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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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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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busdaddy
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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???

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

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busdaddy
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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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Wildthings
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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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whatdoesthisbuttondo?
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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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whatdoesthisbuttondo?
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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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mnskmobi
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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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whatdoesthisbuttondo?
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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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whatdoesthisbuttondo?
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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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whatdoesthisbuttondo?
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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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whatdoesthisbuttondo?
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PostPosted: Today 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. Im leaving in the other one for now, while it feels way mroe 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 relubed 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 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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