Will seized piston rings cause oil fouling?

[Bigyellow]

Well, Here I am again...

Finally got the Tri-Z back together...It ran great, had plenty of power. Then, it started to crap out after the
first 20-30 minutes of riding, as if someone hit the kill switch. After going through 3 new spark plugs, I decided to pull the cylinder and jug to figure what the heck was going on. I was greeted with a huge score mark right across the piston rings, causing them to seize in their place. On a side note, I also noticed the plug smelled
like gearcase oil.

I'm positive that it is not the fuel/oil mix ratio (I run 32:1 Valvoline in it, 20:1 just made too much splooge), the jetting (#500 main jet), or vaccuum leaks (replaced the crank oil seals and bearings during rebuild, made
sure they were fully seated. Also triple checked for even sealer bulge when i rejoined the crankcase halves together. I had to reuse the spring out of the old clutch side seal though, the new one didn't come with one(?))

My question is, would seized rings lead to fouling due to oil being drawn from the gearcase? :wondering

Again, Thanks again in advance

[fcf35]

your not supposed to have any tranny oil in your crankcase and if you do you have a leaky gasket or seal.your premix gas is what lubes the piston and crank.

[barnett468]

Hello Bigyellow



It would be helpful if you could answer a few questions if you want to so we might be able to help you avoid having this happen again.




Finally got the Tri-Z back together...It ran great, had plenty of power. Then, it started to crap out after the first 20-30 minutes of riding, as if someone hit the kill switch. After going through 3 new spark plugs, I decided to pull the cylinder and jug to figure what the heck was going on. I was greeted with a huge score mark right across the piston rings, causing them to seize in their place.

How did you break it in?

How long did you break it in?

Any cylinder porting or head milling etc?

Any engine changes done between the time you took it apart and put it together?

Did you use the same oil and ratio before you rebuilt it?

What did the plug look like that you removed?

Do you know how to tell if the ports were properly chamfered after boring?

What brand piston is it?

Is the piston cast or forged?

How far is it currently bored out?

What was the bore size before?

Was it smoking after rebuild and if so what color was it?






On a side note, I also noticed the plug smelled like gearcase oil.

It should have a leak down test done.






I'm positive that it is not the fuel/oil mix ratio (I run 32:1 Valvoline in it, 20:1 just made too much splooge),

It’s not the cause of your problem






the jetting (#500 main jet),

What size and type of carb is it?

Is this the same jetting you had before you rebuilt it, if not what was it before?

Was this the same carb you ran before the rebuild?

Sounds a bit large






or vaccuum leaks

The only way to tell if you have any leaks is to do a leak down test.


Did you do a leak down test?

Do you know how to do one?

Do you have the tools to do one?






(replaced the crank oil seals and bearings during rebuild, made
sure they were fully seated. Also triple checked for even sealer bulge when i rejoined the crankcase halves together.

OK






I had to reuse the spring out of the old clutch side seal though, the new one didn't come with one(?))

Shouldn’t be a problem but it didn’t help.

What brand was the seal?

US or Chinese made?






My question is, would seized rings lead to fouling due to oil being drawn from the gearcase?

It might, however I would you might have a few more questions than this.

[Bigyellow]

Well , I just took a closer look at it today, and I think I figured out where the fouling was coming from. Not only did the piston crown have a sticky clear residue on it, the exhaust port and the splooge buildup also was sticky as well. Most likely a bad head gasket?

I checked the crankcase, nothing out of the ordinary, except the
normal slight 2 stroke oil buildup.

The seals and bearings were all genuine Yamaha straight from the dealership.


The piston is a forged Wiseco 0.50mm overbore from stock.
As for the rest of it, nothing out of the ordinary, except bolt-on mods.

[barnett468]

Hello


Unfortunately since you did not answer many of the questions I asked I am unable to give you an informed guess as to why it seized. One common cause is improper break in, another is improper jetting. As far as the "goo" goes, its possible its from anti freeze but not possible from straight water. It's also possible it is from old or contaminated gas like if someone put sugar or syrup in it.

Since you did not answer many of the other questions I see no point in asking anymore.

For the second time, you should do a leak down test.

[barnett468]

Hello Bigyellow

If you want to see if your head is flat you can simply put a full size sheet of 600 wet/dry sandpaper on a granite counter top, clean the head, then color the sealing surface with a felt pen, then using moderate pressure, rotate it 3 full turns then inspect. If the felt mark is 100% gone it is good, if it is not then sand until it is. You can remove the cylinder studs and do the same thing.

[barnett468]

Hello

Sorry, forgot, put some water on the paper before sanding.

[fastatc70]

Sorry for the stupid question. Was the cylinder scored. Was the piston installed backward. I have seen that befor.

Was does the damage look like. A gouge, scrape, a scuff. Has it seized? What Are you using for premix. What are you running in the trans.

[fastatc70]

Who did the boring, honing. Was the piston prepped right. Exhaust bridge clearance, ring groove?