Willard's vintage Hotsaw Builds

[Willard]

Good advice!
I'll definitely do more research on pin offset. Some of the newer CR250 in the 1990s had netural centered piston pins. And some of the race series also neutral.

If I have to run a Wiseco 1983 piston I will, if it has the wide cut out on the sides I'll keep the exhaust ports far enough away to prevent transfer port short circuiting.
Raising the exhaust ports 3mm plus thinning the bridge if necessary and a good tune pipe should be all I need to make good flow.

You mentioned removing the lip when matching the head to fit the piston , not sure what you mean.
Thanks.

 

[Bigmac]

So match the this part, (red line in pic) of the band to the angle of the piston dome, if you error, error to having slightly more clearance to the center of the band. The stock head probably has a lip at the outer edge of the band, probably .020 to .040 up from the gasket surface(yellow line in pic)
Have your machinist match the band angle to the piston dome once he dose that, there will be a lip at the yellow line, have him machine it flat so that the band bevel ends with no lip, and then your gasket will be your squish clearance! .040, and you can adjust it with custom gaskets, makes it really tunable. Dose that make sense?

 

[Willard]

You did good explaining Nathan, sometimes when my OCD focuses on something like the offset piston pin I kind of grapple with processing other info bombarding my brain.

On the subject of piston pin offset it's quite simple as it's been around along time.
Just looking at pics on my phone is deceiving. A '83 CR250 piston looks to be central pin but so does my YZ125 piston. I measured it up and it has 3mm offset towards the exhaust side.
The angles of the front and rear skirts does make an opticle illusion.
Offset of the pin makes more h.p. and less friction internally on the bdc and tdc of the stroke with less side thrust pressures.
Like this pic and Wiseco article explains.
From my tests running the YZ125 in reverse rotation there was no difference in running behavior or extra wear from what I could see for the short burst runs I was doing.

http://blog.wiseco.com/what-is-wrist-pin-offset

 

[Willard]

A big thumbs up to Nathan for today was a very productive day!
Solid information with solid numbers, sorry I got side tracked with the offset piston pin. The correct piston will come eventually for this Honda.

 

[Bigmac]

A big thumbs up to Nathan for today was a very productive day!
Solid information with solid numbers, sorry I got side tracked with the offset piston pin. The correct piston will come eventually for this Honda.

There is nothing wrong with the 83 piston, it will work great for you, you just won’t have as much over bore, it don’t think the offset pin will be much of an issue on way or another With the trx piston. Gas gas would start there engine in reverse, to act as reverse in there quads.
Are you feeling better or worse about the offest pin?

 

[Willard]

There is nothing wrong with the 83 piston, it will work great for you, you just won’t have as much over bore, it don’t think the offset pin will be much of an issue on way or another With the trx piston. Gas gas would start there engine in reverse, to act as reverse in there quads.
Are you feeling better or worse about the offest pin?

From my limited research last night I think the advanced offset TRX pin will actually help my reverse rotation engines.
Alot of big hard to understand words get slung in explaining how the whole process of piston and cylinder offset works.
Then there's alot of wacko out the window theory too, Lol.

Looks like around about 1985 when Honda's research and development was on a good roll with horsepower gain and efficiency. I can't go wrong with the ATC/TRX piston. But it wasn't long later when Nikisel was in the spotlight when a US Honda race team member got a years worth of cylinders plated with the stuff while in Germany.

My trouble at the moment is I need a 1983 piston which was Hondas last design series before the Pro Lites...and I need a TRX piston to compare for fit.

Lots to do but not a good time to get machine shop service around the holiday season especially in a busy high commerce nickel mining town.
My 2 saws being converted to reverse rotation both need their cylinders bored and bearings replaced for the different thrust wear patterns that they will have to run with.
I'm still not 100% sure on the thrust pressures with my setup whether there will be more or less on the hot exhaust side of the cylinders.
Cooler running methonal looks more and more attractive in my situation, plus so does old school 24:1 Castor bean mix.
Meantime I would like to just stick a 66.75 piston in the Honda and go from there. But a cylinder bore can't be properly measured with a slide caliper.

What I learned in the past was start small and simple and work my way up with modifications...kind of like everyone else in the business.

Everything in motorsports boils down to the almighty piston and rings.

 

[Willard]

This morning I got on the phone with Wiseco technical support.
He said they didn't make the new Racer Elite pistons for the ATC/TRX but do go back to the 1993 Kawasaki 250.
He suggested if I wanted single ring remove the lower ring. I said I did that back in the 1970's I was hoping to find a dedicated one.
He said they can make me a race piston any design I want but I have to order a minimum of 12.
He suggested I phone LA Sleeve or ESR to see if they have any single ring racer pistons for the ATC/TRX.

I then sent LED a email but seeing it's new years eve I don't expect a reply for a few days.

 

[Bigmac]

I haven’t seen any single ring pistons, from anybody, I don’t think Esr is doing much stock cylinder stuff anymore, Carlos and BDT would also be someone else to contact, he does a lot of stock cylinder work along with Arlan.

 

[Willard]

Happy New Years!!
When I got off the phone with the Wiseco guy I dialed Carlos'# just when my neighbor rang my doorbell.
When I got back to my phone I decided to send Arlan a email with some pictures of my project. Hopefully in the next few days he'll get back to me.

I think single ring pistons is more of motorcycle thing? So yeah if that's the route I go I'm then limited to 68mm which I think is a good enough start.
I'm looking at power to weight ratio here with both my saws. YZ125 weight of a 3120xp and the CR250 weight of an 090 but more compact and ergonomic.
So I gotta quit day dreaming about pistons and get back on the build as I re thought my fuel tanks build and getting them and the rest of the top handle supports mounted.

I just printed off 230 pages of this tuner book's PDF I downloaded.
Published in 1983... author is from Australia. Tons of well written data and instruction that's still applies today. Great read.
Noticed he has a 1999 2nd edition out too!

 

[Bigmac]

Happy New Years!!
When I got off the phone with the Wiseco guy I dialed Carlos'# just when my neighbor rang my doorbell.
When I got back to my phone I decided to send Arlan a email with some pictures of my project. Hopefully in the next few days he'll get back to me.

I think single ring pistons is more of motorcycle thing? So yeah if that's the route I go I'm then limited to 68mm which I think is a good enough start.
I'm looking at power to weight ratio here with both my saws. YZ125 weight of a 3120xp and the CR250 weight of an 090 but more compact and ergonomic.
So I gotta quit day dreaming about pistons and get back on the build as I re thought my fuel tanks build and getting them and the rest of the top handle supports mounted.

I just printed off 230 pages of this tuner book's PDF I downloaded.
Published in 1983... author is from Australia. Tons of well written data and instruction that's still applies today. Great read.
View attachment 216229

Happy new year, I found this article, it’s from weisco, not bad at explaining the single vs dual. http://blog.wiseco.com/single-ring-vs.-two-ring-2-stroke-pistons-which-one-is-better

 

[Bigmac]

I think the rings are a small factor, I don’t think it’s more than a hp or two, or they would all be doing it. Once the piston gets bigger apparently the two ring is a must.

 

[Willard]

330 big bore and up definitely 2 ring for the long haul.
But with hotsaw use the simplicity of single ring would offer much quicker break in and better throttle response in the cold start.
Here's that 2 stroke tuner's PDF from 1983.
Like to see his 1999 2nd edition. Probably more on computer programming for pipes etc.

http://iheartstella.com/resources/manuals/tuning/Graham-Bell-Two-Stroke-Performance-Tuning.pdf

 

[Bigmac]

330 big bore and up definitely 2 ring for the long haul.
But with hotsaw use the simplicity of single ring would offer much quicker break in and better throttle response in the cold start.
Here's that 2 stroke tuner's PDF from 1983.
Like to see his 1999 2nd edition. Probably more on computer programming for pipes etc.

http://iheartstella.com/resources/manuals/tuning/Graham-Bell-Two-Stroke-Performance-Tuning.pdf

Cool I will read it. I read ct had done testing with the big bored 330-350, and if you overheated the ring once you lost 5 hp for the rest of the rings life, and only replacing them could bring the power back, kind of crazy

 

[Willard]

Cool I will read it. I read ct had done testing with the big bored 330-350, and if you overheated the ring once you lost 5 hp for the rest of the rings life, and only replacing them could bring the power back, kind of crazy

Maybe I should take that Wiseco guy up on his offer to build me 12 pistons any design I want.
Looking at their latest Racer Elite piston the armor coating covers the whole crown and ring groove plus the pin bore. Helping to eliminate heat and detonation damage. The skirts are also coated and they claim they form very close to the cylinder eliminating need for ABC sizing.
They make them for the 66.4 2002-07 CR250

 

[Bigmac]

There are a ton of options! There are almost limitless combinations! You could have them make 69mm slungs for the 83 style. You could run a 68mm 97-01 piston and converter to flat top. Sleeve it and run a 72mm bore trx piston...or custom. You could weld or epoxy sub exhausts, weld the corners of the roof of the exhaust port and and have a custom sleeve made for bridgeless exhaust and an oval port with sub exhaust...
It’s fun to build combos in your mind and think of the best thing to try. I think you will be shocked how well a 68 bore 128/130ish 188-192ish combo will run with v3’s and a squish of .040 and custom pipe for the specs, if you lift the exhaust to 198° it wil rev well but narrow the power curve. I don’t thinks you will be much off fully ported power from a top builder.
I have to keep reminding myself it’s a saw not a quad, so it’s different requirements, I am needing to move 350 pound quad and me 285 pound up long hillclimbs, so the torque curve needed is different. I wonder how much gear you can run!!!

 

[Willard]

All excellent points Nathan..this last post of yours I printed off and is in my binder.
Yes lots of interesting things will be found by early summer.
On the subject of reverse rotation with major and minor side thrust I now see no worries with the Honda's long 72mm stroke and tall piston. The high revving short stroke YZ125 seemed happy with it.

Gearing? Yes I'm starting small diameter and will see from there. I'm not building a 370cc big bore so won't be a need for a 18-20T .404 sprocket.
Gearing whether it's sprocket or "chain gearing" all boils down to the size and species of wood.
Just in my little isolated competition field I saw some very fine built engines whether stock appearing or unlimited but common was they had the mistake of too much gearing and a poor cutting chain.

Then when all said and done when everything is balanced out the operator cuts out and is disqualified!! (I'm using my myself as an example)

 

[Willard]

Found this degree wheel on Amazon for $13. Is this what I need?

 

[Bigmac]

Found this degree wheel on Amazon for $13. Is this what I need?
View attachment 216385

Yep, then by a cheap toolless drill chuck and mount it to that and you have a quick change wheel! I used to bolt them on, but the chuck is a life saver!

 

[Willard]

Awesome thanks!
I like yours better it's got instructions on it.

 

[Willard]

Hope everyone is having a great first day of 2020!
No hangovers for me, it's been 1 year now since I last had a drink,Lol.

I'm getting back into Timbersports late in life, I'll be 62 in 3 weeks. Still have lots of kick in me yet as I have been operating my tree service working alone for the last 14 years cutting, climbing, dragging brush, loading rounds.
In the winter off season I lift weights, do a hour once a week at a yoga class.

But it's not all about me. I have a 27 year old son I'm trying to reconnect with.
I found out about him and met him for the first time when he was 5 years old. I was then there for him until he graduated high school. He then worked briefly with me in the tree service. We had a falling out (of course father and son team) and I haven't seen him since, sent him a $100 every Christmas and birthday and only text when we he thanks me.
Today he's doing good, big strong 27 yr old kid, lives out in Alberta by himself, has no kids , has a nice girlfriend, good job and drives a brand new F150.

We've been talking on the phone lots for the last year and he thinks my hotsaw project is cool and he's interested in taking in some shows with me.
It's going to be expensive. I dug out my old 5.5 ft crosscut, trying to buy back my old 6 lb Hytest axe and rebuilding a stock appearing saw.
Already looking at some racing crosscut saws and axes ....not cheap.....