All you Weber Pro's, A couple of questions Options

[Grelber]

When I hold the rpm steady at around 3200 or so, I get a "surge" back and forth (not a lot). Is this due to unbalanced Webers?

Also, where is the best place to get a flow meter so I can get them balanced.

[r_towle]

Please dont bother to try to get thhe car tuned without the synchrometer.

CB performance has them.

Rich

[Joe Ricard]

Uni-syn with a ball in tube kinda sucks but the more expesive one (name ??) with curver scale and needle is good

I set my 914 @ 3000 RPM. both carbs get synched up by adjusting rod length and it is oh soooo smooth.
Then let the carbs sit on the idle stops and play with those to attain the idle speed you want keeping them even of course.

If you really want to drive your self nuts turn the motor off and see if both throttle plates are fully open when stomping on the pedal.

There are some linkage systems out there that are not exactly easy to make work perfectly.

[Hammy]

Uni-syn with a ball in tube kinda sucks but the more expesive one (name ??) with curver scale and needle is good

I set my 914 @ 3000 RPM. both carbs get synched up by adjusting rod length and it is oh soooo smooth.
Then let the carbs sit on the idle stops and play with those to attain the idle speed you want keeping them even of course.

If you really want to drive your self nuts turn the motor off and see if both throttle plates are fully open when stomping on the pedal.

There are some linkage systems out there that are not exactly easy to make work perfectly.

What linkage do you prefer, Joe?

[Joe Ricard]

I have a fabbed up bell crank piece. sorta like the one that Jake sells but a bit heavier duty.
Only thing that we could come up with that would stand up to slamming WOT all day long at an Autocross.

We kept bending the CB hex bar types enough to knock the carbs out of synch. Yes we have a pedal board stop

[chris914]

I set my 914 @ 3000 RPM. both carbs get synched up by adjusting rod length and it is oh soooo smooth.
Then let the carbs sit on the idle stops and play with those to attain the idle speed you want keeping them even of course.

What is your total method from start to finish?

[IronHillRestorations]

Geez, I had a comprehensive tuning post on the old site. Don't know if that's available here or not.

[IronHillRestorations]

Remember the search feature is your friend. Search and then if you can't find it ask. This is from a post I made in Sept of 04.

Assumptions: the carbs have the optimum jet and venturi package (good luck on this one), the float level in the carbs is correct, the cams are correctly timed, the valves are properly adjusted, the ignition timing is dead on, you have the proper spark plugs for your engine, the linkage is good, the fuel is good, the engine is good.

Remember that the mixture and air bypass adjustment screws are precision needle valves, not head gaskets. Use your fingers to tighten them, not your fist.
Start and warm up the engine.
Make sure the two drop links for the throttle linkage are exactly the same length, and disconnected. You can use a 8mm thin igntion wrench to snap them off.
Turn the mixture screws all the way in and then 5 half turns out.
Turn the air bypass screws all the way in.
Turn the idle speed screws out til it just touches, and then in 5 half turns.
Put on your hearing protection and start the car.
Use your STE and find the barrel that pulls the most. We'll call this one baseline.
Balance the barrel in the other carb that pulls the most with the idle speed screw. (if you have a Uni-syn, give it to someone you don't like and purchase a STE airflow meter)
Go back to the other carb, with the baseline barrel. You will have one all the way in, then use the air bypass screws and balance the other two barrels.
Go to the other carb and do the same thing.
Snug the jamb nuts on the air bypass screws.
All six barrels should pull the same amount of air at this point, if not repeat air adjustment proceedure.
Snap the throttle linkage drop links back on the carbs. If the idle changes then you need to barely adjust the linkage mounts so snapping the drop links on, doesn't change the side to side idle balance.
Use the hand throttle or a vice grip and rag to lock the linkage between 1400 and 1800 rpm.
Start back at the baseline barrel and adjust the mixture screw in or out, to get the smoothest running and highest idle, then turn it in 1/4 turn.
Do the same with the five other mixture screws.
If you have to turn the mixture screws more than two turns either way, you've got the wrong jets.
Recheck side to side and individual air balance, adjust as needed.
Road test the car.
If you get snapping and poping out the intake, it's generally a lean condition.
If you get heavy exhaust fumes, or pboofing out the exhaust it's probably too rich.
If you get a flat spot or popping out the intake at between 2800 and 3200 rpm, you probably need larger idle jets.

That's a rough, five minute draft of my carb tuning proceedure, hope it helps!

If it goes good it should take about 45 minutes, if not about three years.

PK cool.gif

[Gint]

Took me less than 5 minutes to find one. Different date though.

ummmmm, back on topic anyone?? Now that's a thought <!-- emo&:lol: -->(IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)<!-- endemo -->

Here's the post I made back in Sept of last year when Trekkor was having carb tuning problems, now he's a carb GURU!!!

Also note these instructions were for the 3 barrel Webers, so you'll have to adapt & survive.



Assumptions: the carbs have the optimum jet and venturi package (good luck on this one), the float level in the carbs is correct, the cams are correctly timed, the valves are properly adjusted, the ignition timing is dead on, you have the proper spark plugs for your engine, the linkage is good, the fuel is good, the engine is good.

Remember that the mixture and air bypass adjustment screws are precision needle valves, not head gaskets. Use your fingers to tighten them, not your fist.
Start and warm up the engine.
Make sure the two drop links for the throttle linkage are exactly the same length, and disconnected. You can use a 8mm thin igntion wrench to snap them off.
Turn the mixture screws all the way in and then 5 half turns out.
Turn the air bypass screws all the way in.
Turn the idle speed screws out til it just touches, and then in 5 half turns.
Put on your hearing protection and start the car.
Use your STE and find the barrel that pulls the most. We'll call this one baseline.
Balance the barrel in the other carb that pulls the most with the idle speed screw. (if you have a Uni-syn, give it to someone you don't like and purchase a STE airflow meter)
Go back to the other carb, with the baseline barrel. You will have one all the way in, then use the air bypass screws and balance the other two barrels.
Go to the other carb and do the same thing.
Snug the jamb nuts on the air bypass screws.
All six barrels should pull the same amount of air at this point, if not repeat air adjustment proceedure.
Snap the throttle linkage drop links back on the carbs. If the idle changes then you need to barely adjust the linkage mounts so snapping the drop links on, doesn't change the side to side idle balance.
Use the hand throttle or a vice grip and rag to lock the linkage between 1400 and 1800 rpm.
Start back at the baseline barrel and adjust the mixture screw in or out, to get the smoothest running and highest idle, then turn it in 1/4 turn.
Do the same with the five other mixture screws.
If you have to turn the mixture screws more than two turns either way, you've got the wrong jets.
Recheck side to side and individual air balance, adjust as needed.
Road test the car.
If you get snapping and poping out the intake, it's generally a lean condition.
If you get heavy exhaust fumes, or pboofing out the exhaust it's probably too rich.
If you get a flat spot or popping out the intake at between 2800 and 3200 rpm, you probably need larger idle jets.

That's a rough, five minute draft of my carb tuning proceedure, hope it helps!

If it goes good it should take about 45 minutes, if not about three years.

PK <!-- emo&B) -->(IMG:http://www.914world.com/bbs2/html/emoticons/cool.gif)<!-- endemo -->

[Joe Ricard]

Geez, I had a comprehensive tuning post on the old site. Don't know if that's available here or not.

Like from Adjust valves and do a tune up with new plugs cap rotor and wires?

warmup the engine
take off air cleaners?
have a beer while engine warms up (optional brand)
fiddle with cable retainer nut to obtain 3000 rpm
whip out favorite carb sysnch tool
between adjusting rod length and observing air flow thigs eventually come out even.
reset cable adjuster till the linkage sits back down on the stop screws
carb will probably be out of synch on the screws. shut it down and have another beer
Now pull all your idle jets and clean them . reinstall
and set mixture once you are running smooth again
then adjust stop screws to obtaindesired idle speed and both carbs are synched by adjusting just the stop screws.

[Gint]

Actually Perry, that thread had some other good info in it as well. I'll have to go and find the article Carl gave me and re-upload it.

http://www.914world.com/bbs2/index.php?showtopic=16655&

[mudfoot76]

Here is a link to the STE flow meter recommended in the posts above:

STE Carb flow meter from CB Performance

[IronHillRestorations]

Like from Adjust valves and do a tune up with new plugs cap rotor and wires?

That would fall under the assumptions I made at the front of the post. Of course we all know what happens when you assume! (IMG:style_emoticons/default/laugh.gif)

[Joe Ricard]

Maybe this is a great place to drop names of those that don't do this stuff and chase thier tales all day.

Then buy into some cobbled EFI or the "carbs suck syndrome" and always suck, Go back to D-jet and then ...... A Ya'll know the rest.
Carbs are not easy specially when you are guessing.

[rhodyguy]

easist way to turn up the idle for tuning is leave the cable alone and turn in ONE of the idle adj screws. the other carb will follow. now the engine should be running fast enough to calm the pulsings (dancing needle on the unisyn). compare the flow readings on the 2 front venturis. if they're way off go thru the pre-dial in proceedure in the cb book, and start over. the first time out can be a bit daunting but after reading the text and following the steps you'll be able to complete the task quickly. the carbs HAVE to be adj and flowing commonly before you start to fine tune.

k

[Gint]

Perry Kiehl

How would you like to see your carb adjustment procedure as one of the first member contributed tech articles to 914world.com?

[IronHillRestorations]

Perry Kiehl

How would you like to see your carb adjustment procedure as one of the first member contributed tech articles to 914world.com?

Fine with me.

[IronHillRestorations]

Maybe this is a great place to drop names of those that don't do this stuff and chase thier tales all day.

Then buy into some cobbled EFI or the "carbs suck syndrome" and always suck, Go back to D-jet and then ...... A Ya'll know the rest.
Carbs are not easy specially when you are guessing.

Is that directed at me Joe? If so please elaborate.

[SGB]

An important addition to Perry's excellent synopsis of the process-
If the idle/ fiddle/ iddle goes on very long there plugs may began to foul, misleading one's conclusion about the carbs. If you think it is all good then it stumbles and farts, check the plugs.

[Joe Ricard]

Nah not pointing at you. But If I read one more shoulda gone back to D-jet I will freaking lose it.
There are some bad or at least advice that will lead you astray here in this thread.

The only reason each barrel on the same carb would be differnt from each other is: valves are not done correctly, vacuum leak, or plugged idle jet. So close all the idle bypass screws and leave them alone.