Trials Australia Forums

Just how I left it so the power valve seals are holding


Looks like some type of corrosion so might put something on then when I put it together


Oil laying around


There is that dark section on the gasket. Looks like it may be leeking. Could be why it idles high and then settles


No odd scratches hear to cause that

Clean enough


Power valve closed, bit of carbon on the tongue


Powervalve open and it looks uncarboned enough for me. I use a caster blend oil at 50 to 1 so was expecting a little more carbon because of the caster component. Nothing to worry about hear, don't think I will take it apart as there doesn't seem the need.

There are some grit scratches on the boar but no real ware.


Nothing to unusual hear


If I wipe my finger on the head it smears


Give the exhaust port a wipe and it's good as new

Wipe with a rag and it's good as new


Think I will just leaves he barrel as is and renew the piston.


nothing odd hear to change that decision




Looks ok

While generally wiping the oil off the piston with a rag I inadvertently wiped the blow patten off the top of the piston.
This is what did not come off with a light rag wipe.
The carbon build up is the dead area that gets the least wash from fresh charge. I'm ok with the uneven patten left to right as it could mean better packing as one side goes more over and the other under. That's the theory anyway.


The front skirt has reasonably little wear with the most being between the inlet and exhaust ports as you would expect. R member the original lubricating holes were 1mm and I drilled them to 2mm and made small cross marks. Will do the same for the next piston.


From this angle there is next to no were


Nothing on the sides except for the scratches I made putting the C clips in.


First no discolouration under the top which means it's just not getting hot enough to colour it. Probably to be expected with the type of use this motor gets plus it's thicker than a cast piston.

Second no sign that the reshaping is having any effect on the piston so will do it again.

No sign of cracks on the inside of the inlet


That side is taking a hammering. Having said that the were rate has considerably slowed since adding the lubricating holes and slots. Will put those there from the start for the next piston.
The bottom edge is also heavenly worn so will put a bigger chamfer in the next piston.

Note the dark section for the gudgeon pin


Wossner does not use oil holes to loob the pin. Instead they use these slight recessed passages. I guess every time the piston goes past the inlet port hole there will be a slight difference in preasure between under the piston and transfer port opening even though both are in n the same chamber.

That has so much information. I just wiped it with a cotton rag.


This will be my last planed rebuilde. It works with one irritating action. The crank feels out of balance.


This is not the furthest perspective but a clear one at some 128 million kilometres

I would say I could see a sealed line through there.


Moist with oil


Still 100% advanced.

I have never hearted it ping. If I were in a hurry I would move it further by 1mm and take my chances.


That's not good in any way. It could easly be one type of failure to another.


Feels familia

That crank has had its go Don't recommend me as your crank builder.


Which one is the new one.

Most of the sound guarde that is not heald on by the cover or straps has fallen off


What's interesting hear is the colour variationon on the stainless steel straps. I'm not 100% sure I know what it is telling me but hear is a go. The darkest part is the hottest, when the exhaust gasses come out the hole pipe gets hot then there is the bounce back which pushes the escaping fresh charge back in. The dark part is where the escaping charge does not get to to cool it.

If this bile were a race bike that lived within a 3-4000 rpm range then I would have expected to see carbon stick around the exhaust port just where it mates with the pipe. That would say to me the pipe is tuned to the ports for a given rev range.
This motor operates over a large rev range and the pipe is not working well for where it seems to mostly works. Now I know that because it's a topend pipe to start with then I added the sound guard which moved the tuned range even further up.

Not much I can do about that and what I have done to counter that is working.


The straps range in colour to blue. The straps are on the out side which means the pipe on the other side of the sound guarde will be hotter. I'm thinking the next colour after blue is red. Can't say I have ever seen a expansion chamber glow in the dark but this one would do it.


The straps may be saying this part is not getting as hot but it's still hot enough to heat the heat proof O-rings till they go hard and breake up. As said before heat equals power.