82 KZ550C jetting

Evening.

I've finally gotten the bike running, plated, insured and I am now licenced. I've put about 1000kms on the bike since.

Bike is an 82 kz550C LTD. Stock airbox, stock headers but the mufflers have been changed. They are baffled, with a silencer installed as well.

While cold, at approx 20-25% throttle at light load (cruise), the bike kind of stutters. Once warm it's gone.

I also noticed that once warm, if I 100% throttle it'll stutter but if I let off a hair then it's fine. I suspect this is possibly a throttle slide height concern. 

Bike otherwise appears to run fine at all other throttle positions and engine loads.

I have a list of things I will be checking and verifying, and those will be priority. This includes verifying that I am still vacuum leak free, re check the float heights, re clean carbs and jets, and re check my air screw settings. 

However, I am wondering about the jetting for the carb. The bike has a different set of mufflers, but is otherwise stock. Mufflers have baffles as well as silencers. I'm just wondering if there's a possibility of a jetting issue or if the stock jets should be up to task. Not really looking for diagnostic specific help, really just if my muffler change is likely to require a change in jetting.

Unless the mufflers are really restrictive, the stock jetting should be fine.
You say there are baffles and silencers. What sort of silencer do you mean? A picture or two might be helpful. 
Getting the float height set should get the fuel level in the correct neighborhood, but the more important issue is the actual fuel level. That needs to be checked using the wet, or clear tube method as described in the service manual. 
Are you familiar with Lou's website?

P.S. Looks like you have an awesome test rider there.

On a stock engine with a air box and universal mufflers stock jetting is recommended. Usually only intake changes (pod filters) will require a jetting change. 

At 1/4 throttle your on the pilot system so you may have to adjust the pilot air screws one way or the other.

What do the plugs look like?

She has been wildly excited about the bike, but wildly disappointed that she can't go out on it (can't reach the foot pegs yet, maybe next year).

As to the exhaust, bear with me. It's chintzy, I struggled with keeping it like that, but it's my dad's old bike and I wanted to preserve it as best I could...I had to resecure everything and it's good now. I know the correct thing would have been to replace them but those warm fuzzy feelings of my childhood made me spend hours making it work

 

It has those silencers that Harley guys put in the exits of the pipes...but these have been flipped around, chopped, ends welded and the go over the exhaust pipes. The muffler slips over it. The muffler is some off brand, but it does have baffles in it.

When I first set it all up my float levels were good, but that doesn't mean I didn't miss something and maybe they aren't, so that is on the check list. I used the clear tube method. Lou's website is basically my Bible haha 

When I set my air screws, I did it without realizing how long it actually takes to get this thing to temp.

I just don't have enough experience with carbs to know how much of a breathing change requires how much of a fueling change

Thanks!

I missed your reply.

 

#4 is an older plug, hence why it's a different colour. I had put new plugs in and within a few kms that plug started acting up. I fired in an older one until my new ones arrive. This picture is after maybe 500kms or so.