Willard's vintage Hotsaw Builds

[Willard]

Ok, thanks, have been curious! The trx is 100mm 100mm and 90mm on the exhaust the 92-01 is square at 100mm it must be the 85-91 cylinder that can swap

I did a quick weight on the 01 crank, it was 8 pounds 4 ounces, digital bathroom scale so it may not be perfect

Thankyou so much.
So my crank might be 3/4 lb lighter, that's alot. Probably why the 1983 CR250R was the quickest on the hotshot against other brands that year.
The wider cylinder stud base is another positive, more room for a big bore sleeve maybe.

 

[Bigmac]

Whats the case bore? I can measure my big bore 350 cylinder at the skirt for you. Superior sleeve used to make custom sleeves for almost anything! He’s has make some cool stuff for me in the past! He welded up and custom made a sleeve for one of my pro-x jugs to use an 80mm Polaris piston stock is 66mm

measured my old 350, it’s about 84mm and it was 79mm piston

 

[Willard]

Whats the case bore? I can measure my big bore 350 cylinder at the skirt for you. Superior sleeve used to make custom sleeves for almost anything! He’s has make some cool stuff for me in the past! He welded up and custom made a sleeve for one of my pro-x jugs to use an 80mm Polaris piston stock is 66mm

measured my old 350, it’s about 84mm and it was 79mm piston

I think 350 big bore would make too much vibration on a CR hotsaw without a counter balancer.
310 would be my max I'd think.
Here's my numbers.
Last pic is on top at 66.50 bore (66 is std)
When ESr/Led bore these cases for big bore they expoxy fill in the cylinder base and top of the cases to allow for the case boring and sleeve boring.

 

[Bigmac]

I think 350 big bore would make too much vibration on a CR hotsaw without a counter balancer.
310 would be my max I'd think.
Here's my numbers.
Last pic is on top at 66.50 bore (66 is std)
When ESr/Led bore these cases for big bore they expoxy fill in the cylinder base and top of the cases to allow for the case boring and sleeve boring.
View attachment 207255 View attachment 207256 View attachment 207257

Wow that’s a thick stock sleeve you could probably bore it out to 310 without a new sleeve! I have gone up to 80mm bore in the stock cases without epoxy on the case boring, lrd did one set I have and for a 350, no epoxy, ya a 310 is going to have less vibes than a 350 for sure.

they go 73.5 bore with about a 78mm sleeve in the trx.

And the stock cases are about 76mm, they don’t bore the cases for a 310

 

[Deets066]

This thread has sparked some interest, I do have a nasty fast ported 700cc engine. Lol

 

[Bigmac]

This thread has sparked some interest, I do have a nasty fast ported 700cc engine. Lol

a 443 twin on alky is good for 115hp the 700cc ones are in the 150hp range

 

[Bigmac]

This thread has sparked some interest, I do have a nasty fast ported 700cc engine. Lol

Do it!

 

[Deets066]

a 443 twin on alky is good for 115hp the 700cc ones are in the 150hp range
View attachment 207262

Had the dynometer on mine at 182 hp

 

[Bigmac]

Had the dynometer on mine at 182 hp

Triple?

 

[Willard]

That's funny
30 years ago when I was winning with my 125 at our local contests, a guy built a Polaris sled engine saw I think it was a triple rated at 100 horse. Lucky for him we were hot starting our cuts off the floor.
He was wrestling with that thing and could only make one cut to my 3 on the clock.
Rules now a days is one cylinder, cold start on go.
Stihl Timbersports 330 big bore cr250 is winning in the cold start 3 cut in 19-20" pine.

 

[Willard]

Wow that’s a thick stock sleeve you could probably bore it out to 310 without a new sleeve! I have gone up to 80mm bore in the stock cases without epoxy on the case boring, lrd did one set I have and for a 350, no epoxy, ya a 310 is going to have less vibes than a 350 for sure.

they go 73.5 bore with about a 78mm sleeve in the trx.

And the stock cases are about 76mm, they don’t bore the cases for a 310

Yep the ole girl is meaty. A 7 stud billet head would look good on it too.
I'm staying with the stock bore for now unless my future builder can convince me other wise.

 

[Deets066]

Triple?

Yeah, Probly too heavy to do anything with really. But it would be cool

 

[Willard]

Wow that’s a thick stock sleeve you could probably bore it out to 310 without a new sleeve! I have gone up to 80mm bore in the stock cases without epoxy on the case boring, lrd did one set I have and for a 350, no epoxy, ya a 310 is going to have less vibes than a 350 for sure.

they go 73.5 bore with about a 78mm sleeve in the trx.

And the stock cases are about 76mm, they don’t bore the cases for a 310

I found this interesting on my YZ125 spare cylinder on 2nd bore oversize at 56.50
Last pic is the CR250R.
Pretty meaty 125, should get close to 200cc big bore.

 

[Bigmac]

I found this interesting on my YZ125 spare cylinder on 2nd bore oversize at 56.50
Last pic is the CR250R.
Pretty meaty 125, should get close to 200cc big bore.
View attachment 207332 View attachment 207333

You have room! I bet you can go 68mm with standard pistons, the trx they have pistons to 69.5, then it jumps to 72mm for the big bore “310” and it’s a 295cc at 72mm and a 305cc at 73.5mm

If a trx piston could work you could bore it out a lot!

 

[Willard]

Would be a very interesting project. Got a NOS std. bore on the saw. This spare cylinder would be great to experiment with.
Find the largest piston to fit the connecting rod and cylinder.
Send the crank and piston to CrankWorks to get stroked and balanced.....$$$$$$
Who knows what displacement I would end up with, Lol.
When I look at the cr250 cylinder despite the size difference it looks so similar inside to the 125.
We see Stihl pistons in Huskies, Husky pistons in Stihls, most things are all relative.

 

[Bigmac]

Lots of guys used to use the 70mm Yamaha 250 piston, but had to relocate the ring stops, that was before weisco started making all the pistons we have now!

If you want to go big, the trx bottom end is the way to go, you can get the hot rod 4mm stroker crank for $260 and a 330 big bore set up for a +4mm stroke for 700, that includes piston and built head, that makes a killer 350cc motor!

 

[Bigmac]

I think your going to be happy with your 250, I honestly think a good port and head work and it will scream. At 72mm stock stroke the piston speed is an issue if you want to rev it to the moon that is already twice the stroke of a Stihl ms440-460-461 so the max rpm is around 8500, 9k plus is going to be a short life. So stoking is better for 8k and less

right now you can get the esr/weisco pistons in 72-73.5 for $177, I know it fits the rod, the dome is probably different thou, I can get you different piston measurements have a 67 68 69 76.5 79 and 80mm pistons on hand for the “86” style piston

 

[Willard]

Nice thing about the Honda cr250 is 1978 to 2001 they share the same con rod kit. Wiseco makes overkill on all their pistons etc.
Those black teflon pistons they make look cool, probably run cooler too.
I'm determined to stick with the right hand ignition '83 crankcase, the '83 cylinder is super lightweight , odd ball 7 stud head that has potential for sealing for big bore, custom billet would be nice.
'83 crank looks to be lightweight compared to newer cranks and has a heavier mag side stub for good durability.
Definitely need to find where it's port numbers are.
Trouble is I don't have a '83 piston yet and the '84 up are different.

Yeah that DC 330 that O'Toole won the Stihl Timbersports with doesn't sound like it's reving that high but sure throws the chips though.

 

[Willard]

So to add before I get into big bore pistons I need to get these engines dressed up with their new hotsaw clothes. Pretty well got everything besides the jet ski carbs from Tennessee and the titanium acorn head nuts and cylinder studs from the UK. Has been 7 weeks waiting now they must be coming across the pond by boat.
Pretty well spent my budget at this stage in the build, as I'm already finding out I'm getting too far ahead of myself not buying the right stuff.
When time comes to rebuild the internals I need that new degree wheel, dial indicator and one of these to properly check the bores.

 

[Nutball]

How's the vibration on a saw like that?