Could it be something totally different? How about the spark plug? If everything is ok in the carb maybe the plug is breaking down when the bike is heated up? Just a thought.

 

Actually, RaceGass, as I mentioned in the original post, I do have the Kouba screw, and the popping is not an issue. The issue seems to be is that my slide may be getting stuck as GaryC mentioned. The Dynojet spring is shorter, which would probably make it weaker but not by much. So I am not 100% sure if it is getting stuck because of that or other reason.
As far as spark plug goes, bike does not run right whether it is cold or warm and runs ok after i take the top of the carb off

 

I'm tellin you the slide is stuck open,,, look at it.
the same thing happened to me and the bike would only idle after a backfire.
change the spring back to stock and drill the slide.

 

IIRC on my old bike, the smog hoses if pinched could cause an issue something like this (but would restart and run right for a bit if you gave it time)

Given that once it acts up it doesn't seem to recover, it sounds like perhaps the sticking slide already suggested. Even if your diaphram is good, it would only take the smallest bit of crap to get stuck in the slide guide for it to hang up and stick. I would get it hot till it acts up with everything ready to pull apart, yank the tank and pull the top off the carb, see if the slide is moving freely up and down, and that the needle is not sticking anywhere either.

Also, did you ensure that when you changed your filter you squeezed all the excess oil out of the outer filter? I've had a couple people bring me small engines that started and ran great but then would start to fall apart under load once they heated up and the filter was the deal, try popping your filter off and see if it helps resolve it.

That's all I got at the moment.

 

Before I change to the original spring will check the filter and try to confirm the sticky slide.
Thanks for all the advise.

 

Listen to me,,,, my bike was new,, or only 1000 miles when i got it anyway..
The slide is NOT a perfect fit nor is it lapped into place with lots of miles on it.
The DJ spring may work in a carb that has been worn into place and slicker than goose snot,, it will not work in some new bikes. my bike it did not work in.
I even tried to stretch the spring to get it to work. I put the stock spring in and no more problems. Then i driled the slide to make the carb work right, which is the way the older kits were. and now it is perfect.
check whatever, but i bet you a six pack you will change the spring and be happy.

 

This is bit off-topic but since we're talking about Dyno Jet kits....

Couple years ago I had KLR650 with all sorts of normal hoop-up mods on it, full exhaust, opened up airbox, and then endless hours of trying to find best jetting for the stock CVK(?)40. I had a DJ kit in it.

Each jetting change made some difference but it was never REALLY good.

I finally gave it to the pros and took the bike to local dirt bike and ATV tuner who did the jetting for me on a dyno + exhaust gas analyzer.
The first thing they asked me was "do you have a Dyno Jet needle in there?"
Of course I did.
According to the tuner guy he ALWAYS, as in every single time, finds best jetting with WITHOUT the DJ needle. Sometimes stock is best, sometimes a different needle from carb manufacturer. But he had yet to come across one single bike or an ATV where DJ needle worked best.

Mine ended up with shimmed stock needle and ran like scalded ape.

Since then I've been just buying jets as I need them and stopped giving my money to DynoJet.

--
Mikko

 

Thanks, gentlemen. GaryC, since it is all put together now, and it is raining like hell outside, I will not be able to reproduce the problem. But tomorrow, I will change the spring out and drill the slide. How much do I drill it again?

 

7/64ths.
I drink Corona's.

 

Let us know what worked out for you. Best of Luck on the repair.