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Carb balance slow to equalize

M

Mickeyluv

Just got it firing!
Joined
Jul 31, 2021
Messages
9
Location
UK
I'm having a problem that I haven't encountered before; when balancing the carbs on my '93 T5 Polizia the right hand side is very slow to equalize - it takes about 5 seconds for that side to catch up and balance at around 3500 rpm, though when they do they are both in sync. The timing and advance are fine, and float heights are 18mm. The right hand side though has an 8.5g fixed white float and the left side a 10g black adjustable float. Needles, jets and slides are identical on both sides and I checked for air leaks. Compression is 165lb/psi left and 170lb/psi right. New plugs, points and condensers. Cables are both operating smoothly with enough free play. Tappets checked OK. Cold start plungers sealing and free to move.

The bike runs fine without misfires, but pickup doesn't seem to be as brisk as I think it should. I suspect it's something to do with the slow response, but can't spot what the problem is. Any suggestions appreciated.
 
Carb synch tool is a matched set of 4 Davida gauges. They're in good order and reliable - no problems at all with working on other bikes, including other Guzzis (T3, Spada, Breva 750) Switching the gauges round or perming any 2 from 4 always has the condition on the same side with this particular bike.

Cable splitters are plastic. The slides are operating together.

I also visually checked the accelerator pumps are both working. There's a healthy squirt from each but it just occurred to me that maybe I should check the delivery, or disable them both temporarily whilst testing.

5 seconds to equalize is an awful long time. I've only come across one other situation like this (with a Kawasaki) whilst researching but there was no conclusion to that thread.
 
Mickeyluv said:
Cable splitters are plastic. The slides are operating together.
Click to expand...
I believe that is your issue. How can you be sure the slides are moving together? If they were They would equalize immediately. I was working on a Mille GT with those darn plastic splitters. The only way I could get it to run right was installing a Tomaselli 2C throttle and having custom cables made. After that sync was not an issue.
 
With a finger in each carb and my wife operating the throttle I can feel the movement, but after reading your reply it occurs to me that there only needs to be a few mm difference to have an effect on vacuum. I'll take the tank off and have a really good look at the splitter. I may be able to machine up a replacement in alloy as a quick fix.

UPDATE - the problem was with a combination of cable routing and the splitter box. On the twin cable side the cables weren't properly seating and as the throttle was being opened I could see the cables gradually settling, only for them to slacken off with the throttle closed. As a temporary measure I've rerouted the cables to give the straightest run and eliminated as much slack as I can. When I have a bit more time I'll make a replacement splitter. Just rebalanced the carbs and everything operates in synch and a short 12 mile run showed the bike had a lot better pickup and is much smoother.

This bike has the police spec Magura controls with the integrated throttle/brake cylinder/switches, so is a more involved job to replace with a twin pull twist grip. I think a set of new cables and a better splitter should solve everything.
 
Last edited:
Mickeyluv said:
I think a set of new cables and a better splitter should solve everything.
Click to expand...
Agree, The older bikes such as the Ambassador and Eldorado used metal cable splitters for both throttle and enriching jets. These worked well. When the bean counters got involved and went to the plastic ones, with age their performance became questionable.
 
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