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PWK Carb Adjustment on a 1000SP

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monkeyodeath:
Just got a '79 1000SP in nice shape. Wasn't running at first but managed to get her going nicely with a little carb cleanout/float adjustment. Was hoping to get some advice from the sage folks on this board.

The PO of this bike fitted it with Keihin PWK carbs after experiencing some issues with the Dell'ortos and wanting to reduce throttle pull effort.

I think these are clone carbs but they seem to run fine and I didn't see anything that seemed too bad upon disassembly to clean them.

My question is -- what's the best way to balance these things? I've got a carbmate and am able to get the idle nice and stable using the directions here: https://www.thisoldtractor.com/moto_guzzi_loopframe_carburetor_-_setting_them_up.html and here: https://www.thisoldtractor.com/moto_guzzi_loopframe_carburetor_balancing_synchronizing.html, but:

- The idle mixture screw, especially on the left cylinder, seems to do almost nothing.
- As soon as I rev a little off idle, the right side shows much higher vacuum.

I realize that the throttle cable setting might be the reason for the cylinder imbalance on throttle, but I also feel like I'm just shooting in the dark as far as adjusting these idle mixture screws.

Just curious if anyone else has pointers or experience running these carbs on these engines. The PO seemed to find a jetting that he liked so I'm hoping I don't have to mess with that, but I'm trying to figure out how to best get the cylinders balanced, both in the speed and mixture screws.

guzzisteve:
Idle mixture I use a Colortune made by Gunson. You see the spark flame in a glass bottom spark plug. Spot on stuff. Also works on FI, push buttons and see it go from blue to orange. You get actual not after the fact w/exhaust sniffer.

https://www.gunsonshop.com/contents/en-us/p209_G4074-G4171-G4172-Gunson-Colortune-See-Through-Spark-Plug-Kit.html

Amazon has it for $150

nc43bsa:
If adjusting the idle mixture screws has next to no effect, chances are the idle circuit is plugged, either in the carb body or the idle jet.

monkeyodeath:
Well, turns out something was going on...

Was riding it today on the freeway and starting to feel a bit dismayed at the lack of power (this is my first time even riding a Guzzi, so was not sure what to expect)...

All of a sudden, the bike stumbled a bit, backfired, and rocketed forward with what felt like twice as much power.

Not sure what was happening before, and what cleared to all of a sudden give the bike some life. Stuck ring? Clog in the carbs I didn't get (I used an ultrasonic cleaner!)? Fuel supply issue? Either way something cleared and it feels much more like a proper large-displacement bike.

Tomorrow I'll re-adjust everything, now that the idle has gone from 1100, where I set it initially, to 3000 RPM.

Frenchfrog:
possibly a blockage clearing

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