Tri-Z tear down, with pics and video

[muthey]

so I opened up my z today to find out where my air leak is, and discovered my front right cylinder bolt was loose. A little to late to just tighten it though. Everything else feels and looks great except the piston and head, curious as to what might have caused the pitting. I run slightly rich so I might have to change a spark plug once in a while instead of rebuilding more often. video is coming as soon as youtube finishes uploading it.

crank seal looks great so why might I have had air pressure coming out of the clutch cover? And with the pitting on the piston should I just clean it up and the head and use it or should I be looking at machining and a new piston?

[El Camexican]

Everything else feels and looks great except the piston and head, curious as to what might have caused the pitting.

Yours looks like it might be from detonation, but degrading pistons, or junk that gets past the air filter can do it too. I'd sand it out as best as you can starting with 240g and working down to 600g.

[muthey]

ok the video finally uploaded and has high quality for the pitting on the piston and head for you guys.

[muthey]

thinking about it, my original air filter was a crumbling mess. I replaced it last summer with a two stage uni, running air filter oil with it. With this being the first time I've opened up this motor I don't know if this was done prior to the new air filter or when it was done.

[elvetost]

Hmmmm that sure looks like detonation to me. Maybe its been like this for a while now as you mentioned..
I'd send the head off to a good machine shop to work the pitting damage out and give it a nice clean up on the mating surface.
A new piston is in order I think also.
How does the cylinder look?

Good luck with it man, it looks like a good base for a sweet project!

Cheers,
Chris

[muthey]

Funny thing is elvetost, is that I am a machinist and have already resurfaced the head and the top of the piston, which the piston came out beautifully. the head polished up nice as well, not as good as the piston but perfectly usable again. I will have this bike back together this week and run her till I need to rebuild it again. Next time around I am going to be building this as an ultimate trail machine. I will be going back to completely stock instead of being bored to 68.5 mm like it is now. I am also planning on making a really nice custom piston for this machine as well. I am going to make it hemi'd and going up to a 36mm carb as well. I also intend on swapping out the tranny as well to a six speed. In essence this will be a silent quad killer when I am done . But that is for a future time not now, I need to do quite a bit more research into all this first.

[MTS]

Looking at your pictures on my crap phone i would say you had a severe cylinder base gasket leak judging by the ammount of oil build up over the stator cover. I would suggest you turn your cyl base flat and check the stud threds on the front left stud. Every case set i have had is uneven and pulls the cyl ears down around the bolt holes causing problems such as air leaks, at the very least use some yamabond or flange sealer on the gasket.

[muthey]

That's what I am going to do on reassembly. I will be putting it back together over the next couple of days and will let everyone know how things turn out.

[muthey]

upon reassembly and a test run tonight I have discovered a couple of new issues now which is going to require a complete disassembly now. My water pump oil seal is leaking and I now have a leak in my cases. so I am going to tear this bad boy down and goi through everything with a fine tooth comb. I want to make sure the next time I run it I am running a machine with no issues. I had no idea my cases were leaking there was no sing of it prior, but now I have coolant pouring out of the cases, but nothing on the stator/ fly wheel side. My feeling is that even if it is the water pump oil seal, I still have a leak in my cases. and if I split the cases I am replacing all bearings and seals, and I am looking for a yz transmission as it should bolt in and give me a six speed that way. I know it is alot of work but I feel it is worth it. when she runs she runs great but knowing what I know I won't run it till all is said and done. If I don't get the tranny no big loss it is just a desire, as if I did I will put a 38mm carb on there as well to make it more like a 86 than a 85.

[elvetost]

Where about is it leaking from man? You may well get away with replacing the seal, these are designed to leak out of the case hole when the seal goes bad, so you can see that and replace them..
Funny how these old bikes turn to a "project" once you start sorting one lil problem out, init...
I'm sure you can get this sorted though and have a problem free machine that you can just enjoy, as you said. These tri-z's are great fun are they not?
Hey good luck man!

[El Camexican]

Funny how these old bikes turn to a "project"!

Not often a perfectly good ride gets tossed into a barn, but in terms of trikes I think we are fortunate. I say that based on how fast it seems rubber and plastics degrade these days on newer stuff and the fact that our 30 year old engines were over engineered compared to todays computer aided designs.

Muthey, what exactly are you thinking of doing to your head? Removing the dome?

Aside from switching to a Cool Head has anyone on here had a Tri-Z head reshaped and is so by who and what were the results?

[muthey]

Where about is it leaking from man? You may well get away with replacing the seal, these are designed to leak out of the case hole when the seal goes bad, so you can see that and replace them..
Funny how these old bikes turn to a "project" once you start sorting one lil problem out, init...
I'm sure you can get this sorted though and have a problem free machine that you can just enjoy, as you said. These tri-z's are great fun are they not?
Hey good luck man!

It is leaking at the front of the motor by the stator, and it is a steady pour, which I did find odd, I'll have to go out and add some coolant and take a pic to be more exact for you guys. It was funny the head gasket that came with the versah kit leaked right off the bat and was dribbling coolant, so I pulled the head and applied some fresh anti seize to the old gasket that came off as that is what was on it and now the head is sealed but the case was leaking coolant. I really dislike the 3 piece metal head gaskets.

[muthey]

Not often a perfectly good ride gets tossed into a barn, but in terms of trikes I think we are fortunate. I say that based on how fast it seems rubber and plastics degrade these days on newer stuff and the fact that our 30 year old engines were over engineered compacted to todays computer aided designs.

Muthey, what exactly are you thinking of doing to your head? Removing the dome?

Aside from switching to a Cool Head has anyone on here had a Tri-Z head reshaped and is so by who and what were the results?

I was able to polish out the damages with out reshaping the head any, but with building my own custom piston I was going to put higher peaks on it and match the head to the the deeper degree of the piston I was going to try and keep as much of the original head gapping distance as original to keep the compression ratio the same, and add spacing as needed. I wonder though if by increasing the dome would cause a hole to be burnt faster by the spark plug. I already have a spare head that was pre machine by flo-tech for high compression, that I choose not to use yet as I want this as more of a trail bike. even with having a hemi'd piston I think I could make it thicker in the center to compensate the more direct force from the spark plug combustion.

[muthey]

I found a pic of a motor that I can show the relative area where it is leaking I didn't see a hole there but I haven't pulled this motor yet. And of course this is not my motor as it is way too clean to be mine.

[muthey]

It was weird as with the metal 3 piece gasket it didn't leak there, but once I put the original in and before I even started it again it was pouring out the cases with a steady stream. My thought is if the original head gasket is leaking to the piston, and supposing my rings went bad in a year. That leak is right below the crank and that means my cases are leaking.