372XP free bee

[Chesterewers]

Sorry, I'm not really getting what your doing? Measuring a cylinder that has already been ported? Then transferring that to a cylinder to be ported? How are you getting your measurements?

no what I am doing is porting a cylinder and to see how much I have changed I measure from the ported cylinder to the stock cylinder. I am trying to check and see if I am in the ballpark on the porting as far as timing goes. If so then I can continue on polish up what I have done and measure with a degree wheel to see how everything looks.

 

[blsnelling]

Your intake sounds fine, but I definately wouldn't have raised the exhaust. 372s are already compression challenged.

 

[Chesterewers]

Your intake sounds fine, but I definately wouldn't have raised the exhaust. 372s are already compression challenged.

Thats good, I will double check my exhaust measurements they may be way less than as I just used a hand file and touched it a little since I am dropping the base gasket, just remeasured got a difference of .41'' on the exhaust side, I read of one person using jb weld on their exaust porting where they messed up and it worked, I hope I don't have to do that but if I must I will. Thanks friend.

 

[blsnelling]

I would never use JBWeld to patch inside a cylinder port. That sounds like a disaster waiting to happen.

 

[Chesterewers]

I would never use JBWeld to patch inside a cylinder port. That sounds like a disaster waiting to happen.

probably would be, think it should be fine to leave it? I also didn't consider that on the one I am measuring it has carbon the the exhaust side, my change may be less if I clean that up and then measure.

 

[blsnelling]

I would just put it together and see where you are.

 

[parrisw]

no what I am doing is porting a cylinder and to see how much I have changed I measure from the ported cylinder to the stock cylinder. I am trying to check and see if I am in the ballpark on the porting as far as timing goes. If so then I can continue on polish up what I have done and measure with a degree wheel to see how everything looks.

OK, I see, I wouldn't do it that way, now you have no idea how many degrees you have changed it. I only raise the ex on 372 when the jug gets dropped, I normally don't go past 100°atdc 160°duration. But I'm also doing a popup piston to help with compression.

Like Brad said, put the jug on the saw and check your timing.

 

[Chesterewers]

I would just put it together and see where you are.

thats what I'll do then, I'll try to study up on the degree wheel use try to figure that out and get the update to this site after that. I don't understand the degree wheel fully yet, and I am advancing the flywheel 1/8 then check it over to make sure everything looks right. Thanks

 

[parrisw]

thats what I'll do then, I'll try to study up on the degree wheel use try to figure that out and get the update to this site after that. I don't understand the degree wheel fully yet, and I am advancing the flywheel 1/8 then check it over to make sure everything looks right. Thanks

You might want to start your own thread on it, and get the advice you need, with using the degree wheel and anything else, without dirtying up this thread.

 

[AUSSIE1]

thats what I'll do then, I'll try to study up on the degree wheel use try to figure that out and get the update to this site after that. I don't understand the degree wheel fully yet, and I am advancing the flywheel 1/8 then check it over to make sure everything looks right. Thanks

Don't bother with advancing your flywheel.

The first thing you need to do after cleaning up the edges of your ports is assemble it and check with a degree wheel before you go any further. To some a degree wheel is very daunting but quite easy to use. If you have gone too far with the inlet you will not be able to remove the base gasket but then that also depends on where your at with the exhaust which will also determine your compression.

Put it together and check with a wheel to see where your at so you can decide what you need to do.

Most all people who play with port timing use a wheel first up to see where they are at before anything.

Depending on what you are doing with the saw, even 162° can work fine, but then you need to do some upper transfer work to get the most out of it. Open up the lowers as others here have stated here. If needed you may have to run a piston with a higher crown to get back some compression and raise the cyl to suit.

 

[parrisw]

thats what I'll do then, I'll try to study up on the degree wheel use try to figure that out and get the update to this site after that. I don't understand the degree wheel fully yet, and I am advancing the flywheel 1/8 then check it over to make sure everything looks right. Thanks

I think you might be confusing ignition timing with port timing.

 

[Chesterewers]

Don't bother with advancing your flywheel.

The first thing you need to do after cleaning up the edges of your ports is assemble it and check with a degree wheel before you go any further. To some a degree wheel is very daunting but quite easy to use. If you have gone too far with the inlet you will not be able to remove the base gasket but then that also depends on where your at with the exhaust which will also determine your compression.

Put it together and check with a wheel to see where your at so you can decide what you need to do.

Most all people who play with port timing use a wheel first up to see where they are at before anything.

Depending on what you are doing with the saw, even 162° can work fine, but then you need to do some upper transfer work to get the most out of it. Open up the lowers as others here have stated here. If needed you may have to run a piston with a higher crown to get back some compression and raise the cyl to suit.

That makes perfect sense, thanks, if I need to raise everything with a gasket then what is suggested for a piston? Thanks I'll take some pics before I put it together and degree it out.

 

[blsnelling]

Just get it together first and see where you are. No use guessing at this point.

 

[Chesterewers]

timing

I measured exhaust port timing it was 152 degrees, no base gasket.

 

[blsnelling]

I measured exhaust port timing it was 152 degrees, no base gasket.

I believe you're stating the duration, rather than the port timing. Exhaust port timing will be close to 100° ATDC. Transfers will be about 120° ATDC. Intake will be close to 70-75° BTDC.

 

[tlandrum]

i run right around the 161 degree mark on my 372xp,my 372xpw is at 165 on the exhaust. you could stand to raise the exhaust some but id go no further that 158-160 depending on your saw.

 

[Chesterewers]

I measured exhaust port timing it was 152 degrees, no base gasket.

intake is 159

 

[tlandrum]

dont go any lower on the intake for now just get your exhaust up to where you need it

 

[Chesterewers]

dont go any lower on the intake for now just get your exhaust up to where you need it

I took a little off my exhaust already and scared to touch it, I have a stock and difference on measure between stock and ported is around .60'' as I posted a little earlier, yes I think I will start a separate posting on this subject to keep this thread cleaner. Sorry guys. Someone else here said not to touch exhaust because compression on 372 is already a problem. I am going to leave it until I get further advice on that part, I am sure it may raise a little with the gasket sealent in there, maybe not?

 

[blsnelling]

on the exhaust side I raised it towards the top close to .60 does that sound like it will work?

I measured exhaust port timing it was 152 degrees, no base gasket.

Something doesn't add up. 152 degrees of exhaust duration is a port timing of 104°. That's lower than I would expect a 372 to be, yet you saw you've already raised it considerably. Are you sure your degree wheel is zeroed? Are you getting the same readings from both sides ot TDC?