Penny-tech carb sync tool

[kevbo]

I have mentioned my carb syncing tool a few times,
but I figure here are some pictures that should
make it a lot clearer.

Boxer twins probably need this the most, however any multi-carb (or TB) bike can benifit, so I put it in eqipment instead of GSpot.

I have seen similar units discribed, but not with
the traps/filters I have. These make the unit work
very well, but do add a little expense. I guess the
cost is 0-$20 depending on how much junk you keep around
or can scrounge.

It is cheap, safer, and a lot more sensitve than mercury
carb stix. Versions can be made up for any number of
cylinders. The one shown is for twins.

Here is the overall view. It is
leaning against a wall as I normally use it. You could
get fancy and make some feet if you wanted. OR you could
be really cheap and omit the backboard, and just hang the
unit from a hook to use it.

[kevbo]

This project should be self explainitory, so no step-by-step construction, but having a list may save a trip or two to the hardware store, so here is one:

Parts list:

This is how I did it. Get the general idea and substitute whatever is in your junk piles. Find some suggestions for changes in subsequent postings.

The list below will work for a twin. See subsequent text for more additions if you want to build one for a 3,4,or 6 cyl bike.


4 ea 2" sch-40 PVC pipe caps. (NOT DWV!)

~2' 2" Sch-40 PVC pipe. (NOT DWV!)

PVC primer and cement...the thin clear "regular" stuff, not the thick stuff. (dries too quick)

~8' 3/8" clear vinyl tubing.

~20' 1/8" """""""""""""""""

~ 1' 1/4" '"""""""""""""""""""""

2 ea 3/8" hose barb x 1/4" MPT fitting...brass or nylon OK

2 ea needle valves 1/8" MPT x 1/8" MPT

2 ea 1/4" hose barb x 1/8" FPT fitting. Brass is better here, as these will get tuged on and nylon may break.

1 board ~ 1' x 5'. 1/2" or thicker plywood, or OSB should be fine.
(Optional)

1 roll of pipe-hanger tape, the metal stuff with the holes. (optional)

1 tube pipe dope. I like rectorseal W/teflon. Teflon tape does not work well on the plastic in my experience....If you tighten it enough to seal, the plastic eventually splits.

1 doz or so wood screws...short enough not to poke through your board, small enough to fit holes in pipe-hanger tape.


Tool list:
1/4" pipe tap
1/8" pipe tap
Tap drills for above sizes (I forget)
Tap handle
Drill motor or hand brace
Screwdriver to suit your screws.
Saw to cut PVC. Hacksaw works good. The cable things are not as good.
File to chamfer end of cut PVC.

[kevbo]

Note that some discriptions of similar tools suggest a yard
stick. I don't have one. The goal is to match the carbs (or TBs)
and if they are mismatched, I don't need to know by how much.

However, it would be usefull to compare various hired wrenches
by how badly sync'd they return the bike. I have seen
a bike left more than 3 FEET off by a genuine BMW dealer
wrench.


Here is a detail of the loop at the bottom. This is
3/8" ID PVC. If you havea Multi-cylinder bike, then add some
tees to make more verticle legs. Number of tees needed
is (# of carbs)-2...so a worst case CBX would need 4 tees.

[kevbo]

Here is a detail showing the water levels in the tubes. I put some
prestone in the water for color, and to kill algae. The level
in the tubes are equal as shown, which indicates a sync'd condition.

They could be an inch off, and you'd still be sync'd as well as
a mercury filled instrument could tell. I have heard of ATF being used,which is even more sensitive than water. Ultra penny-tech could use old fork oil!

Water is plenty sensitive. If I try to get
better than 1/2" match, I am guilding the lilly, because the
reading won't be that close if I ride around the block and
then check it again.

[kevbo]

Here is a detail of the traps/capacitys at the top. You need one of
these per carb. You can omit them if you are too cheap, but don't
cry to me if you end up with a jittery, hard to use tool.


These serve
two functions: First off, they prevent the liquid from being sucked
into the engine in a groossly mis-synced condition. Usually this
would mean one tube got pulled off. Second, they work together with the needle valves (we'll get there next) to form a low pass filter to stabilize the readings.

Mine are 2" schedual-40 PVC pipe, with
caps cemented in place. They are drilled and tapped for the
tube barbs on the bottom, and the valves at the top. DWV spec pipe, will have thinner walls, so may not take the tapping as well.

The length is not critical. I don't off hand recall how long these
are...looks like 8-10" to me. Make them as close to equal as you
can....but don't go nuts over it, as the valves can compensate
for any mismatch.

If you don't have pipe taps, then it may be cheaper to buy various
adapters to connect the large PVC to the tubing. The inlet
could go to the top where I mounted those big vacuum gauges.

About those vacuum gauges on the top of my traps: Total waste of money. The calibration of the two gauges does not match, and even these very large gauges are not sensitive enough to get a good sync. Do as I say, not as I did, and don't bother with the gauges. At least I got them cheap.

You can also see some adapters made from 1/4" clear tubing. I couldn't fine 1/8" hose barbs to fit the valves, so this is my solution. The 1/8" tube fits the TBs on the oilhead nice. I use similar adapters at the other end for the bings on my airhead RS and the Keihins on the Ural. If you only have airheads, you may elect to use 1/4" tubing instead of the 1/8"

[kevbo]

OK, here are the needle valves. These are normal plumbing parts sold as shutoff valves for evaporative coolers or ice-makers, etc. If you put your mounting holes closer to the end of the caps, then you won't have to bend the cross-bar ends up to clear like I did!

[kevbo]

"tuning" the filters:

Check filter matching prior to each use. If the filters are
not matched, deceptive reaings are possible under dynamic
conditions. (blipping the throttle)

1) Close both valves, then open each about 1/2 - 1 full turn.
(first time only...omit this step if just checking match, or
optomizing respose)

Note: If any of your riding buddys are around, now is a good
time to send them for beer or food....the next two steps
look kinda...well you'll see.

2) Put the tubes for both carbs in your mouth. Figure out how to
grip them lightly with your teeth, and keep your toungue away
from them.

3) Alternatly suck and blow while watching the water level in
the tubes.

NOTE: Doing it my way puts some spit on the ends of the tubes, so they
slide onto vacuum ports nice and easy. If you just can't face the threat
of being observed, then you could use another
tee so you could connect both lines to one carb, and blip the throttle.


4) One level will go up and down more than the other. Either
close it's valve, or open the other valve a little untill
both levels track togethor. There will still be a little
motion due to tubing stretch.

You wan't to see just a little (maybe 1/8") jitter in the reading
for good response.

5) When using the unit, if the levels seem to oscillate at low RPM,
then you need to close both valves a little, and re-match them
by mouth again. (steps 2-4 above)

6) If the response seems sluggish, then both valves need to be opened
a little more and re-matched.

[Zip]

kevbo,

I just got a Carbtune II. I'm a noob at adjusting valves, and synching throttle bodies, although I hope to get good at it. Anyone in Western NY want to let me peek over their shoulder while doing this type of work on an oilhead?

The Carbtune II is kind of similar to your set up, at least in a way. It has plastic tubes, with stainless rods that move, to indicate balance, or lack of.

The Carbtune II comes with clear plastic inserts that go into the lines. These act as dampers, and are similar to your needle valves. These plastic inserts have very small passageways, by the way.

Take care,

[Randy]

Kevbo,

GREAT write-up . I had been planning to order a twinmax but hadn't gotten aroung to it. what the hell, after seeing your pics and reading your thread, i think i'll just save the bucks and hassles and just build one of your design. thanks.

one question though. not having pipe taps, couldn't i just drill the appropriate size holes for the barbs and valves and just glue them in with some JB or quicksteel?

[motu]

I'm the tightest wad on this planet - looks like you spent way too much money.For dampers I use those slow release or delay valves that were used on cars in the 80s,you find them all over,but mainly on the vacuum advance units.Set up for full vacuum to the guages or tubes,slow release back to the carb.Lots of different sorts,but so long as they are both the same she'll be right.

[kevbo]

Said Randy:
not having pipe taps, couldn't i just drill the appropriate size holes for the barbs and valves and just glue them in with some JB or quicksteel?

JB weld is good stuff, but I'm not sure how well it bonds to PVC.

Maybe drill a little undersized, and soften up the holes with PVC cement, and then screw the tapered pipe thread into the gooey plastic??

[bradgross]

AWESOME RIGHT-UP!

Makes it sound like even I could do this. Maybe I'll stop by home depot tonight.....

BradG

[Randy]

Originally Posted by kevbo

JB weld is good stuff, but I'm not sure how well it bonds to PVC.

Maybe drill a little undersized, and soften up the holes with PVC cement, and then screw the tapered pipe thread into the gooey plastic??

Brad for your information the above is what i did. then, just to be safe i put a bead of JB around the inside of the threaded area. works like a charm . the only problem i had was getting an airtight seal around the end caps. be sure to use plenty of cement to avoid my problem.

[kevbo]

Originally Posted by Randy

the only problem i had was getting an airtight seal around the end caps. be sure to use plenty of cement to avoid my problem.

Sometime after the first posting, we needed a BUNCH of PVC pipe installed at work for a chilled water system. (industrial cooling application). Money was tight, so me and another guy did the work...Big job, 400+ feet of PVC installed hanging from the ceiling of a highbay. Not what you want to be paying an engineer to do, but look what plumbers charge.

We suffered a spectacualar failure, 3" line blew with about 40 psi water. Shot over 30' and blew through an interior (sheet rock) wall. Big mess but fortunatly not too expensive.

Anyway, we revisited our assumption that we knew how to glue PVC. Using the correct procedure we redid all the joints with no leaks and no failures. (pressure tested to 100 psi, operates daily at 40)

Correct procedure:

0)Buy regular clear (Not heavy duty, or wetordry) glue and purple primer. Heavy glue (gray) is for schedual 80 pipe, which doesn't fit up as well, but it drys too fast for sch 40.
HD glue was our biggest mistake.

1)Cut pipe square. Wrapping adding machine tape around pipe and marking with a sharpie helps here.

2)Use file to remove burrs and slightly bevel outside edge of end of pipe.

3)Prime pipe and socket. Keep after it untill it "wets" old hard pipe will need more primer than fresh stuff.

4) Coat entire socket with glue. Coat it all, but thin enough not to puddle.

5) Coat end of pipe to depth of socket

6) re-coat socket

7)immediatly mate pipe and socket, twisting 1/4 turn as the parts slip togethor.

8)Maintain pressure for 30 seconds to keep the pipe from pushing itself out of the socket (socket is tapered).


Took a lot longer to type than to do.

[Randy]

good advice. i used the correct supplies but not enough glue. i had it all together and was trying to balance the two before i discovered my leaks. so now, do i go back to home depot and start from scratch or try to fix this one? being a cheap bastard i decided to try to fix it. by dripping a bead of cement around all of the joint cracks i was able to get it sealed off. of course this wouldn't work under much positive pressure but with the slight amount of vacuum in this application it's working fine. i hooked it up to my mityvac and it held a good deal more vacuum than it will ever see in it's normal useage.