82 gs 1100 gk with 4 -1 Mac pipe and factory air box, try find proper jets or setting

[Guest]

Am a newbie here, please go easy, i recently been working on a 82 gs 1100 gk I inherited from my best friend who past away, he installed what look to be a Mac black 4 in 1 pipe with factory air box on it. The bike is hard to start, pops and backfires, and I find number 2 pipe not as hot as the others, also pulled the plugs and they seem fouled and very black, and number two plug not dirty at all, spark is good ,tested, added new caps, new plugs, ordered o rings and intake seals, pulled the carbs and will break down and clean, add the seals, try see if I need the change the jets to tune it in to the new pipe, any suggestions would be great, Bikecliffs says change the petcock when you see trouble at the number 2 pipe, carb spot,,I pulled it and it looks super clean, tank clean, help...

[RedBaron]

It's good that the tank is clean and the petcock looks nice. You can work around the petcock for testing by using a rubber cap to block the intake port on the engine and running the petcock on prime. It may be coincidental that the number 2 cylinder is acting up, but it is quite common to have petcock failure. Take special care to thoroughly clean the carburetors. Many people miss things there. I have a GK with a rotten, partially gutted exhaust system, an aftermarket filter, no backfire cage, and no snorkel. I can't recall my jetting but it did require one size of pilot, one or two hardware store washers on the needles and a couple or three sizes on the mains. I should've recorded the specs but I was hand jetting pulling the carbs off one change at a time until it worked well everywhere. My bike really enjoyed the coil relay mod and new plug wires. Seemed to affect cold starting greatly. Order yourself some "JIS" screwdrivers before you start tinkering on the carbs. They're available on Ebay and Amazon. The Vessel brand I've purchased served me well.

[Redman]

Welcome to TheGSR.

Yes, check to see if faulty petcock is responsible for the cyl#2 problems by plugging the vacuum hose, and run petcock in PRIme (but dont leave it there when parked).

What ever the problem is with #2 could be the "hard start".

Have you checked the valve clearance....?

Would be good for you to introduce yourself some in the Owners section . Pictures would be good too.

[steve murdoch]

As mentioned a petcock test, total carb clean and valve clearance check should be on your to-do list.
If you keep the stock airbox and filter you should not have to rejet the carbs.

[1948man]

If you've been at bikecliff's you've probably seen the link to the CV carb cleaning tutorial. Consensus is that it's not really a carb cleaning unless you do the thorough procedure. The exhaust alone might not require rejetting if the air intake is stock and you don't have intake air leaks.