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Fri Jul 08, 2016 8:31 am

Alright I got a new problem.

I put on a different carburettor on my engine since the old one kept carbon fouling my plugs and several mechanics had told me that carburettor was junk. I got a different one that came off a running 1600 DP and installed it this morning.

Started up the first time totally great but after about 5 minutes of running I started getting a ton of white or blueish smoke, can't quite tell which of the two. This engine had never smoked before until now so I assume it's a fuel issue. It also seems that it's beginning to miss fire on plug #3.

It's a 34PICT3 carburettor. What's the correct way of going about the fuel mixture adjustment?

Unfortunately I already traded in the old carb so I can't swap it back to see if the issue goes away.

Your advice is greatly appreciated.

Fri Jul 08, 2016 9:09 am

'Usually' white/blueish smoke is oil burning. Gas burning, or incomplete burning, gives off black smoke.

Fri Jul 08, 2016 9:14 am

Whiteish/blue smoke is oil burning possibly. Black smoke is fuel and smells nasty. Pull the suspected fouling plug and see what's going on. If it's black and dry your running rich. If it's black and moist you may have an oiling issue.
Make sure to check your timing before you adjust the carb. Then go after carb adjustments. I have never had one of those carbs. But there will be a pro tuner coming along soon to give you a hand getting it setup.
Good Luck.

Fri Jul 08, 2016 10:25 am

I took the plugs out and to me it definitely seems to be a fuel issue. A couple of them (3 and 1) came out completely covered in zut. 4 and 2 came out wet but it seems to be gasoline, it smells of it and is translucent.

These were brand new plugs out of the box.

Cleaned them up and ran it again with the same problem. Runs well for a while but eventually comes the smoke and heavy misfiring afterward.

This comes after a vacuum leak repair I did by changing the intake gaskets from manifold to head. I believe this issue has been fixed as the symptoms are different. Originally it would not idle and would slowly get harder and harder to keep it running. During the vacuum leak issue my plugs weren't fouling in this manner either. So I believe the vacuum leak has been fixed and our new problem is this questionable carb. Another reason I think this is a fuel issue is the fact that it starts unusually easy even after having sat for a coulpe nights it started without a problem which I would think indicates a very rich mixture.

Fri Jul 08, 2016 10:48 am

You say you can't really tell if it's white or blue. White smoke would indicate water in the gas. Any way that could have happened? The engine certainly wouldn't run very well.

Fri Jul 08, 2016 11:32 am

Yes it sounds like it's running VERY rich. So go through the carb adjustment procedure, but better still start off there with a tuneup.

Fri Jul 08, 2016 11:38 am

Yeah to me it looks mostly white. There might be a very slight tinge of blue in there but if there is, it's hard to notice. Don't think there's anyway water could have gotten in there. The smoke also smells a lot like fuel and right from the tip of the exhaust it looks more grayish than white. I held a piece of toilet paper up to the exhaust and it got a bit of zut in it. I don't think oil is the issue because the engine was running really well prior to the carb swap minus the spark plugs getting dirtier than they should have. Now it's fouled plug heaven.

I saw a youtube video on adjusting carbs and I tried fiddling around a little. The weird thing is that when I turn the fuel mixture screw it doesn't seem to make much of a difference. I screwed it in all the way til it felt bottomed out and the engine kept running.

Should have never swapped the carb!

Fri Jul 08, 2016 11:56 am

http://www.vw-resource.com/34pict3.html

Fri Jul 08, 2016 1:46 pm

swamvan wrote: The weird thing is that when I turn the fuel mixture screw it doesn't seem to make much of a difference. I screwed it in all the way til it felt bottomed out and the engine kept running.
Hmm. It's possible you have the wrong gasket under the very top lid of your carb. The wrong gasket will block a couple important little holes. A guy just posted with this problem and he had the same thing with the volume screw: it would run with it all the way in. That's something to check.

I would also take the volume screw all the way out and check it against a picture of a new one. Could be yours is damaged or something.

Sat Jul 09, 2016 6:29 am

I suspect your choke may not be working properly. Do you have the 12v black wire connected to the choke coil on the right side of the carb? This powers the heater in the choke coil. Have you adjusted your choke so it is mostly closed at the start of day temps?
When the engine is cold it will close the choke resulting in a very rich state which is needed when your engine first starts up. As the choke coil heats up it will slowly (over 5-10min) open the choke butterfly and the idle will lean out to normal.

When you were adjusting your carb, was it fully warmed up with the choke butterfly fully open? Tying to adjust the carb with the choke closed is meaningless.

Also make sure you adjust the throttle arm screw that rests on the fast idle cam. This should be adjusted to keep the throttle plate open just a hair when the engine is fully warmed up (screw resting on the lowest part of the fast idle cam). I usually start w/ 1/4-turn IN once the screw is just touching the lowest part of the cam. This keeps the throttle plate open just a hair. If I cannot get the engine idling where I like it (800-950rpms) with the bypass+volume screws I may screw this in/out just a bit (1/8 to 1/4 turn). The warmed up idle speed is controlled by a combination of the bypass + volume + throttle screw.
It is tempting but DO NOT use the throttle screw as an idle adjustment all by itself. The earlier 30Pict-1 carbs did this, but the 34Pict- carbs were designed differently. The reason for adjusting the carb screws is to properly set the idle circuit air-fuel flow. If you open the throttle too far you will expose the progression circuit and they will start to flow fuel. The idle bypass and volume screws will have no control over fuel flow at idle.

It is like trying to control the rate at which you fill up a bucket using a garden spout/hose... but someone has turned on a fire hose next to you. Your control of the garden hose spout makes little difference in how fast the bucket fills. This is analogous to the fine control the idle circuit has and the raw fuel that is dumped in when the progression circuit is exposed.

FYI, I hope you cleaned your spark plugs using some solvent or blasting media and not a wire brush? A wire brush could leave conductive traces or spread the carbon between the electrodes creating a short path for the spark. The spark could follow this path instead of jumping the gap and igniting the air-fuel in the combustion chamber. The proper way to clean spark plugs is with glass beads and compressed air. This is dry and non-conductive. Solvents are okay as long as they evaporate and don't leave a conductive path.

Sat Jul 09, 2016 8:15 am

The choke was fully open by the time I tried adjusting it, 12V is hooked to the heater, but I had to open it all the way myself as the choke feels a little crusty. In fact the whole thing is crusty.

Thanks for the information and warnings on proper adjustment. The adjustment screws felt a bit too easy to turn. My previous carb I remember these screws had a little resistance when turning. I took the carb back off and opened it to find that everything inside is covered with a honey like material and that the gaskets around the adjustments screws are really worn, thus the loose feeling when turning.

It looks like i got completely screwed with this stupid carb. I was told it was in good condition and recently rebuilt. :x :x

I'll have to see if I can't get refunded or get my old carb back. If not I'll have to try and rebuild this one. Do carbs ever get to the point where they're unrepairable? I don't think the gasket in here is the wrong one, though by now I see that this is the least of my worries.

I definitely got scammed with this one my dudes.

Sat Jul 09, 2016 8:35 am

Sorry to hear that you get taken. If it were me, I'd just get a rebuild kit and do the work myself. It's easy and along the way you'll learn how it works. Get a couple cans of carb cleaner and get to cleaning.
Good Luck.

Sat Jul 09, 2016 1:18 pm

swamvan wrote: The choke was fully open by the time I tried adjusting it, 12V is hooked to the heater, but I had to open it all the way myself as the choke feels a little crusty. In fact the whole thing is crusty.

Thanks for the information and warnings on proper adjustment. The adjustment screws felt a bit too easy to turn. My previous carb I remember these screws had a little resistance when turning. I took the carb back off and opened it to find that everything inside is covered with a honey like material and that the gaskets around the adjustments screws are really worn, thus the loose feeling when turning.

It looks like i got completely screwed with this stupid carb. I was told it was in good condition and recently rebuilt. :x :x

I'll have to see if I can't get refunded or get my old carb back. If not I'll have to try and rebuild this one. Do carbs ever get to the point where they're unrepairable? I don't think the gasket in here is the wrong one, though by now I see that this is the least of my worries.

I definitely got scammed with this one my dudes.
Wow, I wonder what that "honey" is. Maybe the last person who "rebuilt" it made sure everything inside got a liberal coating of bearing grease.

According to threads here, a surprising number of people find that their brand new from the factory carbs don't work until they first clean them out. So, that is something you'd probably have to do one way or the other.

Hopefully you can get your old carb back. Just make sure they haven't "rebuilt" it in the meantime.

Sun Jul 10, 2016 8:43 am

If one of your carbs is an original Solex, keep it. Many of the places that rebuild carbs will only work on originals and not the clones.
A common wear spot for these carbs is the throttle shaft bores. These can be repaired by adding new bushings. Not something most people can do in their garage.
A proper carb rebuild is more than just spraying with carb cleaner and using a new gasket set. The carb should be soaked overnight in a can/bucket of carb cleaner to break down deposits in the passages. Then rinsed and blown clear with compressed air from a compressor (not a can).

Tue Jul 12, 2016 5:11 pm

Well unfortunately I was not able to recover my old carb and I'm stuck with this old POS.

I looked into getting a brand new one but so far all I can find are the bocar ones. A quick forum search reveals that most people don't have the best of opinions on these bocar carbs so now I'm not sure if I should go for it. What is your take on the bocar carbs?

I believe my old carb was a bocar hecho en Mexico. The one that is dumping gallons of gas into my engine is a solex made in Germany. Looks like these Solex German ones are hard to get and might be worth rebuilding. However I'm not sure how far gone it is considering how awful it's running.

How do I check to see if the bushings are bad? These are the ones that control the throttle butterfly? Just look for play? What other things should I look for to see if it's worth the rebuild?

Tue Jul 12, 2016 6:59 pm

I have a Bocar Hecho en Mexico and it has run just fine for a year and a half, (except for the one time something got into it and clogged up a jet. That was cured with a can of choke and carb cleaner.)

The guy I bought it from had used it as a daily driver since 2006, so I assume the Bocar worked for some if not all of that time as well. I think it's a perfectly OK carb. Basically I get the impression that when people can't get a Bocar tuned, they blame it on the carb. When they can't get a Solex tuned, they blame it on the PO.

Despite ashman30's laudable cautions about how thoroughly you should clean a carb, if I were you I would conduct a test to see if choke and carb cleaner will dissolve the "honey" and wash it away. If it seems to work, keep going: spray out all the channels and jets and orifices till the can is used up. It's only a few dollars. If you have access to an air compressor, so much the better.

Anyway, if your throttle shaft bushings are bad there will be a vacuum leak around them. You can google how to check for a vacuum leak, or search this forum. I've never done it myself as I haven't seemed to have any so far.

Tue Jul 12, 2016 7:23 pm

Thanks for the input. I do get the impression that perhaps some people had sour experiences with their Bocar carbs and this is what's ruining their reputation. However considering there must be millions of them out there, they can't all be bad.

Would love to hear other's opinions on Bocar carbs.

Will begin trying to clean the Solex out tomorrow.

EDIT: Well it seems the solex may be out of the question since I just checked and the bushings on the throttle butterfly have some play. It's just a bit but I'm sure that's enough to cause a vacuum leak. Is there any spec as to how much play is allowed?

Wed Jul 13, 2016 12:32 am

swamvan wrote: EDIT: Well it seems the solex may be out of the question since I just checked and the bushings on the throttle butterfly have some play. It's just a bit but I'm sure that's enough to cause a vacuum leak. Is there any spec as to how much play is allowed?
My Bocar, which, as far as I can tell, is running just fine now, has "just a bit" of play. The only way to tell if you actually have a vacuum leak is to do something like this:

White smoke, or any smoke, is not considered to indicate a vacuum leak. A vacuum leak would lean out your mixture, not enrich it. Ashman just mentioned this as something that can go wrong with a carb that would have to be addressed if someone undertook to have it completely rebuilt. His main point was that, if a person had this problem, it's not something they could normally fix themselves. He wasn't suggesting you have this problem and that it is causing your smoke.

I really think you need to put the idea of a vacuum leak on hold and address this "honey" you found inside the carb. Bocar or Solex, it's not supposed to be there.

Wed Jul 13, 2016 1:11 am

I just rebuilt a carb with the same "honey" looking crud in it you are describing. It was off a baja with a crappy paper air filter that had been sitting outside for a few years exposed and had filled with rain. I disassembled it removed all the jets put it all in a large coffee can sprayed it liberally with carb cleaner with a lid on it so it doesn't evaporate left it overnight used a tooth brush to finish it off blew all passages out with compressed air installed rebuild kit and it worked like a charm. If your choke is sticking it will never tune properly. Clean rebuild make sure every thing is functioning without sticking or binding and you should be off to the races. Also while you have them out check your jet sizes those carbs get lots of modifications due to mismatched distributors.

Wed Jul 13, 2016 12:31 pm

Well I'm not necessarily saying the bushing play is the source of my plug fouling/smoke issue but it might be another issue with this carb. It's a very small amount of play but I don't know how much is too much. We'll see.

I took the carb apart and I currently have it soaking in a bucket. Will leave it there until tomorrow. The choke pull off and accelerator pump gaskets were completely ruined. The fuel cutoff valve has the little plug that goes on the tip broken off and all that is left is the shaft. Can't tell if the metal plug is still stuck inside the carb or if it was just installed with it missing. Most of the honey already came off. Just some stubborn residue left on the bottom of the bowl. None of the jets looked like they where clogged. Don't know about the passages. Wish I had an air compressor. Might try a small piece of wire for the passages.