PISTONS-when left is right, or is it right is wrong

I put this motor together 15 long years ago, rode for two years, then got consumed with some business related joys. Back on the road for a few now, the 10:1 combat motor, and a certain redline crazy old man blew a head gasket last weekend. JS motorsport is getting me a thicker one, lowering compression to 9.5:1

But this is odd, though I put the right one on the right and vise versa, it seems they meant R and L looking from the front of the bike when they stamped 'em on my pistons, I clearly have an intake valve impression embossed on the tops!




So, all I had to do was look at the head to see that the piston makers R (right) was on the wrong side, or the L (left) was on the right side, which was incorrect. does that make any sense?





Additionally, does anyone have an economical source for these base nuts?

THANKS!

Don

I have never seen R or L on pistons but the valve cut on the top of pistons give obvious clues : the larer valve are inlet , and exhaust valves are outside oriented .

For base nuts RGM is selling a kit at 9.9 £ , shipment to Hawai will be more expensive than nuts.
By the way there are also selling a base plate to lower compression a 7.5 £

Lucked out on the piston goof up. i got a bit turned around last month on my Trixie Combat pistons, putting them in an upside down head on bench before flipping it to place on rods in cases. Closer cut outs go to back for intakes, duh, or visa versa. My new Taiwan pistons were marked by a green or red ink on the pin boss. I guessed it when by the boat and aircraft R-L colors but could not remember the code, so just made double sure closer notches placed under intake valves.

If just seek nuts and not a factory 'perfect' rig, might consider SS for lasting brightness. Rockey Point Cycle is a standard source with fair prices as anywhere.

Some pistons are marked R & L and some are not. For future reference the markings are always as if you were seated on the bike. [or car] Jim

I can't imagine how you got away with this, they are swapped.

Anyway you dodged a bullet. My shop has base nuts in stainless steel (www.rockypointcycle.com), also washers or any other Norton fasteners in stainless. I apologize for the plug, but you asked.

RS

comnoz said:

Some pistons are marked R & L and some are not. For future reference the markings are always as if you were seated on the bike. [or car] Jim

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thats what I thought, Jim.... but as is often the case, don't believe everything you read...

Cheers,
Don

DonOR said:

comnoz said:

Some pistons are marked R & L and some are not. For future reference the markings are always as if you were seated on the bike. [or car] Jim

Click to expand...

thats what I thought, Jim.... but as is often the case, don't believe everything you read...

Cheers,
Don

Click to expand...

You must have the motor in backwards. 8)

I also found the same stamping error on a pair of pistons that I fitted recently and was going to post a warning for fellow Commando enthusiasts, thanks Don for alerting everyone. The ones I have are 'Cycle Craft' brand made in Taiwan and I bought them on e-bay USA. The pistons themselves are of decent quality and came without rings, this suits me as I prefer to use original piston rings where possible.

Interesting... A few weeks ago I pulled the head off a spare P11 Ranger motor to find a set of Commando pistons installed...you guessed it...in opposite cylinders. Oddly the pistons nor valves have any marks on them from contact, despite having a fair amount of carbon buildup.

Hi Steve, starboard green light and port , red light...........at least in the merchant navy, may be the warriors go the opposite to make the ennemy they are going astern when sailing full ahead!!! Pierre

No wonder these valve trains are kinda noisy!

The guy that marked them got it wrong. period. Sure tells me something. CHECK EVERYTHING. :lol: :lol: