TOPIC:

That’s a great chart. You can see how the 77-78 were leaned out using smaller pilots and mains. 

Maybe your problem wasn’t the jets. The erratic idle can be caused by valve lash and carbs that need to be synced. If it ran good before with rough idle put it back to the larger jets and set the valve lash, set the idle air screws for best idle and vacuum sync the carbs. You need a fully charged battery and you need to know the voltage at the primary of the coils. 

Has HRM mentioned check the resistance of the coil primary and secondary. Also make sure the points dwell is set and that the points contacts are not flashed and pitted.

Yes valves clearance are good.

The "unseen" issues are the ones that will bite you in many instances, such as the carb boots.  If you are taking off the carbs I would just spring for replacement OEM boots and be done with them.  The perfect time to replace the intake boots is when you have to take the carbs off.  If you have changed anything at all it could have a difference on starting the bike with the kicker.  Battery condition will also have an impact on this.  Lots of things can change on a bike over the course of time and just because it worked well last year or three years ago doesn't mean it will run good today.  I will add that you must vacum sync the carbs for optimal performance.  Can't get away from that one.

Rick H.

No pump means your bike was made early in the year.  I think later ones had a pump.  

Yes, you can see from your chart that the needle jet (located in the carb throat) is an O6 on the '76 model and O5 on the 78 model.  This means it is slightly smaller on your model, but you have the same needles.  So you would get less gas through the main jet in all throttle positions because gas flow in this circuit is limited by the size of the needle jet.  You could attempt to increase flow by raising your jet needle one position.  You would know right away by taking the bike on the highway and cracking the throttle wide open.  If that doesn't work you could change out the needle jets...not a difficult job but you would need to find some O6 jets.

 

wrote:

Before changing your coils, test them for correct resistance.  And check your battery to see if it has the correct voltage.

Have you changed the jet needle position?  I should modify my previous comment slightly.  The needle jet was used in the 1976 version of those carburetors with a needle jet that was one size larger.  You could probably get the same effect from your set by raising the needles to the #4 notch from the top.

Do your carbs have an accelerator pump under #2 carb?

I realized I made a mistake in my comments above so I have modified to correct things.  The mistake was where I said you could get the same effect from your set by raising the needles to "the #2 notch" which would actually be lowering them a notch from standard position.  I should have said "the #4 notch from the top" as corrected above.  That would raise the needles one notch.
 

I will try that. thank you.

Thank you all for your help.
By rebuitd the carbs totally i suppose that i lost the correct sync of them.
I 'm waiting for an emgo carbs sync that i will receive next week. I will work on needles and boots too. Check the battery and coils.
My error make me learn more.

Regards,
Fox