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Tuning the 673 baby kat

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So today we got a break in the weather thankfully. I had been running the stock needles even though I have a 4 into 1 (with a straight through baffle) and twin K&N filters. It ran good but seemed to not pull quite as hard as I had envisioned and the plugs looked a little on the lean side although I could not detect any pinging. So, I pulled the bank and swapped out the stock needles with the Dynojet adjustable needles with the clip in the 3rd position. She sputtered slightly at lower revs in the lower half of the throttle and had a slight hesitation or bog when wacking open the throttle. So, back home, yank the rack again, and moved the needle clip up two positions. Back she ran much better. Pulled good and hard up to about 7500/8000 rpm before she seemed to trail off. She will go to redline but the strength of the pull tapers off above 8 grand. Anyway, no more sputter or only very slightly. And no bog when wacking open the throttle. When I got back I pulled the plugs and they look much better but still maybe a tad rich.

I noticed however that for some reason, the cylinders run leaner to richer from the left to the right as you sit on the bike. I'm not sure what is causing this. I did a bench sync and used my Morgan Tune to sync the carbs about a month ago and haven't run it much since.

Here's a look at plug numbers 4 and 3 respectively. Plug 4 is black all the way down the porcelain except at the tip. Plug 3 has no black down in the porcelain. These where taken at 1/3 throttle going slightly uphill so under load. I haven't done WOT runs yet but will next good weather day.

Thoughts on what would cause the engine to run richer as you move from left to right would be appreciated. Yes, I was stupid and shot the pic opposite of how they are installed in the engine.
P1030503.JPG
 
Re your mixture variation - valve clearances can affect it, float levels can affect it. A poor 4 : 1 can affect it...resynch to start with.

Some years back a friend of mine was racing one of these. 4 : 1 pipe and no other mods. i got fed up with his moaning one day and we did a series of runs drilling the slide vacuum holes until it ran clean and responded well.
Std is I think, 2.8mm. From memory we finished up with 3.15mm.
Std needles too. Does dynojet require drilling the slides ?
 
Yes, dynojet drills the slides which was done. The slide holes do not affect the jetting...
 
Over oiled filters can cause a choke effect and make it rich, filters dont need to be drenched. Ever so lightly spritz them is good enough..just to add some tackiness but not drown them either.
 
stepping out of line with a quick get-away can also produce those results!
 
Chuck, these are paper filters and are unoiled. I will pull all 4 plugs tomorrow and shoot a pics so you cwn see the progession from cyl 1 to cyl 4. Other thoughts or ideas?
 
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