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CR500 port work question

Posted: October 14th, 2014, 10:41 pm
by motardcr500
This was a Pro Circuit cylinder.
Note the differences in the exhaust port?
180 and 182 degrees.
http://www.oem-cycle.com/forum/download ... hp?id=2125

Anybody with any ideas why?
Why not split the difference and go 181 degrees across the port?

Posted: October 15th, 2014, 12:30 pm
by Kuma
that cylinder doesn't look to be ported except for the little grinding on the exhaust ports? and what's up with the crack or split going through the middle of the bridge?

Posted: October 15th, 2014, 1:26 pm
by Roostius_Maximus
starts a little velocity shot, makes a difference without making the feel of port timiing

Posted: October 15th, 2014, 6:29 pm
by motardcr500
A buddy of mine had the cylinder and when I saw ProCircuits mark I had to find out what they did.
In the least it needs to be re-sleeved.
We were comparing it to a Egore cylinder :roll: and a stock cylinder.
Egore's cylinder had a bit more work done then the PC but I'm less then impressed.
I do have paper tracings of the ports as well as recorded the port timing... which was all stock :(

Posted: October 15th, 2014, 8:01 pm
by Roostius_Maximus
I have that info too, but these is actually more accomplished below that. Gorr likes his epoxy work.

Posted: October 15th, 2014, 8:34 pm
by motardcr500
Yeah, whats the deal with epoxy in the transfers?
When my buddy showed me that I was stumped..
Trying to redirect the flow?
Reducing case volume?
I just can't wrap my head around it..

Posted: October 15th, 2014, 8:40 pm
by Roostius_Maximus
He's trying to pick up velocity and his idea at the port opening at the rear transfers is that the flow is pointed at the exhaust port but should cross the cylinder instead.
I know guys with it, heck Ive tried it too, they require less pilot jet but then again most good port work should. It's crisper but it doesn't make more torque, it doesn't make more hp, it smoothness out the low end.

I'm on the other end of the scale, I like to add 16-18ftlbs at 3800-4200 rpm, but carry that a few thousand rom higher and add hp. I don't hold much respect for his stuff.

Posted: October 15th, 2014, 9:37 pm
by motardcr500
Most knowledgeable builders I have spoken to have very little good to say about his work.
It seems the legend is more myth then reality...

Posted: October 16th, 2014, 7:09 am
by hoofarted
Hmm so I guess the big bore 250 stuff isn't up to par either? Been wanting the 265cc kit for both a YZ and a CR. :?

Posted: October 16th, 2014, 9:59 am
by Roostius_Maximus
I don't like talking it up, but the '97-'01 250 engines I've been working on have been working frigging excellent. One guys has one of mine and a DeWayne Jones engine, his buddy a Gorr. They have tried sst, fatty, gnarly, pc pipes, vf 2,3, rad valves, the adjustable external exhaust valve parts, you name it. Got a real good handle on things but keep calling to say that mine pulls harder and smoother everywhere and uses way less fuel.
You already have cases, a head an cylinder. Should tweak on it. :wink:

Posted: October 16th, 2014, 2:53 pm
by hoofarted
Roostius_Maximus wrote:I don't like talking it up, but the '97-'01 250 engines I've been working on have been working frigging excellent. One guys has one of mine and a DeWayne Jones engine,.....
You still talk to Dewayne? Its been a while for me...

Posted: October 22nd, 2014, 8:00 pm
by motardcr500
Thanks for your guys response, I appreciate it.