Yeah, you have to machine the cases. Duncan does a great job doing that, by the way. He apparently has a jig and it comes out perfect--no free hand stuff. If you are going to be riding dunes and trails, I'd recommend the 340. It has tons of torque and is best from low end to 3/4 throttle. If you are looking for a motor that is a little quicker revving and loves 3/4 to full throttle, I would recommend the 305. Don't get me wrong, the 340 is a fast motor. It has a heavier piston, though, and doesn't like to rev to the moon like some of my 250s. I did do the "midrange" porting, however, so that may be part of it. I remember Duncan also offers a "top end" porting. I got it back in 2004 and haven't had any problems. Just replace the piston now and then and clean the PV.
Red Rider's Sand Machine Updated 07/23/14
Nevermind I clicked your link lollooks pretty bad ass man!
Last edited by Fox250R; 02-21-2016 at 12:53 AM.
Red Rider's Sand Machine Updated 07/23/14
I have an ESR 350 in one of my R's, with a 41.2mm PWK, ESR reedblock, ESR full ATC5 exhaust and Eddies trx9 porting. It runs great and has lots of power, really comes on strong in the mid-range and keeps pulling. Having the porting focused to mid-top is a blast, and the big bore displacement makes up for it on the low end.
Now, I have no personal experience with the other fine builders mentioned, but based on the pages and pages of info and feedback I have seen here and other forums you would be hard pressed to go wrong with any of them.
Some folks dog on Eddie a bit now and then, but I have zero complaints about his work and service. His only downfall is that he can be slow, but last I knew it is because he is working alone now. And he usually sends extra goodies at no charge. When I got my carb from him, he sent his new combo jet holder/carb wrench loaded with jets along with it. I didn't even ask for one.He's a good guy.
Side note: My brother and I are beginning to step into learning how to port our chainsaws. I know...dumb huh.. But it has been a great learning experience and seeing the results of your own mods is really satisfying. I bring this up just to emphasize the fact that porting a cylinder for a desired result isn't s simple thing to do. Chainsaws really are a 1-trick pony. They need to spool up quick and maintain peak RPM under a load. I would say they would be comparable to a mild drag port on a bike or wheeler engine. We have been learning alot about these... But let me tell you, I took an R cylinder off my shelf and had a look under it's skirt. You can tell that they are much more sophisticated in their layout and design. And I now have a much greater appreciation for what builders like Selvy, Lehman, Hall, Sanders, and others can do, and then be able to repeat it build after build. My hat is off to all of those guys for the time and resources they have invested in the process!
Trikes:
'85 ATC 350R
'85 ATC 250R
'86 ATC 350X
'85 ATC 350X
'84 ATC 200ES Big Red
'84 ATC 125M
'85 ATC 110
'85 ATC 70/110
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2 stroke porting really is an art form
1985 250r-LED Performance 4mm Stroker motor
1978 ATC70 w/ Piranha 140cc
1972 - K1 - CT70 w/lifan 125cc
2017 YZ 250x- Braap
Youtube channel = http://www.youtube.com/user/ter5678/videos
Hey Bud, I have a power valve 275cc cylinder it's pretty awesome. Also have the pc 2000 cyl. 275cc but not installed yet.
If you want reliable go with Duncan PC 2000 275cc power valve it's the best... You already have the Duncan pipe and silencer!
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Red Rider's Sand Machine Updated 07/23/14
Sent you a PM with my number, send me a text when you get a chance.![]()
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