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Second Bus and First Engine Drop. Need guidance!
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whatdoesthisbuttondo?
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PostPosted: Wed Jun 21, 2017 12:43 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

senseless1707 wrote:
Damn nice build. Was fun to read through it. Going to pull my engine out and do pretty much exactly what you did. Need to get her running and on the road. I am itching to drive it.


For sure, start a thread! Don't make the mistake I did of trying to just do the top end, wasn't worth the extra drop when I found the knock Wink
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PostPosted: Wed Jun 21, 2017 1:54 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

Co is specified in the Bentley, it's measured with a gas analyzer sniffer and is the scientific way to set idle mixture. You can get very close to the spec by playing with the mixture screws to achieve the fastest/smoothest idle and then leaning for a 50 RPM drop, that's just before it starts missing because it's too lean. When fiddling with the screw you'll find if you open it too far the idle speed starts to slow as well, that's too rich, you want to find the happy spot between where it drops off from turning it too far in each direction and then finally turn it in a little bit.
You are correct about setting each carb slightly lean and making up the final mixture with the CIS. The popping may be a tiny leak in the exhaust and no amount of carb tweaking will fix that.
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whatdoesthisbuttondo?
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PostPosted: Fri Jun 23, 2017 8:30 am    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

OK well it was very useful to start playing with mixture individually, I uncovered an issue that I need to sort out first that might be the root of a lot of the small things that have come up.

I noticed that I had to have the mixture screw nearly all the way out for the left carb to run on its own and it sounded like it was only firing one cylinder and then another would kick back in intermittently so the pattern was roughly one one one one triplet triplet triplet one...

Back running on both carbs, we pulled each individual wire, it looks like #3 cylinder is barely contributing, although it is firing. Pulling 1, 2, and 4 we have noticeable RPM drop, while pulling three the idle barely changes, although the idle smooths out a bit when reconnected. We swapped out #3 wire and same issue.

Pulling #3 wire at the distributor cap we have regular spark. The plug tip is hot and the ring temp guage I have on #3 reads like id expect. Plug is fully seated.

So I'm thinking valve issue or rings? All are basically brand new, has new valves, guides, springs, rings, ring gap was good. I don't hear any major leaks from the head to jug, and looking back in this post the lapping job looked like great coverage, no head gasket to worry about, and cylinder shims are at the case end. All torque specs were followed when putting the heads to the case studs. So im tentatively ruling out a leak at the head.

rocker looked normal from the outside, see below. Had adjusted valves recently, just before starting carb tuneup.

Plan is to check valve gap again, then rent compression tester and see what we are looking like.

Any other ideas???

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PostPosted: Fri Jun 23, 2017 10:13 am    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

Could also be a vacuum leak where the manifold meets the head, any cylinder tin pinched between the manifold joint?

What do the spark plugs look like?
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whatdoesthisbuttondo?
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PostPosted: Thu Jun 29, 2017 10:17 am    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

No tin between the head and manifold, nuts are tight.

Checked valves, were a little loose on #3 but barely, adjusted cold to bang on .006".

Swapped plugs and wires again to check #3, still have barely perceptible rpm drop when unplugging #3 at the distributor, maybe 10 rpm (didnt measure but its small, can only hear the increase when plugging back in). 1,2,4 are very noticeable drops of 100 rpm or so (wild guess), they are all the same.

The only thing I haven't done yet is change dist cap but contacts were scraped and made shiny. .

A very nice person lent me a Mac compression tester for a night. Did test, chokes open, warmed up, screw on type unit.

#1 155
#2 155
#3 140
#4 155

All cylinders build quickly to 150 psi then inch up to 155. #3 builds quickly to 135 then nudges up to 140.

Put teaspoon oil into #3, it cranked up 15 psi higher to 150 suggesting some compression lost through the (new) rings. Teaspoon of oil in #1 as control, only 5 psi increase

#3 could possibly be lower as it had biggest piston to cylinder gap of .0045, as opposed to .003 like the others (wear limit is 0.008" so should be OK)?

Plugs are new, but #3 looked a little oily or gassy compared to others, ceramic was a bit more brown:

#3
Image may have been reduced in size. Click image to view fullscreen.


#4
Image may have been reduced in size. Click image to view fullscreen.




Would the 15 psi lower compression of #3 (140psi) have such a drastic effect on performance of that cylinder? Cant figure out why its not contributing as suggested by no RMP drop! Engine idle sounds OK when all going, no noticeable weird patterns...

Is it possible that #4 would be hogging the mixture from the carb? I could see this if the manifold to #3 were somehow blocked but it isnt.

I need a Idea
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PostPosted: Thu Jun 29, 2017 10:37 am    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

Never seen plugs like those in any bus
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PostPosted: Thu Jun 29, 2017 10:44 am    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

The plug from #4 doesn't look like it has been firing. Could be the plug, the wires, or the cap. The mixture would have to be way off for the plug not to fire.

Your plugs should work well enough though I think they are a heat range cooler than stock assuming they are NGK as the stock heat range isn't available in the triple electrode style. I have run them and they seem to do fine.
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PostPosted: Thu Jun 29, 2017 12:10 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

I bought the NGK BP6ET off a suggestion from an old Samba thread:

https://www.thesamba.com/vw/forum/viewtopic.php?t=347157

Had Bosch in there before, thought Id try these... They are a couple mm longer.

These are brand new- only been run for a maximum of 20 minutes while messing with the carbs. The old plugs got mixed up after removal so don't have photo of old number 3 unfortunately. I remember it was blacker and a bit wetter.
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PostPosted: Thu Jul 13, 2017 1:33 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

Not too many options left to check at this point to figure out why #3 isnt cooperating Smile Haven't looked at brake booster.

How do I check for leaks in the brake booster? Will I be able to hear them as easily as vacuum leaks in the engine bay? If I need to replace vacuum line can I just use the regular large braided hose like used for the charcoal canister or breather box?

Is there a chance that if the brake booster has a big vacuum leak, it would affect the mixture to #3 moreso than #4?

If all is OK with the booster i cant really think of anything else to do than drive it and monitor valves and compression over time.
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PostPosted: Thu Jul 13, 2017 7:33 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

whatdoesthisbuttondo? wrote:
Not too many options left to check at this point to figure out why #3 isnt cooperating Smile Haven't looked at brake booster.

How do I check for leaks in the brake booster? Will I be able to hear them as easily as vacuum leaks in the engine bay? If I need to replace vacuum line can I just use the regular large braided hose like used for the charcoal canister or breather box?

Is there a chance that if the brake booster has a big vacuum leak, it would affect the mixture to #3 moreso than #4?

If all is OK with the booster i cant really think of anything else to do than drive it and monitor valves and compression over time.


For a driveway test, just disconnect the brake booster and seal the connection point and see if that makes a difference to #3
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PostPosted: Wed Jul 19, 2017 3:40 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

Yes huge difference!

plugged at vacuum elbow which comes right off number 3 intake. rpms drop 100 percent similar to how the other cylinders were . left connector hose to number 1 leaking hissing . now number one doesn't drop rpm when disconnected. same symptom different cylinder so there's the problem.

connected all back up at engine then disconnected and plugged hose at diaphram, got aboit 75 percent drop.

bottom line is i need to replace diaphragm and all hose back to it as there must be some leakage along the line. main leakage from diaphragm though.

k guess I can look forward to having power brakes and a bit more power with number three contributing properly. Cool

also fyi couldn't hear any leaks at hose and diaphragm but they must be there.




.
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PostPosted: Wed Sep 13, 2017 1:48 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

I replaced the vacuum hose from the booster back, and lo and behold I get a solid RPM drop on #3 now, consistent with all cylinders.

I tuned the carbs once again and have smooth acceleration in all gears now. No more popping when coasting. Not usually any run on.

However, on start up, the bus is not idling on its own until the chokes fully open, and I've narrowed it down to the Central Idle cutoff solenoid which is either sticking or some other problem.

With the engine off it will click a few times and then stick. unscrewing it a little releases it and will click a few more times and then stick.

With the solenoid out the carb and grounded it will click until the cows come home.

When the engine is running the solenoid will click once as I pull the power, but refuses to engage again, even if i unscrew it a little and back in, which seems to unstick it when the engine is off.

A little stumped here... Confused
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PostPosted: Wed Sep 13, 2017 3:04 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

Try a thinner washer under it, thicker washers sometimes don't preload the plunger enough to get it where the magnetic field can grab it easily.
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PostPosted: Wed Sep 13, 2017 4:16 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

I don't have a washer at all under it right now... Ill try a couple thx!
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PostPosted: Wed Nov 22, 2017 2:18 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

Been doing a few things on the bus, here to share/for my record/ dual carb tuning issues (again) at end of post.

new steering coupler in. Was not stoked on how flimsy the new one was, so ordered what appeared to be a better one from C & C in Britain. came with 'OEM' and 'made in germany' but appears to be identical to the other one, still pretty bendable, no sign of interior fabric etc. I'm leaving in the other one for now, while it feels way more flexible than the old cracked original one I took out, I had a buddy watch underneath while I cranked on the wheel and it was not flexing.

Horn wasn't working so we got that hooked back up properly.

Took apart, cleaned and re-lubed up the shift rod. Still clunking in and out of second, no matter how much I tweak the stop plate. Lots of wear on the shaft, pin, and pipe bowl, unfortunately.

New fuel sender has stopped working which is obnoxious, just terrible quality. The first one I was sent wasn't working out of the box and this one has only lasted a year.

Checked behind firewall and fuel sender connection is good. All rubber fuel lines and gas filler are good and not leaking.

Buddy got the aux blower working while I hooked up one side of heat accordion tube replacement, one side not hooked up yet, waiting on silicone cuff. Heat soon.

To Do list includes leaking oil pressure sender, new rubber under front turn signals so they don't fill up like a fish bowl when it rains, lube front end, check wheel bearings.



Back in my own carb tuning nightmare. Been spending hours on these recently.

I think what was going on a few months ago with not running during start up is that the fast idle cam wasn't catching on the left carb; that is best guess for now. Was running great once chokes opened.

Just to try something different, i took the left carb out of the 2L (modified from 1700) in my other -- now parts--- bus. took it apart, ran a couple cans of carb cleaner through everything, swapped over the good stuff from the left carb i took off, such as CIS solenoid. Then reinstalled newly rebuild carb on the left.

Hooked everything up and I cannot seem to tune these things, the idle is just way too high. I have, multiple times:

- Checked for vacuum leaks in all the hoses

- squirted some carb cleaner around the throttle bushings and manifold seal to check for leaks. no change.

- taken off both the right and left carbs and set the throttle stop screws for a 0.1 mm gap on the throttle butterfly, set butterfly at 0.6mm on the fast idle cam.

- baseline starting points of 2 1/2 turns out on the mixture screws on the side of each carb, 2 1/2 out on the idle mixture and 3 out on the idle speed.

The idle is coming in at about 2000 RPM at this setting and i cant get it to lower except by screwing each carbs mixture almost all the way in until they run like cr**. This is with CIS solenoid disconnected and vacuum line from distributor off.

Any diagnostics I can do from here ?? Have no idea why these things are just screaming away.
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PostPosted: Mon Nov 27, 2017 5:40 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

Had some better luck tuning the carbs over the weekend. Man these things are finicky. I think the issues recently are slop in the throttle and fast idle linkages due to excessive wear, and a bad Central Idle solenoid.

My best luck was with taking them off and using a feeler gauge for setting idle and fast idle with throttle stop screws to the specs. Then once carbs back on manifolds, making sure the linkage was not altering the position of the throttle and the throttles were opening at exactly the same time (finger on one, looking at the other), using the cable to pull. However, once connected, the right carb idle screw wasn't touching after a few actuations (while holding the choke open to eliminate fast idle). Would come to rest with a bit of a gap, so had to snug it up a bit. Then did each carbs mixture, got a similar rpm drop with the cutoff solenoids for each carb, then idle mixture and speed, which didn't really do anything due to the CIS solenoid not working and constantly sticking closed. The solenoid is still sticking as it was a while back, despite being in a new carb. I even took some very fine abrasive to the plunger to polish it up a bit and make sure there weren't any burrs. Idling at about 900 anyways when warm so I'll get a new solenoid at some point . I also paid attention to choke placement and lubed any moving parts in there. Seemed to help as this morning started with a nice fast idle and drops down the idle cam nicely. Chokes opening a bit slow though...

So onwards for now... Lubed up the front end. Connected the right heater tube with some muffler parts and the cables. Have some warm air coming through the vents now but ill need to insulate the length and check for leaks if its going to defrost anything this winter...

Loving having a bus that is not full of tools and greasy parts for once:)

Here is the wear on the shifter, around the shaft and the pin, no wonder it's sloppy.

Image may have been reduced in size. Click image to view fullscreen.


and the super dark picture of heater tube installed, using some cheap muffler tube and connections.

Image may have been reduced in size. Click image to view fullscreen.

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PostPosted: Mon Nov 27, 2017 7:05 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

whatdoesthisbuttondo? wrote:
... I think the issues recently are slop in the throttle and fast idle linkages due to excessive wear, ....

If you can feel or see any movement in the shafts you are bound to have issues, it may work OK one day and act up the next, sounds like you need to contact Volkzbitz (Tim) for a throttle body rehab at the very least. Don't beat your head against a wall screwing around with worn out precision parts, when (if) you finally break down and have them fixed you'll be kicking your ass for never realizing how well they can work and why did you put up with them in an inferior condition for so long.

The CIS solenoid may improve with some carb cleaner squirted down between the shaft and body followed by compressed air and a few repeats and poking between squirts, a thinner (or no) washer between the solenoid and carb sometimes improves it's willingness to pull in as well.
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PostPosted: Sat Mar 24, 2018 8:58 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

Timing and dual carb tuning stuff ahead...

Been a while since I've updated, done quite a bit of work to try and achieve a predictable, well running engine, and while I'm closer, and my understanding has improved, still no tuning nirvana Crying or Very sad .

First thing I did was get both carbs fully rebuild by Volkzbits. They look great and everything functions much more smoothly now.

Second thing I did, as a result of a tip from Tim, was to check jetting as he noted they were different in each carb. Yup, looks like one was jetted larger for a 2L it was on. So now I'm running paired, smaller jets in each carb more suited to the 1700. The imbalanced jets likely made previous tuning more difficult. I will post what the current jet sizes are when I find the piece of paper I wrote it on... It took me ages to track down the right numbers for stock jetting on 1700 dual carbs, so they could be helpful for somebody.

Third thing I did was try a different distributor. I ended up refurbishing a distributor today off a 1972 1700 and confirmed centrifugal advance/vac can was operating properly, and installed new points and gapped as per Bentley.

So, overall, things are running, but despite going over Colin's carb tuning procedure god knows how many times by now, as well as setting throttle at idle and fast idle with feeler gauges, there are two problems:

1. the vacuum advance is pulling vacuum at idle.

2. the CIS solenoid is still not consistently retracting when I disconnect and reconnect the spade to set individual carb mixtures, and I suspect The CIS is just not working as intended. Im not yet sure why. Solenoid has 13 V at the spade and I have tried 2 separate solenoids on two separate left carbs.

In any case, here are a few facts with how its running with the new distributor:

Set valves .006", checked compression an it's good- a bit lower in comparison n #3 but still plenty of compression. Used a little mini video camera on phone to go into cylinders and confirmed all valves opening and closing as intended while rotating through each one.

So, new distributor is in and timed to 28* btdc at 3400 rmp, both hoses off, so the max of the centrifugal advance.

At this timing, the idle falls back to 2* btdc 850 rpm.

With both hoses on, idle is way back at 14* btdc 900-950 rpm.

with only vac advance hose on, idles at 14* btdc 900-950 rpm.

with only vac retard hose on, idles at 10*atdc, a bit rough idle, sometimes dies when you pull off the vac advance off.

At idle there is slow but steady vacuum on the advance hose and a stronger vacuum on the retard hose.

So I can't figure out whats going on with the ported vac advance. the throttle plate is set at spec, yet somehow the advance hose is sucking away, even under 1000 rpm, when it should be out of play. hmm.

Central Idle circuit is hissing as it should although something seems off.

- mixture screw seems to have no effect whatsoever.
- idle speed will drop beyond the last turn of the screw to closed.
- when i cover the CIS briefly and take my finger off, engine speeds up strongly for a few seconds (covering hose would make it richer and put more emphasis on the carbs idle contribution)

Now that I'm writing this, is it possible there is no fuel getting to the CIS circuit? And Im just pumping a bunch of air into the system? How to check?? As I mentioned both carbs were just totally rebuild so I don't think there would be any blockages..

Idea Question
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PostPosted: Sun Mar 25, 2018 8:19 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

Wow, that's alot to get one's head around Confused
I'll take this on like one would when eating an Elephant, one bite at a time.

Vacuum on the advance port at idle isn't good, either the throttle plates are open too much or the plate is in upside down or the wrong one, the port shouldn't be exposed when they are closed.

CIS solenoid being lazy may be due to a thick washer between it and the carb, try a thinner one or no washer at all and see if it smartens up.

-14* @ idle sounds like a 73 distributor, did you confirm it's a 72 with the numbers?

CIS screw(s) having little effect could be related to that throttle plate problem, solve that first.
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PostPosted: Sun Mar 25, 2018 11:47 pm    Post subject: Re: Second Bus and First Engine Drop. Need guidance! Reply with quote

Thanks for reading through it all... OK, one step at a time...

Throttle plate issue first.

I have confirmed the left carb is a slightly different model than the right carb. When I sent two carbs to be rebuilt I sent a L and R that looked best to my inexperienced eye. Should have sent a matched pair, but at the time I thought all three sets were off 1973 1700's. Unfortunately, it looks like the pairs were not clones and had some subtle differences. All are PDSIT 32/34 2/3. Perhaps the rebuilt carbs can still be made to work together...

So, the installed left carb has the screw-in accelerator pump arms (is this diagnostic?) and is number 445-1. Left carb throttle plate upper surface has one cut out on left side, towards the front. The vacuum port is towards the rear and is not visible, I assume it's being covered by the thick plate. The throttle stop screw is just touching and I'm confident throttle plate gap is correct. I am still getting vacuum at idle.

The right carb (384-2) has cotter pin style accelerator pumps. I tried the vacuum advance hose on distributor to the vac tube on right carb and my timing works better from here, 10* atdc, but a low 700 rpm. Vacuum only at partial throttle, none at idle. The tiny vacuum port is higher up inside the right carb than in the left carb and totally exposed when throttle plate is shut. This throttle plate also only has one cut out, towards the front.

Can I leave the left throttle plate as is and just use right carb for vacuum? The two cotter-pin style left carbs I have both have 2 cutouts on the left throttle plate, and the varnish pattern indicates the thin part of the plate still covered the vacuum port. So maybe this was important?

Just swapping the vacuum source did not fix my CIS problem (still no effect from mixture despite confirming there is air hissing from intake, solenoid plunger out of play, mixture needle seat looks OK, and fuel is getting at least as far as the mixture needle).


A little more background in case it is helpful... I am concerned I have created monstrous Frankencarbs with some of the swapping I have done...


Two other left carbs, cotter pin style, also have larger openings on the brass vacuum advance tube than on 445-1.

To correct an earlier statement, distributor is from an early 1973 1700; it's an assumption that it still had original distributor. I can pull the number if need be.

Both left and right carbs are now jetted:

Main: 127.5
Air: 140
Idle cutoffs 55

Are jets always matched? Some of my observations suggests they were not on the three pairs of carbs I have. Let me know if it might be important to know which were jetted with what originally and I'll see if my notes were good enough...
_________________
1973 Campervan. Stock 1700. Dual Solex carbs. Pertronix electronic points on distributor (stock, not a 009). Engine rebuilt in October 2016.
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