Carburetor help

On my 1982 XJ650 Maxim...

(Once warmed up after riding it for about 30 minutes)

The idle is inconsistent (not erratic). Without touching the idle screw it'll idle just fine, then after about a minute, it'll want to die, then I'll blip the throttle, it'll even out for a few minutes, then without touching it, it'll want to kick up to 4K RPM's, I'll bump the choke and it'll back down to normal idle again, then it's up and down all over again.

...and it's still only getting 15 mpg...

(The carbs have been rebuilt, with a new rebuild kit, to the letter, of the manual, 10 times in the past year)

 

1. Where did you get your kit?
2. What manual did you follow?
3. Did you sync them?
4. What float height did you use?
5. Have you checked for vacuum leaks?
6. Have you checked your air filter?
7. What jets (ALL) sizes are in there? What size slide needles?
8. Does anything change if you have the petcock on PRI instead?

 

Are you seeing drips/puddles of gas under the bike while idling for a long time? Hard to believe it would be running at all if it had a rich enough mixture to get that bad of mileage. But a bad float valve or a float that doesn't...er, float, might be causing one of the bowls to overflow and dump the excess. That could monkey with your idle too.

 

1. It's the finest Chineseum from either fleabay or the jungle website (I don't remember which).

2. Both the factory service manual (yes I have one, and it's awesome) and the Haynes manual.

3. Yes, they've been sync'd, and verified with the vacuum guage set.

4. Float height was adjusted to parallel with the carbs.

5. No vacuum leaks anywhere to be found.

6. The newish air filter has less than 500 miles on it.

7. It still has all of the factory jets (and they're the correct sizes, in the correct locations).

8. No change with petcock position.

 

No leaks or puddles.

(I am smelling raw fuel come through the exhaust)

I was speaking with a friend, and he has suggested that it is either the new needles and seats (China's finest). Or I sucked up some debris. Or a combination of both.

I'm getting ready to pull them off the bike and go through them again...

 

Progress... I think (hope)...

 

That was literally the ONLY issue found, and the problem persist.

 

Dry float height setting is 17.5mm for initial setting. Parallel to body is wayyyyy too low to begin with. The ebay kit scares me.

Reason I asked about jets was to confirm originality of jets and sizes.
Reason I asked about manuals is because there are some known misprints in some.

 

I'll pull them again after work today and readjust the floats as you've said (although it's weird the manual says otherwise) but then again, it wouldn't be the first time the manual was wrong and XJBIKES.COM was right.

 

What does the manual say? I’m curious, not question you ….
17.5mm is the dry initial setting, the “clear tube” setting is your wet setting.

from xj4ever……

 

And just remember that "float height" is a vague statement, and open to individual, subjective interpretation of where to measure "from" and "to".......which is probably why Yamaha stopped publishing such a figure for later model bikes (my guess is that even the dealership techs were doing things incorrectly, and to nip that problem in the bud, they just stopped specifying a "float height" figure). "Float height" is just a kinda-sorta "shortcut" method of getting close---really close, sometimes---to the correct settings which then must be verified and tweaked, as necessary, when measuring the fuel level via the "clear-tube" gauge.

 

Exactly right.

 

Adjusted the floats, and now it's worse.

 

I'll spend a few days later this summer getting it running well enough to sell it.

The thing I'm most disappointed about is, I rode for 25 years, then I stopped riding for 20 years, and the reason I decided to buy another bike and start riding again is for a Memorial Run in honor of the Marines I served with who didn't make it home.

After three years of f***ing with this bike, the universe is telling me, I'm not allowed to honor them on two wheels.

I'll just have to follow behind on four wheels... again. And apparently eternally.

 

Oh poor you....
Listen, take them off, box them up, and send them to someone on here who knows what they're doing. There are at least 2 guys in the US who offer this service. Problem solved, admittedly it will cost you a few dollars, but they are not gummed up scrappers, so should be done in a day. I think I've offered you this advice before, so I don't expect you'll take it, but it would be really nice to hear your bike goes as well as it looks.

 

Detroit isn't far from Mora MN if you think about it, send the carbs here and I will set them up on my 750 SECA to the book. Unless something is drastically broken I can get them working right.

 

@Brhatweed, you in Mora? I have cousins out there.. If I ever swing their way on the XS, we sh0uld try to meet up!

 

Late but... What is your compression like.
Being CV carbs, this has a fair bit to do with it.

These carbs don't just suck, they rely on it.

 

Old Akkerman funeral home

 

Thus far...

 

If it were me, I'd be tempted to replace those jets. The pilot looks pretty munged up and the main looks deformed. Are they that chewed up in real life?

 

Carbs should be set according to the factory manual using tubes to observe the level and that must be within 1MM and not the float height from inside. This might be your trouble all along. Please see the post by Hogfiddles above.

 

The jets are actually in great shape.

The sight tube method would be phenomenal, however, the drain screws are completely seized into the bowls. I've tried heat and quench to no avail, and then I tried a screw extractor, again to no avail. And new bowls don't seem to exist. So the only option is float height measurements and trial runs.

It strikes me as odd that there were what, about a million motorcycles made that used these carbs, and that's like the one part that doesn't exist. Life would be so much easier if you could just buy new carbs.

 

I've seen good used bowl's and these aftermarket clear bowls around for a reasonable price, doing the dry set isn't going to get things fixed.

 

You wouldn't happen to have any links for those aftermarket bowls ,would you?

 

Let me see a pic of the drain screws as they currently are.
In hundreds of bowls, I’ve had a total of ONE that I couldn’t extract.

 

They're just hollow holes now (from drilling and attempting to use a scew extractor).

 

I found the dry setting was way out on my carbs, had to redo it several times to get the actual levels correct, I never understood why, but without doing the wet check I wouldn't have known. All my drain screws were seized, I failed with one and had to replace the bowl. You absolutely must wet check.

 

Need clarification... is the measurement taken from the lip (red) or the gasket surface (blue)? I've seen both answers given. When set to that gasket surface (blue) the floats are virtually parallel to the carb body (which I'm told is too flat) And it runs very rich (but it runs).

 

I've always used the blue, and the manuals I have looked at also say the blue.

I use a tool similar to this to check them.

 

If I used that tool, it wouldn't reach the blue. It'd hit the red.

 

It's tricky to get it to seat down in there, but it can be done if you angle it right. Alternately, just adjust the measurement by the height of the flange to compensate.

 

Just to confuse matters more, when wet setting the floats, the fuel level is measured from the flange, so the red arrow in your pic.

 

Sorry, didn't realize that pic got attached with my last message. That's the section from the manual explaining how to measure the float height dry. It's out of the 900 manual, but should be the same for all of them.

 

Okay, have them set to 17.5 mm from the gasket mating surface, and I've been trying for half an hour to get the bike to run. It'll only start from starting fluid, then it'll die out. It seems completely starved of fuel. And the only way I have ever been able to get it to run, is with the floats parallel to the carb body, but it ran VERY rich, and only got 15 mpg... but it ran and drove... I'm at a loss here.

 

I take that back... no sooner than I posted that, I hit the starter button, and she fired right up, and would only idle at 4,500 RPM'S... so I backed the idle screw all the way out, and the RPM'S didn't drop one bit... I may have to pull them again, and readjust the butterflies... again.

 

The idle screw isn't even touching the throttle. The choke isn't engaged at all. The floats are set at 17.5 mm, and the butterflies are completely closed... and it's still idling at 4,500 RPM'S.

DOES ANYBODY KNOW WHERE NEW CARBS CAN BE PURCHASED FOR THIS BIKE?

Absolute facts about restoring old vehicles:

1. NEVER install used parts. You're only buying the same problem or a new problem.

2. ALWAYS replace parts that have come to the end of their life, with BRAND NEW parts. Never rebuild old parts.

Any ideas? I've tried everything possible.

 

Well seeing this pic, your #2 and #3 throttle shaft ends are badly bent, so things are way out of whack right from this pic. There is no way to sync this properly the way it is.

Also, it looks like you are measuring float heights from the top of the gasket sealing ridge. You meant from the flat part at the BOTTOM of the ridge, not on top.

 

I had to bend them. When they were at the 90° angle they were supposed to be at, one butterfly was closed, the other was open about 3/16", and turning the screw only opened the already opened one even more (to about 3/8" while the other remained closed). Again, parts that have come to the end of their life HAVE to be REPLACED, not rebuilt.

However, after I bent them, I hooked the vacuum guage set up, and the carbs were all perfectly in sync.

This really isn't about fixing or rebuilding the dead. I need BRAND NEW.

Any sources for BRAND NEW?

 

This pic looks like a car crash, send them to someone who knows what they're doing....

 

Let me repeat: THESE HAVE REACHED THE END OF THEIR SERVICEABLE LIFE, THEY NEED TO BE REPLACED.

If you smash a window, sure, you can glue all of the pieces back together, but it'll never be right after that. You have to REPLACE the glass.

These parts are absolutely no different, at all.

I've restored (complete frame off restorations) cars, trucks, and motorcycles before, and have NEVER had an issue, because 1. I actually do know what I'm doing, and 2. When a part came to the end of it's serviceable life, I REPLACED the dead part with a BRAND NEW part. These carbs are DEAD. They HAVE to be REPLACED.

 

Did you remove the butterfly disks at any point? If so, when you put them back in, did you loosely seat the screws and then allow the throttle to fully close to push the disk in to alignment before tightening the screws? This is best done when the throttle shafts are not connected to each other. (i.e. no springs or screws) If you just drop in the disks and tighten the screws wherever they land, they can be misaligned which will cause all sorts of issues.

 

Yes, it was all done properly.

The issue isn't the quality of the work, it's the lack of replacement parts.

 

At start up, it'll idle, mildly erratically, then once you touch the throttle, the idle is all over the place. Usually high, and the only way to kick it back down, is to blip the choke, but then it won't want to idle enough to stay running until you blip the throttle again.Then it's right back to an erratic high idle.

I've sprayed starting fluid at the boots to check for a vacuum leak, but none are found.

 

It doesn't sound like it's running on all cylinders...........

 

It is, all 4 have spark and fuel.

Sometimes it runs completely smooth, then It'll start running as it is in the video.

It's very inconsistent.

 

I offered and it still stands. Cover the postage/shipping and any needed parts and they will return working correctly and set to the factory service manual. No mods, no excuses and no BS.

Mine have been working rock solid since... last year only opening them up to remove a chunk of junk that got caught in a needle & seat. Bike is a 750 SECA with over 46,000 miles on the dials and it's still very fast for its age even with a 225 pound rider.
Today was a bit challenging in that it was over 96F with a dewpoint in the high-60s. Carbs have #124 mains so it was running rich but still averaging 38 MPG on a 275 mile trip... my arms feel like they're glowing. Point to all this is once those "used" carbs are set correctly they tend to stay correct and don't drift off the mark, what you have there is the Yamaha equivalent of a train wreck that while salvageable is still going to be cheaper than finding a new set of Hitachi HSC32's which I'm not sure exist.

 

What kind of time frame? (How long will it take you?)

 

What do you have in mind? Reason I ask is I'm working as a project manager on a large move but I'd ballpark this to about 8-10 days as everything (and I mean everything) has to come apart and get checked out.

 

I'll DM you.