Well. I compare the rear valves to the front valves and the rear have a lot more crud on them compared to the front. I cleaned the rear really well so they feel like new and cleaned the seats real well. I'm curious if the back cylinder is getting too hot and I'm burning up the valves. I'll throw it back together tomorrow and maybe I'll go up a jet size on the main as I'm only running a 175. Doesn't feel like it's lean but maybe it is.

 

175 does seem small for your build, I'm using a 190 on my basic 1250 conversion and the plugs look nice light brown/tan. With a 185, they were whitish, too lean.

John

 

I had a 185 in there originally when I rebuilt the motor and got a pretty nasty hesitation at WOT. 180 it was better, and 175 and the hesitation went away and at WOT it just took off. But things may be a little different now after the break in period and getting some fuel through the carb.

 

So the only thing I found by taking the head apart was that there was a very small deposit on the exhaust valve up where it would be in the valve guide. That's the only thing that looks like a potential sticking point.

 

Dude, youre chasing your own tail at this point. Youre not burning up your valves- youve done your jetting procedures, imo- you are looking for problems that dont exist. You said it ran great- go ride and enjoy your hard work!

 

There is definitely a sticking valve. I had it once again stick closed on startup yesterday and it is pretty loud clattering down the highway. Eventually it will stick open and that's gonna be the end of it. Then I'll be stuck on the side of the road somewhere. No way I'm just riding it around like this. Frankly it's an embarrassment.

 

One thing that can happen with a lean mixture is the engine will pick up real quick but then holding on to the power will diminish as the engine gets hot.

 

This exhaust valve is pitted already. A valve that only has 3k miles on it should not look like this already.

 

Most of the Evo valves I've looked at between 1986 - 2000 all had some measure of pitting and a less than desirable stem to face concentricity, why I call them junk! They are also prone to warping slightly just under the head. That exhaust valve will tend to get real hot real fast because it's not transferring heat away through the seat as it should.

 

That valve does look a bit nasty for 3k. I’ve got a set of stock heads with 4k on them, let me know if you want a pic of the valve for comparison.

I can pull it next week after I button up my 1275 project.