I need some smart tuners for these couple problems

[Newbiescott]

Hi Team

So my "93 GS has come a long way from its $400 condition I bought it in.  I have gone on several rides but have noticed two unbecoming behaviours.....

Number one.    starting my bike cold. I give it full choke and it starts after a few turnovers and then revs up to about 5000rpm and sits there for 20 seconds and then comes down and idles and then dies.  Then when starting again it seems to not want to start.  So i flip it over to the PRI setting on the petcock and the it starts with no choke and a little gas.  Then again it revs up ridiciously high and then comes down.  I keep it from stalling with the throttle and then once it is warm it idles about 1500 rpm which sounds fine to me.  I dont understand why the RPM peak so high when I have the choke off and the idles screw backed right out......

Number two.  I ride for about 20km Tonight  with the Fuel on.  Everything runs good.  Acceleration is great and I'm happy.  Then the motor starts to Bog and has no power.  I switch the petcock over to PRI and it seems to run OK for a while.  then th motor gets all boggy again and stalls.  SO i pull in the clutch coast to the side and stab the starter button.... motor starts... i pin it and take off again.  Motor bucks and finally accelerates well.  Then i lose power again and it stalls...... i coast around the corner...... I pull over wait 10 seconds and start it and everything goes fine again and i arrive at home.  What on earth could this be

Way outside my diagnostic skills....... i'm guessing fuel but it seems so inconsisitent.  Its like when the engine gets really nice and hot things get stupid.

Any Advice

Thanks Scott

[Big Rich]

When were your valves done last?

[Daeouse]

When were the carbs last done? Is the tank clear of crud? How do all your filters look?

[EdChen]

When were your valves done last?

Good call, I had very similar symptoms when I neglected my valves. They were super tight and after shimming them to the loose end of tolerance, symptoms gone.

My bike would stall when I let it idle, especially when hot. I used to have to keep my hand on the throttle slightly when stopped.

[Newbiescott]

My valves were done this spring.  I changed the shims and all are close to the loose end of clearance.  My exhaust valves are closer to .1mm and the intakes about .076 and .084 roughly.
I also rebuilt the carbs this spring too.  And installed new gas lines.
I have some old gas in the tank from January but have added 12 litres of premium about two weeks ago.
Could bad gas give me these symptoms.

To me I can't make any sense of it.

Scott

[Big Rich]

What about the intake boots? When were they replaced? There's definitely something going on with your carbs by your description. You shouldn't need to swap to prime like that.

When it comes to the "overheating" problem.... I'd start by checking for a fuel starvation issue. I'm guessing you have the original ignition coils on the bike? Coils can break down over time, which lose spark at higher rpm at first, and then overheat and crap out until they cool down.