372XP X-torq 75cc Conversion & Porting

[RIDE-RED 350r]

101/120/78 I'm pretty sure is where mine is at

 

[XP_Slinger]

I like 96 on them. 118-120 and 78 widened.

That's right around the blow down I'll be looking for. Interesting how high your exhaust is. Thanks for sharing Mike.

 

[RIDE-RED 350r]

Just got my numbers out of my old phone: 100/122/75. Exhaust at 70% of bore, intake widened and squared

Kinda want to give it a little more intake time after finding that, like around 78-79.

On the other hand, the fricken thing runs pretty strong. I wonder if the larger intake area I gave it makes up for being 10 degrees short of square with exhaust duration...Probably should just leave well enough alone

 

[XP_Slinger]

Just got my numbers out of my old phone: 100/122/75.

Kinda want to give it a little more intake time after finding that, like around 78-79

Yup I've got adjustments to make after learning more too. My XT ended up at 78 with just the BG delete which I think is right near where it should be.

 

[RIDE-RED 350r]

See above, edited for more thoughts

 

[XP_Slinger]

Let the fun begin.

 

[dustinwilt68]

I like all the build threads guys, keep them coming, run down and grab that 254 next.lol

 

[XP_Slinger]

Just timed the new cylinder, came in at 103/127/76 without the base gasket. So as I suspected the timing of the cylinder blew my plan out of the water a little. Since there's no fun in not grinding I'm gonna set the exhaust at 100 and widen it to 70% of bore. I'd like to keep this engine as square as it is now so I'm gonna set the intake at 79* BTDC. Transfers are going to get raised to 123* for 23* of blow down and shaped more to aim them toward the intake. I'm gonna leave the lowers alone, Joe took the big humps out of his and I'm curious to see if this saw will run just as good with them in there. I think the new charge will favor the primary transfer more if I leave them there. Be back in a few hours, I got some grinding to do.

 

[XP_Slinger]

Took a little material out of the exhaust

 

[XP_Slinger]

 

[RIDE-RED 350r]

Dub dub dubba ya!! Dub dub dubba ya!

 

[XP_Slinger]

 

[RIDE-RED 350r]

Nice work, exhaust all done then??

 

[RIDE-RED 350r]

I like all the build threads guys, keep them coming, run down and grab that 254 next.lol

If it weren't for that 242xp being there begging to be adopted, the 254 is probably what I would have brought home. Next time we go into the junk shed

 

[XP_Slinger]

For anyone following that's curious, here's what 23* of blowdown looks like. The transfers will be opening at this point. The bottom of the ring is where the top of the piston will be in the exhaust port. The port isn't finished so don't critique me too hard yet...lol.

 

[XP_Slinger]

Nice work, exhaust all done then??

It's at 100* and chamfered. Gonna spend more time on the finish once I get the transfers raised and the intake lowered.

 

[RIDE-RED 350r]

Widened to 70%?? If I recall that is just about 36mm on the nose.

 

[mdavlee]

Just timed the new cylinder, came in at 103/127/76 without the base gasket. So as I suspected the timing of the cylinder blew my plan out of the water a little. Since there's no fun in not grinding I'm gonna set the exhaust at 100 and widen it to 70% of bore. I'd like to keep this engine as square as it is now so I'm gonna set the intake at 79* BTDC. Transfers are going to get raised to 123* for 23* of blow down and shaped more to aim them toward the intake. I'm gonna leave the lowers alone, Joe took the big humps out of his and I'm curious to see if this saw will run just as good with them in there. I think the new charge will favor the primary transfer more if I leave them there. Be back in a few hours, I got some grinding to do.

Primary is the one with the big humps..

 

[XP_Slinger]

Primary is the one with the big humps..

Thanks Mike, I always manage to confuse the nomenclature. Makes me second guess leaving them there.

 

[XP_Slinger]

Widened to 70%?? If I recall that is just about 36mm on the nose.

Yep, 35.98mm