porting suggestions anyone?

[jaguar]

Screwed up the cylinder with a broken piston so I'm going to have it sleeved down here. The machinist can also do a little porting while he's at it. I ride MX once in a great while so I don't want to lose too much off top. But I'd like more mid-range. I have less since the two side valves are epoxied in the open position. The center valve still works. Bike has a Pro-Circuit platinum pipe that really enhances the top end power. I did an experiment to see if lowering the exhaust ports (all 5) would help. I put 1.5mm of epoxy on the ceiling of all 5 ports. It burned out quick but I did notice the upper mid-range gain noticeable power. So at least I'll have him leave an edge/overlap of 1mm on all 5 exhaust ports. (He starts out with an unported sleeve).
Any suggestions from people with porting jobs for more midrange?

 

[MX175]

You epoxied the exhaust valves open? And you want more mid-range power? I don't have exhaust valves, but I thought that the point of the exhaust valve was to give you a good mid-range and then a kick at the top. Wouldn't removing the epoxy and keeping the exhaust valve clean and operational give you the mid-range that you're looking for? If your in South America, maybe Jeff Fredette or Eric Gorr would sell you some porting specs. Eric has a two-stroke performance book available (Amazon or Barnes and Noble websites) that may have suggestions.
Good Luck,
Mark
KDX175
KDX200
XS850 Special

 

[jaguar]

yeah, maybe I should of explained why I did that. The darn things kept breaking!!! twice a year. bad design so I just epoxied them in the open position. The bike still has mid-range but there's definitely a step-up in power when you hit a certain high rpm. I'd like some of that high rpm power in the mid range.

 

[B]

Hi J,

Im just having afull engine rebuild done at the moment as my SR is sounding pretty bad now. But still its done a lot of miles.