# should I make a milling saw from a KX125 engine?



## Moddoo (Feb 13, 2007)

Hey guys,
I have been drooling over some of the CSM pics you all have posted up.

I just remembered that I have a late 90s kx125 engine laying around.

It seems like I could fix a bar and chain to it and make a vertical milling saw pretty easily.
I have access to a machine shop, and am pretty handy.

There are some 30"+ maples and oaks down on a friends land. I was hoping to cut some nice boards, but don't have $1000 for a big saw.

I have heard of people making hot saws with bike motors, but never thought of putting one to good use.

So what do you guys think?


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## Railomatic (Feb 14, 2007)

*motors*

The motor you mention is not really suited to the job of driving a mill, they are heavy on fuel and have elitively low torque characteristics.
A better choice would be a Honda GXV 390 or similar, they give around 13 bhp, which is good enough to drive a band of 24 inches or so.
If you shop around you can buy the Chinese copy of this motor for about the 200-250 dollar mark, cheaper if you buy mutltiples and they are now every bit as good as the genuine motor.


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## Moddoo (Feb 14, 2007)

Thaks for the reply Railomatic.
You speak of driving a band, but I am thinking of making a portable chainsaw mill. Fuel consumption isn't a concern, and I thought the engine would be overkill for a 36" bar.


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## Railomatic (Feb 14, 2007)

*engines for a CSM*



Moddoo said:


> Thaks for the reply Railomatic.
> You speak of driving a band, but I am thinking of making a portable chainsaw mill. Fuel consumption isn't a concern, and I thought the engine would be overkill for a 36" bar.



I see now, the engine would drive things I suppose, but you are going to have difficulty in changing the horizontal engine shaft into a vertical position, you can use a gearbox to overcome this but that's extra cash to spend.

A honda GXV or similar has a vertical shaft with which to connect straight to a harvester sprocket, and you can buy them as a bare engine, that's without a tank and the pull start, they do have an electric starter fitted.


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## IndyIan (Feb 14, 2007)

I always wonder why more people don't use a non-chainsaw engine for their chainsaw mill, but I guess its hard to adapt an engine to drive a sprocket and tension the chain properly. 
The KX engine should have atleast twice the power of a stihl 090 or husky 3120 but you would have to put a fan on the radiator for milling use. I wonder about longevity of the engine compared to a saw but I'd guess you could get atleast 100 hours between rebuilds. Would you use the transmission and clutch? You could use 1st gear for the wide stuff and 6th for narrow boards!
Sounds like a fun project!
Ian


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## Moddoo (Feb 14, 2007)

Hey guys,
I suppose a chainsaw clutch would be the best choice. I'll just adapt one to the output shaft.
Rail- no gearbox needed, just run the chain vertically with a guide on top of the log for the saw.
Ive been thinking about the cooling. I'll bet I can find a magneto with a lighting coil from another bike that will work on this engine. That could run the fan. I've got a small fan from a streetbike, and the radiator from the KX.

I figure the bar and some chains and maybe a magneto will be about my only cost, other than my time.

Anyone else ever done this before?

I should do some searching about hotsaws, the "hotsaw" site is pretty empty though.


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## Railomatic (Feb 15, 2007)

IndyIan said:


> I always wonder why more people don't use a non-chainsaw engine for their chainsaw mill, but I guess its hard to adapt an engine to drive a sprocket and tension the chain properly.
> The KX engine should have atleast twice the power of a stihl 090 or husky 3120 but you would have to put a fan on the radiator for milling use. I wonder about longevity of the engine compared to a saw but I'd guess you could get atleast 100 hours between rebuilds.
> 
> The KX engine produces about 33 bhp at the crankshaft shaft SAE, by the time its puts that power through and down to the rear tyre it a lots less,
> ...


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## Moddoo (Feb 15, 2007)

Railomatic,
Somehow, I think you are not understanding me.

Are you saying that a 33 hp chainsaw will not be powerful enough to mill a 30" log with a 36" bar?

The KX engine has much more flywheel mass than a chainsaw engine.
The magneto and clutch assembly are huge compared to a saw, not to mention the heavier crankshaft.

Maybe I'm missing something, but 

>>>I am not making a band saw<<<

Anyway, Does anyone know if there is a chainspeed limit?
I'll have to check into the gear ratios in this tranny, but the engine will easily turn at 14000, and I could turn the chain as fast as I want.


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## daemon2525 (Feb 15, 2007)

*Be Careful*

I think that it would be possible to have TOO MUCH power.

If you turn the chain too fast, or start breaking them, It could be dangerous.


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## iacornfed (Feb 15, 2007)

*"murder" cycle engine*

Heh give it a try and tell us how it works! Be sure and post some pictures. You know what I say. Spare parts and a wild imagination are the mother of invention.


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## Railomatic (Feb 15, 2007)

*info*

Not to sound bias, political or other about this thread, here is what I have found using various motors for driving chainsaw mills, >>>not bandsaws<<<.

Coupling that motor to drive the chain and bar, in what ever way chosen reduces the reliability, the clutch from a chainsaw will not take that kind of power.

The best results for any given chainsaw mills I have made in the past, have been via a 4 stroke motor 13-16 bhp, coupled either direct to the engine or via a comet type rise and fall clutch, the same as a lot of snow machines use.


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## IndyIan (Feb 15, 2007)

Moddoo,
Just thinking about it, I don't think the final drive ratio even for 6th gear would be fast enough to drive a chainsaw chain fast enough to make the engine work hard enough...
You follow my thinking? My 372 has a chainspeed of 20metres/second (i think) or about 72km/h and that's direct drive. I doubt top gear on a 125 would be any higher that 2 to 1, ie two motor revolutions to one drive sprocket revolution. 
Here's some info I found on the yamaha website for a yz125

Primary Reduction Ratio 64/19 (3.368) 

Secondary Reduction Ratio 48/13 (3.692) 

Gear Ratio - 1st Gear 31/13 (2.385) 

Gear Ratio - 2nd Gear 29/15 (1.933) 

Gear Ratio - 3rd Gear 27/17 (1.588) 

Gear Ratio - 4th Gear 23/17 (1.353) 

Gear Ratio - 5th Gear 24/20 (1.200) 

Gear Ratio - 6th Gear 23/21 (1.095 
I don't really understand what the primary and secondary reduction ratios are, 48/13 could be the drive chain sprockets? I would assume the primary reduction occurs before the gearbox so in 6th gear the drive sprocket is turning 1/3 the engine rpm. 
Anyways, I would figure out how fast the drive sprocket actually spins before you get too far in your planning.
Ian


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## Moddoo (Feb 15, 2007)

*Hmmm*

Thanks for the input guys.
indy-
Another chart I found, similar to yours, shows the kx with 6th gear @ 1:1
This would mean the sprocket for the chain would be spinning the same speed as the engine.

Rail-
I agree that a 4 stroke engine @ 13-16 hp may work well for a chainsaw mill.
A CVT "clutch" system is more than I want to deal with on this project.

I see your point, however, simply compare the kx engine to a large chainsaw engine (that has been proven to work well for a CSM) and they are nearly identical besides the 6 speed tranny and clutch on the bike motor. + the kx has triple the power.

Some of the hotsaw guys cut the entire tranny off and run the chain directly off of the crank.

Maybe to start, I'll skip the chainsaw clutch. just fit a sprocket to the output shaft, and use the bike clutch if I want to.

I don't want to cut it to pieces right away.

Hell, if it don't work out, I can always just bolt the 36" bar to my ms290 and call it a day:hmm3grin2orange: 

Please keep the comments coming. I'm not starting this tomorrow, so plenty of time to hash out the details.


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## lewisconroe (Feb 18, 2007)

*how about a 10 horse vertical engine*

Railomatic- Could you please post some pictures of a 4cycle motor on a chain saw mill. This sounds definetly interesting, especially if you have done it on a mill like a granberg or similar, thanks




Railomatic said:


> Not to sound bias, political or other about this thread, here is what I have found using various motors for driving chainsaw mills, >>>not bandsaws<<<.
> 
> Coupling that motor to drive the chain and bar, in what ever way chosen reduces the reliability, the clutch from a chainsaw will not take that kind of power.
> 
> The best results for any given chainsaw mills I have made in the past, have been via a 4 stroke motor 13-16 bhp, coupled either direct to the engine or via a comet type rise and fall clutch, the same as a lot of snow machines use.


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## lewisconroe (Feb 18, 2007)

*how about a 10 horse vertical engine*

Railomatic- Could you please post some pictures of a 4cycle motor on a chain saw mill. This sounds definetly interesting, especially if you have done it on a mill like a rail style mill, thanks




Railomatic said:


> Not to sound bias, political or other about this thread, here is what I have found using various motors for driving chainsaw mills, >>>not bandsaws<<<.
> 
> Coupling that motor to drive the chain and bar, in what ever way chosen reduces the reliability, the clutch from a chainsaw will not take that kind of power.
> 
> The best results for any given chainsaw mills I have made in the past, have been via a 4 stroke motor 13-16 bhp, coupled either direct to the engine or via a comet type rise and fall clutch, the same as a lot of snow machines use.


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## clintb (Feb 18, 2007)

http://www.msnusers.com/sawmill/shoebox.msnw?action=ShowPhoto&PhotoID=2 My homemade saw, 16hp.


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## Railomatic (Feb 19, 2007)

*Honda, Briggs CSM*



lewisconroe said:


> Railomatic- Could you please post some pictures of a 4cycle motor on a chain saw mill. This sounds definetly interesting, especially if you have done it on a mill like a rail style mill, thanks



Yes I will as soon as I have another one made, I have no picures of the first couple I made, because I never had a digital camera back then, I went off these and concentrated on CSM's instead.

I never thought anyone would be interested in such a mill, I suppose prices for everything from motors and the like have come right down in price, since china has come on line, prices here in the UK control everything, if you double those prices from the USA equivalent you have your UK price.

Here in the UK a Husquvarna 346 XP is two and a half times more than some US outlets, if I lived in the states it would be a whole different ball game, as I have lots of wares I could make and sell much cheaper in the forestry arena.

But I'm not so I will just have to keep on paying through the nose for saws etc.


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## redprospector (Feb 19, 2007)

Modoo,
You may have a cooling problem, but you can always make a "hot saw" if things don't work out. There is a guy I compete with that runs a kx125, and it's fast. Take my word for it, loose the tranny. You can machine the crank to accept an 088 clutch, and it holds up.
Here is a pic of my kx250.:biggrinbounce2:


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## scottr (Feb 20, 2007)

clintb said:


> http://www.msnusers.com/sawmill/shoebox.msnw?action=ShowPhoto&PhotoID=2 My homemade saw, 16hp.



Clint , I'm trying to see how you coupled the the vertical shaft crank to the sprocket drive for the chain . The picture is not clear .


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## clintb (Feb 20, 2007)

http://www.msnusers.com/sawmill/shoebox.msnw


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## scottr (Feb 20, 2007)

clintb said:


> http://www.msnusers.com/sawmill/shoebox.msnw



Thanks for the pictures . Do you remember the pulley diameters and the sprocket rpm that worked on the chainsaw mill ?


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## clintb (Feb 20, 2007)

sprocket from Bailey's HS404 C12 05, 12 pin. Pulleys from Surplus center , 1-BK28-E, 2.95 OD, 1" bore, 1-BK77-E 7.45 OD 1" bore


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## scottr (Feb 20, 2007)

clintb said:


> sprocket from Bailey's HS404 C12 05, 12 pin. Pulleys from Surplus center , 1-BK28-E, 2.95 OD, 1" bore, 1-BK77-E 7.45 OD 1" bore



Thanks again .


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## Stevensam (Feb 22, 2007)

Hey Clint,
That's an awesome set up, I've been planning on building something similar now for a few months.

Currently I run a Procut CSM with a Husky 3120 and a 'Rake' simplesaw homemade bandsaw with 16hp Briggs.

Anyway, I was wondering what the speed of cut is like compared to a larger chainsaw mill, that's if you've had experience with both. I use my Procut CSM to open the log up for the bandsaw to finish the milling, might be faster sawing if I do the same thing you did with the 4 stroke CSM?

Thanks, Steve.


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