Using a degree wheel

[jb-chainsaws]

Okay guys I may come across as a complete simpleton, but I've actually never degree'd a saw.

I understand the basic principles but my main question has always been:

How do you figure out how many degrees equates to what distance of piston travel? As in if my Transfers were 120 and I wanted to change that by 3 degrees, how do I figure out how much to grind?

 

[mdavlee]

I mark the piston with a pencil at 120 roll the degree wheel to desired and mark. Pull cylinder and measure the difference. The stroke changes as the crank rotates with the dwell times. Mark the piston close to the port you're trying to move.

 

[Magic_Man]

I put a ring in the cylinder, run it up to where I want to be with the piston. Pull it apart and mark the bottom of the ring.

 

[jb-chainsaws]

Both great ideas, thanks chaps

 

[Al Smith]

You need to first remember to "zero" the wheel before you do anything in order to be accurate .At zero degrees or 180 it takes more movement of the crankshaft to change the location of the piston as opposed to 90 degrees .

What you do is get the piston top dead center,set the wheel,rotate clockwise,until you detect movement,jot the number down,then counter clockwise and note it . If for example you get 7 degrees one direction and 3 the other you move the wheel so you get 5 plus and 5 minus .The wheel then should be pretty much zeroed .If you don't keep the wheel zeroed you will be off .

If say you want 100 degrees after top dead center and you go past it in your checks ,reverse rotation by say 30 degrees then turn it back before you mark it.That way it takes out what little slop can be in the rod bearing piston pin etc .It won't be much but it can be some .

One thing to keep in mind .It's real easy to grind metal off a port but it can be a beech to put it back on . It's not a race to see how fast you can do it .Measure twice cut once or in my case measure 6 times .

 

[Red97]

To take using the ring 1 step further.

Measure the distance from the bottom of the ring to the top of the bore. Cut a piece of card stock to that dimension. Then you can check the card stock for accuracy with the degree wheel.

Then put the card in the jug and use it as a guide. Grind to the card.

 

[jb-chainsaws]

To take using the ring 1 step further.

Measure the distance from the bottom of the ring to the top of the bore. Cut a piece of card stock to that dimension. Then you can check the card stock for accuracy with the degree wheel.

Then put the card in the jug and use it as a guide. Grind to the card.

Apologies but I don't follow why you're measuring to the bottom of the ring??

 

[Red97]

Apologies but I don't follow why you're measuring to the bottom of the ring??

With the jug upright (as sliding it over the piston) Piston would be touching the bottom of the ring.

Hence you measure from the bottom of the ring to the squish band. That is the measurement to make the card.

 

[jb-chainsaws]

Ah sorry of course, a ring in the bore up top of the piston, gotcha. I just don't read things properly sometimes, I'm Not too bright but I can lift heavy weights

 

[Mastermind]

I'm Not too bright but I can lift heavy weights

I can fart really loud.

 

[Duce]

I can fart really loud.

So, that was not a sonic boom I heard at the Grayling Air Base!

 

[Mastermind]

So, that was not a sonic boom I heard at the Grayling Air Base!

I'm pretty bad ass.....powerful even. But sending one to Michigan is probably outta my league. lol

 

[Joe Kidd]

I'm pretty bad ass.....powerful even. But sending one to Michigan is probably outta my league. lol

You could Fedex one in a mayonnaise jar darkened to preserve freshness.

 

[Mastermind]

You could Fedex one in a mayonnaise jar darkened to preserve freshness.

Yeah Jeff........you're gonna do fine here at OPE.

 

[cus_deluxe]

Nothing worth contributing here, im a degree wheel tard. Carry on.

 

[Tor R]

I normally set the TDC by using soldier, when they are knocked flat checking squish there is still some resistance left when turn back and forth over TDC, +/- 3-4°, makes it kinda easy to narrow down correct TDC.

 

[MattG]

I'm Not too bright but I can lift heavy weights

I can fart really loud.

What I'd find most useful is some description as to how the wheel is actually fixed to the crank. From most of the vids I've encountered the wheel seems to be further out from the engine centre than the bar studs, whereas the crank end at the PTO terminates at a plane closer to the centre than the ends of the studs. It seems that some kind of extender must be getting used.....can anyone explain please?

PS I can lift weights and fart loud, but not at the same time. That would be messy.

 

[CR888]

Many use a 1/2" drill chuck with the degree wheel bolted to the chuck.

 

[jb-chainsaws]

PS I can lift weights and fart loud, but not at the same time. That would be messy.

I done that once, not a bright move

 

[MattG]

Many use a 1/2" drill chuck with the degree wheel bolted to the chuck.

Think I get it........so is that how you put your rig together too, @Mastermind ?