Wossner piston question

[hotrodaj_2]

Alright, we've covered the "normal" problems that it could be. Let's delve into the really unlikely/strange.

It is completely possible that you have an airleak that only shows up during operation.

Were the cases lapped smooth before assembly?

OEM base gasket installed?

Have you ever lost, even a little bit, any transmission fluid?

What's the history of this crankshaft? Is it possible that it's not in spec for run out?

Oh ya, now were getting deep. Ok, airleak only when running? Do u have examples because idk. The cases were not lapped. I split cases and reassembled before I learned that it is something done often and might be needed. No leakes there with leakdown. squirted everthing with soapy water along with reading leakdown guage. All gaskets are Cometic. Never lost any tranny fluid. I know nothing about bottom end. When I bought it there was some problems with the top end so it is possible the bottom end has problems also.

 

[sicivicdude]

I've seen a blaster engine leak but pass a leakdown test TWICE!

One was when the head gasket was leaking only under heavy acceleration. Didn't figure out why until splooge started to drip out.

The other was a crank side collar leaking under vacuum but not under pressure!

Leakdown test is NEARLY full proof and 99.9% of the time will ensure a leakfree engine. However that's not 100% guaranteed and yours sounds like it might be one of the .1% cases, unfortunately.

 

[hotrodaj_2]

I just remembered this, The spark plug will get oil around it sometimes. I have tightened it to the point of almost stripping it and it stops but I feel you dont have to tighten a spark plug that tight.That could be the problem.That has always bothered me alittle. I might have a problem there.

 

[sicivicdude]

What's the cranking compression on this engine and what fuel are you using?

You shouldn't have to tighten a spark plug like that at all. NGK B8ES spark plugs have a crush gasket that goes to basically finger tight plug 1/4 turn or so. That should be all that's needed if the mating surface is in good shape. If you have a problem with the mating surface, you may need to give that head some attention.

 

[hotrodaj_2]

What's the cranking compression on this engine and what fuel are you using?

You shouldn't have to tighten a spark plug like that at all. NGK B8ES spark plugs have a crush gasket that goes to basically finger tight plug 1/4 turn or so. That should be all that's needed if the mating surface is in good shape. If you have a problem with the mating surface, you may need to give that head some attention.

Well, I again forgot what the comp. is after all this time. Ken Oconnor did my head and it was pretty high for pump gas but very runable. I think in the 150ish range. I agree, a plug with a crush washer should seal when thightened slightly. Im gonna look into that plug mating surface. I think I'm sucking air there. I forgot all about that but it could cause it to go lean, but plug looks fat, hell idk.

 

[sicivicdude]

In the "150ish" range sounds good. You're generally safe with any sort of acceptable jetting up into the 160's.

I don't think that a leaking spark plug is going to let in any appreciable amount of air but under hard acceleration, hardly any at all will cause it to go lean some. I wouldn't attribute scuffing on the piston to a seeping spark plug but I've seen stranger things!

 

[hotrodaj_2]

In the "150ish" range sounds good. You're generally safe with any sort of acceptable jetting up into the 160's.

I don't think that a leaking spark plug is going to let in any appreciable amount of air but under hard acceleration, hardly any at all will cause it to go lean some. I wouldn't attribute scuffing on the piston to a seeping spark plug but I've seen stranger things!

I'm hauling ass or parked. That's how I do it. I wonder if I had a air leak that is causing a lean condition, would it show up on the plug or could it be rich looking and still causing a overly hot piston condition?

 

[sicivicdude]

If the spark plug is leaking air at WOT, it should show it to be "leaner" than it really is. You should actually be "safer" than if you have an airleak somewhere else inside the engine.

Again, I don't *think* that the leaky spark plug is the problem, only something that probably needs to be addressed...

 

[hotrodaj_2]

If the spark plug is leaking air at WOT, it should show it to be "leaner" than it really is. You should actually be "safer" than if you have an airleak somewhere else inside the engine.

Again, I don't *think* that the leaky spark plug is the problem, only something that probably needs to be addressed...

Cool, I'll address the plug issue a.s.a.p. I wanted to tell you that the member heatlbj6 that just posted a pic of his piston and you replyed. My damn piston looks something like that after one day riding. Ya, I have issues.

 

[Blaaster]

Cool, I'll address the plug issue a.s.a.p. I wanted to tell you that the member heatlbj6 that just posted a pic of his piston and you replyed. My damn piston looks something like that after one day riding. Ya, I have issues.

That is a typical example of too "lean", or a leaky exhaust flange causing air to be sucked in instead of the expelled fuel charge.

I have had occasions that a cracked carby boot tested fine but on flexing it leaked.

Vibrations and a cracked boot may be a problem.

 

[OConnor Racing]

It's tough to say without seeing the piston. Do me a favor and pull the pipe and silencer. Repack the silencer and check the condition of the old packing. Is it full of oil? Inspect the neck of the pipe where it exits the cylinder. Is it wet and full of carbon? I've only seen this a couple of times but it's worth a shot. The pipe could be contaminated and pushing junk back into the cylinder during scavenging. The crap will come up the transfer ports and scratch the piston and cylinder. It's a good idea to clean the inside of the pipe after every rebuild. It's a long shot but who knows?

 

[best]

Good call (of course!) Ken, which gets me thinking of another thing...

We all know the pipe is sort of a "supercharger" that works with resonance and pressure to pressurize the cylinder before the exhaust port is closed.
Part of that process is a very calculated restriction at the stinger to generate that pressure.
If that muffler is soaked in oil it raises the pressure and temperature of the piston.
The scratches you see may be scuffs from high temperatures and pressure.

Over the years I have had scratches and scuffs appear immediately on new pistons.
Annoying as hell, and usually because of some oversight on my part.
(You cannot expect me to remember EVERYTHING can you?)
Grit left in the intake tract, cold working a Wiseco, burr on a port, stuff left in the crankcase, dirt on the fingers, etc.
I started as a teenager working on a dirt driveway and it has been a long learning curve.

The good news is that often the damage is little more than cosmetic. Keep running it.
Especially with something as hard to replace as a BBK cylinder and piston.
It might make a difference for something like a race engine, but if there is no embedded grit or pinched ring, keep going.
Good to find the source of the problem and learn from it however,
and learn to make a judgement call if it is a fatal flaw or can be lived with.

Steve

 

[hotrodaj_2]

It's tough to say without seeing the piston. Do me a favor and pull the pipe and silencer. Repack the silencer and check the condition of the old packing. Is it full of oil? Inspect the neck of the pipe where it exits the cylinder. Is it wet and full of carbon? I've only seen this a couple of times but it's worth a shot. The pipe could be contaminated and pushing junk back into the cylinder during scavenging. The crap will come up the transfer ports and scratch the piston and cylinder. It's a good idea to clean the inside of the pipe after every rebuild. It's a long shot but who knows?

Hey Ken, good to hear from u again. You raise a good point. I repacked once and it looked wet. I hav'nt repacked many silencers so I did'nt really know what to look for. I also sand blasted and painted the pipe because it looked like crap. I did clean the inside of pipe but to be honest, not that well. The neck of pipe is wet and has some carbon. It will ooz a alittle oily substance out of pipe around exhaust flange while riding also. It's possible this is the reason for my troubles. It's gotta be something strange like this.

 

[sicivicdude]

Slickerthanyou has blast media left in his toomey after the powercoater got done that fried a set of rings but I find it hard to believe that you've been through several top end rebuilds and you would STILL be having an issue with foreign material (other than say, carbon from the exhaust which ALL 2 strokes are susceptible to!) blowing back....

 

[slickerthanyou]

Slickerthanyou has blast media left in his toomey after the powercoater got done that fried a set of rings but I find it hard to believe that you've been through several top end rebuilds and you would STILL be having an issue with foreign material (other than say, carbon from the exhaust which ALL 2 strokes are susceptible to!) blowing back....

I sure did! Never even thought about checking it! More than a cup full to be exact! I was devistated when Ken suggested I pull the pipe and dump it all out, it just kept comming out! I used water and compressed air to remove it all from the pipe, However I was sure that this top end wasn't gonna be last very long. I had a bad compression tester o-ring which made me re-ring for no reason at all- then procedded to rip on that motor since with no issues I kept an eye on compression and only lost 3 psi from new build to (sand injection YIKES!), to harness issues, and that motor runs super strong in fact I have to get a longer swinger as it's hard to 'get on it" with out the front wheels pointed to the sky in first four gears, It's a bit hard on the trails/rocks doing hills when you can only be in 2nd gear and need to give it gas and the front end goes straight up! But give me some open space It's powerband is right where I like it!

I think I have pics of the piston and cylinder at home on my computer after I thought i found low compression , but was my tool! i'll post later

 

[hotrodaj_2]

I'll check pipe. I'll be sick if I get sand out of it. I probably have 10hrs (and a couple bores) on it sence I sand blasted it. I would think it would have blown out by now but maybe not. I'm thinking if it was sucking sand that it would scratch stuff fairly consistantly. I"m getting more of a 4 corner seize type of scratches. Thats why I asked if Wossners grew more or faster than a Wiseco. I'm finding out that it's not a piston problem, something else is going on. You guys have gave me some great ideas though.