Willard's vintage Hotsaw Builds

[Willard]

I am running a 38mm on my 363cc, guys are making 170hp with twins on alky and 41mm carbs, bigger isn’t always better on carbs, I have jumped up from 36 to 38mm and gained everywhere too, it kinda depends, I usually favor the little smaller

nice looking carb!

I picked this racing carb because I know the throttle response a jet ski has, they're insane quick.
I think it will fit good for the Honda and I'm sure the little high revving 125 will have no problem with it.
I have one other Mikuni 38 to order but last second I'm off for now. It's the same carb I ordered but factory built for alcohol. If the 125 works out with the 38 gas carb I will run this alky 38 on the cr250r.
https://www.jrracecar.com/mikuni-38mm-super-bn-carburetor/

 

[Bigmac]

I picked this racing carb because I know the throttle response a jet ski has, they're insane quick.
I think it will fit good for the Honda and I'm sure the little high revving 125 will have no problem with it.
I have one other Mikuni 38 to order but last second I'm off for now. It's the same carb I ordered but factory built for alcohol. If the 125 works out with the 38 gas carb I will run this alky 38 on the cr250r.
https://www.jrrace.com/mikuni-38mm-super-bn-carburetor/

Thats cool. There were years that many of the manufacturers put bigger carbs on 125, than they they did the 250’s! I think the only two builder that build pipes and motor are led and bdt, both good R builders too, Arlend is a good guy, I would recommend talking to him, we talked pipes for an hour over the phone. I know he is busy but it’s always nice to talk to them, same with bdt, Carlos is cool, and he has Kenny Roberts building his pipes in house, they also build esr’s pipes, both great shops!

 

[Willard]

Thats cool. There were years that many of the manufacturers put bigger carbs on 125, than they they did the 250’s! I think the only two builder that build pipes and motor are led and bdt, both good R builders too, Arlend is a good guy, I would recommend talking to him, we talked pipes for an hour over the phone. I know he is busy but it’s always nice to talk to them, same with bdt, Carlos is cool, and he has Kenny Roberts building his pipes in house, they also build esr’s pipes, both great shops!

From LED Facebook I studied it with a "magnifying glass" haha.
Yes Carlos is a cool dude, I see his posts on different MX forums he knows his stuff. Chris welds those cone pipes with perfect beads with no filler, unbelievable!
I definitely want to talk to Arlen over the phone, but I know what its like to be busy....I want to spark their interest first with some pics of these 2 saws near finish by either text or email. I'm just a tree guy out in the sticks.
I think Arlan will get a kick out of a right hand ignition CR250.
hotsaw.
Couldn't get that alky carb link to work on here, doesn't have a allowed extension

 

[Bigmac]

From LED Facebook I studied it with a "magnifying glass" haha.
Yes Carlos is a cool dude, I see his posts on different MX forums he knows his stuff. Chris welds those cone pipes with perfect beads with no filler, unbelievable!
I definitely want to talk to Arlen over the phone, but I know what its like to be busy....I want to spark their interest first with some pics of these 2 saws near finish by either text or email. I'm just a tree guy out in the sticks.
I think Arlan will get a kick out of a right hand ignition CR250.
hotsaw.
Couldn't get that alky carb link to work on here, doesn't have a allowed extension

You have a great project, and Arlan will definitely enjoy the build.
I am a big fan of alky for competition, the torque under load is ridiculous! I can run at least two front countershaft sprockets with it...alky loves load!
I highly recommend having a gas carb to purge, it’s a pain, but really let’s you clean it out, I am running redline alky mix, it’s amazing, 20-1

Get ahold of him, it really helps to get his input early! It can really save you money in the long run. It’s like the reeds, I know he is a big fan of c3’s, and that’s part of the package, or the piston, he may have strong opinions on that.
I love this build already!

 

[Willard]

Thanks! It is a great project alright, for our long winters here.
The Mikuni BN bolts right on to the YZ125. Even though it's a 38mm, it looks like a lot of carb.
Not an ordinary 38mm carb this thing will pump, going to have to open up the cylinder lots I'm afraid.
This down draft position is what these jet ski carbs were designed for.

Got a sheet of plywood here ready for cutting, same 16"×20" as the 5mm thick carbon fiber sheet laying on top of it.
There's enough CF here for both saw's PTO sideplate, once piece with the rear handle included.
Got the rest of the 4'×8' leftover sheet of plywood.
Going to take more then once to get the template ergonomic perfect.

 

[Willard]

Found some 36 year old notes when I first built my YZ125J bikesaw.
I phoned Bill Krause Racing for advice who owned a Honda dealership in California.
I had all my questions written out beforehand and then wrote down Bill's answers. One answer was too much compression will hurt your top end and another is the YZ125 no longer connected to the clutch, water pump and transmission will gain at least another 3000 - 4000 rpm.

Funny back in the day with no internet I didn't know who Bill Krause was, got his recommendation from a dirt bike magazine.
But today I google Bill's name and find out he was a machinist and drove race cars all the way up to F1.
Carroll Shelby and Mickey Thompson who he also drove for said he was the best U.S. driver at the time.
At age 33 in 1966 Bill retired driving and bought a Honda dealership which he did very well with.
I like those kind of stories.

 

[Willard]

Got the day old jig stand setup this morning. Profile is level at the intake manifold.
18oz fuel tank sits out front, PVL analog ignition 1 piece coils sits behind it alongside the 5 oz bar oil tank. Ignition coils insulated in a piece of silicone baking sheet.
1.5mm thick carbon fiber will cover them up.

 

[Willard]

Take a look at this run Lawrence O'Toole had here with the Honda DC/ESR/LED 330.
You'll notice its black foam air filter falling off mid way through his last cut. Laying on the floor after he sits the saw down.
Might have given him a little boost.

 

[Bigmac]

Take a look at this run Lawrence O'Toole had here with the Honda DC/ESR/LED 330.
You'll notice its black foam air filter falling off mid way through his cuts. Laying on the floor after he sits the saw down.
Might have given him a little boost.

That filter was probably killing power! Way to short, the esr filter setup it too short as well, on the dyno the max a 50-ish hp, just extending the filter will gain 5-7hp

 

[Willard]

That filter was probably killing power! Way to short, the esr filter setup it too short as well, on the dyno the max a 50-ish hp, just extending the filter will gain 5-7hp

I had one of those foam filters on my YZ125 years ago. Yeah don't breathe as good as they could without modifying. Trouble is on a hotsaw any bigger they get in the road. I modified mine by turning it inside out and shaving off half of the foam thickness, there's a large spring inside keeping it round.
Only wood chips to filter, not worried about dirt.

I saw a nice one on Amazon this morning for $10 free shipping. Different colors, called a bent angle mount dual stage air filter, looks just like my old one did except with the bend mount.
Going to order one the angled mount will offer better visibility to the B/C plus out of the way for my left arm with my carb being in the downdraft position.

 

[Bigmac]

I had one of those foam filters on my YZ125 years ago. Yeah don't breathe as good as they could without modifying. Trouble is on a hotsaw any bigger they get in the road. I modified mine by turning it inside out and shaving off half of the foam thickness, there's a large spring inside keeping it round.
Only wood chips to filter, not worried about dirt.

I saw a nice one on Amazon this morning for $10 free shipping. Different colors, called a bent angle mount dual stage air filter, looks just like my old one did except with the bend mount.
Going to order one the angled mount will offer better visibility to the B/C plus out of the way for my left arm with my carb being in the downdraft position.

Ideally you want the back filter wall to be 5+ inch’s. On the trx you shoot for 9-12” to the back filter, there is a reversion wave that hits the back filter wall and that breaks up the incoming charge, if you look at the led hand cone intakes they address that issue, I know it’s not an option for you, but look to maximize the size of your filter.

 

[Willard]

Ideally you want the back filter wall to be 5+ inch’s. On the trx you shoot for 9-12” to the back filter, there is a reversion wave that hits the back filter wall and that breaks up the incoming charge, if you look at the led hand cone intakes they address that issue, I know it’s not an option for you, but look to maximize the size of your filter.

I was wondering what those cone intakes were all about.... working with that filter. I was thinking extra long velocity stack offering huge peaky rpm but now see it working with the filter. Very interesting, thanks.

So I guess that back wall I'd the 2nd part of the dual stage. I thinned that down where you could see light through it.
Some hotsaw guys just mount domed heavy mashed screen on top of their velocity stacks, just enough protection to keep the bigger chips out.

 

[Bigmac]

Lately have been getting text messages from some top Stihl Timbersports competitor's and saw builders from around the world about my project.
Can't say any names....

That’s cool! Always fun to get there attention!

 

[Willard]

Nothing to show in the build at the moment, still cutting and trying out different plywood templates for the carbon fiber pieces.
Took a break here looking at the YZ125 bar/chain/sprocket options.
Going to run my old General 18" bar I lightened up to 2.5 lbs in 1984
Had that bar originally made at General Chain Bar Co. Tigard,Oregon in 1983 for $50. I supplied the 2 7/8" Oregon roller I bought a few days earlier at Madsen's.
Will run the NOS Oregon 50AL chisel bit chain on it via a 14T .404spur sprocket.
On the saw sitting on the crank is a Danzco 13 pin .375 seven spline large mount sprocket, never used it and never will. It's for sale.
Last pic is the 30" .063" Cannon bar next to the General 18" .050" The 30"will mount on the CR250 with s 16T .404 spur sprocket.
Both bars are 0.160" thick.

 

[Bigmac]

I was wondering what those cone intakes were all about.... working with that filter. I was thinking extra long velocity stack offering huge peaky rpm but now see it working with the filter. Very interesting, thanks.

So I guess that back wall I'd the 2nd part of the dual stage. I thinned that down where you could see light through it.
Some hotsaw guys just mount domed heavy mashed screen on top of their velocity stacks, just enough protection to keep the bigger chips out.

The v-stack and mesh is a good option too. On my twin, there was a 1hp gain going to a filter, I dynoed it without, and with a 8” long k and n, basically no different I tried some pvc extensions and it killed 20hp, a bell shape is important and the air filter isn’t something to overlook!

 

[Willard]

That’s cool! Always fun to get there attention!

Some are good folk and like to help out and others not so nice and are all ears with no advice.
But they all don't want their names mentioned, Lol.

 

[Willard]

The v-stack and mesh is a good option too. On my twin, there was a 1hp gain going to a filter, I dynoed it without, and with a 8” long k and n, basically no different I tried some pvc extensions and it killed 20hp, a bell shape is important and the air filter isn’t something to overlook!

So better to run a bell inside shape velocity stack with filter?

 

[Bigmac]

So better to run a bell inside shape velocity stack with filter?

Yes, or an oversized filter ring/ adapter with a larger diameter filter

 

[Willard]

Before I look into storage here's a couple. The black one on the left I see as a bell. It used to have a grate built in halfways down and had a snap on flange ring to hold the filter.
The silver one is straight walled .

 

[Bigmac]

Before I look into storage here's a couple. The black one on the left I see as a bell. It used to have a grate built in halfways down and had a snap on flange ring to hold the filter.
The silver one is straight walled .
View attachment 207907

The black one is ideal, and if you put the mesh on the top there is more surface area and less restriction. You could even go with a finer mesh and still get better flow or put a filter on top of that