How to use and read timing degree wheel?

[mdavlee]

Wonder how many of us speach Appalachian american here?

A few I'm sure

 

[jmssaws]

Why are you switching?


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Seems it will be easier once learned

 

[Brewz]

Case comp is intake close to transfer open.

Would that mean when I raise my transfer tops to reduce blow down time and get the fresh charge entering the combustion chamber faster, I will reduce my compression because the transfer tops will now be open longer before the piston skirt shuts the intake and begins to compress the fresh charge to push it up?

I noticed my 026 lost compression when I raised the transfers.

I could probably get some back by raising the intake floor with some devcon

 

[huskihl]

To clear up from a couple pages back, for those wondering, intake opening is measured in degrees of rotation before top dead center, when the bottom of the skirt is exposed looking at the bottom of the intake floor. For instance, an intake opening of 76°. 76° btdc is when the intake skirt clears the intake floor. So 76° up to tdc, and 76° back down to when the skirt again closes the intake tract would give 152° of intake duration.
Exhaust and transfer openings occur after tdc. Intake openings are btdc

 

[metallic]

The nice part about working with duration is that there is no need to find TDC. Just rotate the crankshaft until the top of the piston just clears the top of the exhaust port, then zero your degree wheel.

Now rotate the crank through bottom dead center and back up until the top of the piston just closes the exhaust port. Whatever your degree wheel reads is the exhaust duration. Since two strokes have symmetrical port timing, half of your exhaust duration will be TDC.

Shining a small light through the plug hole works great for seeing when the piston crown clears the top of exhaust port. It is also very helpful for when you need to look through the exhaust port to see when the transfers open/close. Intake duration is simple because you can just look into the intake port as you rotate the crank.

 

[Frank bierce]

Nothing to add, but this has been a good read!

 

[huskihl]

Another way to find TDC...kinda like Mike does, only different. I stick a screwdriver in the top of the exhaust port. Bring the piston up so it touches it. Roll the flywheel down through bdc and back up til it touches the screwdriver again. Adjust the wheel or wire so it reads the same ° on either side of bdc. Just have to make sure the screwdriver doesn't move. Recheck a couple times to make sure

 

[jmssaws]

I use a plastic piston stop. I can watch the piston through the exhaust looking for tdc and set my pointer by eye and then screw a piston stop in and be within a degree or two everytime. Anybody else do that?

 

[huskihl]

I use a plastic piston stop. I can watch the piston through the exhaust looking for tdc and set my pointer by eye and then screw a piston stop in and be within a degree or two everytime. Anybody else do that?

I don't have a piston stop, hence my method. But if you turned your piston stop down further, bring the piston up to it...at like 10° atdc. Roll back around and adjust to the same reading btdc, and you'd be perfect.
The first couple I did by eye and was always off by a couple degrees. So I bring it up to a round screwdriver both ways and adjust

 

[jmssaws]

I do screw the piston stop down and check for equal readings but getting close by eye is time saving. I can setup in 30 seconds

 

[huskihl]

I do screw the piston stop down and check for equal readings but getting close by eye is time saving. I can setup in 30 seconds

Yep I figured you knew that.

 

[jmssaws]

I need to make a new wheel, mine so greasy It's getting hard to read.

 

[ft. churchill]

I used to use a spark plug with the porcelain knocked out of it and an allen head bolt welded into it as a piston stop. Then I would adjust the wheel to get even readings on either side of TDC. Lately I've been using a dial indicator mounted to a piece of bar stock that I just set into the spark plug hole and it makes it very easy to park the piston at TDC, then I just move the wheel to read zero TDC. I've been using .035" MIG wire as a pointer. I bend an eyelet in it with needle nose pliers, then anchor it to a convenient bolt.

 

[huskihl]

I need to make a new wheel, mine so greasy It's getting hard to read.

Mine is just a piece of Masonite with spray adhesive and a printed wheel off the net with a hole drilled in the center. Took the chuck off an old junk cordless drill, ground the head mostly off of a bolt, bolt thru the chuck, nut, space, nut, wheel, nut. Sometimes free is perfect

 

[idiotwithasaw]

Guys thank you for providing to this topic. I know I have more questions that I don't even know I have yet. If anyone has any questions feel free to pose them I started this as an open thread for us to all add to, don't be afraid of hijacking this thread.

I really enjoy the willingness of the members here to help others learn, none of the "use the search function" male bovine excrement. Yall are stand up guys for trying to teach a hillbilly some thangs.

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[idiotwithasaw]

Great thread men.

anything you have to add would be very appreciated.

 

[huskihl]

Would that mean when I raise my transfer tops to reduce blow down time and get the fresh charge entering the combustion chamber faster, I will reduce my compression because the transfer tops will now be open longer before the piston skirt shuts the intake and begins to compress the fresh charge to push it up?

I noticed my 026 lost compression when I raised the transfers.

I could probably get some back by raising the intake floor with some devcon

Raising transfers won't have an effect on compression. After compression, the piston comes down 100ish° and exposes the exhaust port. Then another 15-20° before transfers open up. Called blow down. Ignited charge has been used, and is being blown out the exhaust before new charge is being brought in through transfers. Compression would be lower had you raised the ex port.

Case compression would be greater if you raised the intake

 

[cus_deluxe]

Nothing to add, but this has been a good read!

same here, its starting to penetrate my thick skull

 

[Tpagel]

Wonder how many of us speach Appalachian american here?

I have been watched the chain filing thread/ fundraiser chain. Wow

I wish my saw chain spoke Appalachian American.


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[Redfin]

I will reduce my compression because the transfer tops will now be open longer before the piston skirt shuts the intake and begins to compress the fresh charge to push it up?

The transfers are not open before the intake closes. This is what builds the primary compression.

This is what I use to stop the piston to reference tdc from both rotations. Just a same thread longer plug.