Willard's vintage Hotsaw Builds

[Willard]

One thing Honda did do was keep the Cr250r complete connecting rod kit with bearings the same from 1983 to 2001. Other sources say 1978 to 2001.
I'm finding cr250r 2001 parts on Ebay cheaper then my 1983.
But that may be for another built.

At this time I want to develop a 125 and 250 hotsaw with the horizontal profile , downdraft carb and exhaust pipe coiled underneath for the best low center of gravity.
Be able to cut from both sides on the end of a log with no header pipe interference.
All wiring, fuel/oil tanks, hoses and ignition self contained inside the powerhead.
A good change from the old standup verticle saws.

As a matter of fact with the 2001 cr250 square 4 bolt cylinder base pattern the cylinder may be able to be laid back horizontal with the carb up and the ignition on the left , PTO on the right..... billet crankcase and 330 Sphinx cylinder?

 

[Willard]

Correction on my last post:
330 Sphinx cylinder with 7 transfer ports, 4 exhaust ports with a bi directional PVL analog ignition on a reversible billet crankcase. .

 

[Bigmac]

There really are a ton of choices for cylinders, but by far the most is in the trx pattern. The sphinx is trx, the cr is limited to the esr or rare pro-x, or you have to adapt. Honestly 250 class wise, a property ported 83 cylinder and you can be within a couple of hp of the 01, it won’t be as wide of a a powerband without the powervalve and nikasil but that’s not the end of the world, and with proper porting and setup, you could easily make more peek power than a stock 01, the powervalve gets in the way, or you have to do a lot of work like spacing the cylinder and decking the top. Plus it’s a pain to over bore and you are limited to 68mm bore.

if you built custom cases the sky is the limit! Lol I would still go trx pattern.
Back on the hot rod strocker crank, it is trx only, the ignition side it longer and would have to get redone to use in a cr. And I wouldn’t recommend turning the cr to 10k even with the stock stroke it’s a lot of piston speed. The interesting thing with stroking a two stroke, is the increased crank case compression actually aids in higher RPM cylinder fill, it’s like adding a stuffer so it’s a little tricky to build compared to your standard stroke. If I use my same port timing numbers with the same displacement I get a higher revving engine with the stroker and a little loss of bottom, you actually have to run the less port timing with the stroker to get a similar power curve,
And to answer your previous post about a big bore sleeve, the only reason Arlen reports the sleeve is because he can’t punch out the TRX cylinder to 310 without putting a sleeve in it, your cylinder I believe can go to 310 without having to re-sleeve making it just a straight bore up and pork job, properly set up I think your 83 cylinder can be very competitive, especially if you can over bore it.
And in all reality you’re selling your portly out of the 83, is quite good, all of the CR cylinders up until 92, are not a measurable improvement, the 92 to 01 cylinder had a much improved power valve with sub exhausts, that is really the only advantage plus Nickasil. For your build the extra inconvenience of having to actuate the power valve makes it less attractive, in my opinion,So to me it really boils down to how bad you want to have a 330+ displacement cylinder.

 

[Willard]

I think of my '83 engine as a 1985 ATC 1986 TRX predecessor, with out the P/V is sure looks like one.

Like you say it has potential, I think its CR500 style 7 stud head is a positive, it's got a strong crank with the extra length of 28mm mag side stub before it tapers to the key way.
On the 1984 CR250R and on to 2007 they went down to 20mm right where the 28mm main bearing support ended. Lots of broken Hotrods stubs OME included with that weak point.
And that one year 1983 cylinder is really compact, my yz125 cylinder looks twice as big.
I read the 1983 cr250r cylinder had new lowered exhaust ports and raised intake ports from the previous 1982 model.

I watched a video of a guy who could put his thumb through his ported 1986 Ttx250r boost ports (I can just get the tip of my pinky in mine) then he showed where the rear cylinder mount flanges were cracking at the studs...he over ported the boost ports.

Learning lots from videos but there's alot of miss information out there too. Only person on the forums who tells it as it is straight up is Carlos. I'm sure I'll be doing alot of business with him in the near future too.
I get some pictures posted tomorrow with the 2 saws CF plates installed . Then on Wednesday taking the family to the city where I got to buy a few goodies and some aluminum pieces from Metal Supermarkets (great chain to buy some pre cut small amounts from...)
metalsupermarkets.com

 

[Bigmac]

Yes I agree your 83 cylinder is very similar to the atc/trx cylinder, you have more transfer tunnel room than the trx. Oh ya it has potential! Have seen a handful of well preped and ported stock cylinders in about the 265-270 cc range that make 55hp to the wheels of a quad, that’s really good, it’s about 5hp loss to the wheels of a quad compared to a dirt bike, and obviously even more hp at the flywheel. And they aren’t drag builds, mid-top style builds. Have also seen tons of 310-330cc build under 50hp. Prep is huge on these, and sometimes that gets lost in the big builders. I need to spend some time on the dyno,,have a few things to test. And I need to get back on my stock cylinder 67mm bore +4mm stroke build, am shooting for 55 hp to the wheels. Will see! I need a shift shaft an a custom head gasket.
Carlos is a good guy, like I was saying earlier, and they built pipes too, full custom shop, they also do the decomp heads.
The small bore 68-69 mm, stock stroke motor can be vary strong. They rpm a little harder and are reliable, have ran a few up to 240 psi that still reved to the moon, 8500. Super fun and manageable power, it likes to live at that rpm all day, I kinda miss the small motors.

 

[Bigmac]

There are a lot of parts on eBay, 85 cases aren’t bad, and some super cheap 92-01 cases are on there now, I like your build. I think that it will run well if ported correctly the right pipe and prep. A 330cc+ top end will give it a lot more grunt, and lugging power, and be more forgiving, you have to be on your game to make the 250 a killer, but it is possible, and rewarding. Have you looked up Mac dizzy?

 

[Willard]

It looks like Mac Dizzy is charging a subscription fee to join or view their site. All that pops up for me is French automotive.

Had to edit a post of mine. The cr250 crank mag stub on the '83 has a long section at 28mm diameter from the main bearing to the taper near the keyway. 1984 to 2007 it steps down from 28mm at the bearing to 20mm (not 25mm), reason why they have a 20mm oil seal and the '83 oil seal is 28mm.
28mm seal was discontinued due to premature wear from what I can gather. But the '83 has a beefy mag crank stub compared to the newer failure prone version what I hear about.

The '83 crank I'm planning to send to Crankworks with a ProX rod kit and have them rebuild and true it with a welded crank pin.
Balancing might be an option once I get my piston and bore figured out.

Bike saw use in competition is very specialized onto itself, yes very similar build category as to a TRX dragster.
But main difference is a dragster can be revved to the moon before the green light hot start.
A bikesaw in the top competitions has to be cold started on the green and only cut for 2 to 6 seconds normally.
Everything on that engine has to be just right plus the operator's technique starting and cutting 3 cuts within 6 inches of wood,
Lol talk about pressure.

Awesome seeing you have access to a dyno. Something you built?
Research and development is hard to do without one for sure .
This is an interesting site I been following.
https://kopulse.info/w/PjGjU8ti7FjCwhv6s-akLA

 

[Bigmac]

It’s too bad macdizzy is gone, he was a wealth of info at the early stages of the internet, late 90’s early 2000’s, I hadn’t checked in about a year, it used to be subscribing based but also had a ton of free content, his 270 build was available, it was a simple build that made good power.

Ya it’s nice having a friend with a dyno, he owns a shop. I build all of my motors and build a small amount for others, last year did a cool cr500 hill climb build with custom pipe.
Ya the cold start is a unique challenge, it has to be reliable to start and be tuned perfect, a milder tune and good reed are a must! Do you get any pre warm up time?

 

[Willard]

Common hotsaw rules allow 1 minute of warm up.
When the pipe feels hot to the touch it's ready.
There's lots of opportunities building hot saws but with my young family to take care of I have no desire to get into that.
I'm having a hard enough time finding shop time to work on my own as it is. Lol.

 

[Willard]

Couple pictures from over the last few days.
Hard to see the clear Plaskolite sheet but it's there allowing me to drill case screw holes. PV lockoff plates 4 screws are installed.
CR250R template waiting on top.
Going at a snail's pace doing both engines.
The sheet is the same 16"×20" measurement as the expensive 5mm sheet of carbon fiber.
Always cut CF parts oversize to allow for sanding down the cut edges.

 

[Willard]

Sandvik information tells me CF cut edges are strength compromised including drilled holes. They need to be sanded and cleaned up.

 

[Willard]

Making pilot holes.
Can't even turn the radio on

 

[Willard]

When I made the same holes 37 years ago I wasn't so fussy.
But I did make a beautiful 40mm crankshaft dust seal hole.

 

[Willard]

Just now taking the kids to their band practice I trip over my titanium package on my front step.
All the way from Israel.

 

[Willard]

Hour later ...didn't trip on this aluminum order. Couriers are busy tonight

 

[Lightning Performance]

Good thread
I'll finish this page tomorrow.

You don't need no treeten top end.
I'm skinny so when I last jumped on a bone stock, with a pipe, 86' CR250 it still carries the front through four gears with my narrow ass over the bars. Fresh 410 bar on the back, fat pipe, tall rye grass and hold muh beer...
That bike *f-wording moves right. It is stock inside. I drilled the broken exhaust stud out on the bike when he bought it about five years ago. It's real clean never touched. We did the pump and new rads with hoses. He has the matching trike to go with it. That is mint. Sitting in the master bedroom dry stored. He sold the other trike rider. All nice clean 86' models.
86' CR 250's Forever!


The 2001 250 with the 500 is quite a hand full, git on it or move over, coming through.

The either end saw with the under pipe would be sweet

 

[Willard]

Good stories LP!
I call the CR's the top fuelers of the 250s and 500s.
This 1983 CR is my first Honda, I'm impressed enough with its porting and I can't even ride it.
Even the first year 1981 liquid 250 has potential. And I watched a few YouTube videos of some pretty hot 1979 air coolers and rooster tails like crazy at about 40 mph. Those early bikes were really light though.
Yeah the 1986-'87 CR250R had some good mo jo.

Yep both my YZ125 and CR250 will get under belly TRX style drag pipes.
The header pipe will curve to the front left under the mag then come straight back exiting to the rear right.

I will have the honda running reverse rotation like the YZ125 is setup. When I ran the 125 in reverse last spring with the new PVL ignition I felt no vibration in the engine even tipped over horizontal. Some tell me I may get less intake skirt thrust wear which might be a good thing.

 

[Lightning Performance]

The first one I ever jumped on tossed me in two minutes or less. Brand spanking new, first day out 80 or 81 air cooled I think, CR250. It needed handlebars...I felt bad for the guy. Tossed him fifty bucks. He was pissed. Scratch the front fender. Lost it in whoops, fourth gear, no chance....I bailed out and wrecked.

They were light in the first version.

 

[Bigmac]

Good thread
I'll finish this page tomorrow.

You don't need no treeten top end.
I'm skinny so when I last jumped on a bone stock, with a pipe, 86' CR250 it still carries the front through four gears with my narrow ass over the bars. Fresh 410 bar on the back, fat pipe, tall rye grass and hold muh beer...
That bike *frenching moves right. It is stock inside. I drilled the broken exhaust stud out on the bike when he bought it about five years ago. It's real clean never touched. We did the pump and new rads with hoses. He has the matching trike to go with it. That is mint. Sitting in the master bedroom dry stored. He sold the other trike rider. All nice clean 86' models.
86' CR 250's Forever!


The 2001 250 with the 500 is quite a hand full, git on it or move over, coming through.

The either end saw with the under pipe would be sweet

My first 2 wheeler was a cr500, I bought it cheep, piston was starting to crack, so I never ran it stock. Decided to port it and mill the head when I had it bored, put some boysen reeds and put a 40.5mm lectron carb...that bike bit me a few times...looped it out grabbing 5th once, it would power wheelie in 5 at about 80+ it was a handful indeed! 3rd gear was as fast as a 250 in 5th maxed out! I had it geared up a tooth in the front! Cr250 do about 65mph stock a cr500 dose 89mph stock. I never liked the transmission ratios in the 500,,when I drag races it I would start in first, get rolling then click it into fourth and roll on the power, it had a great power curve! I do love the 5 honey!
The cr500 was detuned from 85 on! The cr250 gained about 5hp to the wheel from 85 to 02-03 and then got smoothed out to 07. On the dyno the 02-03 make more than the beloved 2001 cr250, but the 01 had personality and great midrange, where the 02-07 were more lackluster tell the higher rpms. I think honda messed up on the last generation cr, bad port layout and the rc powervalve was to slow, I think the works team put a better battery on them, though I cannot find that info.
I have an 86 trx and a wheeler in boxes, need to get to that or the 89 trx, I don’t have space for them! Lol

I have some good trike stories, have had a bunch of them..built a cr500 powered 85 atc 0n alky and a drag pipe...

 

[Lightning Performance]

The cr500 was detuned from 85 on! built a cr500 powered 85 atc 0n alky and a drag pipe...

Agreed..

I saw one if those way back in eighties at the sand drags. Nasty piece of work on a bad course that night. He stayed on.