Carb trouble

bastard

 

HEY NOW, let's keep it nice eh?

 

was playin actually i got mine runnin today so yay

 

Haha well I guess you beat me. Did you fix your problem?

 

I spent a long time putting the carbs back on today. The boots were such a pain. I had my hopes up. Unfortunately, it still didnt run right. Here are the key points to this puzzle....

It did not idle erratic this time though. I was able to adjust the idle speed this time and was able to get it around 1500 rpms.

If I touched the throttle at all, it shot up to 5k rpms. Sometimes slow and than fast, other times just shot up. It seemed to be dependent on how much I would twist the throttle.

The thing I am seeing that might show a cause of the problem is the bike is backfiring. If I have the vacuum plugs off, I will see flames shooting out of those tubes on the intake boots. So apparently it of course isnt firing right. It is igniting outside of the cylinders, and I am pretty sure it is igniting in the exhaust pipes but I am not sure, I havent seen any flames come out the rear end. This seems to happen mainly on the 1 and 3 carbs, not too sure if it happens on the others.

I attached my manometer and vacuum is pretty close. The number 4 carb has to be allllll the way down to get it even, and that doesnt seem right.

What do you guys think?

 

What do you meen #4 has to be all down. Did you do the valves yet?

 

The synch screw for number 4 is all the way down. I havent done the valves yet, but it never had this problem before I took the carbs off.

 

Okay thats not right. Would you mind telling why you decided to work on carbs to begin with.

 

the bike would die, it would hesitate and always needed the choke to idle

 

First of all was there ever a time when you owned the bike it ran good for you?

 

You will need to check and set your valves before you can sync the carbs. Tight valves will throw off the vacuum and make any adjustment almost impossible. If you pull the carbs again at least do a bench sync first to get things close.

MN

 

Ya the bike has ran pretty good in the past, but I let it sit for a year or two.

Could a valve job be the cause of the bike racing up in rpms and backfiring?

 

I did do a bench sync though before I threw it on this time. When I checked the carbs with the manometer, the vacuum was pretty close. I wasnt able to synch the left side to the right side.

Im not sure if it really makes a difference though since it was doing this before when I first put the carbs back on. At that time I had not messed with the synch screws at all.

 

Oh ya, if I had all of the vacuum plugs off the ports on the intake boots, what might this do?

 

it would suck unwanted air str8 into that cylinder causing the problem you are having

 

+1....the vacuum plugs need to be on! The ports should ALWAYS be covered with something, either a plug or a gauge.

 

Ah, next time I do it, I will make sure the plugs are on. But I still dont think that is the cause of the problem

 

Kinda sounds like you have the air jets in wrong not the fuel jets the air jets easy to do. pop the caps off take a gander. let us know Happy Thansgiving

 

One more thing its a machine. No matter what the engine cannot run any better than the worse performing cylinder it cant. So in order to get the best from it you have do all you can to get it right. Do a compression check on a stone cold engine throttle wide open , adjust the valves easy to do, Test the coils and caps do a visual on the coils if there are cracks spark will jump to the frame, keep records it will make it easier the next time and give you something for comparison in the future. Bench sync and install new plugs after a carb job you cant tune on fouled plugs use fresh fuel with no additives in it. If you have to turn the adjustment screws a lot then something is way wrong. The biggest thing to remember is, NO MATTER WHAT THE PREVIOUS OWNER TOLD YOU ABOUT THE BIKE CHECK IT and 99 times out of one hundred the last thing you did to the bike is probably whats wrong with it right now.

 

Put a full charge on the battery before and during tuning

 

Hm... I am pretty sure the air jets are not in wrong. I made sure of that when I was putting them in. I could double check and make sure.

Before I took it off, it ran, idled fan, even ran with it for a bit. Then after awhile it would die. I found a couple of slides were sticking but now they are all polished up. I have found a few forums on here stating they are having the same problem but they only lead into a dead end and no one states how or if it was fixed. Im going to check what I can tomorrow, might pull them off again if I cant figure something out.

 

IN ORDER:

-valve clearance check/adjust.
-compression test.
-bench sync carbs, set mixture screws at 2 1/2 turns out.
-verify float levels using fuel and clear tube method.
-check intake manifolds for cracks while carbs off, from the inside.
-carbs back on bike, do running vacuum sync.
-throw in a new or clean set of plugs.
-ColorTune and/or plug reading to fine tune mixtures.

Leave anything out? Skip any? Then go back and do them in order, or you will be at it for a while. The reason a lot of threads die out is because people consider things like a valve adjustment or a compression test beyond them or too much hassle so they give up. If they can't get an "easy" answer that works, the bike ends up on CL.

Sometimes there is no quick/easy answer.

 

RAVEN !!!! no my man why are you still working on that thing?? you gotta get your valves adjusted man! didnt i tell you i had a butterly hanging open cause of a bad sync? mine did the idle thing befor i did the paperclip sync and im running perfect man. i know what your problem is that #4 is so wide open it is hanging up when you mess with the throttle just like my bike did. it was funny cause it would only mess up if i gave the bike more than a 1/4 throttle listen to these guys and do the checklist big fitz gave you, im telling you man get those valves adjusted and that #4 will sync like it should and you will be all set. pm me if yo uneed shims if your lucky i might have the sizes you need

 

I did bench synch it. I might try to tinker with it for a bit until I find the time to take a look at the valves.

Can anyone explain to me why exactly the valves could be a problem? I am in desperate need of education for the valves haha.

 

Before I took it off, it ran, idled fan, even ran with it for a bit. Then after awhile it would die.[/quote]
Sound s like your original problem was you were running out of fuel / weak charging system: fuel cock/ filter clogged both? weak charging system corroded wire worn brushes old battery. Different things can cause an engine to run poorly such as leaking valves. Leaking intake valve would let pressure and flame blow back to carb leaking exhaust valve would let unburned fuel mixture enter exhaust system Martha would say its not a good thing.

 

If you don't understand the principles of an internal combustion engine you'll need to do alot of reading to understand how it works.
Just know what the adjustments are and that once they are set properly it should work.
Follow what Fitz said and you'll be fine

For your reading pleasure www.howstuffworks.com/engine.htm

 

Are the carbs you are working on the same ones you posted pics of in a different thread?

 

Yes, they are the same carbs

 

Have tried doin the bench sync then mess with the throttle? Try that don't even do the vac sync then maybe you won't have the hang up problem. If it revs fine and idles back down then your gonna need to set those valves

 

I have done that. I think when it races up it does go down if you give it a second or two. I still kind of suspicious of the carbs being the problem. Ive never had this problem before, and the only human factor involved was me taking the carbs off. It almost seems as if it is getting way too much gas, and Im pretty sure it is.

On Fitz's tutorial, he shows a tool that locks the cam lobe in place. Anyone know where to get one and for how much?

 

It does not lock the cam lobe, it is a bucket holding tool. When the valve is pushed all the way down by the cam you bolt the tool to one of the valve cover bolt holes. Then you turn the engine back so the cam lobe is up so you can pry the shim out. chacal has them or I got mine from Pitboss.com

MN

 

have you checked the throttle shafts for and air leak. mine is doing the same thing my valves are within specs. intake boots are fine but the shaft seals are leaking. do the propane test and see it they are leaking.

 

I agree with Hardlucktx. I think you may have a vacuum leak. Make sure when you propane test that you idle is as low as you can get it to run. when the air leak sucks the propane in the idle will pick up a few hundred RPMs.

MN

 

how do you do a propane test?

 

warm the bike up.Then at idle take an unlit propane torch and hold it at the end of each throttle shaft. If you get a rise in RPMs then that shaft is leaking.

 

*UPDATE*

Today I went and got new plugs for the vacuum ports. I plugged each one and started the bike. It always starts right up now and did get a single backfire, but it immediately it races up to 5K rpms. This time I let it go to see what would happen and it just runs up there and stays there. I tinkered around with everything, adjusting fuel-air, bottoming out all synch screws. I was just trying to see if any difference occurred. I also unhooked the throttle cable completely from the linkage. Nothing changed. It keeps running up to that high idle. I have pretty much adjusted the idle knob all the way until it feels like it is going to fall off. No difference.

The last thing I did before I called it a day was try pushing down on the throttle linkage with a flat blade. The idle dropped down to about 2500, I dont know if it would go down anymore, I dont like using excessive force on things. So now I am thinking maybe something is bent in the linkage or something I am not sure of to keep to more open than it should be.

I do not think its a vacuum link, or even the valves. The bike ran before I took the carbs off and never did any of this. So I am inclined to think that I did something wrong with the carbs. Any suggestions?

 

Even with the Main idle knob/screw all the way out this would only insure that #3 carb butterfly is closed the other three could be open quite a bit more. When the butterfly is opened just a touch more than completely closed the pilot jet /needle screw has no effect on the engine because it is being bypassed thats those little tiny holes you see when you look inside at the top of the throttle bore. If you pull the carbs and take some pics maybe someone can point out whats wrong

 

http://www.xjbikes.com/Forums/viewtopic/t=28613.html

Here is the forum to my build process

So essentially it could be way out of synch? I tried messing with the synch screws, but nothing happened. I have also done a bench and manometer synch with no difference.

 

Have you done ALL of the above steps including the compression test after the valve adjustment?

How about the float levels?

Here's the issue: Like you said, you "probably screwed something up in the carbs."

OR NOT.

But what you DID do was lose all of the previous adjustments, and the adjustments in these carbs are FINE, MINUTE differences. That's a normal part of servicing carbs, all of your adjustments are reset "to zero" as it were.

You now need to RE-ADJUST the carbs. However, if your valves aren't in spec achieving that adjustment is going to be next to impossible.
I gave you a checklist; I also said "do them in order, or you will be at it for a while."

But you haven't gone through the checklist, in order, and you're still hammering on it. No surprise. If you keep "messing with" things (your words) out of order, you're still not going to get it solved.

You don't have "carb trouble" you have "methodology trouble." http://xjbikes.com/Forums/viewtopic/t=24010.html

'nuff said.

 

What Fitz said ^^ .....3 weeks, 6 pages and no joy...METHOD, not fiddle with this fiddle with that, will get it running purrfectly. If you'll pardon my bluntness..

 

Ok Raven,

So you got some new vacuum plugs, and your playing with the sync scews with no vacuum gauge. STOP MESSING AROUND, YOU NEED TO START OVER.
Follow what Fitz says.

MN

 

Did you do another bench sync after you plugged the ports? What are you using to sync?

Allow me to second what fitz says with a little more elaboration.

You don't need the bucket tool to check the valve clearances. Just take the valve cover off (12 6mm hex bolts), get a feeler gauge (cheap at your local auto parts store, make sure the smallest one is smaller than what the clearance needs to be), and make a list of the clearances. Post them here.

If you do find that some are out of tolerance, you can use a thick zip-tie, bent to a L shape, to hold down the valve from inside the cylinder. Still no expensive tool.

You can borrow a compression tester from the autoparts store too.

You messed with your floats, I saw your post. Make sure they are set right, do it again...we all make mistakes.

Bench syncing requires a screwdriver and a 3x5 card cut in 1/4 in strips....not hard to do. Match 1, 2, and 4 to how open 3 is. It's a bench sync, it's not gonna be perfect, you just have to make sure you can get it running enough to adjust it to perfect once it's running.

Check your plugs, if you really are getting too much fuel, your plugs will be very dark. You don't need to guess about these things. I'm willing to bet good money that your plugs are light, if not white.

Turn your screws to 3 turns out. Don't touch them until you are ready to tune. Your bike should run fine at this setting for a little while. Not perfect, but fine.

Now....i'm willing to bet this is your problem. You need to sync, but first you need to bench sync b/c you messed it all up while messing with it. You have to do all those other things above now for the same reason, but once you sync properly your butterflys will *close* at idle, not be left halfway open like they are now, as shown by your ability to close them from idle by pushing down on the throttle. Look at your plugs, they are white because you're running with open butterflys (bottoming out the sync screws) and closed pilot screws. Nothing changed when you did these things because you were making the existing problem worse, not better.

Your situation is not new, or unique. Just listen to those who have done this a hundred times before.

One more thing...don't tell bigfitz I told you this, but if you follow my post here just from the "bench sync" part, you will probably get it running. It is unlikely that your valve clearance and compression changed since you had it running last, and your float level don't make that much of a difference at idle. Not that you don't need to check those things, but I understand that time is money and limited resources need to be budgeted.

 

Fitz saw it anyway.

And that's mostly true; however if one cylinder currently has a way-out-of-spec valve, it's going to make the vac sync a major headache.

The carbs WERE adjusted ok, so that one valve slowly dropping out of spec over time wouldn't have caused any major issues, just made the bike start to run a little poopy.

However, NOW the carbs are out of adjustment, and readjusting is necessary. But that won't be possible on an out-of-spec pot; and there's no way to get back to where it WAS.

And since the adjustment of the carbs depends on adjusting them to each other, 1-2 then that pair to 3 and 4-3, one out of whack is gong to throw the whole thing off because like I said you have no way to get back to where it once was.

A quick compression test will give you a heads-up on an out-of-spec valve; do a compression test. If they all match, valves probably ok. If you have one or two "soft" cylinders, then a valve check and possible adjust is in order BEFORE you'll be able to get a good sync.

It's just physics.

Like I said before; this process is up to you. DO IT ALL, IN ORDER, and be done. But skip steps or get them out of order and you will be at it for a while. And that is exactly what is happening.

I don't just make stuff up to make life difficult, and I'm not a resto-Nazi. I've been through this; it's frustrating as hell if you try to shortcut the blasted sequence. DO IT ALL, IN ORDER, or keep beating your head against the wall.

 

I knew you would! You don't skip the details. That's why your bikes run so well.

 

It would be nice if you could post some pics of the carbs when you take them off to bench sync if you can. View of throttle bores, sync screws, slides

 

Lol a resto-nazi.

Well I will take them off today, take pictures of everything and start over from there. I will give it one last shot at fixing the carbs, I hate starting to work on something and than stopping in the middle to work on something else. I guess I have to look at the big picture though. The next thing on my list has been a valve job, I knew that when I took the carbs off.

Also, I am pretty sure it is running rich, the carbs were black last time I checked. But I do not think it checked it all too recently.

 

raven, thats gonna be your best bet, i really do think correcting #4 cylinders gonna help out alot then you can be sure your getting the right sync, even though you said you already ran it on a bench sync alone and no improvement?? :cry: :lol: did you try thr propane thing yet? im sure its ok to use carb cleaner too, unless im mistaken then you can know for SURE you dont have any intake leaks. you said carbs were black? where? did you mean spark plugs? im gonna remove mine and put new properly gapped ones in mine just for shits and giggles. we are waiting for you pics

 

That's not a "valve job." A valve job involves pulling the head and refurbishing the valves, guides, seals, etc.

You just need to do a simple valve ADJUSTMENT, a normal part of the maintenance procedures. http://xjbikes.com/Forums/viewtopic/t=14827.html

And if you've got black plugs, you really need to be looking at your float levels before putting the rack back on too. Don't skip over the float levels and end up pulling the rack AGAIN when it still won't run right.

Plus we need the results of the post valve-adjustment compression test, to be sure there isn't another underlying issue.

BEFORE trying to adjust the carbs. As a matter of fact, doing a compression test with the carbs off makes it even easier and more accurate. (Remember to unplug your TCI.)

I'm gonna say this once more, then I give up: JUST GO BACK AND DO EVERYTHING, IN ORDER, AND BE DONE WITH IT.

 

this advice from fitz is just phenomenal. thanks for all your support fitz, it goes a long way for others with not as much experience

 

Fitz, I will probably see about doing a compression test tomorrow or Monday. Will this work for me?

http://www.harborfreight.com/flex-drive ... 92697.html

Also, what should the normal range be for a cylinder?

I really do appreciate your help Fitz, I am sure I will be able to get it running.


Oh I did think of something today, before when the bike was initially doing this, I did not have the carbs attached to the air box. The second time I tried, I had the vacuum plugs off. It would idle, but if I hit the throttle it raced up rpms and would come down have a second or two of lingering there. After taking a look at it, it is possible that the throttle blades were being a problem and sticking. I did take them off again after messing with the synch screws. So it is possible for it to be completely out of synch now. Then again.... I did close every synch screw, and it was still racing.