Carb settings: stock but with 4into1?

[Guest]

I'll start off by saying I haven't done any plug chops yet, but I will hopefully when I get home. It's been a process getting this bike up to date on maintenance and road worthy, and I'm finally to the point where I can fine tune it.
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My bike is stock mechanically except for a 4 into 1 header and exhaust which looks like the V&H one, but has no markings. I did a valve adjustment and synced the carbs (they were almost dead on already). It starts up instantly, only needs the choke for about 30 seconds, settles at 1,200 rpm idle after warming up. No hanging idle, it doesn't bog at all, pulls hard from 0-85 (haven't taken it faster then that yet), no flat spots or hesitation, no surging, no spitting on acceleration, it does pop though if decelerating at more then 5,000 rpm (there's probably a pinhole or two in the pipes, and I know the gaskets are nasty).

It all sounds pretty good, but when I pull my plugs after a ride they look lean, like very very very light tan. What the heck? I haven't adjusted the fuel mixture screws yet, but there aren't any other signs of running lean other then the popping. Could it be leaning it out a lot when decelerating and thats why it's reading lean, but fine otherwise?

[DannyMotor]

Youve got to do a chop. Your jets are fine, but you may want to raise your needles one ring on the clip. (Meaning move the circlip down one spot on the top of the needle).

This will richen up your mid range from 1/4 to 3/4 throttle and get rid of that popping... probably make your plugs a bit deeper brownish too.

[Agemax]

a light tan colour on the plugs is what you should be looking for, not chocolate or white but a nice tan "biscuit" colour

[DannyMotor]

The way hes talking it sounds like raw pancake batter. Biscuit is perfect. Brown eggshell is too dark. Tasty plugs make me hungry... mmmm.

[Toasty]

Yep, they look like raw batter. Sorry if this sounds dumb, but do I need to do chops on new plugs? The ones in there now only have a few hundred miles on them.

[DannyMotor]

Yep. New plugs will give you the best accuracy.

Do this... start and warm the bike up on the old plugs. Once its to operating temp, swap in the new plugs. Get on, start no choke and GO. Get going about 5500 RPM at 1/2 to 3/4 throttle... so 3rd gear-ish. Hold it there for a few miles. After a few miles pull the clutch, dont let the throttle close, hold it over 1/2... and flip the kill switch... close the throttle and coast to a stop. Get off and pull a plug. Check the color. Adjust accordingly.

[hampshirehog]

Don't do anything until your exhaust is sealed properly or you'll be chasing your tail.

And as your bike is a 550 with CV carbs wearing the standard airfilter etc, the only other alteration being a 4-1 I would be very surprised if you had to do anything other than tweak your mixture screw. As it's running fine and only weak (the popping) on the overrun(when you have your throttle closed ie it's only the pilot circuit in play), messing with anything else will prove fruitless.

I've done loads of 550s (fitted with CVs and VMs) with 4-1s and never changed jets or needle positions.

[Toasty]

The mixture screws would make that much of a difference? I thought they are for the mixture on idle, and dont make much difference in the rest of the powerband?

[DannyMotor]

Listen to this man... I thought you had VMs not CVs. The mix screw does a lot.

[hampshirehog]

The mixture screws would make that much of a difference? I thought they are for the mixture on idle, and dont make much difference in the rest of the powerband?

The mixture screws are part of the pilot circuit. Not to be confused with idle or tickover - they are different terms. Unless you ride like a nutter or live in town most of your riding will be done on the pilot circuit - about 1/8 throttle opening and less. When you are decelerating and have the throttle closed off your pilot circuit is still allowing a small amount of fuel / air in to the engine (enough for the engine to tickover). If you have popping then it suggests you are running lean.

However, if your exhaust system is leaky, like I said above, you'll get all sorts of false info so you need to sort that first.

[Agemax]

Yep. New plugs will give you the best accuracy.

Do this... start and warm the bike up on the old plugs. Once its to operating temp, swap in the new plugs. Get on, start no choke and GO. Get going about 5500 RPM at 1/2 to 3/4 throttle... so 3rd gear-ish. Hold it there for a few miles. After a few miles pull the clutch, dont let the throttle close, hold it over 1/2... and flip the kill switch... close the throttle and coast to a stop. Get off and pull a plug. Check the color. Adjust accordingly.

hit the kill switch before pulling the clutch or else the engine revs will rise rapidly. try doing it within milliseconds. kill switch/clutch.
a plug chop should be done at WOT under load

[celtic_ink]

bit of a side bar...

will the fuel mixture screw help enough with pods and stock exhaust, also?

[hampshirehog]

will the fuel mixture screw help enough with pods and stock exhaust, also?

No - not on it's own. You're in to much more tinkering with pods.

[celtic_ink]

No - not on it's own. You're in to much more tinkering with pods.

oh happy day...

[hampshirehog]

oh happy day...

GS750 8 valver? I would try raising the needle one notch (4th position) and 120 mains. That will get you ballpark.