Dellorto Dhla 40's

[LaikaTheDog]

I have just recieved a manometer to synch my carbs, it works perfectly, however it shows a significant discprepency between what I expected from my carbs, what the manual says and the results on my dellorto's;

the vacuum generated by the carbs demonstrated that they were well off synch,
I won't get into flow rates but the readings were as follows:
cyl1 verrrry low...almost not registering a vacuum at all (I have blocked the light pod vacuum tube off the inlet manifold to try to fix this)
cyl2 highest
cyl3 low
cyl4 high

according to the manual I should balance the lowest value on the one carb with the lowest value on the other (cyl1 & cyl3 for me), if I do this the engine gets very rough and is close to stalling.

If i balance the carbs using the highest setting on one versus the highest on the other (cyl2 & cyl4), then it all makes sense, a small adjustment and they match up perfectly and engine runs well.

but the manual then says that I should use the "bypass screws" to even all the values.......where are they !!!! i have looked all over and cannot find them anywhere, no online dellorto manual or the Lotus manual identifies them, can someone here help me. At the moment cyl 2 and 4 are matched, cyl 3 and 1 are matched, but now I need to even them across all barrels.... :unsure:

[john.p.clegg]

i found this problem a while ago,it seems that the "later" versions have these balance screws.
us poor relatives have to put up with slightly "bending" the bar holding the butterfly plates
John

[bs982367]

The first series of DHLA 40 carbs (with apparent and bigger richness screws) do not have these balancing screws ; only the later versions with the smaller richness adjusting screws have them.
I prefer to use the "old " balancing system device (vacuum body with a ball moving into a transparent sleeve) connected to the inlet port of the carbs and this works very fine.
It works also fine on my motorbike and I get a better tuning than with the actual system (with hoses) !
The only problem we have is that we cannot balance the bodies separately as I do on my motorbike (as you know, the "vacuum" is related to many elements and you cannot get with an old engine the same values on every cylinder).
So do not expect a perfect balancing if you have uneven compressions !

Edouard de Grand Ry
SE SE 1969