Premature ring wear?

[gasgasman]

Couple weeks ago, my bike was hard to start. It felt like the compression was low.
Friday night I ran a compression test and it was 90psi.
Threw some rings in it and it came up to 150psi-this was before I started the bike.

Seems like I'm having to put rings in it every 4 months or so.
The last tear down, there was .040 ring end gap clearance. The cylinder measured out ok and the hash marks were still visible on the cylinder.

Last night when I took the cylinder off, the power valve was very dry and the pivot pins actually have rust on them.
I'm using Motorex oil and race fuel.
I wonder if that's my problem? There are no signs of dirt ingestion at all.


I did pull a bone head move while removing the cylinder. I was rushing (had to ride in the am) and pulled up on the power valve rod, which dislodged the actuator balls. So I had to pull the side cover off and fix it.

[Brian]

How often do you ride?
If you ride 2-3 times a week, every week for 4 months. Might make sense.
Do you ride in the upper revs a lot?
You said you measured the cylinder last time, was it on the tighter end of the tolerance?

[gasgasman]

I ride almost every weekend, 50-60 miles.
I do rev the bike a lot.

The cylinder was replated by Millenium.
I thought it was over-bored. But they measured it against the piston and it was within spec.

[Brian]

Hmm based on what you have said..sounds a little short on life.
I'm not sure what are some common causes of short ring life...I have some guess but I would just be listing lots of stuff that "could" affect it. I don't know enough....

Someone will probably chime in with some knowledge or maybe you could call RB or Eric Gorr, they might be able to give you some insights.

[nick790]

could be a tone of things.
lean mix?
lean jetting?
done any deep river crossings and taken in water?
air filter fitted correct?
i'd check the simple thing first, then question the internals.

[widebear]

Originally Posted by gasgasman

Couple weeks ago, my bike was hard to start. It felt like the compression was low.
Friday night I ran a compression test and it was 90psi.
Threw some rings in it and it came up to 150psi-this was before I started the bike.

Seems like I'm having to put rings in it every 4 months or so.
The last tear down, there was .040 ring end gap clearance. The cylinder measured out ok and the hash marks were still visible on the cylinder.

Last night when I took the cylinder off, the power valve was very dry and the pivot pins actually have rust on them.
I'm using Motorex oil and race fuel.
I wonder if that's my problem? There are no signs of dirt ingestion at all.


I did pull a bone head move while removing the cylinder. I was rushing (had to ride in the am) and pulled up on the power valve rod, which dislodged the actuator balls. So I had to pull the side cover off and fix it.

What kind of air filter oil are you running and why race gas, are you over 200psi cylinder pressure?

[Eric K]

Aside from more use = more wear, the 2 biggest factors I have found for ring wear are dirt ingestion and the amount of lubrication.

No air filter stops all dirt. Some dirt gets through. As the filter collects more dirt it becomes less effective at stopping dirt. The dirt that doesn't get collected in the filter goes right into the engine. Clean and very thoroughly oil the air filter every ride. On very dusty rides, I take an extra filter and replace it half way through.

I have found that more lubrication = less ring wear.

My data points with AmsOil Interceptor...

At 50:1 fuel/oil ratio top ring end gap increased 0.006" over 91 hours of ride time.
Compression was 195 psi at the start of this period and 198 psi at the end of this period.

At 38:1 fuel/oil ratio top ring end gap increased 0.001" over 93 hours of ride time.
Compression was 188 psi at the start of this period and 204 psi at the end of this period.
Also note, early during this time period my water pump seal went bad and all the coolant went into the transmission, so the engine also experienced an overheat cycle.

[gasgasman]

Thanks for the responses,

I run race gas due the poor fuel quality here and pinging. 32:1 mixture.
Twin Air filter, cleaned every 4 rides.

I use the PJ1 spray on air filter oil.

I'm leaning towards the Motorex oil not providing enough lubrication.

[widebear]

A 32-1 fuel oil ratio should provide plenty of lubrication no matter what your choice of oil. You stated that you spotted some rust on the power valve pivot rods, are you certain that its rust , race fuel can leave rusty coloured soot deposits that in your case could be mis- diagnosed as rust. The point of the query re: your choice of air filter oil is that a mechanic, machinist friend of mine as well as others, ktm talk engine builder Caflash have reported seeing abnormal top end wear strongly believed to be a result of the choice of air filter oil, the two that come to mind being my machinist friends negative experiance with Silkolene and Caflash's with No Toil aka no oil. A trick that I use to keep things in the cylinder lubricated between rides is when I shut off the bike at the end of a days ride I open the throttle fully and imediately hit the kill switch which draws in a oily fuel mixture that wont get burned but instead coats the internals till the next time the bike is fired up.

[GMP]

Girard,

At 80 hrs my top end measured out like new, both compression and dimmension. I replaced it for fatigue reasons and piece of mind. I know you guys have a lot more fine dust down there so maybe that is a factor, but you should have a good baseline from your last two GGs just like me. I have never seen a dry rusty PV in any of my three GGs. Mine is clean but with a good coating of oil. I've run nothing in any GG but Amsoil Dominator @ 36:1.