34 carbs: wondering if I could get lucky.... thinking out loud

emzdogz

emzdogz

Aunty Em
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Getting close to time when my project bike ('80) could maybe be started up. I still need some parts, which have to wait til my tax refund (next week, I hope) so I'm trying to do all I can beforehand that doesn't require purchasing parts.

Pulled the carbs off yesterday. The original carbs for this bike are gone, as I used them on a '79 I used to have. So I got these replacement ones from eBay way back then, thinking I'd have them to use whenever I did get to this bike. Which is NOW!
Glad I got them when I did, as they are in really nice shape and I only paid $10 for them. (several years ago) But these have never been on a bike of mine before, so this bike never ran with this set of carbs on it.

The idle screw covers have never been drilled out. And it really appears the bowls had never been off before yesterday either, as the screws were in perfect shape. The outside of the carbs was real cruddy, just from sitting wrapped in an oily rag all these years, but the insides were amazingly pretty clean looking. The bowls were kinda brown, but not anything you could call "sludge".

There's 3 things I DON'T want to do.

a. remove the top and mess with the diaphragms
b. remove the needle jet and floats
c. (not sure about this one) mess with the idle screws

I have blown through everything so far with carb cleaner and air from compressor. Poked through what I could with a piece of wire. So far, no holes have appeared clogged.

I lost one of the damn pilot jet caps. sigh....
and I deserved to lose it. Blew the 1st one off and in a few minutes - get this: I FOUND it. In a bunch of leaves.
Like a dummy, later I blew the 2nd one off and tried to follow its arc as it flew and I could tell where it came down - but it bounced and I couldn't tell where....so it's really and truly "lost".
Of course I'll find it in like 5 years....

So I ordered new ones. They were a little dry-rotted anyway, and did not fit snugly.

I'm guessing the diaphragms are in nice shape.
But eventually I guess I might need to access this area if I have to try and shim these needles.

Also, I do worry a bit that the area under the idle screws might be clogged, or that that tiny o-ring is also dry-rotted or otherwise no good.
But I'm also thinking that since that area over them has never been drilled out, hmmm...maybe everything in there is in nice shape.
Trying to remember from the old 34's I had, where the hole is, in the tunnel, by butterflies maybe? that accesses that area.

Wondering if I could just squirt carb cleaner in and let it run back out and that would be enough of a cleaning.

Trying to weight the risk and annoyance factors.

It's easy enough to pop these on and off, so I think I'm going to go forward like I said and then if there's a problem, pull them back off.

just thinking out loud......
:laugh:

ps: it just seems like there could be sooooo many reasons why this bike probably won't run.... be funny if it starts right up.

pps: another thing occurred to me, re: the elec starter. To use the starter, why must I have the starter solenoid at all? why can't I just touch the loose end of the starter cable to the pos terminal of grounded battery? Wouldn't that make the starter turn the engine?
I'm just thinking of trying that at first, before I finish wiring it completely. Like wire it as a kick only bike, then touch starter cable to battery to use the starter. Then when it runs and all, go ahead and wire in the starter solenoid and a button.
Is this ridiculous? tell me why?
:doh: I'm sure there's some huge reason, I just can't think of it.
thx, and Happy Monday
 
You can't clean the carbs properly unless you disassemble them further. The slide/diaphragm assemblies need to come out. You should have pulled them 1st thing so there was no chance of exposing the diaphragms to carb cleaner. It can ruin the rubber diaphragms. The mix screws need to come out. There's no way to ensure the idle circuit is clear unless the screws are removed. The needle jets need to come out. They are often all gummed up.

A few years ago I stopped by a newbie 650 guy's house. He had the motor pulled with the carbs still attached. He was scrubbing the outside of the carbs with a toothbrush and solvent. I asked him what he was doing. He said "I'm cleaning the carbs". Needless to say, that bike hasn't run yet and probably never will, lol.
 
yeah I hear you, I really do. I'm just not sure if I'd do more harm than good. The idle screws, never having been messed with are probably set just right, plus the diaphragms are probably seated just perfectly. In the past I've found it hard to get them to sit just right in the circle. I think I will go ahead and pull the floats and needle jets though.
These carbs - they're like their own little universe.
 
5twins said:
There's no way to ensure the idle circuit is clear unless the screws are removed. The needle jets need to come out. They are often all gummed up.
Click to expand...

so in other words, the stock 34 carbs ALL had to have those solid covers over the idle screws drilled out? So anyone who took their Yam, say, to a dealership back then for carb work, received them back with those covers drilled out?
 
In order to adjust or clean the mix screws, yes, the covers had to be drilled out. The dealer could install new ones though, after the job was done. Your mix screws are probably not set in the ideal spot now anyway. It can vary from bike to bike and depending on what mods or jetting you have. Since the carbs came from another bike, if they are set, they're set for that one. Pull them and re-install set at somewhere between 3 to 3 1/2 turns out, then fine tune from there.

The slides will need to come out to remove the needle jets. The needle jets in the 34s push up into the main carb bore for removal. They don't pull out of the bottom like on the 38s.

The floats don't absolutely need to be removed but if you want to inspect/clean the float needle seat and the area beneath it then, yes, remove the float. The float needle seat has an o-ring on it that seals it into the carb body. Many times, that needs replacing.
 
Last edited:
if your solonoid is bad you can touch both bolts of the solonoid at the same time to the pos battery lead via jumper cable. It'll start the bike but its a PITA to do this way.
 
I would not recommend starting the bike as you propose by touching the cable from the motor to the positive terminal of the battery. The sparks generated this way could ignite any hydrogen gas that vents from the battery.
 
pamcopete said:
I would not recommend starting the bike as you propose by touching the cable from the motor to the positive terminal of the battery. The sparks generated this way could ignite any hydrogen gas that vents from the battery.
Click to expand...

oh wow I didn't think of that. I tested my newly wired brake light this way over the weekend. No sparks there, really, but I guess a starter motor is a much different beast.
So there could be hydrogen gas even with a sealed type battery?
 
pamcopete said:
A sealed battery does not vent unless is is being overcharged.
Click to expand...

since you mentioned fumes though, in general I now think this is not a good idea. When I did it with the tail light pigtails the other day, the gas tank was empty, carbs hadn't seen gas in years. Once it had gas in it, I'm sure I'd have thought twice about the possible spark thing.
OK, well that takes care of that.
thx!
:thumbsup:
 
emzdogz said:
yeah I hear you, I really do. I'm just not sure if I'd do more harm than good. The idle screws, never having been messed with are probably set just right, plus the diaphragms are probably seated just perfectly. In the past I've found it hard to get them to sit just right in the circle. I think I will go ahead and pull the floats and needle jets though.
These carbs - they're like their own little universe.
Click to expand...

I cleaned my carbs without removing the mixture screws, which are still capped. If it works it works, no need to be a racer. Remove the pilot jet and make sure carb cleaner comes out the hole below the mixture screw. For the jet, use a screwdriver like the ones that come in those little bit sets - straight sides, not trapezoid. My bike runs great with stock everything carb, including mixture screw setting. I see people here with problems to solve with their carbs once they start changing things. Maybe they're racers or something; we're not.
 
emzdogz;

Don't agonize over adjustment of the mixture screws. Its a very simple job.

I use the dead cylinder method to adjust the mixture screws............very easy..........takes very little time.

To sync the carbs is also very easy...............just make up a u-tube manometer with some plastic tubing from Home Depot.

As others have mentioned...........do a complete disassembly ..........double check all passageways are clear. Read all the info on Carbs in the "Tech" to get up to speed on the technical side of the carbs.

If you need details, just PM me.
 
emzdogz said:
plus the diaphragms are probably seated just perfectly. In the past I've found it hard to get them to sit just right in the circle.
Click to expand...

A trick to getting the diaphragm back in in a circle is while its out, don't let the rubber lay on anything. Don't just lay it on its side. It disturbs its shape memory enough that it can make getting it in again a little hassle. I usually set it aside with the metal piston on a table edge with a book on top of the piston, and the rubber not touching anything and it sits right back down in the carb again perfectly. You do need to take the pistons and diaphragms out.
 
today I pulled the floats and float needle and that brass tube with the screen at the bottom of it that the float needle goes into. The screen was perfect. Nice and silver in color, nothing plugging it at all.
I'm trying them as-is. I'll report back how they work - if I was wrong I will totally admit it. And, thanks for all the help and input.
 
here's a couple of unfortunately out of focus shots of the screen that in the bottom of that brass tube that the float needle goes into. As you can see, they are perfectly silver, no brown sludgey color and you can see through them perfectly - this is without having cleaned them or sprayed them or anything. So far everything inside this set of carbs has been so clean....as soon as i get the stupid rubber plu I lost for the pilot jet, I'm just gonna put them back on and see what happens.
 

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