Dual IDF 40s on 2.0. Was running fine in upper RPM range (4k and above) then pulled carbs to fix problem with accel pump (pin missing through throttle). Now I am unable to rev past 4k under load. Under no load I am able to rev fairly high but then starts to bog and have to wait to rev high again. Checked timing and advance appears to work correct when using timing light. Timing changes as rev up to 3500 RPM. Timing set at 34 at 3500 RPM. Pulled jets again today thinking just maybe missed something. Changed fuel filter. Fuel pressure seems good at carbs. Looked at plugs and doesnt appear a rich condition. Is there anything else I can check on ignition? I pulled cap and everything is clean under there.

Double checked timing and went down to 27 from 34...same result. Checked point dwell and it was a little high, over 50. Went down to close to 44..same result.

What kind of distributor are you running?

Check all your plugs.
It sounds like you are not running on all cylinders.

This can even be caused by a valve problem.

If required, pull all plugs & clean them, then drive it under a good load (like up a hill), then shut it down and pull over, check the plugs again right on the side of the road.

Look for one that is different from the rest.

What jets and vents are in your carbs?

Distributor:

022905205 that is the VW#
0231181009 is the Bosch #

Jets etc:

Idle jets: 52
Main jets: 115
Air: 200
Emulsion tubes: F11
Venturi: 28
Bowl: 55
P jet: 50
Pump valve: 55

Any other suggestions on this? Where else could be clogged on these carbs? The weird thing is that they worked fine before pulling apart so I am really confused. And it would seem that if I messed them up I would only lose power on one side unless I really messed up both sides which I would hope is unlikely.

The part number matches a 1.8L distributor. Check to see if the mechanical advance is working correctly. A stuck advance will cause the symptoms you are experiencing.

Maybe you could..... check your plugs?

So you know WHICH barrel is causing the problem?

Yes it is a 1.8 distributor with the vacuum advance disabled. It seemed to smooth out the acceleration curve better than the previous 009 I had on it. I checked the advance as far as using a timing light to watch the timing advance as I increased the throttle. I set the timing at 27 degrees while at approx 3500 RPM and when it falls back to idle the timing does change and go down. Does that mean the advance is working properly or should I check something else?

With regard to plugs, I have new plugs coming in tomorrow and plan to replace them all to get a good reading on them.

With regard to plugs though, would one plug prevent the engine from being able to get past 4000 RPM or would it just lose power?

Are both carbs synced together? Is one by chance not opening with throttle advance?

Then you set the timing wrong. On a 1.8, or in this case, a 1.8 distributor, you set the timing to 7.5 degrees at 950 RPM.

Setting it like a 1.7 or 2.0 will affect the drivability.

I have them synced up perfectly and checked them again at higher RPM and they both advance properly.

The only thing I can think of at this point is the fuel starvation although I would assume that I should be able to run off just the bowls themselves for a bit. However, the fact that both carbs seem to be suffering the same problem makes me think it may be the issue. I may be wrong, but if one carb, or even one cylinder, was not working, wouldnt I just lose power and not suffer from a lean condition across the board and almost die out after 4k? I wish I could post a video so you could see how lean it gets as it falls off.

When I first got it I had lots of problems running consistently due to trash in the tank ( didnt follow the advice of everyone here and clean my tank as the very first thing). After doing so the problem went away but I sometimes had problems with the hoses under the tank getting pinched until I got those run correctly. Although this doesnt feel the same way, it is quite similar.

As far as checking mechanical advance on distributor, does doing what I did with the timing light confirm that or does it continue to advance after 4k? I did only set it at 27 and still cant get past 4k. Could that be it? I may still have my 009 (ugh) I suppose I could check. What about condenser or points? Could those cause this issue?

So timing setting is a function of the distributor? I understand the principle of advancement when accelerating but I never knew why it was different for the 2.0 vs 1.8. Is it only due to the way the mechanical advancement works? Can you explain that?

I will try that and report back.

Thanks!

When it reaches total advance on a 1.8L distributor is different from the 1.7 and 2.0. So setting it like a 2.0 will result in the advance falling off too soon.

An update on this problem.

Yesterday evening I changed the timing to match that of the 1.8 distributor I have on (7.5 at 9500). I drove to a friend's house a few blocks away and barely made it. The popping/snapping from the carbs was even worse that before. I changed out the fuel pump with a rotary from CB, emptied the tank completely and put in new gas, new plugs. Still same snapping from all carbs (not one in particular). Set timing back to about 27 at 3500 which helped a bit but then still falling off at 3500-4k and popping back through carbs.

I pulled one of my carbs to see if I might be missing something. My next thought is to put my old 009 distributor back and see if the problem disappears. Could the distributor be failing in such a way to cause this or is that solely based on points? I have extra set of points as well but they were from the old 009 so not new.

A buddy insists it is carbs since it was working fine before pulling them off. I understand that makes the most sense since it was only after pulling them and cleaning them that I have the problem. I am just confused how I could have messed them up so bad as to cause the exact same problem on both carbs.

Now I didnt buy a 'kit' to replace float needles, diaphragms, washers, o-rings, etc but everything looked fine. Should I go ahead and get a kit and start from scratch or is it more likely that something else was assembled incorrectly or a got some trash in the exact same spot on both carbs? Should I strip them and soak them?

The suggestion that I made above: Check your plugs after driving under a load will tell you if all cylinders are firing and if one (or more) are overly rich or lean.

At the races my brother pulls his plugs after every race.
It is a very common way to diagnose a problem.

It can help determine if your problem is ignition or fuel related.

Make sure all the plug wires go to the right plugs!

Thanks for the advice! I am going to check the plugs in the morning and see if that gives me any indication of what might be happening and where. I am also going to try a different distributor as well.

I am sure I will most likely be pulling those carbs apart again and getting a full rebuild kit for them at this point. I will probably soak them in carb cleaner a bit as well once I strip them down.

Is there a walk-thru anywhere on stripping, cleaning and rebuilding IDF's? I have used a can or carb cleaner for soaking before on small engine carbs but not a Weber. Is there anything I should be cautious about? How long can I leave it in the cleaner? Any other tips are appreciated! Any sources for rebuild kit? I found this one on ebay but it is so inexpensive compared to Redline etc it has me a bit nervous

http://www.ebay.com/itm/Porsche-914-vw-typ...Mzy&vxp=mtr

or

http://www.ebay.com/itm/Weber-40-44-48-IDF...j4e&vxp=mtr

With any luck I will be back on the road soon

Things to check in the dizzy:
No cracks in dist cap
Do you have a rev limiter rotor (if the springs wear out, they will cut out early)
Does the dist rotor shaft have any play in it (does it wobble?)

You can also run it in the dark and look in the engine bay.
Bad wires can cause arcing to the tins, carbs, etc.


When I rebuilt my carbs I used the ultrasonic parts cleaner from harbor freight





Dont be tempted to stick wires in the passages to clean things out.
Use carb soak & compressed air to verify all passages are clear (WITH safety glasses)

Well its definitely carbs although no idea what about them. Plugs #2 & #3 look ashy like lean foul and #1 & #4 look perfect. Any advice on what I might look for on that?

If one side (bank/carb) is different from the other side, it is unlikely it is a spark problem.

my next guess is that the carbs are out of synch.
Do you have a synchrometer?

IMO, they are an absolute must for dual carbs.
Even with the tangerine racing linkage, you have to set them at one place (RPM range).

Unless those plug wires are crossed.
2nd the carb synch problem.

I am still waiting on some rebuild kits to come in but after cleaning these things thoroughly I am amazed how much crud was hiding inside of them. I am starting to think that it may have been a problem either a problem with the seats for the main jets or the transition ports, or both. The pic is of the crud left in the cleaning liquid after two days. The liquid itself went from almost clear to almost black. I could barely see the bottom of this container with an LED flashlight.

So my question is this, Tomlinson always talks about how a small piece of trash can cause huge problems in these things. And granted, there can be a lot of trash hiding inside if them; I know that now. But after really getting to know these things, the channels inside from place to place seem huge. It would seem that it would have to be a substantial piece of debris to really stop something up. I get that the flow characteristics of air/fuel etc can change based on trash in the bores etc. But can it really cause them to just stop working? In my case, could it cause the transition from idle to main circuit to fail completely?

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