Old Open Port Transfers

[Thesandman]

Ok I'm backwards. BG would give me more room

 

[Thesandman]

I could file base down .030". What I would do is cut notches all the way around .025 deep then draw file till all disappear.

 

[Thesandman]

I do need a carb that has .750 bore or close.

 

[Redfin]

I have your first post several times. What info are you requesting?

 

[Thesandman]

I have your first post several times. What info are you requesting?

I'm wanting info on the transfers. Size, shape, uppers, lowers and duration. My saw is cutting great on anything 10" to 12" or less but loses 1500 rpm in 18 to 20" dead ash. Just need more power for big stuff. Everything else is fine.

 

[Redfin]

Ive never farked with that jug but I like new ones.

If it were mine, Id cut the base .03”. Highly suggest you get someone to put it on lathe for ya.

You would end up in the range of 102/129/69. I like the direction of the uppers. Once cut I would not touch the ex. If you dont mind going back into it for more. Grind the primary side uppers completely flat to a nice round corner on outside edge and grind the seconds pointed up towards the plug. Hard to tell from the pics if the seconds are pointed that way but it helps if seconds open a few degrees after primaries.

I would grind the int to 74ish. Run it like that, then take some more duration out the trans. If it gains great, if not you can gain more bd raising the ex a tad.

 

[Redfin]

Be careful to not change the shape of the uppers. They look good as is.

I would not muck around in the lowers either other than to case match where needed.

 

[Redfin]

Any progress?

 

[Thesandman]

I just finished removing .030 off cylinder base but can't find base bolts to test. I have to cut wood for my elderly cousin tomorrow so maybe get cylinder on next week(fingers crossed). I could test compression and timing on original saw. I'm worried about my recoil start.

 

[Thesandman]

I bought a set of oem rings and a aftermarket piston and rings but piston seems really heavy. I won't know till I get original off rod to compare. I also ground flywheel key .020" so if everything is safe I should run it next week without anymore changes just to see what is going on. The trans is pointing low towards int and almost twice the size of int port so should be good. I have same carb as on 3700 so think a bigger one is in order. Venturi is .650"

 

[Redfin]

Im sure there are quite a few places to grind on that piston to lighten it up a bit.

 

[Thesandman]

I removed the cylinder on #2 and it appears the secondary transfer is blocked quite severely(perhaps 30%). I really don't see flow path thru crankcase to trans. The ramp that leads into trans seems blocked also but I'm thinking just open feed ramp to match trans at cylinder base. I'm thinking there is some hp to be had here.

 

[Thesandman]

Upon further review it seems feed ramp to trans is smaller on both sides. At least air flow isn't hitting a lip it's dropping into larger trans tunnels so slowing as pressure drops. I don't want to grind on them and get junk in crankcase.