Enrichment problem! (Choke = runs on one)

[Tombo]

So I've been putting time into my 1980 special model - I pulled the carbs and found the floats to be set WAY too low - which is probably why my bike had been running like shit.

While I was there, I went ahead and cleaned all the jets - and the PO, though she never got it running, did a GREAT job cleaning it (not so much work for me).

I only had enough time to take them down, clean em up, set the float levels, and button her up before bed time last night - and DMV time came this morning - so I didn't get a chance to balance carbs or set the mixture. (nor did I "wet set" the floats, or even measure using clear tube method yet)

The bike runs infinitely better - good solid idle, good even acceleration, good throttle-down response from the motor, etc.

But the STRANGE thing, is that the bike will only run on one cylinder when in choke.

Any ideas? My guesses would be some type of air leak in the enrichment circuit - perhaps one of the rubber sleaves is cracked or something, so it isn't drawing gas. (btw, I know it's not drawing gas, because when I first got it running poorly pre-float level adjustment, the same cylinder wasn't firing, and was spritzing gas that would drip out of a small hole at the header/muffler juncture). The bike, like I said, runs awesome - and once I have it started, I just switch the choke off, and let it warm up at normal idle speed (which kicks the other cylinder into gear!)

Tomorrow before work, I will wet check and/or wet set the floats, adjust mix screws with COLORTUNE and sync carbs, and if I have time, go and get me a set of bent feelers (or bend the feelers I have in favor of buying a new set for my XJ).

 

[HoughMade]

The floats should be set to 26mm if you set them to 32mm as the manual says, that is not right. Running on one cylinder at idle is a classic dirt in the idle-circuit issue. You may be able to narrow yours down to dirt in the enrichment circuit, but until you set the idle mixture, there's no way to tell. The reason why it runs on the other cylinder after warming up is that I would imagine it's drawing though the main jet.

 

[Tombo]

*Just as my manual says in the revisions section, I adjusted floats to 26.5mm
*If you re-read my entry, you'll see that I said it ones on one cylinder in CHOKE (not during warm up). In other words, If I take it off of choke, then even while still cold, the other cylinder kicks in.
*I'm not POSITIVE, but I am pretty damned sure all the jets are real clean.

Update to previous thread - I did the "propane test" on my carb holders - and the right side holder seems to have a bit of a leak. I will be ordering new ones. But even with that - both cylinders fire (Looking through my colortune plug) - but from time to time, I noticed that the cylinder in question will "skip".

Once I get my holders in, I will do one more pass at the carbs.

 

[Tombo]

I did a valve adjustment this morning - they had been too tight to get a .003 in there - in the 9k of this bikes life, not sure they ever adjusted them! (btw, the rocker sound was practically silent before I put them in spec - now I know what ya'll are talking about )

But now that I think about it - when I was balancing the carbs afterwards, I noted a MUCH higher vacuum reading than before - nearly to the top of my Carbtune pro's reading. I had attempted to balance the carbs a few days ago, and the reading was more towards the center of the reader. What does this mean!?

 

[16VGTIDave]

Higher vacuum = running stronger! Well done!

Dave

 

[arfstrom]

Update to previous thread - I did the "propane test" on my carb holders - and the right side holder seems to have a bit of a leak. I will be ordering new ones. But even with that - both cylinders fire (Looking through my colortune plug) - but from time to time, I noticed that the cylinder in question will "skip".

Once I get my holders in, I will do one more pass at the carbs.

I have wrapped my intakes in that vinyl tape, that can handle temps to 500 degrees. and wrapped both my intakes with it. I did not prove that I had a hole in my intake holder. there is dry rot, so I just wrapped it. FUBAR posted a good solution for $64. made with aircraft rubber, then he also purchased a diaphram too.

http://jbmindustries.com/Yamaha650.html

Go here, and check things out. here is the thread, http://www.xs400.com/forum/showthread.php?t=8398
I still think that the enricheing passenges are fowled, based that its just when the clutch is pull, and its the only side. (I have been wrong before) Still needs cleaning. give it a shot.
Tobie

 

[Tombo]

Tobie - it is when the CHOKE is ON when i get running on one cylinder. Realistically, it can really only be a dirtiness problem - so I will probably have another look when I have them apart.

I have carb holders from mikesxs coming in, they are $48 for the pair. I like the idea of a replacement diaphragm though! A good lower priced option.

 

[arfstrom]

http://www.xs400.com/forum/showthread.php?t=8645

I found this guy had the same problem. I knew it wasn't the first time I read that symptoms. This is what he did to fix it.

 

[XSLeo]

If those carb holders are made the same as the ones for the XS650, then they won't last long. The alcohol in gas eats the rubber fron the inside. The JBM's are a much better product.
Leo

 

[Tombo]

Update on this - with the current set up, I've put probably 200 miles on the bike getting something like 55mpg. Starts first or second kick on half enrichment, and warms up normally. Good solid performer - I have it just about redline on in 6th, which was a "pinned needle" for the stock speedo. I would say it runs pretty good, but not perfect - idle is very strong, same with lower revs. If I open her past 3/4, super smooth acceleration.

The 1/4 to 3/4 on the throttle is a little jumpy/jerky, so I assume it is running a bit lean in that area. I've heard that lifting the needle is a good route to go here - but before I do that, I have JBM diaphrams on the way - I want to try those first.

Still runs on one cylinder on full enrichment. While I have the carbs off for the diaphragm install, I am going to soak the bare bodies in my carb dip, and then take the compressor to the enrichment circuit. Up until this point, I have seen marked improvements on the performance of the jets from using just the spray berryman's - but I want to see if I can't get this full enrichment issue taken care of. Here in foggy San Francisco, it is generally mild, but want to be prepared for the cold if necessary.

 

[kevingkruse]

@arfstrom
I never completely fixed my problem. I cleaned my carbs a couple more times, boiled and sprayed, it seamed to help a little. It doesn't completely die with full choke anymore but when I do pull the choke all the way out, it gives a strong hesitation, where it almost wants to die, then it slowly catches back up to around ~3/4k, half choke goes up to the same ~3/4k but it doesn't give that hesitation when I pull it out to half. I'm wondering if I should buy new choke plungers and dust seals but who know, maybe its still a little dirty, very hard to tell. But I'm not sure if I ever had that problem with the cylinder not firing with the choke out, never looked for that, id probly notice though.

Hope you find your problem though.

 

[arfstrom]

I am Lucky, I think now I can get away with a an Italian tune up. http://www.dictionarydb.com/Italian tuneup
You might be there too. I know I have accidentally forgotten to take the choke off the the middle notch. I drove it a few miles. I guess I hope it just makes that passage cleaner.

When I finally put it together, (Prior to it running) I was getting a lot of backfiring. When I went though the bowl another time, I found a piece of paper towel in one of the holes. So that was a day prior to me realizing I had a hole in my float.

I just checked PowerSportsPlus, and the choke stuff, Items 14 though 17 are all on the obsolete. meaning that there is no inventory. (except eBay) I suspect those items you have are just fine. Perhaps Drewpy can opt in on this conjuncture? Since your lucky enough have a nice winter, You can do more Italian Tune-Ups. the whole 1/4 to 3/4 thing I have no Idea. I know I have seen postings that explain which passenges are used for certain amount off power (for lack of better wording) The amount of carburations at lower gears/WOT wide Open Throttle. My bike at WOT is usually about 75 mph, with an apparent max at 80 ish. I suspect if I would hold in place long, and not worry about the local county mounties the RPM speed is 7500 or so, and it seems to want to continue to build momentum. I still haven't adjusted my left jet, so the left side is running rich, and I only get 44 mpgs. The only weird thing I feel moving up and down the gearing is the Clutch gears sometimes take a moment or two to settle. before I realize I am fully in gear. perhaps that means I not backing off the throttle like I should, or I really do have to replace the Clutch/springs. (on my list for this winter). (I have upgrade to a 17T drive sprocket, which allows the throttle to be 400 RPMs lower than MPH reading)

Thanks for letting me ruminate.

 

[Tombo]

Arfstrom -

The top speed of these bikes should be around 88mph. Even with my bike running "ok" and "not great" as I described, I easily redline 5th gear, and seem to be getting the max speed that most people report here.

If you are idling ok, and get that type of speed, you are probably 90% there - but if you aren't able to redline 5th, I would think it's either a weight i thing (which I weigh about 210 fully dressed with riding gear), Or you might need the 1/4-3/4 adjustment I'm talking about.

The needle jet (not sure that's the nomenclature) IS your 1/4 to 3/4 adjustment. It is controlled by the slide, which in turn is controlled by the diaphragm.

Not knowing the history on the carbs, your diaphragms (like mine) COULD have been exposed to carb cleaner - which acts to make the diaphragm rubber expand - which would cause a lean problem.

Even if they were in awesome shape, these carbs said to be "factory lean" - and so "raising the needle" is sometimes needed in order to richen the mixture at the mid revs/ mid throttle.

I will report back here after I get my JBM diaphragms installed - but based on my research, I think that this might solve my problem, and would undoubtedly improve any system with the original diaphragms (rubber ages.)

-Happy tuning, and I'll report back!

 

[arfstrom]

I think I might be ordering both the JBM diaphragms/Carb holders from there, as well as New clutch this winter. Its winter time here, temps have dropped to 30 degrees F to 40 as the highs. I have made the bike easy for me to start working on her, during the winter months. The seat and the fuel tank are off. and soon I will have made my order, probably to powersportsPlus. Soo Next summer will be awesome! (as a 400 can be )

 

[XSLeo]

Tombo, on dipping the carbs, you need to remove the throttle plates and shafts to remove the throttle sahft seals before dipping, the carb dip will eat those seals.
arfstrom, raising the needle will richen the mix in the 1/4 to 3/4 range. I might make sure all the other jets and passaages are clean first.
Leo

 

[kevingkruse]

So I have been closely listening to my bike as I start it up, and I think it is also only running on 1 cylinder upon warming up with the choke. I'm guessing that because it takes a minute or 2 for the idle to slowly go up and up is that the not firing cylinder is firing here and there, then more and more, until it shoots up really quick to like 5k rpms, when it does that, I know its warm. I never thought it wasn't firing one one cylinder, just that the idle was getting higher on both cylinders. Tombo, does your dead cylinder start to come back to like after a little with the choke on?

 

[Tombo]

Kevingkruse - it sounds like we are sharing a similar problem. However, Since my bike will start up pretty much fine in half choke, I just do that, and haven't waited to see if the other cylinder will kick in on full enrichment. Perhaps I will try that just to see - but I don't think that it's supposed to be that way - plus it seems like letting it run on one cylinder is bad for the bike (thought that is only a guess).

Perhaps you should quickly touch both pipes while it's warming up, and see whether it is truly running on one during warm up. You'll know, because one will be cold. If it is, then keep your eyes here - I will be getting down to the bottom of this one way or another.

 

[arfstrom]

I don't know If I mentioned it here yet, one of the best advise I got early on was to just to unplug one of the Plugs. if it continues to run, your fine, then test the other side. to double verifiy the system operation. Then that saves on touching hot pipes. hope you both luck. Tobie

 

[drewpy]

I don't know If I mentioned it here yet, one of the best advise I got early on was to just to unplug one of the Plugs. if it continues to run, your fine, then test the other side. to double verifiy the system operation. Then that saves on touching hot pipes. hope you both luck. Tobie

the tci does not like that idea and may sulk and refuse to work that side again!

 

[arfstrom]

Those overly too Smart electronic parts, Making us have to think, of a right way to make sure our stuff is working.