the bar/cut zone. your building technique is quite a bit advanced then mine. i like it. 

the 84 exhaust port sure is big but i haven't found an the issue with it, the one time i did have an issue is on my first rebuild i did on the bike i didn't have the FSM and the exhaust port has a bulletin about how to chanfer the exhaust port to not catch rings on it. interestingly i have cylinder jugs that has the recall done on them and also one that haven't (pics attached) 

going 3mm over was fun for sure but lead to a load of headaches with pushing coolant before i realized why, i copper sheet would have been the simplest i was young at the time and didn't think about that. i ended up cutting an o-ring grove around the combustion chamber then using gasket maker to seal the coolant part. i do like the 7 stud design, lots of clamping force evenly spread.

i wasnt sure what i was going to do with the coolant, that's a good idea really. i see I'm going to learn a lot from this thread.

i had no idea about the chain and have never even looked into what i needed, i assumed id be running the same type of 404 chain that's on my stihl 084

i wonder if an 83 head would bolt on the 84 bottom since i'm not using the ATAC system, i guess i can just buy a cheap base gasket and that will let me know, or if you ever are feeling board maybe you can grab the measurements on the 4 base studs























Offline ehp

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Re: HolmenTree bikesaw projects.
« Reply #18 on: April 16, 2020, 09:28:05 PM »
if you want to cut fast you need the taller tooth and the bigger the wood the higher tooth makes a bigger difference. if your cutting small wood 3/8 chain will cut fast on the 125, I would not put it on the 250

Offline ehp

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Re: HolmenTree bikesaw projects.
« Reply #19 on: April 16, 2020, 09:31:23 PM »
I put my bar oil in where the coolant went in the jug


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