Running/idling problems, backfiring...old gas?

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Bonsai

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I picked up a bobbed 1982 xs650 a few days ago. Spent the first day or so learning the shifting idiosncrasies these bike apparently have and it seemed to run smoothly. Only issue is the neutral issue and the starter is beginning to wind out.

Here is where I think I screwed up. At the end of my shake out run the other night I threw some gas in it from a gas can and put her away for the night. Went to start it last night to ride it to a meeitng and it was very reluctant- sputtering and backfiring, dying on idle.

Old gas....

SO... get up this morning, drain the gas tank and refill with fresh gas. Start it up- pretty much the same thing, maybe not quite as bad- finally get it to idle without having to keep on the throttle. Hear the occasional backfire out the right pipe and a "burping" sound that I think is on the right side. There is a rare backfire through the carb. Everytime I put it in gear it quits unless I really lay on the throttle.

Managed to take it up the block and back but it kept stalling whenever I stopped.

I know nothing about this bike- apparently "stock" motor but has pod filters and drags... the builder is in the military so I don't have ready access to info but apparently he is pretty competent around bikes and it seemed fine the other day.

I put it on the battery charger. Is this something that will work itself out? What else can be going on? Trashed the carbs? Clogged fuel filter?

Thanks in advance!
 
old gas loses the most volatile elements first, so the octane rating goes way down to the point where you're running pretty much on kerosene.

It's not going to do what you expect, it'll diesel and worse. I recommend flushing the floatbowls and tossing in some seafoam for good measure.

unless the gas you put in was polluted, you're probably ok.

One thing that CAN happen though, is that dried, varnished crud from the float bowls can dissolve and float into the jets, clogging them. Did that on a bike once and had to replace the needle jets on everything. there was a cloudy yellowish film on the bottom of all of the float bowls that had softened up overnight on me and started leaving bits in my go juice.
 
That happened to me and I lived with it for a year. Just replaced the pipe gaskets and tightened up the carb seals (think there was an air leak). And it runs like a champ
 
also of course you want to shoot the carb boots with carb cleaner while it's running and see if the idle changes. also check your vacuum diaphram lines and vacuum diaphrams
 
The first thing I'd do is learn how the carbs come off.
Second learn what all the bits and pieces are in those carbs.
It sounds to me like the pilot circuit is stuffed and not flowing.
Running very lean.
And there ain't no magic bullet fer it.
If you don't want to or aren't able to clean them yourself there are several on the board who supply that service. Check the shop and classified sections.
Next to the tank. How bad is it? It will have some crud in it gar on teed.
Maybe just a rinse with the petcock off will do it.
Might as well inspect the petcock operation while at it.
You can find reference articles and pictures in the tech section.
Welcome to the site and good luck!
 
The tank is fairly clean- its a peanut tank not stock...

There was a trickle out of the line when I drained it. Not a gush- prolly took 20 minutes to drain a gallon-to a gallon and half.

I watched it idle - it has clear fuel lines and did not see fuel flowing even when I hit the throttle. Not sure that means anything because it does not seem to be starved for fuel.

Any value in pulling the plugs?

I've cleaned carbs before - harleys and hondas... so this will be new but not alien.
 
Before you do any of those other things don't overlook draining the float bowls completely. Very good advice everyone but don't forget the obvious, it was fine the other day he dumped in some bad fuel and now its not ...
 
check your plugs. They're probably fouled.

it sounds to me like *perhaps* the PO (and i'm making assumptions here) put on pods and shorties then said "better go up to ridiculously large jets now that i'm moving more air" - which you're actually not.

Take the carbs apart, clean them, check the jet sizing and put everything back to stock if it isn't. Check float level ("i'll raise the float level cause that will give me more fuel!" :facepalm:) and generally everything. go back to stock settings (the only exception to this is if you have the 'mercan needles/needle jets for your bs34's - get the cdn ones. Which isn't really an exception, since they're still stock) and then figure it out from there.

And quite frankly, you'll probably be quite happy with everything stock.
 
Checked out my set up before church - Mikuni KOGYO with pod filters - "red" media and chrome XS covers.

I assume these are the less desirable ones from Mike's XS that I'm reading about?
 
www.amckayltd.com/carbguide.pdf Read this, print it out read it till you see it in your dreams.
On your pod filters, if there is a lip around the inside where it goes on the carb, this lip can block off the ports in the carb bell. You can trim off the lip where it blocks the ports.
Leo
 
Right plug black and smells of gas. Left plug somewhat black but contact is brownish... haven't had time to look up the diagnosis chart but it's pretty straight forward.

Started okay and went to idle fairly quickly without having to throttle it much.

Sprayed starter fluid around all the boots on the right hand side with no change. The boots to the motor look old- have cracks - but appear to not be leaking.

Blue flame out of right pipe about every 3 seconds, seems to alternate between smaller and then longer.

Right pipe has been cooler through all the diagnosis...

Have not pulled the pods to look for lip... tomorrow...

Can the float bowl be removed without taking the whole carb off? While I'm interested in what the PO may have changed on this carb I'd rather be riding... :banghead:
 
020.jpg


Torn pod filter? Wet with gas...
 
Sounds like mine.
I just bought mine last month and have only done riding down the ally. Mine has 2-1 exhaust with pods too. it backfires because the carbs are not set and need re jetted for the pods and exhaust. If yours is anything like mine, and it sure sounds like it- You need new plugs. Don't even try cleaning them up, go get new ones. I've got autolite xp63's. Mine did just want yours is doing, the backfiring is fouling out the plugs. put news ones in and give it a kick. If it's the plugs it should run great for a few days until it fouls the plugs again.
Put new ones in before you tear the carbs apart. You will need to anyways but this way you will know what the problem is and it will only cost you a few bucks and less headache.
 
It would appear that these carbs have probably not been apart- at least not in the last <400 miles that are on the bike...

Any hints appreciated- right now its me and the PB Blaster...
 
Got all but one top screw out. Multiiple heat, tapping, etc. Will not budge- heated it enough to jack up the rubber parts of the choke/ignition so I'll be hunting those parts down. Not sure if I should really pursue it or not if I don't need to access the top of the left side...

Diaghrams/slides look like everything is okay on the top end...

Everything looks pretty clean. There was some white crud on the right side pilot jet, gunged up the spring, etc.

Of the markings I can tell

137.5's on main

42.5 pilot jet

Did not mess with the needle jet as the right side looks clean.

I have UNIs on their way and a set of baffles... going to replace all the hardware with fresh. Should be here tomorrow- going to reassemble and see what happens.
 
Last ditch attempt to get the final screw off- slot the head...Dremel worked... and it gave me an excuse to go buy the new quick attach mandrel since I needed more cut off wheels...

Home Despot had none of the frickin replacement hardware I wanted so it's off to McMaster-Carr.

Oh, and come to find out the pipes were already baffled- does this significantly affect jetting, etc.?
 
mine was jetted for pod filters and stock exhaust, i changed to drag pipes and baffles and now it runs richer than it did before...
 
Alright, I finally have everything together, new UNI pods (the smaller gray ones) put some 91 octane in it, new AL63's and it fired right up. Still get a slight popping on the right carb but it is better. I have new JBL boots so I'm going to replace the cracked stock ones and see if that fixes it...
 
Or it could be the exhaust bolts that tightened two whole turns... that would have been a fun thing to lose...
 
Fail... still runs like ass, quits when you put it in gear unless I layed on the throttle.

Noticed some smoking on the left pipe through the pipe wrap.. wondering if the PO hid something under there. Parked it in the driveway and forgot to turn the petcock off and found a puddle of gas under it- leakeing out the pod filter...
 

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