Willard's vintage Hotsaw Builds

Bigmac · Jan 22, 2020

I ran the numbers...it is crazy mild!! 178/119 if you decked it .040 or 1 mm to keep it simple, you would need to lift the transfers .080 or 2 mm to get 128° timing. And the exhaust...you would need to lift the exhaust .200 or 5mm to get 193 and 6mm to get 196!!!

got me thinking....trx piston 3mm shorter, you could cut .020-.040 off the base and 4mm ish of the top and the transfers would be 128-130 and the exhaust would still need to be lifted 2-3mm, crazy! Or she would love a stroker! Lol

Bigmac · Jan 22, 2020

That’s a crazy amount of grinding! Lol, I think you might cut into the water jacket on the exhaust port, 5-6mm is extreme, measure the depth of the water Jacket above the exhaust. I would probably build a 1.5 mm spacer and a second .020 gasket and mill 2.5mm off the top, so raise the cylinder 2mm and cut 2.5 off the top to get zero deck, then lift the exhaust 3mm to get 128/193 ish.

Willard · Jan 22, 2020

I'll measure the water jacket in the morning plus re check my measurements just to make sure.
So when the port ceilings get raised are the floors raised too?

Stroking sounds like it might be a good option.

Bigmac · Jan 23, 2020

So if you spacer it yes, or the trx piston yes, the floor would raise or effectively raise it and that would be good because it’s low now. A 4mm stroker would also work, the ports are so low you could stroke it and space the cylinder, it’s a pretty open slate for a builder, and huge gains from stock!!

Willard · Jan 23, 2020

I have lots on my plate here. I better do this right, not every anyone gets good advice like this.

This morning I'm rechecking my measurements with rings installed this time. See if the old base gasket is swelled up from prior cleaning.
Chase the threads on the 2 bad base studs and torque down to spec all 4 corners.

Will check the 66.75 P/C too and record.
Carbon fiber will look alot better after final sanding and the addition of rosewood pistol grips.

Willard · Jan 23, 2020

Checked both cylinders, numbers on the 68mm were still the same 43/59.
The 66.75 cylinder because of its smaller diameter came out at 42.25 mm on the exhaust and transfers at 58.25.
Measured the water jackets. 68mm cylinder averaging 40 mm deep above exhaust ports. 3 mm to spare but the liner is 10mm thick so some room there to blend in the higher ceiling.
The 66.75 cyl is 41mm deep.

Checked the YZ125 ports.
23mm exhaust/ 37mm transfers. Both bottoms at 50mm.

4mm stroker crank? Crankworks can build mine for about $400 with balancing.

Willard · Jan 23, 2020

Also checked my cylinders central boost intake port for measurements. Their 23.67mm wide at the inside bore side and the TRX piston pins are spaced at 28mm.
If the piston doesn't twist in operation the ring ends shouldn't clip. But a little more then 2mm on each side doesn't offer alot of protection.
Also the TRX rings at BDC are still 6mm above the bottom corners of the port where it gets wide.

Bigmac · Jan 23, 2020

$400 isn’t bad for a custom stroker and balance! You would probably need to trench the case unless they clearance the rod like hotrod dose. So if you did a 4mm and build a 1mm spacer plate and add a second base gasket .020. the piston should be .020 out the hole and timing would 127.6° transfers and if you lifted the exhaust 3 mm to 40 it would be 190.5° It would also be a 275 at 68mm bore it would be a powerhouse at those specs, with a custom pipe to those specs it would be mean, super wide powerband and minor portwork needed, basically lifting the exhaust 3mm, you could drop the ports or not, I haven’t tested both but have a few theories on it! Lol

what’s the yz rod length?

Bigmac · Jan 23, 2020

I think I found the length, 98mm... wow it’s aggressive! 202/137!! I would mill the base 1mm and it would e 199/131, that would be mush stronger imho

Willard · Jan 23, 2020

Bigmac said:
$400 isn’t bad for a custom stroker and balance! You would probably need to trench the case unless they clearance the rod like hotrod dose. So if you did a 4mm and build a 1mm spacer plate and add a second base gasket .020. the piston should be .020 out the hole and timing would 127.6° transfers and if you lifted the exhaust 3 mm to 40 it would be 190.5° It would also be a 275 at 68mm bore it would be a powerhouse at those specs, with a custom pipe to those specs it would be mean, super wide powerband and minor portwork needed, basically lifting the exhaust 3mm, you could drop the ports or not, I haven’t tested both but have a few theories on it! Lol

what’s the yz rod length?

Stroking at this stage is still a distant idea but yes Crank Works does do the rod clearance mod.

I know a good welder here. He can weld titanium to steel. Very talented tig welding aluminum like boat props etc. Even taught me how to bend aluminum 5052 with its grain.
I'll have him look at the water jacket whether he can build up a layer so I can raise the exhaust 3mm. While we're at it fill in some of both sides for future auxiliary ports.

The YZ125 is a 50mm stroke. Below is the 1982 specs for the YZ bikes that year. 31PS/HP (off of crank)is pretty good for a 125 back then when about 4 years earlier a CR250R was only putting out about 26.
Last pic is the Beretta rose wood pistol grips I'll mount on the saw's rear handle. Only $30 for the 2 halves.

Willard · Jan 23, 2020

Bigmac said:
I think I found the length, 98mm... wow it’s aggressive! 202/137!! I would mill the base 1mm and it would e 199/131, that would be mush stronger imho

Hey thanks! Yes rod length I was thinking 50mm stroke like I said above. It's actually ported for mountain road racing reason why it had a 6 speed trans. I noticed the piston edges areca little above the transfer floors. 1 more mm lower I might have to radius the edges.
She rips. Last time I put a tach on it it was hitting 14K with a short burst and running plenty rich.
I'm putting a lot of thought and design into it lately. Will post pics when I get more to show.
Power to weight and compact ergonomics is where this little 125 will shine. I put about $400 US worth of titanium studs bolts etc. into it. Plus another couple hundred $ of carbon fiber. The PVL analog ignition is good for 20K rpm so they claim .I think more like 16K but it'll never see that.

No titanium for the Honda but in a year or so will save up and buy it some for it too.

Bigmac · Jan 23, 2020

Willard said:
Stroking at this stage is still a distant idea but yes Crank Works does do the rod clearance mod.

I know a good welder here. He can weld titanium to steel. Very talented tig welding aluminum like boat props etc. Even taught me how to bend aluminum 5052 with its grain.
I'll have him look at the water jacket whether he can build up a layer so I can raise the exhaust 3mm. While we're at it fill in some of both sides for future auxiliary ports.

The YZ125 is a 50mm stroke. Below is the 1982 specs for the YZ bikes that year. 31PS/HP (off of crank)is pretty good for a 125 back then when about 4 years earlier a CR250R was only putting out about 26.
Last pic is the Beretta rose wood pistol grips I'll mount on the saw's rear handle. Only $30 for the 2 halves.
View attachment 220161 View attachment 220162

To me it’s not worth welding, just spacer it, even a talented welder would distort the bore, if you planed on sleeving it then maybe, but then I would consider taking out the bridge welding the corners of the port to make it round/oval and maybe add sub exhausts, but if you haven’t done it, or have the proper tools it is super difficult, and you have a good chance of ruining a cylinder. You have to decide a path on on an engine build, you can’t go one way and then change your mind, without starting over. If you port it stock stroke, that’s it, no stroker later without changing the cylinder. It you maximize a cylinder and setup it’s hard to go in another direction, .040 in port heights is a lot, like the 125, it is road race ported, more so then even drag porting, dropping the cylinder.040 is would get it into the drag port range and widen the power curve considerably

strokers are something you need to plan from the get go, if not it’s ok, just letting you know now!!

Bigmac · Jan 23, 2020

Willard said:
Hey thanks! Yes rod length I was thinking 50mm stroke like I said above. It's actually ported for mountain road racing reason why it had a 6 speed trans. I noticed the piston edges areca little above the transfer floors. 1 more mm lower I might have to radius the edges.
She rips. Last time I put a tach on it it was hitting 14K with a short burst and running plenty rich.
I'm putting a lot of thought and design into it lately. Will post pics when I get more to show.
Power to weight and compact ergonomics is where this little 125 will shine. I put about $400 US worth of titanium studs bolts etc. into it. Plus another couple hundred $ of carbon fiber. The PVL analog ignition is good for 20K rpm so they claim .I think more like 16K but it'll never see that.

No titanium for the Honda but in a year or so will save up and buy it some for it too.

That’s awesome on the ti! I have been looking into for my banshee! That stuff is spendy! The pivot bolt for the swingarm is $240, was looking into a it rear brake rotor, 180, but it turning weight, so thinking pretty hard about it! I have already dropped 40 lbs with a chromoly chassis and some deleting

Willard · Jan 23, 2020

Thanks!
Yes I have alot of information to decipher through for the next couple months before I pull the trigger on engine modifications.
I like to get both saws running stock first especially the Honda since I never had it running yet.
Have both in the wood with no internal mods. Get used to that power and then go from there. I will have the spare P/C in the modification process by then hopefully.

Willard · Jan 23, 2020

Bigmac said:
That’s awesome on the ti! I have been looking into for my banshee! That stuff is spendy! The pivot bolt for the swingarm is $240, was looking into a it rear brake rotor, 180, but it turning weight, so thinking pretty hard about it! I have already dropped 40 lbs with a chromoly chassis and some deleting View attachment 220174 View attachment 220175

That is one very cool looking powerhouse of a machine !
I bought titanium out of Toronto and Titan Classics out of the UK . They sell alot of Honda bike stuff.
Really nice stuff out of the UK but pricey.
I bought some from AcerRacing out of Los Angeles plus got my carbon fiber from them too.

Willard · Jan 23, 2020

Willard said:
That is one very cool looking powerhouse of a machine !
I bought titanium out of Toronto and Titan Classics out of the UK . They sell alot of Honda bike stuff.
Really nice stuff out of the UK but pricey.
I bought some from AcerRacing out of Los Angeles plus got my carbon fiber from them too.

torontocycle.com out of Toronto Canada. Good prices.
AcerRacing makes titanium wheel studs for Lamborghini Ferrari etc.
So that proves how strong their titanium is.

Bigmac · Jan 23, 2020

Willard said:
torontocycle.com out of Toronto Canada. Good prices.
AcerRacing makes titanium wheel studs for Lamborghini Ferrari etc.
So that proves how strong their titanium is.

Thanks, I will look into it, might get some ti sprocket bolts and rear rotor bolts too

Willard · Jan 24, 2020

Bigmac said:
That’s a crazy amount of grinding! Lol, I think you might cut into the water jacket on the exhaust port, 5-6mm is extreme, measure the depth of the water Jacket above the exhaust. I would probably build a 1.5 mm spacer and a second .020 gasket and mill 2.5mm off the top, so raise the cylinder 2mm and cut 2.5 off the top to get zero deck, then lift the exhaust 3mm to get 128/193 ish.

I'm liking this approach with the stock pistons rather then go the TRX piston route.
With my crank being within normal wear limit spec on the big end sides I fear clipping the TRX rings if the piston should twist in operation.
If I rebuilt the crank to tighten it up then I might as well get it stroked.
I definitely will get a degree wheel and measure the port timing rather then rely on my cheap caliper measurements.
I got room to raise the exhaust 3mm. Will have to lay down a layer of some high temperature rated cold weld on the floor of the water jacket for extra upper port wall thickness.

Willard · Jan 24, 2020

Looking at my CR250R hotsaw's crankcase this morning I'm thinking there has to be a better way. ESR is selling Honda stroker crankshafts for $300, endless variety of custom performance parts that I can't put on my 1983 CR250R engine.
Plus I'm relying on these cut up crankcase halves to not flex, crack under WOT, but I still want to run my '83 cylinders.

Quick search from my metal supplier's aluminum inventory I find aluminum Mic 6 cast plate up to 3 inches thick.
Now so I buy 2 pieces each 3" thick 6"×6" square.
Can anybody see where I'm going with this.

Willard · Jan 25, 2020

Another project for winter of 2020-2021.
With easy cheap access to thick mic6 aluminum tooling plate and a simple milling machine at the local machine shop would enable me to make my own hotsaw crankcase ridiculously simple.

So many possibilities could be accomplished in so little time then messing around with a used CR250 crankcase.
Future looks good.

Willard's vintage Hotsaw Builds

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