The Triumph Dolomite Club - Discussion Forum

I know that there is a simple answer for this and that I will be shot down in flames for asking, but seriously, I don't know the answer to my question:

The left hand carb on my Sprint HS6 has a little outlet to connect with the vacuum on the distributor.

If i can drill a similar hole and fit a connector on the right hand one, can I use two vacuum gauges, one for each side, to synchronise the carbs?

If I cannot drill such hole, can I use the homemade equipment such as this that you see on youtube to calibrate motorbike carbs?

https://www.youtube.com/watch?v=Y_WDF6glD5k

It would be easier to just use some tube and your ear or a correct carb balancing tool. At idle you'll hardly get any vacuum plus you'll be measuring at completely the wrong place.

Why the wrong place? Isn't that an inch or two away from the place (air filter side of carb) you'll be hearing with the tube?

Yes and inch or two away, but on an item that is very small therefore it's miles off. Plus you need to measure the air entering the carb which has a 1 1/2" - 2" hole in it designed for sucking in air. There's nothing to be learnt from measuring the amount of vacuum going though a 2mm hole. Plus as I said the amount of vacuum you'll get at idle will be minimal. Trust me it'll be far easier to use a piece of pipe and your ear. Plus using your method you'll need to drill another hole in your carb which will just spoil it.

I had an old 6 cylinder Ford Zodiac that I ran on 3 SUs on an Aquaplane manifold. I fitted 3 vac guages to this setup and had them in a pod on top of the dash. Off idle they were a fairly good guide to how well the carbs were synched and the display impressed the punters. But my MKI earhole was more accurate for tuning! So in the end they were just an interesting bit of bling!

Steve

SprintMWU773V wrote:Yes and inch or two away, but on an item that is very small therefore it's miles off. Plus you need to measure the air entering the carb which has a 1 1/2" - 2" hole in it designed for sucking in air. There's nothing to be learnt from measuring the amount of vacuum going though a 2mm hole. Plus as I said the amount of vacuum you'll get at idle will be minimal. Trust me it'll be far easier to use a piece of pipe and your ear. Plus using your method you'll need to drill another hole in your carb which will just spoil it.

I see your point and I'm not disputing it at all. Unfortunately i am the kind of person who prefers a digital level than one with an air bubble. I don't trust my ears (standing too close to club disco speakers fried one of them in the 70's )and would prefer to see something that tells me that the synch is correct.

To use 2 guages why not use the breather pipe tubes and reduce the diameter with a rubber bung to suit the small pipe from the guages? Just a thought.

Tony

tony g wrote:To use 2 guages why not use the breather pipe tubes and reduce the diameter with a rubber bung to suit the small pipe from the guages? Just a thought.

Tony

Don't those exhale air? I am using the servo connection at the moment, with one gauge

No they suck. Pull a pipe off and put your finger near it

Tony

tony g wrote:No they suck. Pull a pipe off and put your finger near it

Tony

ok, that would be great - somehow I always thought they were like the breather pipes you find on the rocker cover in some cars.

Thanks for that!

Yes the pressure comes from the cam cover and is sucked into the engine

Tony

http://www.ebay.co.uk/itm/like/29068279 ... 931&crdt=0

You need to get one with the right diameter rubber bit for your carbs.

https://www.youtube.com/watch?v=320H04Hh1vE

GTS290N wrote:http://www.ebay.co.uk/itm/like/29068279 ... 931&crdt=0

You need to get one with the right diameter rubber bit for your carbs.

https://www.youtube.com/watch?v=320H04Hh1vE

That's a good price for a genuine one of those, I'm quite tempted.

I use a Morgan Carbtune on my Yammy motorbike, an out of sync carb is very noticeable to performance on that 4 carb setup.