Carburetor: Are these backwards?

Hello xj'ers!

My ride is a 1981 xj650. Had some yahoo do some carb work on it claiming it needed to be cleaned and adjusted. Long story short he never fixed the problem so I hired a guy who was reputable. He tore the carbs apart and put everything back together. He said many of the Jets were installed in the wrong places and the sync was way off. Anyway, he got the bike to at least start. However, it's running super rich and blows out a decent amount of black smoke. It's rideable for about 2 minutes before it wants to stall out. It also acts weird when you give it gas. It kind of sputters until it hits a certain rpm then it's like turbo mode, then you switch gears and do it again till it eventually chokes out and dies. When I come to a stop I have to rev it up to keep it from choking too.

Anyway, the guy who got it to run told me that the mollywhopper who worked on it before super glued the diaphragms to the grove in the carb body and therefore he wasn't able to pull them out. I know what you're thinking, but let's stay with the question first:

The reputable mechanic told me that he's pretty sure the 2 jets below the tab, underneath the diaphragm are reversed. He also said the #1 carb seemed to be ok as it wasn't burning as hot. About 2 weeks after I got the news I finally sat down and chiseled 3 of the 4 diaphragms out with damaging them. Guess which one I wasn't able to get off? You got it, the #1 carb. So now I diaphragms out of 1, 2 and 3, but can't compare them to the carb that he thought was correct.

Here's my main question - can anyone tell by looking at the picture whether jet #50 and jet #195 are in the correct holes, or are they indeed reversed as the mechanic thought?

If they are correct, where would you look to next fix the problem?

And yes, the carbs need to be thoroughly cleaned before putting back together. You don't need to school me on that, I already know how important it is!



Thanks a ton guys!

 

I saw this answered in another thread. You or your mechanic will need to remove those brass plugs @ each carb without damaging the mixture screws that are directly under them.

Gary H.

 

Thanks for the advice, Gary!

 

if you can find the thread with the pictorial "Your carbs are naked you may be able to tell it ids the jets

the pilot AIR jet is on the engine side of the carb. both mikuni and hitachi

 

I'll check my notes tomorrow, but they just might be reversed.

I offer total carb rebuild services, too. You can easily see what I do, just read through some of the forums.

If you wish to talk, send me a conversation.

Dave Fox

 

^^^^
"They" say that no one will get your carbs as clean as yourself.
However, if I lost several fingers and couldn't do it myself I would send my carbs to Hogfiddles in a heartbeat.
Believe in the banjo on the moon!

When the banjo comes back to earth, does it shrink?

 

pilot air jet # 50 in front engine side of carb
main air jet #195 airbox side of carb

they are in correct position

 

No, but it weighs more

 

http://www.xj4ever.com/inside your carbs.pdf

 

No they are NOT in the correct position.

Large one goes to the front of the carbs, the smaller one goes in the middle. See example:

 

Thanks to everyone who replied! I do agree with Hogfiddles. According to the pictures, my jets are reversed. When I have time in the next few days I will switch the Jets and see what happens. As soon as I do, I'll be back to report my findings. Thanks again for all your help guys, and keep your fingers crossed for me!

Regards

 

Update:


OK guys, I was able to get all 4 diaphragms off and reversed the Jets to the correct positions. Yes, I also cleaned the carbs!


All 4 plugs were fouled to the point where the bike wouldn't even start. I took each one out, cleaned them and sanded just a little off the prong and the probe. Then I resembled everything and now...


It starts, but I'm getting lots of pretty rapid backfiring. Mostly from the exhaust but also from the carbs.


What could possibly be going on? I swear I've spent more hours working on this bike than any other project in my entire life and am to the point of nearly giving up on this thing.


The only other question I have is when I re-seeded the #50 and #195 air jets, I screwed them all the way down. Is that how I'm supposed to do it or do I need to turn them back a bit? If so, how much?

only other question I have is when I re-seeded the #50 and #195 air jets, I screwed them all the way down. Is that how I'm supposed to do it or do I need to turn them back a bit? If so, how much?


It almost seems like it ran better with the Jets in the wrong holes!


It almost seems like it ran better with the Jets in the wrong holrn them back a bit? If so, how much?


It almost seems like it ran better with the Jets in the wrong holes!

es!

most seems like it ran better with the Jets in the wrong holrn them back a bit? If so, how much?


It almost seems like it ran better with the Jets in the wrong holes!


Any ideas?

 

Sorry about the repeat in text. Not sure what happened there!

 

Yes, the jets should be bottomed out.

The backfiring - I believe it could be a symptom of out of spec valve clearances . . . Did you check the valve clearances?
http://xjbikes.com/forums/threads/airhead-valve-adjustment-with-pics.14827/

 

Your bike was dialed in with incorrectly located jets. Putting the jets in the correct location is causing problems. Re-set everything to the running synch start point. Dial it in from there.

Gary H.

 

In addition to valve clearances..... you bench sync? Running sync? What the condition of your air filter? Got a fuel filter? Drained, cleaned, dried the tank so there's no water? Air leak at the boots? Mixture screws way off? Etc...

My first two thoughts, in order, are:

1. Possible water in the tank
2. Not synced yet

After that, there's a lot that can cause it....

BUT-- if you haven't made sure valve shim clearances are in spec, you're gonna end up doing it all over again.....

 

Get some new plugs, too. Many times, when plugs get badly fouled, there's no "bring them back" to life.

 

It could be possible that water may have gotten into the carbs/engine since the pod filters have been off for a week or two and the bike has been outside, although covered by carport. I doubt it's actually gotten in the tank though. With all the hands that have been on the bike I tend to think it's a carb adjustment of some sort.

I also think Gary H could be on to something. If you're right Gary, what would you adjust first? Do most people fully seat the air/fuel mixture screws then turn them back approximately 2.5 turns and go from there? I've never messed with mine so that could be the/one of the culprits.

As far as valves, I've never messed with them either. I guess I could go to Napa and get some shims but the job in general seems a bit intimidating to be honest.

It's also worth mentioning that I do not have a colourtune tool but the last reputable guy who worked on it said he did bench sync it.

Let's assume it's a carb problem, unless someone strongly dissagrees. In order of likliehood, what are the first 3 things you would do?

Thanks again everyone for all your help and advice. Everyone's comments are greatly appreciated.

 

Valve shim check is NOT hard to do!!! Just read up on it.

Bench sync is only to get the bike to state that it will stay running long enough for you to do your running sync. If a running sync has never been done, of course it won't run well. If the valves have never been checked, of course they need to be.....

Yup, plugs could easily be a culprit too---

But you have stuff you must do first....

To set the mixture screws, you MUST turn them all the way down first..... You can't turn them out from bottom until you turn them down to the bottom to begin with. ( well, I guess someone could measure in thousandths down and turn only that far, but I would be done setting all four before you get done turn down just one if you tried to do that next to me.)

 

All the advice given are most of the answers you need. There are certain things that must be done to make it run right. Cutting corners will cause many headaches and frustration. Follow the advice given. We'll talk you through whatever help you need. Seriously, you've got this.

Gary H.