OK, I rebuilt the top end on my 87 250, got it together and played around with jetting and the power valve and got it running really well. The shop that did my jug gave me gaskets, but I decided to tear it back down after about an hour of break in and replace the base and head gaskets with OEM, and after putting it back together, something has changed. It revs up nice, runs strong, but when I let off the throttle it doesn't idle down right away like it did before. I'm going to take the carb boot back off and look for cracks, but I don't know why it started doing this after replacing the gaskets? I know these are prone to leaks at the base gasket under the intake, but would I be able to take the jug loose to dab some sealant back there without taking the head loose or should I get new gaskets again? I will also be building a leak tester this week to check the seals, but I don;t understand why it did this after replacing the top gaskets.

I'm running an Aaen pipe, FMF silencer, 250 on the main, needle in the 3rd clip, Uni filter with no lid, 32 to 1 with Klotz and 93.

I wonder if I can pull my top end up a little bit and put some sealant around the base gasket and slide it back down without breaking my head loose? It just seems a little strange for it to leak anywhere else right after I replaced those gaskets since it was fine before I did it. I've checked the throttle cable, and I just checked the boot and it seems to be ok so that's why I was thinging it's the base gasket. When I look at the new one I just took off, you can see where the case halves come together on it, it looks darker on one side like it was a little higher on that side? The new gaskets don't even 10 minutes on them, but I don't know about reusing a head gasket ever.

Yeah, I'm going to get everything to build one this week, It's just very strange that it was running perfect before I changed the gaskets. It's the stock 34 with a 37.5 pilot, it had a 240 main, but I went up to the 250 to fatten it up a bit for break in.

I just put my new cylinder on last night. Done a leak down test. I had a leak around the back left side base bolt and also around the small bolt in the middle of the base up around the exhaust. I took cylinder and used Suzuki bond on it. Going out to check again now.  But if you don't  want to take your head gasket off to take the cylinder off to use silicone , take the motor mounts off and your swing arm bolt and pull the motor to the side so you can slide the cylinder off. If you have Cool head you can take the jug off  while the motor is still bolted up. Hope this helps you