Colortune wierdness

Many of you helped me with advice during my 550 Seca top-end rebuild last year (which was part of a ground-up refurb), and I've since put a couple thousand miles on her. And BigFitz helped me with my "disappearing oil" problem (wrong viscosity, duh). Thanks, all.

It's bugged me, though, that top end seems to be 75-80 mph, and when I did a plug chop, it looks too lean to me.

Because I'm running 4-into-1 exhaust and K&N pods (both carryovers from the PO), I had a set of upsized jets I ordered from Chacal "just in case".

I put them in, and when I re-synced and then Colortuned (valves are newly in spec, and YICS tool was installed), the Colortune plug BARELY changes color throughout the full range of mixture screw adjustment -- on all 4 carbs. It wasn't like that with the stock jets. I remember that I could see each "stage" of color change with the stock jets in. Is this common? I ended up re-adjusting the mixture screws "by ear" after the Colortune didn't get me in the ballpark. I'm about 4-1/2 turns out. She seems to have more throttle response on the highway now.

I'm thinking about ditching the JC Whitney muffler and getting a Supertrapp to get some backpressure adjustability and better sound, but now I'm unsure if this Colortune thing is a problem I should address first -- or if I should upgrade the muffler and see if it clears itself up after the baffle adjustment on the new muffler. Just wanted to get your experienced suggestions.

 

Top end on a 550 Seca is a lot more than 75~80mph; I regularly end up running 90 just keeping up with traffic; bike tops out around 115 or so. (No fairing though.)

Which jets did you change? Mains and pilots, or just mains? And by how much?

 

Fitz, the only time that 550 would do 115mph, is if you rode it off a cliff......

 

Well, I'm sure it wasn't the 120 indicated although my new speedo is relatively accurate. It's still pulling hard passing 105 indicated. Maybe 112.

 

Yep, during my 10-year history with this bike I've personally confirmed it should easily bury the 85mph speedo. But I've not been able to since resurrecting it after getting it back (non-running) from my ex-wife.

Anyway, I changed the mains to 117.5, and the pilots to 37.5. These were the next available sizes larger than stock.

 

Top speed listed at 112mp/h. With a tailwind or a longer gear ratio 115 is very possible. Plus that was a Yamaha engineer riding that factory XJ who was afraid to screw anything up or wreck.

I would agree that your looking at a loss of sufficient fuel there. Even poorly tuned you should be able to get to 100. Make a list and check all possible causes off, that way you can narrow it down.

 

I run the taller gear ratio (of the two that came stock depending on year) and a 4.00 rear tire so maybe 115 is possible.

But Wiz is more likely right; I'll stand behind 112.