Just pulled the head and jug and...

[spepple]

So i got my ignition issues figure out, so i pulled the head and jug to see where i'm at with my smoking/oil blowby issues. i pulled the top and bottom compression rings off and put them in the jug and gapped them, i've got 28 thousandths on both. Theres no crosshatching left. and i've got little side to side play on piston to rings which is probably from the bigger gap. Should i bore .5 over and put a new piston in, or whats your guys opinions?

[trike savior]

that is not how to measure a piston and bore. All you are checking is piston ring end gap which tells you nothing. You need a micrometer and dial bore gauge. Micrometer the piston and then you set your bore gauge to that measurement. then you put the bore gauge in the cylinder and measure twice at the top of the cylinder 90 degrees apart and twice at the bottom. a usable bore and piston needs to be .001-.005 piston to cylinder clearance. I have allowed as far as .007 but that is real loose but had no noise or oil burning with fresh rings. The top and bottom measurements of cylinder need to be within .003. top of cylinder takes a beating from all the explosions.

[spepple]

I know I have mics theyre at my dads, I know how to do it.

[spepple]

This isn't my first motor surely wont be my last. I know its hard to give input with exact measurements. But was seeing What people would say.

[barnett468]

i pulled the head and jug to see where i'm at with my smoking/oil blowby issues. i pulled the top and bottom compression rings off and put them in the jug and gapped them, i've got 28 thousandths on both. Theres no crosshatching left. and i've got little side to side play on piston to rings which is probably from the bigger gap. Should i bore .5 over and put a new piston in, or whats your guys opinions?
that is not how to measure a piston and bore. All you are checking is piston ring end gap which tells you nothing. You need a micrometer and dial bore gauge.

I know I have mics theyre at my dads, I know how to do it.

This isn't my first motor surely wont be my last.Well since you have these tools and say you know how to measure the things Trike Savior mentioned, it would be helpful if you simply told us what the amount of taper and out of round is in the cylinder, the piston to cylinder clearance and the measurements of the piston just below the bottom ring, half way between there and the bottom and 1/4” up from the bottom as well as the piston mfg if known and whether it is forged or cast.

You can look at the edge of the rings with a magnifying glass and see if they were seated.

Your ring end gap may be too big or too small.


Is it a 2 or 4 stroke?

If it’s a 4 stroke, did you use synthetic oil for break in?

What size is the engine?

What model is the bike?





I know its hard to give input with exact measurements. But was seeing What people would say.Without at least most of the info requested, my opinion is that you simply bore it.

[barnett468]

So i got my ignition issues figure out, so i pulled the head and jug to see where i'm at with my smoking/oil blowby issues. i pulled the top and bottom compression rings off and put them in the jug and gapped them, i've got 28 thousandths on both.

...whats your guys opinions?

EXAMPLE

Honda says that if either the first or second ring has more than .020" end gap on an atc200 engine, they should be replaced.

One general rule of thumb for NEW ring end gap on a 4 stroke is .004" per each inch of bore size.

Since the bore of a stock atc200 is slightly over 2" the ring end gap on the first two rings should be around .010" - .012", with .012" being a more safe/cautious gap.

[spepple]

yeah ring gap tolerances are listed as .008-.016. Since I'm off today I'm going to take it to a local shop and have him do the measurements since I'm positive it'll need bored.

[six]

If it's already torn down u might as well bore it out.

[DohcBikes]

If it's already torn down u might as well bore it out.

Wrong.

If it doesn't need bored then there is absolutely no reason to bore it. The only measurement he has given us is ring gap. This could be due to worn rings, its not that far outside the service limit. This also does not guarantee that the rings were allowing blow by. There are several other factors to an engine that burns oil than just the rings.

As stated before, the only way to know if it actually needs bored and not just lightly honed is to properly measure it with the proper tools.

Theres more than one very knowledgeable person trying to help and guide, you asked, so try to let us help.
It may save you time and money. But, if you've built engines before, have the tools and you know your stuff, then I digress, but I'm not sure why you asked.

It would be nice to have some measurements, its very hard to determine the proper course of action without em. Thank you and good luck!!

[trike savior]

agreed. boring it because you have it apart is a waste of money. In the probably 50 engines I have rebuilt, a very small amount needed boring. want to say 5. PISTON RINGS ARE A WEAR ITEM. I have even saved cylinders that the piston melted down and left aluminum on the cylinder. some careful work with sand paper removed the aluminum and a good hone made it look like nothing ever happened. As long as all measurements are in spec it would be stupid to bore it.

Also, you are better off measuring yourself unless you trust your machine shop. like everyone these days, they need work too.

[Howdy]

So i got my ignition issues figure out, so i pulled the head and jug to see where i'm at with my smoking/oil blowby issues. i pulled the top and bottom compression rings off and put them in the jug and gapped them, i've got 28 thousandths on both. Theres no crosshatching left. and i've got little side to side play on piston to rings which is probably from the bigger gap. Should i bore .5 over and put a new piston in, or whats your guys opinions?

I just seen this and your location. Welcome neighbor!!!

I would take the jug up to CBS( Napa ) in Celina and have Satch or the other guy check it out for you. Tell them Howdy sent ya. These guys do all my cylinders since I got rid of some of my tooling. It is cheaper for me in the long run.
Howdy

[tri again]

Yeah, numbers have different values for a reason.

We had the 4 cyl engine top jobbed by a cert aircraft mechanic who forgot to set the ring end gap.

Welp?
crossing the ridge, trying to find an updraft and altitude, the sob instantly sounded like a jackhammer blowing hot oil all over the windshield and in through the door cracks.

Ring gap was set too tight and took the top of the piston off and fractured/separated the head from the jug when the rod and piston came back around.

Landed uphill under a powerline but couldn't give directions to get a ride home except not to go the way we did.

Why am I telling this?

ring gap can be significant.

[NeverLift]

agreed. boring it because you have it apart is a waste of money. In the probably 50 engines I have rebuilt, a very small amount needed boring. want to say 5. PISTON RINGS ARE A WEAR ITEM. I have even saved cylinders that the piston melted down and left aluminum on the cylinder. some careful work with sand paper removed the aluminum and a good hone made it look like nothing ever happened. As long as all measurements are in spec it would be stupid to bore it.

Also, you are better off measuring yourself unless you trust your machine shop. like everyone these days, they need work too.

Just a tip for everybody. Put the sand paper down. To get aluminum off a steal cylinder wall use a little muriatic acid (menards or home depot sells it) on a q tip and swab it a few times it dissolves right away.

[DohcBikes]

Ahhh... the age old sandpaper debate. Here's my opinion.

If you are going to hone your cylinder anyway, fine sandpaper has been used by so many people so many times its not even funny. It works fine if you are careful, especially when the buildup is below the area of ring travel, which in my experience it often is. It is not even close to as abrasive as the hone, and when used conservatively a properly honed cylinder will show zero evidence of the sanding.

Once again this is only my opinion, and im not trying to argue with other methods, they work too. There's more than one way to skin a cat, just depends on how sharp your tools are.