Jetting!???

[mysterious_rider]

Hi guys, I tried jetting my bike a while ago and it didn't really work. Basically my bike runs a bit on the lean side (straight through end can fitted with no baffle)

It runs 122.5 and 125 jets. Why are these different sizes? If I swapped them around the bike would pop like no tomorrow on anything above idle.

What jets would you suggest?   I tried fitting 2x 127.5's in there, and the bike wouldn't even start. I might try again and make sure the vacuum hoses are on 100%

the bike runs well enough just don't want to be running too lean and wreck the engine.

Any ideas? Thanks.

[gsatterw]

Uhhh....that sounds wrong. Read up on jetting gs500's here: http://wiki.gstwins.com/index.php?n=Upgrades.Rejetting

Assuming you have older model carbs, you probably need 40 pilot and 125 main. So one 40 and one 125 per carb. You should not have a 122.5 in one and a 125 in the other.

[mysterious_rider]

That's what I was thinking. Don't understand why one is smaller, still, the spark plugs are the same colour. Took it for a bit of a spin and the plugs have coloured up okay. They are a grey/ light tan colour so I guess they're good. Still, I wasn't completely ragging it so this might change. I'll have a look at the link, cheers.

[00sanchez]

There are a few reasons why you may have different sized jets. The first being human error. The previous owner may have ordered the wrong part or got sent the wrong part and never bothered to check before putting them in. If the carbs were synced like this, you would have issues when matching jet sizes. The second reason may be that one carb is pulling more gas or air than the other and the previous owner figured they could patch the problem with different jets. If it's the latter, you will have an underlying problem.

I'd get a matching set of 125s and some 40 pilots if you don't have those already. Make sure the jets are nice and clean if you're using old ones. See if there are any washers on the needles. There might be one on one and none on the other.

Another thing I'd check is spark. If your bike wont even start when upping the jet size one notch, I'd worry that you have weak spark issues... but I don't think the main jets are used to start the bike either, so who knows. It sounds more like dirty pilots to me.