porting help 371xp

[CFM]

Hey guys, new to the forum and new to the world of porting 2 strokes. Ive done research on the subject for a day or two now and still having troubles. I've knifed edged the supports in transfers and cleaned the casting slag throughout. My next step might be to remove the cylinder wall in front of the transfers.... am I going to far or what for a work saw? I have a new bb kit that actually looks pretty good, yeah I know lucky me. Timing numbers and sequence if any one has them and the effects or idea of remove the cylinder would be of great help. Just nervous about going to far and winding up stuck in between fully modded and half. I don't plan on milling the jug or reshaping the piston, so I'm trying not to lose to much velocity through the transfers... thanks guys :bang:

 

[edisto]

I don't understand what you mean by "remove the cylinder wall in front of the transfers"?

 

[super2nr]

Don't remove the cylinder wall in front of the transfer port,that would make it an open port cylinder.You get more power from closed ports.You can remove a small amount from the top of your exhaust port and widen the sides a little,but not too much,if you widen too much the piston won't close the port any more!
If you open up the bottom of the intake port you have too open up the transfer ports some more to stop puddling from happening.
Don't forget to chamfer the edge of the port .
good luck on your build.:biggrin:

 

[mark09]

Hey guys, new to the forum and new to the world of porting 2 strokes. Ive done research on the subject for a day or two now and still having troubles. I've knifed edged the supports in transfers and cleaned the casting slag throughout. My next step might be to remove the cylinder wall in front of the transfers.... am I going to far or what for a work saw? I have a new bb kit that actually looks pretty good, yeah I know lucky me. Timing numbers and sequence if any one has them and the effects or idea of remove the cylinder would be of great help. Just nervous about going to far and winding up stuck in between fully modded and half. I don't plan on milling the jug or reshaping the piston, so I'm trying not to lose to much velocity through the transfers... thanks guys :bang:

I just got done porting a bb kit on a 371 the port timming numbers should be around this exh/opens @ 100* tranfurs/open @ 131* and intake/opens @ 76*. the intake on my bb kit was way to high so check that. You can take some off the bottom of the piston skirt on the intake side to lower it . getting more duratition from the intake will add power. dont go to wild with the tranfurs. just cleaning them up is good. widening the ports is a must dont go over 70% of the piston size or the rings will fall out in the port. there is a good thread on this in the hot saw forum the title is port timming on my 371. good luck,mark

 

[CFM]

Thanks for the numbers mark, your time is very much appreciated.