According to Klemm Vintage :
www.klemmvintage.com/
Piston scoring / seizure and hard starting can be caused by air leaks leaning out the mixture. They have an article on how to pressure test your engine. While I haven't ridden my 71 RT1B in the last 20 years, I am in the process of a frame up restoration and took their article seriously enough to test my engine.

Air blew out of the crank seals, finding new ones was no easy task. I eventually e mailed the original seal manufacturer Ars - (Arai Seisakusho Co. Ltd). asking where I could buy their seals. I received a reply from EAI Parts that they have the seals I needed in either Viton or rubber. I went with Viton. The crankshaft seals need to be a TC type seal - double lip, spring loaded to stop leakage in either direction.

EAI Parts has - is an E Bay store (eaiparts.com/). My seals arrived in a few days, were the right ones,
and my crankcase will now hold low pressure.

While I could have possibly found some NOS (New Old Stock) seals, I wanted seals made in the last few months that haven't dried out on the shelf for 50 years.

I'm not sure crankcase sealing is the root cause of your poor starting, or is any part at all.

Please let us know what you find as the root cause.

The problem isn't finding a place that can sleeve it.The problem is finding a sleeve.

Just an update where I'm at and a recap so there won't be so much scrolling neccessary..The bike as of late has been difficult if not impossible to start.It ran crisp right up to redline with no issues other than a little piston noise.When I couldn't start it about a week ago, I decided to pull the head and re time it. At this point I decided to just pull off the barrel and have a look,which is when I noticed the missing piston circlip and score in the cylinder,long story longer I also remembered seeing this score when I first bought the bike and had the head off to time it and thought hmm,why does it still run so good with a scored cylinder and just disregarded it then and buttoned it back up and she started first kick for the most part till recently.
      Where I'm at now is, after pulling the stator, I noticed a broken black wire not contacting the condenser. I soldered that back on and have continuity there again. What seems odd is the bike still had spark while this wire was obviously not contacting but there are other wires there as well so maybe they still provide spark. Onto the piston and cylinder. The piston has 80 75 marking on top which the machine shop that measured it, verified this means it's 3rd O/S. They said they can't fix it unless I can provide them a sleeve and new piston because everything is discontinued even in the aftermarket piston and sleeve manufacturers.
    What I'm thinking of doing now is to just get the parts back from the machine shop,hone the cylinder put another new set of .75 rings on the piston and slap it back together and see if the broken wire to the condenser was the real reason it wouldn't start. I already know it runs with the cylinder score so a hone and new rings wouldn't hurt I wouldn't think.........would it?

I think that's a good plan..  Except I don't see any reason for new rings or honing. 

And there are other options than your local guys like I mentioned earlier if you decide in the future.  Like repair and plating.  These guys are magicians. They will give you a free estimate/assessment if you decide on repair.

www.millennium-tech.net/serviceInfo.php?id=29

Probably better to just keep eyes peeled for a different cylinder...  member 1971DT250 might even have something in his stash?  Or Enduronut.  Or DEET.

You have good plans & i guess rings & a scratch wouldnt hurt. But can go to 1mm over if you realy wanted. Does sound like broken wire is 'it'. Would still spark with plug on top of the motor but not under compression if the condenser is bypassed. I'd guess you've found theproblem. Just a note, i run a 2X5 piston kit in mine which is YZ400F & 82mm, Think i shortened the skirt by 5mm to match the 360 piston or gets close to the flywheels. I do know i forgot to shorten one of mine & is still running but gets close at BDC. Best of luck.
www.internationalmotoparts.com/oemparts/...c78642e/crank-piston

I have RT3 NOS cylinders with NOS standard, first oversize and second oversize pistons and rings. Send me a PM if you are interested.

On one of my RT3 regular riders restored by someone else I experienced a lean runaway condition after I put about a thousand miles on it. The cylinder and piston were on the fourth oversize. The shop discovered that the cylinder liner separated from the jug near the base causing an air leak. The liner was very thin. The RT3 liners start out at 4mm thick when new. This one was at 2MM. For comparison the DT3 starts out at 5MM thick. Since the RT3 generates more heat than the DT3 It was recommended to me not to go past the second oversize.

So I bought 4 NOS cylinders for the RT3 plus cylinders for the other DT1s and RT1s and DT3s I have along with pistons and rings. I should be able to get another 50 years of riding out of them.

  Forums are the best thing since sliced bread, no? Thanks to everyone for all the replies, I now have a number of different options. Last forum I was on was a Porsche one which was just as helpful as this one. I seem to end up with vehicles that have problems with cylinders. An 86 930 Turbo I owned detonated and blew a hole through one of the cylinders and a forum member there was able to provide me with a standard set of perfect used 3.3 Turbo pistons and cylinders for $500 bucks. Turned out the guy who built the motor for the last owner set the timing catastrophically high at 35 degrees ! No wonder that car pulled so hard (until it didn't)!I'll post a couple pics of the bike we're discussing to put a face to it,so to speak. If I can figure out how.

Beautiful bike!