250R motor questons

[Burns350R]

To bad you didnt get on here earlier. I know there are several of us that would have paid you to swap cases for a set that are cracked in the tranmission for your good ones.

Its a shame you cut up a perfectly good set, they are getting hard to find.

[Hammerman]

To bad you didnt get on here earlier. I know there are several of us that would have paid you to swap cases for a set that are cracked in the tranmission for your good ones.

Its a shame you cut up a perfectly good set, they are getting hard to find.

Yeah I'm beginning to see they are getting hard to find. If it makes you feel better the left side case was already gone when I got this basket case. I went looking last night and about chit when I seen what cases were selling for. I then realized that there was probably a good qty of junk cases that I could find. I did pick up a case left and right for 40.00 bucks that had the trans casing broke. If you guys have some junker that the crank case is still usable I may be able to use them later on for other builds. That would keep me from junking good cases! Appreciate the info guys!

[morse250r]

Nice pipes ! Great work

[Hammerman]

Thanks, they are my favorite to build! Looking forward to building this 250 pipe. I'll keep you guys posted as I do it.

I see you are from Silver Lake MI. I'm a Michigan Native but live in NE Indiana now. I've been to Silver Lake a couple times back when I rode dirt bike, had alot of fun up there on the 4th of July weekend. I haven't been there is probably 15 years now.

[deadly]

To bad you didnt get on here earlier. I know there are several of us that would have paid you to swap cases for a set that are cracked in the tranmission for your good ones.

Its a shame you cut up a perfectly good set, they are getting hard to find.

While I certainly do agree about the ORIGINAL cases being hard to find, IMHO it's not really a big deal with ESR providing cases soon.
I wish someone would step up and start making the entire tranny set. The yukon gears aren't the full set. THAT is what's going to screw us not the casings.

And I was recently schooled on a method that shows what would normally go undetected as a bad gear. THAT is scary. Gears that look 100% good are in fact cracked. I'm going to start building a new bottom end as a spare. I'll have my bike till the end of time (end of year?) lol

[C-Leigh Racing]

Oh man, I know somebody going to have some numb hands, after a few minutes of running that saw.
Your going to need to get that crank balanced as good as can be, or else it will jump out of your hands when you start revving it up.
One thing on the 250R engine you need to be sure of, where the crank comes out of the case on the clutch side, make sure you have a good seal in that area, because it is easy to get an air leak past that crank spacer. Any play in that main bearing will cause a bad seal from the crank moving around.
In our case with the complete engine on a quad, we run the transmission oil level higher than oem spec & the oil to an extent from keeping that seal wet will save us from getting an air leak in that area. If there is a air leak there, by the extra oil being present it will cause the engine to smoke like crazy, a tattle tail of sorts.

That case looks to be the metalic gray color, so that is saying it is the 87 year model, unless they have been painted by someone. The old 85/86 year model 250R cases, were thicker cast around the outside up under the crankshaft, so that gave you more metal like when trenching for the rod like if you were buiding a stroker engine.

If you'll go to the Eddie Sanders Racing site, you can see a pic of that CR250R ignition adapter plate he has & get an idea, but that plate only sell for like 70 bucks from him & would be a lot less machining for you to figure out.
On the CR ignition, the quad guys normally use the 2000 & up year model systems, but it wouldnt make that much difference in the year for what you'll be using it for, so an early model ignition system would work fine & probably be cheaper a well.

I'm an old saw man myself, worked many years doing repairs on just about every brand. Did a lot to figure out how to make customers saws work & cut faster & live longer. I guess you could say I'm old school, cause I sure love those ol Homelites & Polands.

Now, I want to welcome you to the site, thanks for joining.
I think by you coming here, we can help you & by the looks of what you do, you can help us, & that is the basics of this site, helping each other.
Thanks, again for joinig & keep us posted on your work.
Neil

[Hammerman]

Good information. I was looking at the crank seal on the PTO side and seen it had the crank spacer to ride the seal. Not sure how I'm going to do that just yet but it will get done! The vibs should be pretty decent without the counter balancer in place, not really any other way to balance a single cylinder motor without one. But if all goes as planned it will only run for a few seconds, this won't be something that has long extended cut, just wood cant racing. I did find the spacer plate, I think you are correct it will be less hassle to buy one rather than mill one out. I'm a fan of all saws, I really like the Dolmars, Husky/j-red and the Stihl in that order! I own around 30 saws myself most are ported. THanks for welcoming to this site I will hang out and see what you all do, it been some years since I've been exposed to the 250r's! Again thanks for the info!

I found a old pic of a real clean 250r that my friend owned in the background, it had NOS 250R plastic on it.

[SKYDRIFTER350]

I like the Daytona!!! oh yea...nice 250.

[Hammerman]

I decided to on with the saw today because I didn't have any material to make some expansion pipes.


I used the digital read out on my mill today to track the coordinates off the bolt pattern of the right hand crank case. I put them all on paper and I'll transfer all the data to auto cad so I can model it in 3D and create to scale patterns without wasting to much time and materials. More to come on that.






Without a good starting point on how to make the patterns I decided I needed something to compare to. I know in the past looking at some of the bikes saws out there they just look awkward to run and hard to handle. I decided my goal is to make it feel like a 120cc saw as far as ergonomics go. I want the handles to be in per portion to that of a 3120/880. I set my 880 up to the 250 block to see if it could be done.





Looks like I've got a start point now!





WIth the height gage I can map the holes of centers on my map and set the angle of the case in autocad so I can get a accurate idea of what it may look like. I set 2 points to measure from using the table top as my "bench mark" no pun inteneded!








You can see the right triangle I drew so once I get the holes drawn in Acad I can figure out what that angle is going to be for now. It is a starting point at least.

[Hammerman]

I made these wood templates to get a idea of how it will fit up and how it will look. I'll probably mock the whole chassis up with wood before making the final pieces. Not sure what it will be at this point, depending how much it will cost me it may be made out of carbon fiber with reinforcement where needed embedded.