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'85 Honda Nighthawk throttle problem.

4K views 12 replies 6 participants last post by  2005GZ250 
#1 ·
With the engine running and in neutral, if I rev the throttle and then release it, the throttle grip and carb linkage all snaps back but the engine speed takes a few seconds to decrease back down to idle.

Likewise when I am riding and I squeeze in the clutch and release the throttle the engine revs way up and takes a few seconds to decrease. Hard to make a nice smooth shift.

Carbs have been cleaned and bike runs well otherwise.

Thank you for any opinions.
 
#2 ·
Welcome. I'd look for a vacuum leak. Check the hoses for cracks. Could also be a timing issue, but I'm not experienced with that.

Please fill out your profile. Give a little, get a lot.
 
#4 ·
Either a vacuum leak or an intake leak (either between a carb and a manifold or a manifold and a head). Check for visible leaks, and with the bike running spray a little WD-40 around the intake manifolds. If the idle changed, you found your leak.
 
#5 ·
With the engine running and in neutral, if I rev the throttle and then release it, the throttle grip and carb linkage all snaps back but the engine speed takes a few seconds to decrease back down to idle.

Likewise when I am riding and I squeeze in the clutch and release the throttle the engine revs way up and takes a few seconds to decrease. Hard to make a nice smooth shift.
Had one. Mine did that a LITTLE too. More on the order of 1/2 to 1 sec.
I think many high compression engines are done that way on purpose so that you don't abruptly close the throttle and lock the back wheel. That delay was much less on my Kawi 600-4 because it has a "slip clutch".

Hard to tell without being there if your situation is "normal" or not. If it is not working right, my guess is that the fix would probably be fairly easy, quick and inexpensive. Alas, I don't know what controls the throttle down timing. A visit to a dealer might be in order.

Sounds like you need to work on your timing a bit. Close the throttle BEFORE you pull in the clutch. ;)
 
#10 ·
Yes check from the carbs to the cylinder head. On my '73 Suzuki GT750 if the idle mixture screws are not set right it will do the same thing as your nighthawk and will also surge on deceleration.
 
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