High altitude move - stumbling

give it an EYETALLION tuneup, mega dose Techron and drive the pee out of it before getting technical..

Those jets you show are the mains. You might want to go down on the mains from 115 to a 110 or a 105.

The ones that make the most difference are the idles: i.e. under 3000 rpm, where you drive a LOT. Those jets are in picture #4 under the fuel hose under the slotted brass screw.(I'm going to guess you have .50 or .55 idle jets) They may or may not be the size that's on them.

You may also have to reduce the amount of accel squirt as well.

All due to the thinner air, but 3500 feet isn't that high. I didn't re-jet for my trip to North Carolina and we got up as high as 6000 feet. Nobody else did either.

It is possible your car is jetted too rich as is for the lower altitude, and the 3500 feet just pushed it into pig-rich and undrivable.

Or most probably, a plugged idle jet...I'd clean them FIRST and see how it goes. If it still runs like crap, look into smaller jets.

Going from sea-level to 3500 ft isn't going to make the car stumble and fall on its face. There's something else wrong.

@Stan Galat posted:

Going from sea-level to 3500 ft isn't going to make the car stumble and fall on its face. There's something else wrong.

I agree. My mountain runs regularly involve more than 3500 of vertical. I live at 4500. Most local pass summits are ~9000.

I agree with those who say it's something else besides the jets.  I'm thinking the three month layoff results in clogs and/or water in the gas.  Ethanol is hydrophilic and will attract water over time.  If you use gas with ethanol in it and didn't use a fuel stabilizer, then that could be the issue.

Thank you everyone for your answers! Please excuse any ignorant questions I have... I promise they come with gratitude for your advice and patience!

When I parked it I did use a fuel stabilizer! I posted about it on here before I did it and got some great advice!

I was looking up how to change the idle jets and/or clean them... does anyone know what carbs I have? Also, what do you use to clean them? In order to order different ones, what size would you suggest?

@Carlos G I undid that screw for the idle jet holder to clean them... and now I find myself in a bit of a conundrum as it appears as though the jet is still in the hole. It's pretty impossible to get it out. How would one do that? gahhhhh. This is how we learn, right?!

here's what it looks like in there...

They certainly look like Weber 40IDF carbs to me.

I really don't think you need to change anything. Clean yes.

Get a pick and hook tool set or make one from a piece of wire and pull the green O-ring out. Put it back onto the jet holder that you took out. Using a pair of really skinny needle nose pliers, fish the jet out. You might have to get some special right angle needle-nose pliers in a Speedster engine bay, or possibly remove the carb. After you get it out, VERY VERY gently spread the ears with a thing screwdriver. This will tighten the fit into the jet holder. Worst case: if the jet breaks they aren't expensive and are readily available.

Buy a tweezer set from Harbor freight:

https://www.harborfreight.com/...eezer-set-93598.html

Alright... so I finally got that jet out. It's a 50. Can I just mention how friggin hard it is to access these?! haha. It felt like I was a surgeon, and there's another one on the back carb too?? and then both sides?! good lord. I do have a love/hate relationship with these sorts of challenges.

Okay, so I need to get a bit of advice on next steps:

I put a carb cleaner in the fuel and that did not make a difference. It still runs rough and when I accelerate it struggles to the point where I put the clutch in and save it from dying... then it goes back to idling normally. It's weird... it's like as I give it more gas when it's in gear it starts to feel like it's not getting enough. (or maybe too much?!)

It definitely has a fuel smell when I park it (more than normal) -- would you recommend adjusting the fuel mixture? Should I change out the idle jets? and/or the main jets? If so, to what size do you guys recommend?

I can understand the love affair with these as it makes driving it worth it so much more appreciated!

Everything was running perfectly before and parked it and it had just been serviced... so I'm at a loss here. When I parked it I had a friend start it every few weeks and I did put fuel stabilizer in the tank.

I just want to drive her as the weather is getting better and better!!

Any help would be appreciated. I'm in Calgary, Canada if there anyone else here!

Cheers,

Mark

Well, let's get this discussion going so you can reliably get out on the road.  Let's start with the idle circuit:

1.  Find your fuel filter(s) by following the fuel line away from the carbs.  There might be more than one filter and they may be on each end of the car (front/back).  Make sure there aren't any kinks in the fuel line causing loss of fuel.  Replace any fuel filters that you find - they may be full of crud and causing a loss of fuel such that it idles OK but can't operate at much above idle 'cuz there ain't enough fuel getting to the engine.

2.  Changing the idle jets won't affect any change in the raw gas smell when stopped.  That is usually caused by a gummed-up pilot valve in the float bowl leaking fuel into the bowls and overflowing when it's parked after running.  (also, sometimes it can cause black smoke under acceleration because of running rich - Do you see any smoke?)  Sometimes you can detect a stronger smell on one side of the engine than the other when recently shut off, and THAT pinpoints which side needs attention.  Look around the outside of both carbs after it's been running and now shut off and see if any of the carb seams are leaking by looking for a slightly darker, wet color on the outside.  

To service the pilot valves you'll need a service manual for the carbs:  There are a couple on the CB Performance web site by Bob Thomlinson, one for Webers and one for Dellortos.  Pick whichever one fits and find out how to clean and set up the pilot valves (you end up setting the float height and that's critical for good operation so maybe something for an experienced mechanic).  This might be something for someone with carburetor rebuild experience to do the first time.  Maybe ask if you can watch so you can learn how to do it.  Maybe buy him/her lunch for showing you.  * See #4 and maybe add that to his/her list to do for you, too.

3.  Jets:  the 50's you have should be in the ballpark.  If anything, you could drop down to 45's but if it was running OK before on the 50's then it should be OK now with them.  Instead and assuming that it had been running OK and just has a clogged jet, then go ahead and remove each jet (all four of them) and blast some carb cleaner through them (use the needle tube on an aerosol can).  Once the jet is blasted and before you put it back, go to the carb and blast straight into the hole where the jet resides - several seconds should do it, then replace the jet just as it was.

4.  * Carb cleaner in the gas tank takes at least a tankful run through the engine to make a difference, maybe two tanks, and that's at a high concentration.  I prefer Seafoam, but CRC or Gummout should both work OK but remember, it takes TIME for it to work.  It's always faster to remove the jets and blast them with carb cleaner (aerosol can with needle tube) and replace them.  Don't forget to gently turn the mixture screws all the way in til they hit bottom while counting 1/4 turns til they stop so you'll know where they were to replace them at the same point, then remove them and blast.

5.  Anything beyond these four steps would, I believe, be getting into the advanced range and you might strongly consider taking the car to someone experienced on carburetors to help out as you might also be looking at a potential vacuum leak or something hard to diagnose like that.  While it might be easy for him/her to diagnose and fix, the potential for inadvertently screwing something up if you attempt repairs is high and the whole point of all this is to get you back on the road, NOT get you through "Carb Tuning 201".

Honestly, cleaning them out is not that big a deal. You don't need any advanced degrees. If you follow my instructions, you can clean the carbs without taking them off the car. But you have to follow my instructions, and you can't skip any steps.

You have Spanish Webers, which is a GOOD thing.

Before you do anything, check your fuel pressure. This is OFTEN overlooked, but important. No more than 3.5 psi with Webers. Period. If it's over, it will NEVER run right.

1: Disconnect the battery, OR massively tape/insulate the hot wire on the alternator.

2: Remove air filter tops and air filters.

3: Remove the 4 nuts on ONE carburetor that hold the velocity stacks and air filter base/linkage in place. Use a magnet on the nuts and washers so you don't drop them. Remove the two velocity stacks. Gently lift the air filter base up, keeping tension TOWARD the center of the car. There should be a spring inside the hexbar on both sides. You don't want them to fly off! Gently release the tension and grab the springs.

4. My advice, do one carb at a time. With the air filter base removed, you can lay the hexbar down, making sure it DOES NOT TOUCH the hot post on the alternator. Remove fuel hose, usually just a hose clamp.

5. At this point, you can follow these instructions:

https://mirrors.disavowed.jp/w...c.com/weber_tech.htm

If it's easier for you, the carb can be removed and cleaned on the bench.

FWIW, I use 10mm(plus 1mm for the gasket, so 11mm total) for the float height and 30mm for the drop. The drop isn't as important as the cutoff valve, but both should be identical.

And just removing the idle jets and cleaning them is NOT the whole job. The entire idle CIRCUIT must be cleaned. This involves the idle mix screw AND the idle jet. Both must be removed so the circuit can be flushed out. Carb cleaner squirted through the circuit both way works. Some carb cleaner will squirt into the main fuel well, that is where the idle fuel comes from.

My money is on goo in the float wells and idle circuits. You will most probably see white goo, black dirt, and possibly some varnish in the float wells. I cleaned the wells with the carbs on the car a few times. Lint-free rags are a must here. Paper towels or cheap rags will not do.

6. Do the other side.

7. Reinstall one carb top, tighten all the hardware, then lightly grease the hexbar springs and balls. Re-assemble, carefully.

8. After all this work is done, you'll need to synchronize the carbs. Do it engine HOT, not cold, not idling for ten minutes. You MUST drive the car and get it HOT, the synch.

Any questions, read Mark Harney's articles referenced above, or ask here. If I don't respond(doubtful) PM me.

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Mark, you are getting good advice from Danny and Gordon, both here and in the links they provide. The Mark Harney articles Danny links to are the generally accepted Old Testament on Weber setup and tuning.

But there is a quick-and-dirty test you might try before pulling everything apart, especially since you say the car was running well before you moved.

I live close to sea level, at the foot of the Sierra Nevada mountains, and my carbs are tuned for that, but most of the good Speedster roads around here are up in the foothills, so I drive at higher elevations a lot. Up to about 4000', there's no noticeable performance hit. By 5000', there Is, and up at Lake Tahoe - 6000' - the engine is definitely down on power, and the idle has dropped noticeably.

If I'm staying up at Tahoe for more than a day or so, I'll do a quick tweak on the 'idle mixture' screws to raise the idle back up and help low end response. As a test, you could do the same to see if that makes any difference. It's possible your jets and idle circuits are clean, and you just need a slight retune. If so, the engine should respond to this little test.

Try backing off (unscrewing) the 'mixture' screws about a half-turn. Do each one the same amount and note how much you turn them so you can set them back to where they were if this makes things worse. The screws are marked 'idle jet adjustment' in the photo Carlos posted above. They're knurled, spring-loaded thumbscrews, made to be adjusted by hand.

It's probably a good idea to do a complete teardown, cleaning, tune, and possibly a rejetting, as Danny suggests, but this might make the car more drivable for now.

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You're right Mitch. Except you're going the wrong way. Altitude means less dense air. So less air. You need a proportionate amount of less fuel at the same time(which is clockwise or in or less).

As was suggested before, 3500 feet is not going to change things enough to re-jet or even tweak the screws.

For reference, I live at 711 ft (+/-) above sea level, and am jetted with a wideband Lambda meter.

I've driven my car from here to Kalifornia on I80, across Nevada on US50, and up from San Luis Obispo to Las Vegas on CA58 and I15. I've taken the car all over the golden state, from sea level on CA1 to over 9000 ft in the Sierra Nevadas.

The car ran great pretty much everywhere at sea level and across the high plains, a bit rich over the Donner Pass, and would barely idle at the Yosemite east gate at Lee Vining. I never touched a thing, and the car ran well up to about 7000 ft.

The problem really, really has nothing to do with jetting for 3500 ft of elevation.

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Um, yeah, leaner, richer, in, out, less dense, more dense, ipso facto, QED.

Except the last time I did this, I could swear I had to back them out to get more idle revs at altitude. Maybe that's only in 'R' months?

I do know that someone comes on here alla time lecturing us about how the idle 'mixture' screws don't affect idle mixture at all, but rather the volume of stuff that gets spritzed down the hole when the butterflies are shut, or nearly shut.

Don't know much stoichiometry.

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As someone mentioned further up this thread, if the carbs were tuned on the very rich side at sea level, they could start bogging at 3500 ft. Only way to know is to adjust them or put a wideband O2 meter on it. Right?

@Sacto Mitch posted:

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Um, yeah, leaner, richer, in, out, less dense, more dense, ipso facto, QED.

Except the last time I did this, I could swear I had to back them out to get more idle revs at altitude. Maybe that's only in 'R' months?

I do know that someone comes on here alla time lecturing us about how the idle 'mixture' screws don't affect idle mixture at all, but rather the volume of stuff that gets spritzed down the hole when the butterflies are shut, or nearly shut.

Don't know much stoichiometry.

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Yeah, And?

Mitch sings "don't know much about stoichiometry, don't know much about Italian carbs"

He he he!

@Michael Pickett posted:

As someone mentioned further up this thread, if the carbs were tuned on the very rich side at sea level, they could start bogging at 3500 ft. Only way to know is to adjust them or put a wideband O2 meter on it. Right?

You or I would know a lot by pulling a plug or two as well, but I think we're sticking Mark's head under the business end of a firehose here, and expecting him to come up refreshed and ready to roll.

The thing we're asking him to do has frustrated every single one of us, to the point that some of us have of wished the earth would open up and swallow the stupid car and put us out of our misery. Guys sell their cars with <500 mi. on them with some "no garage room" excuse or another when we all know it was the dreaded idle jet

... or maybe the ignition pickup module loosened up. Or maybe the manifolds are falling off and the whole thing is sucking large gobs of air downstream of the carbs themselves. Or maybe the entire main-jet stack backed out and is laying beside a velocity stack. Or maybe a plug wire is burnt and making poor contact.

The possibilities are endless. Every single one of them has happened to me.

Regardless, we're asking that he do this right out of the chute and without the background, tools, or spares which would ensure that he was able to get those carbs apart and back together again without a brass thingie moment. We're offering support as we sit in our offices or dens or kitchens 1000 miles away, throwing out best guesses (which almost never get to the root of the actual issue). I'm waiting for somebody to suggest the stupid Tomlinson manual. If Mark had wasted his time and money on all of this back in high-school, he would have ensured that he was inadequately compensated for the rest of his life - but he also would be equipped and outfitted to do what we are asking.

Even if one has the knowledge, tools, and background - something as uncontrollable as one's physiology often plays into this. I've been told I've got "Chevy hands". I struggle to find gloves that will fit over my paws, and I tend to break things trying to get them just tight enough. Pulling jets on Weber carbs in a pan-based replica engine bay requires hands the size of a small child's, but with the strength of a pipefitter's - and the delicate touch of a mother with her newborn. It requires almost contortionist levels of dexterity and being deeply, madly, and passionately in rut with your car just to get at the front jet. The back ones require some sort of deal with the devil or taking a sawzall to the inner fenders of your car. These are skills useful in almost no other endeavor in life  - not even with other cars.

It's madness.

Calgary is a big city with a lot of loose money floating around. Surely there's somebody with the tools and the shop to diagnose and repair the car without treating it like some freak-show oddity. Even better would be an aircooled club that populated by at least a few guys who work on their own stuff. I'll bet Mark could have his car running well in an hour if there was somebody to help walk him through it.

As it stands with our interweb troubleshootin', I'm not so sure we're even aiming at the right thing here. He says it idles fine - it struggles under load. Perhaps we're chasing the red herring because it was suggested to him that maybe he would need to rejet. If it's load related, I'd look hard at ignition before I dove into the black heart of darkness. 95% of all carburation issues are ignition.

Either way, I'm tapping out. I'll be anxiously monitoring this thread for a resolution. Good luck, Mark.