Thanks 678, bike is running sweet again, so simple. After tearing into it and checking everything, Joel Thailand pointed me towards a simple fix. The ECU connectors were dry.
Pulled the ECU plug, sprayed some WD40, and we are laughing.
Anyway it was a great opportunity to check my valves and learn.

Wow, never heard of a connector going dry. Is that like having it get light corrosion aka tarnished?

I know sometimes the guys at the shop used Tarnex on some electrical plugs. Then I think they put on some dielectric grease to protect the connection. Absolutely on the one plug on the 84-87 Gold Wings that resided beside the battery and tended to get a bit of acid mist in them.

Starting issue
 

This post was very helpful in my first shimming adjustment. Thanks to everyone who has contributed.

After doing the procedure and shimming two valves, I immediately started the bike. Before it started there was one backfire through the exhaust that worried me a little. But it ran and warmed up completely. Seemed very smooth.

Then I removed the carb and rejetted for summer altitudes. Dynojet, clip, mixture screw. Also drilled out the starter jet with #77 bit. Again I started the bike briefly by adding some gas to the bowl.

Today I got everything back together and... it won't start. Every couple tries there is a sneeze-like backfire through the exhaust.

What could have gone wrong? If it had not started immediately after resinstalling the cams, then sure I did not align the marks on the cams.

I do remember there was a little question on exactly which cam teeth to put the chain on. Did not take a photo unfortunately but I distinctly remember the marks were lined up with the edge of the head. However I did not follow the service manual instructions to turn the crankshaft over twice and check the alignment (p. 5-20).

Any ideas before I tear into it again? Thanks.

If it ran after the valve shimming but not after the carb work I would double check anything that you could have disconnected to remove the carb. Check basics-spark? compression? Fuel? It needs all three of those to run. Compression/cam timing should be ok since it ran after removing the cams. Make sure that you have a good spark at the plug. If that checks ok then try spraying some carb cleaner into the carb throat during cranking and see if the engine will bark. Good luck...

Excellent tutorial. Thanks for posting this (assuming you are still reading posts here!)

I've done this before on a Triumph 100 years ago but I had a question. Went ahead & checked my valve clearance last week, exhaust was 0.15, intake was fine as well (0.18?). My question is this; I could only check the gaps on the left side due to the camshaft cover blocking access to the right side of the engine. I figured removing it would release the cams & not give an accurate reading. Is there a way to check the intake/exhaust valves on the right side (cam tensioner side) of the engine? I didn't see it. thanks.
2014 klx 250s with 5500 miles, stock.

Are you talking about the kawa 250?
When you pull the valve cover you have access to all the tops of the valves for measuring, .... try harder.

Yes, a 2014 klx250. When I removed the valve cover, I could only see the intake & exhaust buckets on the left side. The camshaft cover is covering the right sided valves, isn't it? Crap, maybe I'm getting too old. thanks.

Look closer-they are obscured by the cam cap. You have to maneuver the gauge a bit to slide it under the lobe but it's possible.

Shims for sale in the mail
 

You can buy a kit as said, or buy the shims in 5 packs for under $10. I needed two sizes to re-shim since two of the four in the bike could be used for other valves. I had suggested it could be a possibility to set up a thread for sell/buy of shims by members here. I'd sell the ones I have for a couple bucks and postage, just because. It helps everyone to do so and there is no need to pay for shims you won't use. If nothing else a person doing valves could post a thread for size needed. A shim taped to a piece of paper in an envelope for $2.00 wouldn't be horrible to pay to cover postage and handling.[/QUOTE]

Im derek. I'm just bought a 1997 klx 300. The bike was at a time and was not running when I bought it. The carb was also needed to rebuild. I got the carb from B and B cycle restoration. Great guy by the way. I checked my valve clarences but I still wouldn't start with the new carb. Turns out the exhaust was within speck but the intake was way out of speck. Turns out there were no schims in the exhaust cups. This is my 1st time ever working on a dirt bike. I'm pretty sure I need 3.00 for both valves on intake side.