Mystery Mod

V

Vince

Hero member
This is in my Pantah, bit off-topic but it least it in a Delordo carb. I haven't started the bike for a couple of months and stupidy didnt run the carbs dry. So a week ago I tried to start it and long story short it ran on one cylinder. The rear was the dead one, so I pulled the carb and found a golf ball-sized bunch of white fluffy crystals also blocked main and idle jets. So I then dropped it off with Marty to go into his Ultrasonic tank. Today I also dropped off the tank taps and the other carb, no white crystals in the front carb. But here is the really odd bit Marty found the idle jet was, in reality, a 105 min jet that had been soldered up and redrilled. I know both previous owners and I have owned it for 10 years and have no idea who did this to the idle jet, BTW it was at 2 1/4 turns on the mix screw and idled and ran fine. Big mystry
 
I concur and strike back with Piet's subline: If it ain't broken, fix it until it is!

I have seen weired timings (ignition), carb settings and other things on almost any Laverda I came across. You spend more time trying to sort one thing after the other rather than go back to factory settings and go from there. to many changes can mask the route cause of an issue. You might not recognize it until you have a serious engine issue. Been there, have seen it, never need it again.

And I never trust what owners tell me what they already did or checked. you never know if they checked it correctly or went into the wrong direction with their attempt to fix issues.
 
Someone must have somehow stripped the thread in the carb then someone tapped it to MJ size and modified the jet. Better than chucking out the carb.
 
Tippie said:
Someone must have somehow stripped the thread in the carb then someone tapped it to MJ size and modified the jet. Better than chucking out the carb.
Click to expand...

Actually, main jets are available for Dellorto carbs with the smaller 5mm thread.

piet
 
It surprised me that a main jet would fit but someone on the Pantah Facebrake site said the same as Piet.
Quote


John Wittmann Really to finish off re-drilled main jet(s), it needed to be measured on flow rig, but for roadsters unflowed jet(s) weren`t absolutely necessary. On small Dellorto carbs the main jet, in this case #105 is the same thread size as pilot jet in bigger Dellortos, hence soldering & re-drilling. In Pantah PHF36 carbs std. pilot jet is 65 (60 at a pinch or 45 for smaller carbs), but not critical (is in main jet ) as enough adjustment with pilot screw. I`d say main jets over 140 are too rich for a Pantah 500 roadster. I see so many 74mm pistons with black combustion deposits in my basket from conversion to 600, but I agree the rear cyl. needs bigger by one point main jet, road or racing.
 
I think I might know how that odd jet got there. When I first acquired this Pantah it had gummed up idle circuit. That got sorted and I replaced all the jets with the recommended sizes from Gowys and attempted to tune it. After that, it had piss poor ability to accelerate off the line. I went arround in curcles for a few months repeating my tuning attempts and finaly gave up and took it to the local Dino bloke. Three days later I got it back and it was back to its old self. Pulled hard off the line, I asked what he found and he said the carb sink was way off. He adjusted it by feel and the click when the slides closed, and that's all he said. Seems I stuff up using my Vacum Gauges to sink the carbs. This bloke owned a bevel and knew Delordos and I bet it went on the Dino and he fitted this idle jet and didnt tell me. Be interesting to see if the other carb has the same soldered and redilled jet. It went well with them in so I will let sleaping dogs lie.
 
I found out that using Vacum gauges definitely didnt work on my Pantah. It took some time for that penny to drop. I will definitely either run the carb bowls dry or drain them next time it's put away being used. I never know how long it will sit after a ride and this sitting for months with cat piss like fuel in the bowls is not fun to sort.
 
You must get some shit fuel up in NSW Vince  :o
Never really had that drama in my bikes down Sth  :)
Remove the bowls once a year for look see..... generally only find small amount fine rust  and couple of droplets of water. Nothing to really worry about.
 
The first and failing carb has a huge amount of this white fluffy cristal, shocked me how much was there. The working carb has a tiny amount of hard debris in one corner of the bowl, obviously the same fuel. I cleaned that first bowl before Marty saw it, there were remnants of it around the jets. He has seen way more carbs and had zero ideas about what this was. He said maybe the tank lining but surely if that was it would be in both carbs.
 
It's a steel tank and I never use Ethanol fuel, but who knows whats in the browser. This bike, TL Pantah was bought and immediately filled with a 25-litre fibreglass Imola style tank and solo seat back in 1984. That was run like that for years and then the previous owner started noticing the slides were sticking. A little while later the bottom fell out of the tank, this I think was pre-Ethinol, I think he was running that original Shell high octane, Optimax. I am not positive on this but whatever it was it eat that tank He then bought a steel TL tank and it had that ever since. You can see on the inner tank that there appears to be some kind of bumpy surface liner. It came that way so I don't know what it is.
 
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