Exaust port mod. question

[MikeP]

I have an OS RG outboard powerhead I need to replace. I have a new motor and found that the exaust port on the old one is bigger, the top of the port is raised and it's a little wider at the top.

 

[MikeP]

Here is a picture of the stock piston sleeve in the case, the top of the port is already above the case opening and the bottom is raised above a little, if I match the new exaust port the top of the port opening will be even higher than the case opening.

I thought matching the case to the port opening was better so I thought I would ask.

Mike

 

[MarkScott]

I always tried to get an even flow out, no areas with sharp drop offs. Then again, what do I know? :lol:

Mark.

 

[Mike Hughes]

Just looking at the picture of the sleeves, it looks like the flange of the new one is thicker. This will put the new sleeve higher in the case. If the distance from the top of the sleeve to the top of the port are the same between the two than the larger flange is going to raise your timimng numbers for the thick flange sleeve. It looks like there is a difference between the distance from the bottom of the flange and the exhaust port also.

It is always a good ideal to go through the timing numbers again when you change parts on the motor. Do you have a caliper? That way you can measure the sleeve. It does not take much to change it to a point where it will not run good at all.

Mike

 

[waterbug]

 

Mike

 

Are the sleeves the same height from the top of the port up to the sleeve flange.... I'm in IMPBA and we can mod the port on the case or anything else on the inside of the engine .......[ Sport 21] I don't know what rules you run by in the land down under.......

 

On my XM case, I opened up the top and cut the bottom of the sleeve port flush with case...... and took a emery board and took the edge off the bottom inside of the sleeve so the piston didn't hang up...... My sleeve is going to peel anyways...... it was made before OS refined the nickeling process.....

 

Those little dental picks come in handy to mark the case...........If it is a mod engine then opener up...!!!! shim the sleeve and cut the head button to set clearance..........

 

 

I'm with Mark .......What the hell do I know...........call or Email Rod G.

 

 

 

 

 

 

[waterbug]

 

**** ..........Mike H we where typing at the same time.........There are too many Mike's in here.......... :lol: :lol: :lol: See I thought this Mike P. was in Aussie land........... :huh: . Washington

 

 

This should be in the OB Forum......

 

 

[MikeP]

Hey, thanks for the replys.

All parts are identical. The old one has been reworked a little and the new one is stock.

I want the new motor to run just like the old one did, but I can't help but look for a little more.

Mike