Drilling Vacuum Slides - size??? '82 GS(X)400

[TrikerJoe]

Ok, so I've drilled out my vacuum slide hole to 1/8" (3.14mm).
I also have a spare set of carbs off a gs400TX and when I measured the springs, I found them to be about 4mm shorter than the ones in my carb (107/108mm compared to 111/112mm), so I swapped in the shorter springs.
I can now blip it through midrange to WOT and have done some drag style plug chops and the plugs are coming up white.
I am guessing that I need a larger main jet than the 140 I have in there, unless I am missing something???
I will also post an update on my carb tuning thread...
Thanks for your interest!

[GregT]

Not uncommon to need a larger main jet with a 2 : 1 pipe.
Just make sure you're using the right heat range plugs - too hot a plug will give you false readings.

[Mekanix]

Once you hit wot the slides are usually all the way up. Your getting the most air but not enough fuel.

Midrange is the oposit as greg says.

Start your tuning with the best main jet. Once its giving you nice plugs at wot. Then you can tune the rest.

Id say go to 150's and see if you can get the plugs darker. Then step down to 147.5, 145, 142.5 and see where its happyest.

[TrikerJoe]

Not uncommon to need a larger main jet with a 2 : 1 pipe.
Just make sure you're using the right heat range plugs - too hot a plug will give you false readings.

Greg, I'm running what the manual calls for as stock, NGK DR8ES-L.
Do you think I will need to change my heat range for the mods I've done? I don't know anything about plug heat ranges...

[GregT]

8's will be fine.