Can the main jet wear?

[Guus de Jong]

I have got a GS400 which has run about 65.000 miles
I have problems getting de idle speed correct. I have checked and ajusted alle carb parts and all is according the manual. Is it possible that the main jet is worn and needs to be replaced by a new one or any other part of the carb (needle etc).

[Tarbash 27]

did you adjust the air screws? how are the pilot jets?

[Guus de Jong]

Yes I checked the pilot jets but could not get it idling on a constand low speed

[koolaid_kid]

In theory it is possible that they could wear. In reality, it is highly unlikely. More likely scenarios include dirty/blocked passages, adjustments (which you have been working on) and synching the carbs.

[chuckycheese]

Yep

I totally agree with "The Kid". Replacing properly sized jets is usually a waste of time and money..but getting the carbs cleaned and synched is a 'sure fix' for so many problems.:-|

[KEITH KRAUSE]

The main jets aren't going to wear from fuel flow. They can get plugged/varnished up from old fuel and dirt/rust though.
If your carbs have the pilot circuit feeding through the main jet, then the poor idling may be from partially dirty mains. It could also be several other things.
Dirty pilot circuit could do the same thing. Dirty carbs in general.
Mixture screws adjusted wrong.
Dirty air filter.
Poor spark.
Poor compression/burning oil.
You could be describing an intake leak too. Does the bike idle significantly higher from cold to hot?

[spchips]

my vote is intake leak.

[focus frenzy]

when was the last valve adjustment???

[bwringer]

I also vote for intake leak.

How're the o-rings?

http://cycleorings.com/intake.html

http://bwringer.com/gs/intakeorings.html

Also check the airbox and the airbox/carb boots.

And kudos to whoever put 65,000 miles on a GS400 and to you for keeping it going! You gotta ride 'em to keep 'em alive.

[brveagle]

Sounds like intake orings to me too.... One of the easiest fix's, but for some reason always neglected.

[Road_Clam]

I have got a GS400 which has run about 65.000 miles
I have problems getting de idle speed correct. I have checked and ajusted alle carb parts and all is according the manual. Is it possible that the main jet is worn and needs to be replaced by a new one or any other part of the carb (needle etc).

The main jets have nothing to do with your engines idle (or lack of). The pilot jets, and the air mixture screws dictate your engines idle.
You could also have a bad inlet needle and seat.

[Guus de Jong]

thanks

Thank you all for the suggestions
Conclusion for me is not to replace the jet. I have replaced the O rings a few months ago so no false air. I cleaned the carb too.

What I have not done yet is getting them synched. I will try that first.