Piston crown photo, what's it showing?

I see little to no witness on the gasket sealing area and if any, it is equal from on side to the other. Don't go torquing needlessly.

I see a hot spot that may indicate a poor seating valve, burn hot on one side and cold towards the exhaust side.
It might suggest you would have carb balancing issues as well. An effect, not a cause.

You have done so much work yet have not ventured into the most performance enhancing aspect of the Commando motor and that is the head. It doesn't have to be modified to be awesome, but it does have to be in right, tight, proper, and sound in the valve train.

Since you enjoy it so and have the time, get that thing off and checked out.
And don't give up on the copper gasket just yet.

Yes, the carbon layers are not that unusual at all but quite expected and not at all what got my attention to post the photo, expect that the more carbon jug also revealed mixture and combustion processes swirl or stagnation. Where the piston shows the clean crown on inside of barrel, just above that I find a thumb sized blast cleaned area on head chamber where the intake pulse strikes head then deflects swirl past exht valve. I have felt the effects of vortex generator lips and flow directing vanes in a few of my engines and when it works right its a significant kick in the pants. I've got a spare standard head I plan to mess with on Trixie Combat someday, but it too sucessful like it was on Peel, then I'll remove it to spare the rest of a poor factory grade Commando that just ain't up to it. Will send to JC to flow bench and see what its measures. I think a couple lip ridges just beyond the intake valve and a Signh groove or two in the squish band on plug side of rim between exht valve plus some dimples in a pasley pattern on the piston crown inner area just might be pleasing to feel.

pvisseriii said:

I see little to no witness on the gasket sealing area and if any, it is equal from on side to the other. Don't go torquing needlessly.

I see a hot spot that may indicate a poor seating valve, burn hot on one side and cold towards the exhaust side.
It might suggest you would have carb balancing issues as well. An effect, not a cause.

You have done so much work yet have not ventured into the most performance enhancing aspect of the Commando motor and that is the head. It doesn't have to be modified to be awesome, but it does have to be in right, tight, proper, and sound in the valve train.

Since you enjoy it so and have the time, get that thing off and checked out.
And don't give up on the copper gasket just yet.

Click to expand...

I had the head reworked by Dean Collinson 4 months ago. I had a burned valve and it got stuck open just a tad, enough to create a ugly sound till I pulled over. I dont have stuff to cut valve seats or the skills yet to do the head so I took it his way. He replaced the valve and checked it all out cleaned the thing up for me and I considered that completed. I dont have a problem pulling it apart again if I need to. Just dont feel all that confident with dismantling the head without the proper tools etc...

This is one ofthe reasons I offer gapless rings - tighter seal, less blow by

Here is an interesting picture.


A while ago (few months) I fried a valve (left side) and it siezed in the head enough to create a tap sound and make me get a tow home. I took the head in and had it lookked at but I also took pictures then. Notice the piston tops look the same! The pistons I have now are replaced as is the bore and rings...



Looks like whatever is giving the right cyl an issue now was there before I did the bore and rings....