Honda Twins banner

1 - 4 of 4 Posts

·
Registered
Joined
·
25 Posts
Discussion Starter · #1 ·
Bikes idles good until it warms up. Once warm the idle becomes erratic and does not respond well to adjustments. The engine acts like it hogging up or running rich at idle. I should mention that the bike runs strong other than this warm idle problem. Points, timing, and Valve lash are adjusted to spec. Carbs have new rubber seals on the tops.

Any suggestions for a fix. Thanks
 

·
Registered
Joined
·
555 Posts
Chasing a similar problem on my 360. Do you have to use the choke to start it? You may be running too rich in general - when it’s cold, the air can’t hold as much vapor, so some of the gas that would otherwise make it to the cylinder via the idle jet condenses before it gets there, giving you an appropriate A/F mix. When it’s hot, that vapor stays in the air and gives you a rich mix. You could try leaning your idle air screws a bit.

Other thoughts:
Counterintuitively, it could be electrical. Do you put the bike on a charger when it’s home? The battery might function well when it’s slow charged/topped off, but if it’s dying and not taking a good charge, or the r/r is going bad...things get finicky on a weak battery, so that’s an idea too.

Could also be a warm vacuum leak. When the engine heats up, the rubber expands - the boots from the head to the carbs, especially if they’re original, can expand and have cracks that aren’t present when cold. This sounds like a good place to start to me, as this would prevent those other adjustments from doing anything.
 

·
Registered
Joined
·
25 Posts
Discussion Starter · #3 ·
I raised my floats from factory spec 21mm to 23mm and the idle is much more stable. Perhaps the difference in fuel used in 1976 and today has an impact on how a older bike gets tuned?
 
1 - 4 of 4 Posts
Top