CR500 port work question

motardcr500 · Post by **motardcr500** » October 14th, 2014, 10:41 pm

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?

Kuma · Post by **Kuma** » October 15th, 2014, 12:30 pm

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?

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » October 15th, 2014, 1:26 pm

starts a little velocity shot, makes a difference without making the feel of port timiing

motardcr500 · Post by **motardcr500** » October 15th, 2014, 6:29 pm

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

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

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » October 15th, 2014, 8:01 pm

I have that info too, but these is actually more accomplished below that. Gorr likes his epoxy work.

motardcr500 · Post by **motardcr500** » October 15th, 2014, 8:34 pm

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..

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » October 15th, 2014, 8:40 pm

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.

motardcr500 · Post by **motardcr500** » October 15th, 2014, 9:37 pm

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...

hoofarted · Post by **hoofarted** » October 16th, 2014, 7:09 am

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.

http://www.youtube.com/user/500bigbore · Post by **Roostius_Maximus** » October 16th, 2014, 9:59 am

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.

hoofarted · Post by **hoofarted** » October 16th, 2014, 2:53 pm

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...

motardcr500 · Post by **motardcr500** » October 22nd, 2014, 8:00 pm

Thanks for your guys response, I appreciate it.

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CR500 port work question

CR500 port work question