1981 gs550 dies breaks up after 5500rpm, what size mains?

[Guest]

I recently purchased a 1981 gs550 with a 4-1 exhaust and have added k&n filters. The bike runs fine up to about 5500 rpm and it starts breaking up. I was told I need bigger main jets. I'm currently running 2 sizes larger than stock, though I cant remember what size they were. What size should I change to?

[tom203]

Here's a chart

http://members.dslextreme.com/users/bikecliff/images/carbspec_float_height.html#A01

It's likely this new-to-you bike needs a few maintenance issues addressed- look for bwringer's common issues in this link

http://members.dslextreme.com/users/bikecliff/images/GSR_Greeting.html

Welcome- your problem could be wrong jets or a petcock that doesn't deliver enough fuel to carbs, but suspect everything - don't put much faith in PO's efforts.

[koolaid_kid]

First, you need to run through all the basic maintenance Tom pointed to.
Next, you can try just changing the mains. However, I strongly suggest that you first pull the carbs off and see what is in there. For pods and a pipe, it is strongly suggested that you bite the bullet and go with a DynoJet STage 3 kit. With a pipe you can generally get away with just a main jet adjustment. With pods and CV carbs, not usually.