81 GS550 cuts out at 4000 RPM

[john121]

Just finishing up a four year (I'm Slow) rebuild project on a basket case GS550. The Carbs have been rebuilt and since I'm running PODS and open four into two pipes I changed the mains to 100 up from 92.5 and the pliot jets to 12.5 from a stock of 10. The air screws are at 2.5 turns out and the needles are stock and at the stock setting. It starts and runs fine but when riding it won't go past 4000 RPM - just seems to run out of fuel. I'm not running and inline fuel filter and fuel seems to be coming from the tank ok and the tank cap vent is ok. I'm going to replace the fuel petcock as the origional has a vaccum leak so I plugged the vaccum port on the Carb and am running it on prime. Should I raise the needles a notch or look at something in the ignition system? It is electric ignition and seems to be functioning well but who knows. The plugs are looking a little lean but it's tough to get a good reading due to the cutting out situation. I'm kinda stumped so any help will be appreciated.

[Nessism]

Install some mufflers.

[john121]

Mufflers are on I just drilled them out quite a bit. I had the same problem prior to drilling them out.

[mike_of_bbg]

One potential failure mode for ignitors is that they cut out at higher RPMs. Not saying that's what's going on, but it's a possibility. In any case you should do a pretty thorough check of the ignition system.

[Nessism]

Jets are too small.

[john121]

Thanks for the help. I ordering some larger jets and will try that - I'm pretty sure that's the problem. I did do a plug check and it looks way to lean and the engine seems to be running a little hot. I don't want to screw it up so will wait untill I get some bigger jets and see what happens. I keep telling my self this is supposed to be fun so I need a little patience. I won't have the jets til later in the week but will let you all know what happens.

[john121]

Got the jets in today went up to 105 mains still a little lean but much better. I am going to pitch the EMLGO Pods as they flow too much air and are junk in my opinion. I will take a look at using K&N filters which are better anyway. I may have to restrict my exhaust a bit to build a little more back pressure. I know I'm on the right track just will have to dial it in some more. Nessism, you were right on with your advise and I thank you. Mike I will also be looking at upgrading my coils as I think they are weak (They are stock and old).