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jets don't match

  • Thread starter Thread starter Rein
  • Start date Start date
R

Rein

Guest
so i'm putting the bike back together and I notice something. The small air jets (in the intake side) are size 155 on my 650GL. In the service manual, it says size 150, and a fellow GS member confirmed that he has size 150 in his carbs, same bike

Right now the bike runs a little awkward. She starts at the push of a button, idles like a clock, but when giving it throttle, she hangs at 1500-2000 before dropping to 1100, never lower. Has symptoms of an air leak, but I've gone over the carbs twice to check for any loose fittings, and already put on new carb boots and o rings. Carbs are clean with new orings as well. The only other part that I can think of that would give me problems is the airbox. Maybe a crack somewhere is letting air in, gotta pull it out to check.

So, either my airbox is cracked and leaking, or the airjets are too large? Should I replace the jets with what the manual specs state?
 
There were some subtle changes to jet sizes on some bikes in some parts of the world when these bikes were new - Suzuki had to lean some bikes right down to pass the emissions tests. So it is possible that your bike has the right air jet, even though it's bigger than than spec.

I would try and hunt down an air leak somewhere before swapping jets. Also, just checking, have you done a carb synch as poorly balanced carbs can give the same symptoms.
 
hampshirehog said:
There were some subtle changes to jet sizes on some bikes in some parts of the world when these bikes were new - Suzuki had to lean some bikes right down to pass the emissions tests. So it is possible that your bike has the right air jet, even though it's bigger than than spec.

I would try and hunt down an air leak somewhere before swapping jets. Also, just checking, have you done a carb synch as poorly balanced carbs can give the same symptoms.
Click to expand...



I would obtain the proper sized jets and replace the existing units. AT LEAST you'd have a baseline established and can then see what to do next based on engine response to the change.
 
From 150 to 155 is pretty minor, I wouldn't worry about it unless you have a box of spares just laying around. The hanging idle is from either the mixture being too lean or the carb sync being way off. Where are the mixture screws set? I'd open they up to 2.5 - 3 turns and see if that helps.
 
mix screws are set at 2.5 turns out.

I didn't do a vacuum sync, but when I put the carbs together, they all seemed to open at the same rate, and the same position at the throttle stop.
 
Didn't do a synch, didn't set the mixture screws to highest idle, and you are wondering why it idles funny?
It might have a leaky airbox?
Did you even adjust the valves?
 
tkent02 said:
Didn't do a synch, didn't set the mixture screws to highest idle, and you are wondering why it idles funny?
It might have a leaky airbox?
Did you even adjust the valves?
Click to expand...

It DOESN'T idle funny, it idles perfectly. Returning to idle is a different story. In fact, sometimes the rpm needle zips up and down like it should.

I was told (in a previous thread here) a bench sync should get them close enough, and shouldn't cause these problems. Is there a difference in using the vacuum gauge and just using a

Idle screws WERE set to highest idle, and reset them to 2.5 as nessism suggested. Screws were previously set to less than 2.5 turns out.

Valves were set long ago, like I said, starts up immediately, idles like a clock, all valves are within spec.

I said it might have a leaky airbox, because I haven't had time to pull it off. The GL model airboxes are particularly nasty to get off. I was able to inspect the manifold that the airbox boots connect to, and that one is fine. I have a feeling that the l shaped box with the unifilter might be the problem. Perhaps the regulator being mounted by suzuki right under the airbox has damaged it.
 
Last edited:
So I pulled off the air filter cage and inspected, looks fine, but I had a suspicion that the UNI filter wasn't in good condition, so I replaced it with my spare K&L, and bike runs perfect.
 
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