Help with synching individual Dell

[gravee]

Being new to dual carbs, are you saying having someone else crank the engine and I am in the back holding open the throttles on the carbs?

I disconnect coil wire and turn the key for a bit. Car is warmed.
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1967 Westy

[modok]

Always open the throttle for doing a compression test.

[gravee]

So do what I said to do above?

Thoughts on mixture screw not doing anything?
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1967 Westy

[67rustavenger]

Pull all the spark plugs.
Have someone crank the engine at least ten revolutions with the throttle held wide open the entire time.
That will give you the best result.

Good Luck.
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[gravee]

Thanks for the idiots version. Appreciated.

Surfing the wave of knowledge and ignorance.
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1967 Westy

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I don't know what you mean by "have someone hold the throttle open", when you can hit the gas pedal from the driver's seat and do the same thing.

Just make sure the coil wire is removed so it doesn't start.
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[modok]

I guess you can have a whole crew helping, but it's not necessary.

rig the throttle open with bailing wire and/or vise grips, or perhaps a brick You can figure it out.

If you are using a handheld thumb switch with alligator clips on the starter to activate the starter, then there is no need to disconnect the ignition, because it isn't on.

[67rustavenger]

That's exactly what I meant John.
I was trying to make this as simple as possible a procedure for the OP.
You already know all the tricks to get this done

[gravee]

John,

You are 2 for 2 on this thread for the clear logical solution- swap the idle jets and hold down the gas pedal.

Sort of like assuming the horse is a zebra but the other way around.

thanks

It may be a couple days as my neglecting the little kids time is used up for a bit.
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1967 Westy

[gravee]

Some additional info that may be useful: I recently realized that with steel pushrod tubes that I have to set valve lash differently. I have now been running them at .002 which was recommended as it is still breaking in.

Also- I have tested compression for many years with single carbs and never did so with the throttle wide open. PSI typically seemed normal- in the 100- 125 range. Are single carbs different in this way?
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1967 Westy

[AlteWagen]

easiest thing would be to swap the carbs and see if the problem follows the carb. If it does you know its the carb if it doesnt you know its the engine.

You mentioned you bench set the throttle plate to .003, did you measure just one or both on each carb? Ive seen several sets with twisted throttle shafts that would present with the same symptoms. Sometimes you can just twist it back, other times you need to replace the shaft if it is real severe.
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If you have all the spark plugs out AND it's a single carb engine, the cylinder you are testing will suck air in the open plug holes, so the carb doesn't have to be open. If you leave the plugs in, the closed throttle is a restriction, and you can't get an accurate reading. Think.

[67 Sunroof]

I believe in my dellorto manual they are VERY specific about making sure the two throttle plates have the EXACT amount of clearance or one carb will “lead” the other.

[modok]

Every carburetor configuration will be a little different. most carburetors have high idle cam.....what position is that in?
open the throttle, you eliminating that variable.

[gravee]

So just checked compression with throttle open- that makes a difference!

1- 126
2- 126
3- 136
4- 126

Number 3 was the cylinder that the carb was not responding to fuel/air mixture screw being turned all the way in.

Valves were just adjusted. Seeing what a big difference the throttle being opened made I wonder could there be an issue with the throttle on #3? I have the air correction jet opened on that cylinder to try to get the air suction balanced between the two cylinders on that carb but I imagine that is small difference in the big picture.

I also connected a vacuum gauge to the manifold on the 3/4 side (no port on 1/2 side)

No pull at idle
off of idle it bounces back and forth between 5-15
around 2000-2500 I can get it to sit fairly still around 8
over 2500 it goes crazy bouncing back and forth between 8 and 2 o'clock and all over the dial.

Not sure what this means but I bet someone has thoughts...

The #3 plug was fairly black- sooty, not oily. So rich but fuel/air doesn't seem to do anything???
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1967 Westy

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be careful on terminology. I suspect you have the air bypass screw opened (it's not an air correction jet).

[gravee]

Thank you. It is the small screw next to mixture screw towards the center of the carb.
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1967 Westy

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always begin tuning with all of them closed.
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[gravee]

Thanks John,

I started with the air bypass screws closed My concerns started when synching the carbs. The #3 barrel was 2 pounds less than #4. I turned out the bypass screw to try and correct but could only get it a pound less on the gauge. Then I found that turning in the fuel mixture screw all the way had no effect and the engine ran the same turned all the way in.

I checked engine compression to make sure that was not the issue. The results are above. I was just wondering if in some way having the bypass screw turned out could have enough effect to cause the compression reading to be higher.

It drives pretty good at higher RPM. Lots of popping and cracking at idle or low speeds with carbs synched to each other.

Fuel mixture screw having no impact is my real question at this point. I am just wondering if there is an issue with the carb.
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1967 Westy

[gravee]

I was hoping someone might have some guidance for me for some weekend wrenching.

Two options:

1. Swap the carbs and see if the issue follows. Last time I did this I had to pull the engine, but I put in funky tall nuts which might allow to pull manifolds with engine in. A lot of tweaking of filter bases/ linkage etc, though maybe I could just have her warm and hopefully fire up with all that stuff on as is w/o linkage. Compression is posted above. Not sure the issue is in the engine but would love to hear thoughts. The only other thought is my human error- I cut the rods and adjust valves but I have double checked rod length and know how to adjust valves. Heads? Compression was 136 so getting plenty of compression

2. Try to determine why the fuel mixture screw has no effect on number 3. Did not sense a vacuum leak with propane or WD 40. Could try and re-clean jets on top. Are there any other parts that could use tweaking or cleaning that might be responsible for this problem?
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1967 Westy