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1982 GS450L High revs after warmup

  • Thread starter Thread starter Dust-it
  • Start date Start date
D

Dust-it

Guest
This bike sat for 13 years with fuel in it . After very extensive tank and carb cleaning I am at wall with the high revs at closed throttle .

Very pliable head to carb boots with new O-rings.
Stock air box with new OEM oiled filter
Stock exhaust
New O-rings on the needle jet tubes that were removed from the bowls and cleaned
Stock 115 main and 17.5 pilot jets
9,300 mile one owner bike with 130psi a side compression
Carbs were cleaned and dissembled up to the point of removing the butterflies and shaft.
The mix screws also have new O-rings and seem to have little affect with setting from 1 to 3 turns out.
Motor runs hard all the way to 9,000 on the road but when it has a 6-7 miles of warm up wants to hang around 3,000-4,000 RPM
Is running for sure lean and the plugs show it , no cable hang ups or choke enricher plunger issues.

Were do I go from here ?????????????
 
Very pliable head to carb boots.....but still the originals? That's the first thing I would look at. As the engine warms up, so does the rubber which can cause an air leak around the boot if there is the slightest crack.
 
Classic symptoms of a large leak somewhere on the intake side. I would look at the boots first to make sure they're actually sealing all the way like Big Rich says.

Another thing to look at is the airbox. I don't know offhand what the 450 airbox looks like but on the shafties it has to be well sealed with weather stripping. Any extra air coming in where it's not supposed to can cause a lean condition.
 
Set the pilot screws at 3.5 turns open for one. Have you vacuum sync'ed the carbs yet?

Agree that it sounds like an air leak. Airbox boots must seal to the ends of the carbs, and the airbox lid sealed too.

Good luck
 
If you look at the intake boot clamps.. are they all the way tight and sides touching.... like they will not tighten any farther???
if so, the rubber has SHRANK..... with new boots the clamps will tighten down enough, but still have a gap between the sides. I had this same problem on a 400 AND a 450.. the boots were leaking. On my old boots, when they were tightened as far as they would go, you could still SPIN them around on the boots. I replaced the clamps with hose clamps but eventually replaced the intake boots (pipes) 'cause I was afraid of them.
 
First off thanks for the replies . No I have not tried to vacuum sink the carbs yet ,also have not checked valve lash waiting on tool shipment .
So although a replaced the carb boot O-rings and cleaned the mating surface I saw no change . The carb boot clamps are bottoming out will remove them and try an automotiv
wider clamp just to see if I can get any improvement and then order new boots if needed.
I was experimenting with reducing intake air flow by covering the air box intake and made things worse in that the RPM increased. That seams to be telling me I might be pulling even more air in the front side of the carb causing an even leaner condition. Also the pilot air screws have little affect any were from 1 turnout all the way too over 3 turns out. If I turn them in to 3/4 turns out I did get it to slow down but cracking the throttle would return to a high RPM hang up.
Carb boots seam to be at least part of the problem, would not have thought as tight as they are that it would still be able to pull enough air to upset the mix.
Thanks for the advice and I will put it to use .
 
Check the Newbie Mistakes thread linked in my signature. You are making several common mistakes so the info may help you. For example, you haven't adjusted the valves nor vacuum synced the carbs yet, so trying to figure out what the idle issue may be is causing you to spin in circles. Do all the maintenance first, then see what, if any, problems remain. Not the other way around.
 
I agree fully with the above post and am sourcing the tools to do the carb sync and valve adjust . Going to pull the valve cover today and verify whether or not I have a tight exhaust valve. If necessary when the tool arrives I will put them back in spec .

Thanks for all the help will post again when I have done those maintenance steps .
 
Valves adjusted and timing checked . Wide new clamps installed on my cyl. to carb boots with new O-rings . With the mix screws closed down all the way it will idle smoothly after an extended warm up and runs well through out the RPM on the road ??? I must have something still not clean in the mix circuit
, opening the mix screws continues to elevate the RPM with idle adjustment backed all the way off and throttle cable with 0 tension on it . Turning out the screws is not richening the mixture . Pilots are 17.5 no bleed as was stock for this bike (82 GS450 L). Does any one know more about how the mix circuit passages bring more fuel as you turn them out and in my case increase air leaning the mixture?
 
The stuff about turning down the mixture screw all the way sounds like your throttle plates are open too far when on idle stop screw ( thus mixture is being oversupplied here) look at this pic


image.jpg
 
Well it seams I have solved my lean idle problem . With the availability for the non bleed pilot jets being so slim in the smaller sizes I installed size 20 pilots with the bleed holes . I now have some room to adjust the air mix screws and both sides are at about one turn out .
 
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