Super Jet ADA head oring question (zero comp)

[sharkcus]

Quick history on my setup:

I have a fancy ported 61x cylinder. Stripped all head bolts because this

Drilled out, helicoiled, and used bigger bolts. They have a more coarse thread. The bolts go in tight and give no indication of backing out.

I was out yesterday, did a WOT run on my way back in, maybe 20-30 seconds? Ski randomly died, but started right back up....but it wanted to die if I didn't give it throttle. It still ran enough to get me back in at a decent speed. There were no visible signs of problems on the motor. All bolts were in and appeared tight.

I got home, did a comp test, coupler side cyl was normal. Stator side cyl had 0 compression. I figured I blew the oring.

I pulled the head off, all bolts still appeared tight. The piston was not carboned up at all compared to the working cyl. The oring looked to be perfectly good. Piston looks good, rings appear okay.

I guess my question is, when you blow an oring, doesn't it melt or literally blow out? If my bolts backed out enough to let compression out, wouldn't it melt the oring? Because it didn't. Oring looks mint.

 

[Scraggly]

reeds?

 

[Matt_E]

Reeds affect only primary compression (case compression), not secondary (cylinder).
If the gauge shows zero and the bore, piston, and rings look fine - you f'd up the test or the gauge is broken. Sometimes it's easy to accidentally hold the Schrader valve on the gauge open while cranking.

 

[sharkcus]

Test was good, gauge is good (worked fine with other cyl). I thought for sure it was an oring, but they looked okay. I can't imagine them staying "okay" during the combustion process while leaking/blown.

I'm going to reassemble when I get home tonight and test again and maybe take her out to the lake. I think I'm going to torque the bolts a little more. Someone said they go 38ft lbs on the girdle bolts. I won't go that high, but... I am going to give the head bolts a little more.

I have a feeling that I'm going to end up buying a new 61x cyl and having it re-ported. I have a feeling these stripped bolt holes in the cyl really effed things up and helicoils aren't up to the task. Just trying to make it to winter.

So "blown" orings are always visually obvious, right?

 

[ProSouth]

Put oil on top of the piston (not much, like a cap full) and retest. If it goes up, you just bought yourself a topend.

 

[sharkcus]

(I did just buy a topend lol)
Tried that last night, no change. It HAS to be the oring, I just don't know what else it could be. Tonight I'll check for the sleeve/cyl evenness. Even though it appeared tight and girdle was tight, I just don't trust those coarse threaded head bolts.

 

[Matt_E]

1. A blown o-ring is obvious.
2. A blown o-ring will not cause zero compression, only a slight drop.

Put your finger over the spark plug hole and crank. If it's really zero compression, you'll feel no pressure.
In my experience, zero compression happens only because of something really really obvious - hole in piston, chunk of piston missing, etc. Even a pretty badly scarred bore will not cause zero compression.

 

[ProSouth]

Well... I'm thinking, you might have warpage going on. Or your bolts weren't doing what you thought. There's nothing wrong with fine thread. They're plenty strong enough

 

[ProSouth]

What you think about a crack Matt? Maybe hard to see without any thing forcing any air through it...?

 

[sharkcus]

Frick.



okay I'll find out tonight I guess. The head is already off. I'll reuse the orings for testing because they look perfect. (I just ordered a bunch from mcmaster carr). I'm just going to bolt it back together and test compression.

Stupid question... Let's just say several head bolts DID back out a little for whatever reason (they did not). Wouldn't the girdle bolts be enough to hold it tight to at least get SOME compression? I would think so.

edit: also wanted to say that it would make the lopsided starting sound while cranking, as in, one had comp, one didnt sound. So it's definitely not a testing error.

 

[heynagel]

What about decking the cylinder and head. When you had the engine blow up maybe those bolts blew out enough to warp your cylinder??? I don't know just throwing it out there.

 

[sharkcus]

FRICK FRICK FRICK FRICK FRICK.

I re-attached head, made a perfect seal. Zero comp again. Checked out piston very closely. There are a few little knicks on the edge. Took a look at the cylinder wall and found that. I THINK it might be a chunk of ring that did it. Can't see where it's missing, but there are is nothing else it could be. I don't know why I would break a ring in the first few hours of running it. No signs of overheating. I wish I had a definite cause. I *MIGHT* be able to hone it out. I'm not sure it's wise to reuse the (new) piston. I also realized it was the same cylinder as last time. I'm thinking maybe the piston/rings were messed up the first time. GRRRR

How would YOU proceed? Hone it, thrown in a piston/rings, and ride out the season?

 

[Matt_E]

I think your starter, battery, or both need attention, too, if that mark there is giving you zero compression. Not saying it doesn't need to be fixed, but the motor must be spinning slowly enough to let all trapped air volume escape through that little mark right there.

 

[sharkcus]

Well, I think it's missing a chunk of ring too. The little knick itself is nothing. I'll pull it tomorrow.
And cry. Lots of crying.

 

[Matt_E]

Missing ring would do it.

 

[motozachl]

I bet your going to find a piece of ring melted to the side of your piston bud

 

[sharkcus]

Me too. I'm a bit apprehensive about throwing a new piston/rings in there because I'm not entirely sure what caused the failure. I'm also hoping I'll be able to hone that out. If not, eff it, I'm just getting a new cylinder...with all the problems I've had with clamping the head down.

I'm like this close --> |-------| from just buying a maniac motor and not dealing with it. I know it's a pretty simple fix, it's just been one thing after another this year and I'm frustrated. Okay Marcus. Pull yourself together. Simple fix.

 

[sharkcus]

Piston and 2 sets of rings on the way, thanks to jet maniac.

I just THOUGHT about buying them and instantly I had a PM in my inbox saying they would be at my doorstep tomorrow.

Going to clear off the aluminum, hone it a bit, replace both sets of rings, and go through it all with a fine toothed comb. I have a feeling that because this was the same cyl that had the head lifting issue, maybe something got caught in there and I didn't notice it when I replaced bottom end.

 

[Dmac80sc]

Did you say you had a problem with the same cylinder before? Who did the port work?

 

[sharkcus]

Did you say you had a problem with the same cylinder before? Who did the port work?

The original problem was me using a riva head and not realizing it was thicker than stock. I ran it for a year on my old stock setup with stock bolts. Switched to a maniac/blue top end and stripped out every single head bolt on my first ride, only to find out they were only threaded in 3/8" of an inch. Surprised it lasted that long. The head only actually lifted on the stator cylinder which is the one that later failed. It's probably unrelated, other than maybe some junk (thread material) got in the cyl and went unnoticed. Went to an ADA head.

However... When I was FIRST installing the pistons, I could feel the rings catching on the very bottom of the stroke when I turned the crank. I figured that was normal on a ported motor....mostly because I'm a moron. As I think about it, I wonder if there was a problem with the chamfer. That shouldn't happen, right? I wonder if that screwed up the rings.

Is it okay for me to go in there with a dremel and smooth out the edge a little or will I eff things up?