Idle

George Hirvela

George Hirvela

Joined
Mar 4, 2014
Messages
57
Country flag
Will a loose timing chain cause my idle to stay high after riding for a while? My carbs seem to be closing and the slides move as they should, I haven't checked for manifold leaks yet but I noticed the loose timing chain through the inspection hole.
 
To my knowledge, no. High idle is usually the carbs. As you say after riding for a while, try loosening the carb to manifold nuts slightly. If too tight the slides will bind due to carb body warp.
 
Are they original carbs? Before I switched to Amal Premiers my idle was all over the place.
 
George Hirvela said:
Will a loose timing chain cause my idle to stay high after riding for a while? My carbs seem to be closing and the slides move as they should, I haven't checked for manifold leaks yet but I noticed the loose timing chain through the inspection hole.
Click to expand...
Unlikely. What about heat soak in to carbs, causing excess fuel evaporation/leaning of the mixture? How hot are float bowls when the idle is too high?
 
If you are using the original points a sticking centrifugal advance unit, or one with weak springs can cause the idle to not slow down. If you can get the idle to slow by dragging the clutch a bit, and then after putting it in neutral it stays at a nice idle around 1000 RPM, but then if you rev it up and then it won't slow down again (unless you drag it down with the clutch) It might be the advance unit.
 
tricatcent said:
If you are using the original points a sticking centrifugal advance unit, or one with weak springs can cause the idle to not slow down. If you can get the idle to slow by dragging the clutch a bit, and then after putting it in neutral it stays at a nice idle around 1000 RPM, but then if you rev it up and then it won't slow down again (unless you drag it down with the clutch) It might be the advance unit.
Click to expand...
Not using points, and it stays up until it's cooled down...
 
George Hirvela said:
I'll put a temp gun on it. What's a good range?
Click to expand...
Unsure but gasoline will boil at something like 40-50 Celcius I believe. If fuel is too warm it might affect mixture (leaning it) and raising idle.
I just touch the bowls and if much hotter than "warm" , then may want to use thicker insulator "gasket" 'tween manifolds/head and even add another insulator carb/manifold. I once had a float bowl on a single carb setup too hot to touch after five min fuel stop. Throttle grip would not rotate closed from a pre-start roll on. After a few minutes it did snap closed as carb cooled off more. Later fitted second insulator and issue never happened again.
 
George Hirvela said:
They are Amals I don't know if they are stock ones...
Click to expand...
Look if they have a removable pilot jet opposite side where the Air mixture screw sits. If not then they are not the new Premier type amals, but might still be new original style.

Having a good strip down and thorough pilot jet clean out with piano wire or proper sized micro drill always important to do. Got to get proper spray through to the two tiny holes in the carb throat before re-assembly.
 
George Hirvela said:
Will a loose timing chain cause my idle to stay high after riding for a while? My carbs seem to be closing and the slides move as they should, I haven't checked for manifold leaks yet but I noticed the loose timing chain through the inspection hole.
Click to expand...
Sorry - a bit late in here.
Timing chain - inspection hole?
Do you mean primary chain? I am unaware of any timing covers with inspection holes.
A loose primary chain should not affect idle speed unless it is very loose - could cause snatching plus bad noises.
Cheers
 
Don't the late model/MK111 timing cover have a timing chain inspection hole beside the points cover.
George Hirvela said:
Will a loose timing chain cause my idle to stay high after riding for a while? My carbs seem to be closing and the slides move as they should, I haven't checked for manifold leaks yet but I noticed the loose timing chain through the inspection hole.
Click to expand...
What sort of weather are you riding in, if it's a high temp day and if you are running crap oil in your motor could be running hot which causes the idle to run high when stopped or riding in stop go traffic, when I brought my Norton new back in 76 the recommended oil was GTX but found I out in hot days when pulling up the idle down was high, but after fitting an Lochart oil cooler and better oil that problem went away and the bike ran cooler and idle came back to normal, after 46 years I am still running the same oil cooler, hot days can cause high idle.
 
ashman said:
Don't the late model/MK111 timing cover have a timing chain inspection hole beside the points cover.

What sort of weather are you riding in, if it's a high temp day and if you are running crap oil in your motor could be running hot which causes the idle to run high when stopped or riding in stop go traffic, when I brought my Norton new back in 76 the recommended oil was GTX but found I out in hot days when pulling up the idle down was high, but after fitting an Lochart oil cooler and better oil that problem went away and the bike ran cooler and idle came back to normal, after 46 years I am still running the same oil cooler, hot days can cause high idle.
Click to expand...
Yes, they do.
 
You must log in or register to reply here.
Back
Top