drz suddenly wont start

Went to go for a ride today and sure enough there were problems.

Heres the background: The bike has been consuming oil for the past 1000 miles since I did a big bore upgrade. Other than that it has been running fine, and yes i have been super meticulous about keeping a good amount of oil in it. I made sure fuel was flowing, can smell gas out the pipe, and cleaned the air filter. I pulled the plug and it there was a good amount of soft carbon build up around the edge of the plug, but not much on the electrode. I had a spare new plug so i put a fresh one in.

The no start issue is like this: turns over freely, nothing sounds bad. It does fire but only while i have the starter button pressed, with full choke, and half throttle. It will sputter the whole time the starter is engaged.

Im thinking my valves may have a good amount of carbon on them resulting in a bad seal and low compression. the weird thing is the fact it will fire and run for a second and then die under the conditions i stated above.

Im pretty mechanically inclined so im really just looking for a little push in the right direction. I know the rings didnt seat after the big bore upgrade so i have a new set and a gasket set on hand. Pulling the top end off is this weekends project.

Rings were my guess on oil consumption and not firing.

I think a compression test is the first place to start, then go from what you find there.

intake air leaks have caused no-start conditions
on a coupla my 'thumpers'
o-rings get smashed flat
gaskets and boots fail

Did you change the jetting after increasing the displacement?

It's probably not this but here's something simple to check that I felt really dum finding after hours of trying get my drz started. If the reserve hose is not in properly then the main hose doesn't get any fuel. Must be a suction thing. Mine wouldn't start after changing the spark plug and that was it.

I did not re-jet after the big bore, i was told i did not have to. The reason being that the bike comes stock pretty lean, and adding displacement would result in a richer mixture. that makes sense if you think about how a carb works.

I did some work to the carb today to try and see if that was the issue. Cleaned the pilot and main, and just did a good overall cleaning. Hit the starter and same thing. Starts for half a second while my finger is on the starter with half throttle. Otherwise it just sputters.

Gonna put some time aside, look for a willing friend with a garage, and pull the top end apart in the next week or two. Unfortunately I have a lot of time tied up with work and travel currently.