Subject: Re: Cam Noise/ carb synchronization
Author: Patrick Hayes
Date: Dec 17, 2000, 11:32 AM
Post ID: 1704501225
In a message dated 12/17/2000 10:00:08 AM Pacific Standard Time,
plsc-@tycoelectronics.com writes:
| I don't have a hole in each intake manifold so I couldn't do the vacuum method. This mechanical syncho method seemed to work well for me. Objective is to get the slides to be at equal openings at all throttle settings. |
Probably will start a war, but:
1. You can easily add vacuum test ports to your older intake manifolds.
Just drill and tap. You need to use a spot facing drill to create a flat
disk on the outside surface so you get good sealing during normal operations.
Remove the screws and add your carb stix ports to the openings. There are
tips on this in the old MGNOC tips books. If you need a copy of the tip I'm
sure someone can dig it out. Or, find a junked Guzzi with the newer
manifolds with the ports built in.
2. "...at all throttle settings..." Nice idea, but simply not possible.
You CAN'T get the two slides to always be the same. Lots of slop inside the
carbs. You've got these great honking cables with lots of drag. If you have
an older throttle you have one upper cable joining two lower cables in a yoke
device. You can't make them or keep them constantly with the same vacuum.
At least not for more than a few minutes. So, the important adjustments are
only TWO. First, when the slides are at the bottom and resting on the idle
needles, are the two intake sides drawing vacuum the same? If not, adjust
the big screws. Please be sure to blip the throttle with each minor
adjustment. You DON'T want to just turn in the screw and have it lift the
slide. The load forces are too great and you risk bending the needle and
gouging out the slide. Just crack open the throttle a tad and turn the
screw a tad. Now , after adjusting for equal idle vacuum, just begin to
barely crack open the throttles. The carb stix will clearly show which is
opening first because one column will drop before the other as that side
opens and its vacuum deteriorates. Adjust the cables so that both columns
begin to drop (the slides lift off the idle needles) at exactly the same
time. This is where it is important. Low rpm, no speed, you're just pulling
away from a stop. Imbalance at this point will be the MOST obvious and have
the MOST detrimental effect on the drivability of your engine and longevity
of your driveline parts. Imbalances at 3/4 throttle, doing 80 mph will be
infinitessimal in relation to the effect of imbalance at the "crack open"
point. So, since the entire linkage is imperfect, do your balance at the
most effective place and forget everything else.
3. I've tried every mechanical method to do this. Most will make you happy.
NONE come anywhere near close to the precision of mercury colmns. In fact,
if you adjust everything perfectly, even with the mercury stix, and then
take a ride around the block, you will find it just a tiny bit off. Do it
again and it will again be a tiny bit off after a brief ride. The problem is
that the instrumentation is simply more accurate than the mechanical
carb/cable system. Kind of like using a micrometer to measure the thickness
of your bed mattress. The instrumet is fine, but everytime you get on and
off the mattress returns to slightly different positions. So, close is as
good as you'll ever get with a mechanical connection system between hand and
carb.
Flame on.
Patrick Hayes
Fremont CA
EV, EV, SPII, V-65-C, Monza, SuperAlce
MGNOC L-403