Tri-z Piston Failure

[Just-Tri-It]

Closeup macro picture of the plug (With the threads removed if posible?)

Best I can get of the plug.

[Dirtcrasher]

He wants to see the lower portion of the porcelain...............

[Just-Tri-It]

He wants to see the lower portion of the porcelain...............

I don't know how to remove it without destroying it.

[Billy Golightly]

Put the plug in a vise, take a hacksaw about a 3/8 half inch from the end (where the ground strap is) back towards the top, and hacksaw down until you hit the porcelian (You'll know when you hit, the blade will get really "slick feeling" rotate till you've cut all the way around it and the threads+groundstrap fall off. Take another pic for me

Its hard to tell in the blurry picture but it looks like youve mistaken the gray from melted aluminum for a black rich condition.

[Just-Tri-It]

It'll takes some time but I'll get it.
Would leaking crank seals contribute to this or cause it?

[Billy Golightly]

It could cause a lean out condition, yes.

[tri-Z ripper]

welcome to the club, did you have your cylinder honed before installing new top end?

i got lucky and shot the piston pieces out the exhaust.

[Just-Tri-It]

Actually I had just got the Z. I bought it from a guy who said he bought it and it was way too fast for him and he just let it set up 4 or 5 years. I got it and I changed the plug, gas and fluids but forgot to check the water pump. After the chops seemed to be ok I took it down a 5 mile trail never getting over 3/4 throttle. It quit on me and I thought the float was sticking as it just died in the road. After a minute it started back up and I came in. Next day I warmed it up and got about a mile down the road and it fell flat on its face again and wouldn't start. I noticed that it had no real compression as I kicked it over. Pulled it back and let it cool a little before doing any further inspection. Cleaned the carb again and found that the left back vent hose was stopped up but the other two were fine. Reinstalled the carb but no good. Pulled the plug and covered the hole and no compression on finger at all. So I pulled the cylinder and this is what I found. The first owners used to race it some I was told. Maybe the mixtures they were using began the process and the seals were weakened from sitting so many years and the water pump beginning to fail all conspired against it at the same time and caused it.
If I replace the crank seals while it's down would I have to split the cases?
Thanks



ATTACH=CONFIG]120566[/ATTACH]

[k00leo]

well damn, at least you got the west coast swingarm going for yah.

Very nice looking tri-z

[Chazz of Blades]

Quickly man! That Z needs a heart transplant!


But as billy said, lean condition *could* cause an overheating like that, but without further info I don't know.

[tri-Z ripper]

well read on how to pin your water pump impeller as i dont think there is any billet ones left around, if it is that bad i would consider replacing the crank bearings and seals as well as new rod with a top end. certainly not cheap, but will keep it reliable for the rest of the time you own the bike! Yes seals require splitting cases! Then to reseal with yamabond. Don't be afraid to ask with help here.

[WilliamJ]

It would have to be really lean. Much more likely it was a bad combination of too much ignition timing / low octane / high compression. Poor cooling would not help. Likewise a hot day can also contribute but that's not the case at this time of year. Scuffing is probably piston clearance going too small as it overheats from the detonation.

It is classic detonation. You can burn through a piston in no time at all when detonation starts. You cannot wreck it running too high an octane. It won't help power but it certainly will not hole a piston. You need to work out what CR you are running and you need to check your ignition timing. If in doubt retard the timing at least 5 degrees and see what effect it has. If you are not sure about the mixture then richen it up a little. Use the best gas you can find if you are running high compression.

Ethanol laden gas is bad stuff - authorities in Europe have just released a report slamming the 10% Ethanol as damaging to car engines as young as 6 or 7 years old. There is a date for this to be introduced but for the time being we are getting 5%.

Bill

[code200k]

I've read ethanol affecting 2 strokes but not octane..........

New gas, more octane??

yes i meant ethanol sorry guys..long and tireing night

[Just-Tri-It]

Is there a manual besides the oem service manual that gives a detailed step by step process of disassembling and reassembling the engine for a total rebuild?
Thanks.

[Mosh]

Is there a manual besides the oem service manual that gives a detailed step by step process of disassembling and reassembling the engine for a total rebuild?
Thanks.

No. But here is a link to a good video series I posted, that used with the Z manual should walk you right through the process. It is a newer Yz 250 engine, but all steps are about the same.

NOTE!!! On a Z engine, the Input shaft end gear on the left side of the case (by the clutch arm) can be installed eiter way. One way is right, the other is wrong. Pay VERY close attention to the gear as you split the case and keep it oriented in its correct posistion


http://www.3wheelerworld.com/showthr...ed.&highlight=