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]

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.

 

[blitz11]

Having ridden in Houston in April (well in the back of the group as I am slow as molasses), I am wondering about dust ingestion.

I brought an oiled air filter with me to Texas, and after riding two days in the Sam Houston Forest, my air cleaner was really dirty. One look, and I was glad to have brought a spare. I generally change air filters after every weekend.

Now, Girard is probably not riding in the dust cloud I was, but I am thinking that a 4 ride service interval on the air filter might be insufficient. As Erik K pointed out, the more dirt on the filter, the more likely it is to pass dirt (although K&N argues that point, saying the dirtier the filter, the better the filtration). Personally, I'd rather install a clean air filter than a dirty one.

I would suspect that dirt ingestion would also lead to some accelerated piston wear. Has the piston skirt wear been tracked?

I know people bad-mouth No-Toil, but I've had really good luck with it. What appeals to me is that if you put enough on your filter, it stays tacky, yet it cleans easily with Oxy-Clean. I've used other oils which don't clean off as well, and that dirt retention can cause a problem. The fact that ALL of the tackiness is gone with a good cleaning indicates to me that with sufficient rinsing, all residual dirt is gone. You really start with a clean filter with no retained dirt.

My $0.02.

blitz

 

[GMP]

I agree with blitz on the NoToil, as I've also been using that exclusively on all my GGs for ten years now. IMO, I see no reason to bash it if its applied properly. The mistakes I see people make (the ones I made at first) are from being in too much of a hurry. First you have to shake the hell out of the product to mix it before aplication, and also if you buy in a bulk size and transfer to a smaller bottle. Second, after its worked into the filter, you have to evaporate the carrier alcohol completely before installing the filter. I use an old hair dryer and it makes quick work of this job, just dry it till you no longer smell alcohol. I never had any dust in the airboot, and while normally my rides are not too dusty I have been in some extremely dusty conditions for hours. My bike sat for a year and when I finally could ride and checked the filter, it was still evenly tacky with no oil pooling at the bottom.

 

[Eric K]

From AmsOil test data on automotive air filters dated 12 July 1999...

(Ref SAEJ726 test)

Filter.......................Percent Efficiency
AmsOil TS-31.............99.5 (this was the older oiled foam type filter)
Fram CA326...............99.4
K&N E-1500...............94.9

Percent efficiency is how much dirt flowing to the filter is stopped in the filter.
The rest goes past the filter into the engine.

Doing the math...

AmsOil let 0.5% dirt past
Fram let 0.6% dirt past
K&N let 5.1% dirt past

The K&N let 10 times as much dirt past as the AmsOil filter under SAE test conditions.

 

[gasgasman]

Girard,

you should have a good baseline from your last two GGs just like me. .

Excellent point. My previous Gas Gas' went almost a year on the piston and rings.

I'm convinced it's the Motorex syntetic oil. I have run that oil exclusively in the '07 bike.

My power valve bearing were also bone dry.
What's wierd is there are no signs of any lack of lubrication on the cylinder or piston.

 

[widebear]

The only thing that I can think off that would cause such a complete and thoroughy dry burn would be using race gas with late ign timing. I'd like to see a picture of the piston crown?

 

[gasgasman]

Here's a shot of the piston. Those are NOT detonation marks, more like ash deposits.

Exhaust side. You can almost see "rust" deposits on the ring blow-by areas.

Intake side. The rings are frozen in the lands.

"Rust" deposits.

Most people hate spooge, in this case spooge would be a good thing.

 

[GMP]

Maybe that oil has a low flash point. The piston has more carbon on it than mine did at 80 hrs, but mine still had most of the moly coating and everything was really oiled up good and wet. The Amsoil doesn't seem to burn off but blows through the motor. PV parts are just stained brown and oily, with a small amount of carbon on the main flap. I do think a little spooge is a good thing, it shows oil is going completely through the motor. I had similar results on my older KTMs with Motul 800 and Redline, both ester based synthetics.

Oh, with regard to K&N filters, junk. I have large K&N pod filters on my Ducati over the velocity stacks, as they came with the kit. I made custom slip over "pre filters" out of filter foam that I oiled with No-Toil as I do not trust K&N. I had a drop in K&N in the stock airbox, and after a few K miles the inside of the airbox (clean air side) had obvious dust coating the plastic, and this is on a road bike ridden on nice roads in good condition. Next time I have the bike apart for a valve service I'll try and find a UNI filter replacement for the K&Ns.

 

[widebear]

Those pictures I.M.O). rule out the problem being one of dirt entering the engine so it more likely is a combination of a very dry race gas in conjunction with a oil that is not race gas compatable. I dont think Motorex is a bad oil, Cactusreid swears by it, his bikes have a millions hours on them and in his case the oil is performing in no way like yours,main difference being we are on 94 premium pump gas in our local.

 

[gasgasman]

Here's the folow up:

I switched to the semi-synthetic Motorex (had a bottle laying around).

Rode the past couple weekends.

The tail pipe looks oily now, where before it was a very dry grey color.
I pulled the power valve cover off and saw that the bearings now have an oily sheen to them.

Like Glenn said, the oil may be "burning" off too fast to provide the right lubrication.


So thanks to everyone for all the tips etc.

I will switch to another brand of oil.