Problems starting sometimes

ive got a 1982 xj750 Seca and sometimes it takes ages to start. I pulled the plugs after trying to start it and they were dry. The carbs were rebuilt early this year so I know it’s not them. If I start it and it dies then takes ages to start. Once it’s running I can turn it off and it starts right up straight away. Should I get a rebuild kit for the petcock because I know that hasn’t been done yet.

 

Did you clean the small jets in the float bows (the jet the brass tube goes into) as they are critical to the enrichment circuit when the engine is cold. I had the same problem with my XJ 900f and after cleaning (I also adjusted the valve clearances) the bike starts every time.

 

Is this a mainly a cold start issue? Is it after the bike has set for several days or more?

 

Yes always a cold start issue after it has not been started for a few days.

 

I had the carbs completely rebuild. The bike ran perfect but has only just started having the problem after it been sat for a few days and always on a cold start

 

I don't ride very often and have similar issues and have found that it is the carbs emptying from evaporation - I am a bit iffy on how many days this actually takes and if it varies a bit between summer and winter.

What is odd is I can't just turn the petcock to prime to fill the bowls. I know the petcock flows freely in the prime position, but when the bowls are empty or low and I set the petcock to prime and look at the clear fuel filter fuel only flows mometarily when I tap on the carbs with my fist.

I have to do this quite a few times while observing the clear filter until you can tell the bowls have filled. The bike then fires right up. Oddly enough if I don't do this after it has set for several days it will initially fire up but just for a brief moment, as if there is a trace of fuel tucked away somewhere for that initial start.

So, try setting to prime next time before you start it, and if you have the clear fuel filter make sure fuel is flowing to fill the bowls.

 

+1 .
Using the prime setting works for me. I have no noticeable signs of fuel leakage on the bike either (carbs, airbox crankcase).
-If my bike sits more than 3-4 days, its either grind the starter for several seconds to crank, essentially long enough to open the petcock with engine vacuum, or use prime to top off the carb bowls. First
I flip it to prime, wait a moment, then flip it back to run, then hit the starter. Vroom! No choke required in the summertime, a little when its below 40 degrees..
Good luck.

 

Great stuff i will try the prime when it happens again. Thanks for the replies