Straight pipes, no idle?

I cleaned the carbs, set everything right and my bike ran great. I took the mufflers off(after the h pipe) and now it won't idle and barely wants to start. To start it I have to open the throttle a bit then about 3 seconds after I close it, it stalls. I don't suspect the carbs being dirty because it ran fine before and the carbs are synced. I also don't suspect a vacuum leak because again, it ran fine before. I tried adjusting the mixture screws. They are about 2 1/2 turns out and that's where I'm at now. 2 1/2 turns out, 3 second idle then stall. What do I do now?

 

You have no back pressure , why did you pull mufflers anyway? I would either get new mufflers or put the old ones back on , lot better than having to synch and mess with the carbs , I should have asked are you running dreaded PODS this and no back pressure can cause all sorts of issues with the carbs , might have to go up on the jet size and experiment ( READ why I hate Pods ..flat spots ) When you say you "cleaned carbs" did you take them to church FULL tear down breaking the rack soak carb bodies and replaced shaft seals ? Spray cleaner will not cut it will not get into the small passages. If you have not read it yet go to xj4ever church of clean this will save you a lot of trouble , Len at xj4ever has the butterfly shaft seals to replace you have to break the rack . The carbs kits on eBay DO Not have these seals. I did my carbs the right way to them to church and got religious with them , have not touched them since ...Good Luck this was just my thoughts .

 

I have the stock air box on. I pulled the mufflers because they made my bike sound like George Jetsons "car" lol. And I wanted it a bit louder. So adjusting the idle mixture screws won't fix the problem?

 

These 4 cylinders are supposed to sound like George Jetson's car. If you want loud, get a 2 cylinder

Not trying to be sassy or disrespectful to you, but the quiet is what I like about the XJ's.

 

...........

 

Back pressure: The myth and why it's wrong.

"One of the most misunderstood concepts in exhaust theory is back pressure. People talk about it with no real understanding of what it is and what it's consequences are."

Link to a good article regarding exhaust. I have built many a custom exhaust in my proffessional career but this article explains much more simply than I could here.

Put simply an exhaust on a 4 stroke engine should have zero backpressure. Any pressure build up reduces the engines efficiency.

http://www.gomog.com/allmorgan/exhaustbackpressure.html

 

Did you fit an inline fuel filter after cleaning the carbs?

And just what do you mean by cleaned?
Did you break the rack and fully disassmble the carbs?
Throttle shaft seals were replaced?

 

I did fit an inline fuel filter. And by cleaned I mean I took the bowls and everything in them out. Got some cleaner and blew air threw all the holes. Did not replace any parts. What I'm not understanding here is it ran fine before I took the mufflers off. So I suspect it has to do with that. The only problem is it doesn't idle. If I hold the throttle open I can still put it in great and ride it. But as soon as I close the throttle is putts then stalls.

 

You probably dislodged some crap when you kind-of-cleaned the carbs, and now you have plugged passages.

Do the full Monty.
IN THE CHURCH OF CLEAN

 

So again it ran fine before I took the mufflers off. And all 4 passages/carbs are clogged?that doesn't seem likely

 

you can run the bike with exhaust completly removed and it will idle

 

It doesn't seem likely because your example is a bit ridiculous.

Even if you dislodged some crap in ONE carb (seem more likely?), you could lose your idle. Problem is you don't know if it's cylinder 1, 2, 3, 4, or 1 & 3, or 2 &3....

These aren't the carbs from 4 wheeled vehicles. Hell, even the tiny old VW Beetle carbs I rebuilt seem simple in comparison because they are a much bigger unit with much bigger passages, and much bigger tolerances. You seriously can't skip steps here. Excuses won't make your bike idle again.

 

You take the rack back off, get the deluxe rebuild kit from XJ4EVER, go to Church (wet set float levels). Bench synch, colortune, running synch. (I repeat the last two steps).

Put the mufflers back on, and report back with the idle performance.

 

are you starting it with the choke?

 

If you wonder why everyone is pushing you to get back into the carbs? If you have not taken them to church and really cleaned them, you are more or less just waiting for a fuel issue. I cleaned them more then 0ne time and can tell you that if you have not broken them down and cleaned them like the "Church" shows you, well then you too will be cleaning them several times. It is just many of us tried to get around the carbs cleaning bit, there is just no getting around it if you want your bike to run correctly.

Good luck and keep us updated.

 

The original mufflers are very free blowing to begin with, and there's virtually no back pressure to begin with.

 

If you have done the carbs Completely,
Including shaft seals then it will idle with no exhaust system at all. Sounds like an automatic pop gun.

 

So what I did today was I warmed up the bike, took the tank off and got a bottle with a hose and hooked it up for gas. Started the bike and as it was running I adjusted the mixture screws. Got it going good at around 2500rpm went to lower the idle and it got screwed up again. Went back to the mixture screws and idle adjustment screw. Back and for for about 45 minutes. I was getting frustrated because I couldn't get it to run as good as before. Got it better then when I started the thread but not as good as before. So I shut the engine off, took the bottle off and put the tank back on. Before putting it back in the garage I said what the hell and started her up again and poof ran at 2500rpm adjusted the idle screw, got it down to about 1050-1100 no choke. Ran just about as good as before. Needles to say, my newb self is a bit confused.

 

did you remember to plug the vac hose when you used the bottle?

 

You forget to plug the vacuum hose to your fuel valve while running on the bottle?

 

Great minds think alike but fools never differ

 

I don't plug the hose---I remove it and connect the Morgan Carbtune Pro to all four vacuum ports

 

I don't use a vacuum petcock. It's plugged at the carb boot.

 

What tools did you use as you ping - ponged back and forth between synch and mixture screws?

 

Just a screw driver?

 

Oops.

You have to get some kind of reference so you can see what the changes you make are doing.

The bare minimum for mixture is a good set of ears (idle drop method for mixture), and a vacuum gauge (for synchronzing)

 

Well technically that is the correct answer. . . .

But yeah, like Kmoe said.
For me personally I use a colortune and 2 bottle manometer plus the screwdriver. I do listen but can not discern the happy spot compared to the measuring tools feedback. I imagin if one dos the task often enough you can hear when it is dialed in.