Changing port height

[Andrew1289]

I happend to notice a riva cylinder for sale. It has race porting. 80 degree exhaust port and 115 transfer ports.

This would be bad for freestyle no?

Is there a way to lower the exhaust port, easily. Maybe mill the top of cases a little? Some how use kawi pistons? Maybe with epoxy? haha

Thanks guys.

 

[waxhead]

you could remove the sleeves and machine the base of the cylinder this would poke the piston out the top of the head then clearance the head to accept this

 

[egbrig]

Is it posible, yes but for guys like Wax its just work, for most others it will cost alot of $$$ and most likely blow up the engine once or twice.

 

[waxhead]

Yes thats a very good point if you have to pay for the service you may as well get another cylinder ported

 

[Andrew1289]

Thank you for the replys!

Hey WAX, to save me from having to take the sleeves out and then try to match them up good again. It is possible to just mill the top of the cases and then get new domes cut to accommodate the piston sticking out?

 

[restosud]

you could mill the cases but will have to trim bottom of sleeves as well.

 

[waxhead]

Yes you could mill the cases but then the cases are also modified and no longer work on anything else. I would modify the part thats already to much first

 

[Andrew1289]

Thank you.

 

[#ZERO]

Don't mill anything, just sell the race cylinder or trade it for one with freestyle porting. :biggrin:

 

[Andrew1289]

:grumble: :tapedshut::biggrin::smokin::shocked:

 

[masterblaster]

Those old riva cylinders with that high of porting are worthless for our kinda riding,those port times would = something like 200 exh duration and 130 transfer duration. even resleeved $$$ the casting on the back on the exh would have a huge gap being that high,and the transfers roofs wouldnt line up. you would have to push the pistons really far out the top to get close to freestyle porting if you milled the base.

 

[OCD Solutions]

How do you figure out the degrees of porting without a degree wheel...roughly? I have a 62T 760 cylinder that was ported for racing by TLR and it has tons of bottom end. The exhaust ports have been raised 2mm from stock but what does that equate to in degrees? How does mine compare to the cylinder the OP is posting about?

 

[sjetrider]

just get the compresion up to bout 220 and run race gas and she will hit fine on bottom.

 

[egbrig]

Torr, I told you the port timings and my opinion in confidence to keep you from biting off more than you could chew. I could fix that cylinder to work but I don't have the time, infact I have already figured out how to ajust the cylinder to get it to run right for surf riding. The guy selling it was honest about the cylinder. I as well as others here keep alot of info off the boards so as not to mess up a sale or invite negative dialog that would take away from someones wallet.

 

[masterblaster]

eric,didnt get that pm from you,I just used the base lines of a 61x and adjusted 2 deg of duration per deg of timing. Do you know the seller? at least this way anyone here that would buy it knows what they are gettin into?