Rejetting for 4into1 pipes on gs850glt

[noahjar]

Hello, I need help with jetting my carbs. The previous owner put a set of 4 into 1 pipes on my 850GLT and it runs good all the way up until 7k and then it will start to run lean. I have confirmed the factory jets are the same. I have synced the carbs so that isn't an issue. Any advice on what size I should go to? Thank you!

[Nessism]

It's trial and error. Is the airbox installed? A header doesn't typically cause big jetting issues, but removing the airbox and installing pods does.

Taking your comments at face value, try bumping the mains two steps and see what happens.

[zed1015]

Delkevic list their exhausts as needing no jetting changes when using the stock air box but it sounds like you may need to go up a size or so on the mains if there are no other faults or changes causing the issue.

[noahjar]

Delkevic list their exhausts as needing no jetting changes when using the stock air box but it sounds like you may need to go up a size or so on the mains if there are no other faults or changes causing the issue.

I see well I will give that a try! I do have a NOS airbox installed, the previous owner had a trashed the one that came with the bike.

[noahjar]

After doing some digging on Delk's website and some general searching, i might actually have a set of MAC pipes. This changes a lot

[lizzywhite45]

If your carbs are synced and jets are stock try going up one or two sizes on the main jets to fix the lean spot after seven thousand rpm Make sure you are running the right airbox too since that affects jetting a lot

Also confirm which pipes you actually have Delkevic and MAC can need different jets

Start there and see how it runs

[Rob S.]

Try removing the airbox cover. That was the only mod many 4-into-1 pipes required.