Anyone know where I can get the tool to synchronize the SU carbs? I had one several years ago, think is was call a unisync.

den;

If you have an undeniable need to buy a Unisyn, I expect they might be a bit tough to find nowadays...check with the British vintage car supplyers. I do recall IPD has a slightly different type in their most recent vintage catalog.

I find that "Listening Tube Method" is not particularily accurate because the placement of the end of the listening tube is critical and will hugely effect what you hear at the other end...varying it a bit when placing it at the two carbs negates any accurate induction volume comparison which might be drawn.

Instead, I use the "Look and Listen" technique...(after assuring linkages are synchronised), I start, set the idle, and Look to compare the amount which the dashpot is lifted due to induction (in fact: the induction raised dashpot of the carb is really similar to the induction raised indicator of the Unisyn), and I also stick my head down as well as possible between the the carbs to Listen and compare the induction noise directly...a diddle here and there on the idle adjustment screws to even them up, and the engine purrs like a Singer sewing machine! Trust your ears! I cant remember the last time my Unisyn made it out of the toolbox...wanna buy a used one?

Cheers

Ron,
Thanks for the info. Can you tell me how I would make sure the linkages are synchronised? The last PV I had was almost 30 years ago. I used to sync. the carbs all the time but don't remember the linkage adjustment. I might take you up on the used Unisyn offer.

Den;

"sync. the carbs all the time"??? Why?...they don't need it that often!...didn't you have a girlfriend you could give your attention to (failing a name, I'm making the presumption here, that you are a guy)?...then again I've found that SUs are STILL lower maintenance than just about ANY woman!

Synching SUs:
Assure carb linkages are synched first by visual inspection of rods and joints external to carbs...and excessive slop or wear is not going to make adjusment any easier! Linkages should be activating carbs at as close to the same time as possible. I like to lube ball/socket joints with graphite grease which even if it gets displaced, the remaning graphite particles still lube (and silence).

Only after a good inspection and lube of the external linkages should you proceed inside....(engine OFF, choke deactivated)...remove air filters, prop up dashpots (i.e. small piece of cardboard), and with a light, observe the action of the throttle plates of the two carbs as you activate the throttle linkage...check back and forth from carb to carb, adjust linkage clamps to assure they are activated at the same time...this is also a good time to check and adjust that the fast idle mechanism activates the throttles similarily when choked...when satisfied, remove dashpot props, start engine, and after engine is at normal operating temp (thermostat opens), adjust idle while observing dashpot lift...adjust individual carbs to make the lift and induction sound at idle as similar as possible (as prevously described). That should do it. Replace air filters.

Cheers

Thanks for the info.
All the time really meant checking at tune up time, about every 10K and you are right, the girlfriends needed much more maint.

Dennis

I think it is Unisyn.
I believe I saw it in the IPD catalog for oldtimers.
I've got one but I never use it. I just set the linkage to where both carbs
are completely closed and tighten it up so that they just start to open at
the same time. Since the manifold has balance tubes it seems to work OK.
Another way to check is to get a small piece of hose, put one end of it in
your ear and hold the other end in one hand sticking about 1/2" or less into
the open carburetor (aircleaner off) and then stick it into the other exactly
the same way. Should sound identical in both. If one is louder close it some
or open the other one till they sound alike.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma