372 builders, port numbers any idea's how she will be?

[lostone]

OK, started getting some numbers last night on my 372xp build. Curious as to what builders think on the numbers. I don't know enough to even be dangerous at this time but if I am correct my upper transfers are going to be the weakest point on this thing.

Blow down is large if I am correct also? and if I am correct this will give the saw some torque but at the expense of response and top end?

OK the numbers:
New 50mm OEM piston and cylinder.
Base gasket delete:

Squish is .0215

Exhaust opens 100 degrees ATDC/Exhaust closes at 80 degrees ABDC (160 degree duration, correct?)

Transfer opens at 125 degrees ATDC/transfer closes 55 degrees ABDC (110 degree duration, correct?)

Inlet opens at 105.5 degrees ABDC/inlet closes 74.5 degrees ATDC (149 degrees duration, correct?)

 

[lostone]

The upper transfers are leaving .070 (yikes) at BDC.

 

[lostone]

The exhaust port after marking out the gasket, there is .060 at the widest part.

 

[lostone]

Then there is the lower transfers.

 

[lostone]

What other info should I try to get?

 

[U&A]

Following


Sent while firmly grasping my redline lubed RAM [emoji231]

 

[lostone]

Hmmm, Is this section of the forums just not that active?

 

[cuinrearview]

@huskihl

 

[huskihl]

My numbers work better after some lathe work. I don’t have my notes, but E102 PT120 ST124 I78 is pretty good. I match the lowers to the gasket and don’t widen the intake much

 

[lostone]

Contestant No.2 is a Farmertec build with a used OEM crank and Nachi C3, used OEM black unlimited coil, OEM seals and gaskets, OEM intake boot and OEM carb, Tygon fuel line and Stens fuel filter, OEM oil hose. I will also be using a OEM Flywheel on this build and Flippy caps to make it run stronger. I plan to put an OEM cylinder and piston on it later or a Hyway 52mm pop up cylinder and piston (I haven't decided yet).

For now and a way to learn and play with it these numbers are the 50mm farmertec cylinder and piston that came with the kit.

Base gasket delete:
Squish=.0385 (ugly isn't it)

Exhaust closes at 79.5 degrees ABDC/opens at 101.5 degrees ATDC (157 degree duration, if my numbers are correct).

Tranfers opens at 128 degrees ATDC/closes at 52 degrees ABDC. (104 degree duration, if my numbers are correct).

Inlet opens at 105 degrees ABDC/closes at 75 degrees ATDC (150 degree duration, if my numbers are correct).

 

[Yotaismygame]

Hmmm, Is this section of the forums just not that active?

That would be correct.

Are you not doing any machine work? I have no clue how a 372 woods port only will turn out. Never built a woods ported saw.

 

[lostone]

That would be correct.

Are you not doing any machine work? I have no clue how a 372 woods port only will turn out. Never built a woods ported saw.

Running the numbers for right now. I PM'ed you before about having you work on the OEM build, just need to get the $$$ up for you (take me about a week) to have you port it once it's all together which is my biggest issue now since there is so much going on I only have a little time here and there to play with it and put it together. The Hutzl will be for me to play with and learn about porting later. I'm not posting this to get "magic numbers" just to help me understand the numbers more for later.

Thinking about getting (((( this )))) for my X-mas gift to myself. I will eventually get my lathe and mill but moving next spring so will probably wait until after the move for those.

Where I haven't taken the time yet to understand the reason for this and that I am just using this as somewhat of a reference point to see how close I am coming to it in stock.

 

[trappermike]

If you checked your port durations and they are correct they are far from being performance numbers!
I would like to see the intake at 155 degrees, exhaust at 17o degrees and transfer at 118 degrees for woods port.I normally never gives specs because everyone on the planet will disagree somehow. Compression between 140 and 180. When grinding the ex. port higher compression will lessen,don't worry as long as comp. is 140 or more you will make more power.

 

[Yotaismygame]

M

If you checked your port durations and they are correct they are far from being performance numbers!
I would like to see the intake at 155 degrees, exhaust at 17o degrees and transfer at 118 degrees for woods port.I normally never gives specs because everyone on the planet will disagree somehow. Compression between 140 and 180. When grinding the ex. port higher compression will lessen,don't worry as long as comp. is 140 or more you will make more power.

Mike good to see you posting. You’re saying an exhaust port at 95 degrees?

 

[trappermike]

Well I'm saying 170 ex. dur. is good,
if you wanna be a bit conservative the 168 dur. would be ok.
The transfer port duration is very low,and increasing it will bring big rewards,but it is not always easy to do...

 

[trappermike]

Correcting too low transfer port duration can give huge power rewards you may not expect,increasing this motor's transfer duration will give a great power increase.

 

[trappermike]

But you tell me- How much transfer port duration does a good motor need? I'd like to hear opinions on this...
I've been building race 2-stroke motors since early 70's,so what's the concensus today.What duration should transfer ports be in a powerful engine- anyone's opinion?
110,120,130?...

 

[Yotaismygame]

But you tell me- How much transfer port duration does a good motor need? I'd like to hear opinions on this...
I've been building race 2-stroke motors since early 70's,so what's the concensus today.What duration should transfer ports be in a powerful engine- anyone's opinion?
110,120,130?...

I come in piece and enjoy talking about porting. 110-130 transfer duration is what most saws I do end up at. Majority have a blow down of 17-22. There are exceptions. I've yet to build a saw with a exhaust duration of more than 166. But I don't build race saws, just modified work saws. Ive never even attempted to build a race saw...

 

[lostone]

Thanks for the information, I am keeping an eye on this thread. I just received my second OEM P/C kit in yesterday for when I do finally put the hybrid together. Been having to do a lot of work on the house the last few weeks and haven't had a chance to play with the builds since we are about to move.


Toyo, which lathe is it you have? I have been looking at a Sheldon but he is a bit high on price for it right now. It's an 11" swing and he's wanting $2500 but not much stuff coming with it and for that I figure I may as well add to it and get a Precisionmatthews PM1440GS.

 

[Yotaismygame]

Thanks for the information, I am keeping an eye on this thread. I just received my second OEM P/C kit in yesterday for when I do finally put the hybrid together. Been having to do a lot of work on the house the last few weeks and haven't had a chance to play with the builds since we are about to move.


Toyo, which lathe is it you have? I have been looking at a Sheldon but he is a bit high on price for it right now.

Logan 210. Perfect for doing cylinders. Wouldn’t say it’s the the most amazing lathe ever though.