RIDE-RED 350r
Here For The Long Haul!
- Local time
- 9:11 AM
- User ID
- 839
- Joined
- Feb 8, 2016
- Messages
- 3,228
- Reaction score
- 12,761
- Location
- Blossvale NY
And it was a complete success!!!! 
The saw I did is my 372 XP-Dubya, 75cc version..
Awhile back, I did a muffler mod, base gasket delete, lower transfer matching/beveling, and took the big humps out of the exhaust side transfers.. It did make a difference and I was happy with the results...
Today, my brother XP_Slinger and I got the degree wheel out and tore down our 372's.
Best I could determine, stock port timing was exhaust:113, Transfer:128, and intake:75 (BTDC) with blowdown of 15.
I changed transfers to 124.5 (target was 125) and left exhaust and intake as they were with running no base gasket.. I also widened the exhaust port from the appx 29.5mm that it was stock to 35mm as I remember seeing somewhere that a good mod to the exhaust port is to make it 70% of bore width. That 70% was actually just shy of 36mm, 35.98 to be exact.. But I went with 35mm as I didn't want to push it too much. I also blended and enlarged the entire exhaust outlet all the way out to the muffler mount flange and matched the gasket, heat shield and muffler opening to the newly enlarged exhaust outlet...
To say this made a noticeable difference is an understatement!!! I actually NEED an unlimited coil to be able to really tune it in and take advantage of the extra RPM it can now readily and quickly spool up to. Tuning is tricky with the limited coil.. If I turn it out so it is 4-stroking from actually being a little rich, it dogs pretty bad in wood. So I turned it in till it cut well and it seems pretty close now.. It would be alot easier to tune with an unlimited coil in it. I am so happy with how this turned out!! I don't think I am going to change it any more from here, it's hard to imagine how much better it could be than it is now.
I almost raised the exhaust 2 or 3 degrees, but figured I would try it without raising it first.. And at this point as strong as it runs, I think I'm going to leave the exhaust right where it is...
I just want to thank all of the people here who are so generous with their knowledge and advice!!! Without people like you guys, I would never have dug into my saw the way I did today... Everything from threads like the porting theory thread, to Randy's handy how-to videos for finding TDC, using a piston ring and index card material to find out exactly how far to grind ports and so on and so forth...This forum and it's members kick ass!!
By the time we got both saws back together and running through some cookies we were losing daylight, so unfortunately I don't have any vids to post up... But I will definitely make a vid or 2 tomorrow and post it up.. But I think I'm going to borrow the unlimited coil out of my 357 and toss it in the XP-Dubya for tuning/testing purposes.. and I want to see just how high this thing will spool up now.
Speaking of the 357, I'm thinking of trying the same approach with that saw... It too has the muffler mod, base gasket delete, and lower transfer matching/beveling. Think I might just try raising the transfers and widening the exhaust. Unless of course anyone has any pointers on what the 357 likes in terms of porting..
The saw I did is my 372 XP-Dubya, 75cc version..
Awhile back, I did a muffler mod, base gasket delete, lower transfer matching/beveling, and took the big humps out of the exhaust side transfers.. It did make a difference and I was happy with the results...
Today, my brother XP_Slinger and I got the degree wheel out and tore down our 372's.
Best I could determine, stock port timing was exhaust:113, Transfer:128, and intake:75 (BTDC) with blowdown of 15.
I changed transfers to 124.5 (target was 125) and left exhaust and intake as they were with running no base gasket.. I also widened the exhaust port from the appx 29.5mm that it was stock to 35mm as I remember seeing somewhere that a good mod to the exhaust port is to make it 70% of bore width. That 70% was actually just shy of 36mm, 35.98 to be exact.. But I went with 35mm as I didn't want to push it too much. I also blended and enlarged the entire exhaust outlet all the way out to the muffler mount flange and matched the gasket, heat shield and muffler opening to the newly enlarged exhaust outlet...
To say this made a noticeable difference is an understatement!!! I actually NEED an unlimited coil to be able to really tune it in and take advantage of the extra RPM it can now readily and quickly spool up to. Tuning is tricky with the limited coil.. If I turn it out so it is 4-stroking from actually being a little rich, it dogs pretty bad in wood. So I turned it in till it cut well and it seems pretty close now.. It would be alot easier to tune with an unlimited coil in it. I am so happy with how this turned out!! I don't think I am going to change it any more from here, it's hard to imagine how much better it could be than it is now.
I almost raised the exhaust 2 or 3 degrees, but figured I would try it without raising it first.. And at this point as strong as it runs, I think I'm going to leave the exhaust right where it is...
I just want to thank all of the people here who are so generous with their knowledge and advice!!! Without people like you guys, I would never have dug into my saw the way I did today... Everything from threads like the porting theory thread, to Randy's handy how-to videos for finding TDC, using a piston ring and index card material to find out exactly how far to grind ports and so on and so forth...This forum and it's members kick ass!!
By the time we got both saws back together and running through some cookies we were losing daylight, so unfortunately I don't have any vids to post up... But I will definitely make a vid or 2 tomorrow and post it up.. But I think I'm going to borrow the unlimited coil out of my 357 and toss it in the XP-Dubya for tuning/testing purposes.. and I want to see just how high this thing will spool up now.
Speaking of the 357, I'm thinking of trying the same approach with that saw... It too has the muffler mod, base gasket delete, and lower transfer matching/beveling. Think I might just try raising the transfers and widening the exhaust. Unless of course anyone has any pointers on what the 357 likes in terms of porting..
Last edited:
