• Don't overlook our Welcome Package, it contains many links to important and helpful information about functions at VHT like posting pictures and sending PMs (private messages), as well as finding the parts you need.

    AD

86 450 Rebel needs to be completely warmed up before riding

ckahleer

ckahleer

Well-known Member
Joined
Mar 10, 2022
Total Posts
64
Total likes
0
Location
GLEN ALLEN
Not a big problem, as the bike runs great after it warms up. But something is not quite right, as no other bikes I have owned have needed this much warm up time. (5 to 7 minutes).
When cold, the bike starts with choke on, after 30 seconds the choke can be turned off and will idle fine, but will stall out if you give it gas. After 3 minutes, you can start revving it in neutral, but if you try to ride it, it will bog down or stall out when pulling out.
 
Need a bit more information.
Compression?
Correct NGK plugs installed?
Stock air box?
Carbs have been sync'd and mixtures set correctly?
How does it run once it's hot?
 
LongDistanceRider said:
Need a bit more information.
Compression?
Correct NGK plugs installed?
Stock air box?
Carbs have been sync'd and mixtures set correctly?
How does it run once it's hot?
Click to expand...

Compression was within specs when I tested it 6 month ago. I don't remember the numbers.
Plug insulator and electroids are tan color. I believe plugs are correct. But not with the bike now to verify.
Everything is stock. Carbs, air box, filter, exhaust.
Carbs are clean and synced. The mixture screws are out about one turn more than ideal, in an attempt to fix this problem.
Runs great once completely warmed up.
 
I would check the timing with a timing light and watch closely while trying to raise the rpm. This sounds like the advance isn't functional.
I specify NGK because it's fairly well known the other plugs don't work well.
 
Problem solved by shimming the carburetor needles .100".
My first attempt at shimming was .080". All most fixed, But still a little hesitation.
Second attempt was .140". No more hesitation,but to rich at idle, even with mixture screws all the way in.
Third attempt was .100". No hesitation after a 2 minute warm up and can get idlle mixture correct with mixture screws out 3/4 turn.
I'm sure by shimming the needles, I'm compensating for another issue, but what?
 
I imagine your carburetor's accelerator pump isn't feeding the engine properly.
When you removed and clean-out the carbs,then filled them with fuel,did you notice if both the small brass nozzles in each carb throat were spraying toward the engine when you worked the throttle pulley just 'off idle' ?
 
By raising the needle you've richened the mixture and since it cured the issue that would mean you have a vacuum leak somewhere.
I would remove and check the air cut valve diaphragms, if those have cracks/holes/etc. they would lean the mixture
 
bilbikek411 said:
I imagine your carburetor's accelerator pump isn't feeding the engine properly.
When you removed and clean-out the carbs,then filled them with fuel,did you notice if both the small brass nozzles in each carb throat were spraying toward the engine when you worked the throttle pulley just 'off idle' ?
Click to expand...

I'm not familiar with these carbs. Do they have accelerator pumps. ?
I would think the vacuum leak might be an issue.
 
You must log in or register to reply here.
Back
Top Bottom