125-200cc Transfer port/gasket matching

[Zomby woof]

I had an unfortunate incident this morning on the CR150. Battling for position, I dumped it in a creek and filled the crankcase with water. So the top end's apart again. Looks like no damage (so happy), but while I have it apart, I was wondering if it makes sense to gasket match the rear transfer port to the crankcase. Base gasket matches perfectly on the bottom, not even close on the jug. I have experience porting 4 strokes, but none on 2 strokes, and don't want to do the wrong thing.

 

[juicypips]

I place the gasket over the cases and use a blade to trim off all the over hang in the cases, it will make a difference you won't notice it but it will.

 

[Zomby woof]

Don't need to

Base gasket matches perfectly on the bottom.

Nobody else? Surely somebody here has some porting experience

 

[juicypips]

Well if it matches on the base then you need to ease the transfer on the cylinder just blend them in with a rotary burr.
Use the gasket as a guide score the transfers with a scribe and do a gentle job creeping up on it.

I skim read over matching base I do apologise but it's not a gasket problem then it's just too much material on the cylinder.

Walt is the go too guy with porting on this site.

 

[wallybean]

The cases were designed to match up with the old style 7 transfer port cylinder and the base gaskets match that. I do trim a bit on base gasket at the exhaust port side of the transfers where it sticks out a bit on the cylinder. Really very little to gain from enlarging the rear transfer to the gasket unless you also port the rear transfer in the cylinder to be equal in height to the side transfers. You want to duplicate the angle to the cylinder that is there presently. If you do work with the lower part of the rear transfer, making it taper from a larger opening to its current size in the first 1/2" will help port velocity a bit. Remember you really don't want to polish this or any of the transfers as you want to keep a turbulent flow characteristic at the surface to avoid fuel air oil separation.

 

[Zomby woof]

Awesome.

That's exactly what I thought, but didn't want to take material out of the port and find out later that I shouldn't have. Not going to touch the rear transfer, just the mismatch on the sides.

Thanks for the answer!

 

[johnnyboy]

I match all mine in that area 125 144 165, Ever since I was a kid I have always done it, Some bikes really used to get very noticable gains to matching the cases to the jug ect but in the case of the Husky motor the gains if any are barely noticable but it makes me feel better inside that my premix has the best chance of finding its way out of the exhaust port with the least possible obstructions on its journey to making smoke .

 

[Miezie666]

I had an unfortunate incident this morning on the CR150. Battling for position, I dumped it in a creek and filled the crankcase with water. So the top end's apart again. Looks like no damage (so happy), but while I have it apart, I was wondering if it makes sense to gasket match the rear transfer port to the crankcase. Base gasket matches perfectly on the bottom, not even close on the jug. I have experience porting 4 strokes, but none on 2 strokes, and don't want to do the wrong thing.

Like johnnyboy said- i also do made these parts are matching on every bike- thats just to make me feel better....