78 xs

[Nederman]

Before I go through the carbs once more I thought a second opinion would be smart!
This bike sat for 15 years so I cleaned the VERY dirty carbs and changed the oil. All looks ok with the carbs, diaphragms are fine. I put the carbs back on without the airbox initially to see if it would run. Started up and idled fine. Took it for a quick run down the street and it screamed! However, right after that it began to bog heavily and without full choke would'nt of made it back. This appears to be the pattern. Next day ran fine breifly then would bog badly. I figured if the carbs were at fault then it would run poorly from the beginning. Might a vacuum problem exist or could the carbs still be the issue?

[mack]

Fuel supply

Next time out and it boggs down again, crack open the gas cap. There is a vent hole in there that will be plugged.

[ManagerMike]

Running out of gas?

There are filter screens in the tank, they are part of the fuelcock assemblies, they may be restricted such that it will allow the carb bowls to reach full at idle but under load the bowls are running out of gas. JAT.

[tcoop]

It could be plugged vent, kinked fuel line, clogged filter, a stiff diaphram in the petcock (or disconnected vaccum hose) or debree from the tank getting in the carbs. But it does sound like a fuel problem.

[soccer4m]

fuel filters??

Have you put in a pair of inline fuel filters to stop any crud from the tank in yet??? If not,,,,do it asap. You probably will have to pull the carbs off again and clean, if there is crud causing the problems then its an easy fix. Just clean em again, make sure you have a couple cheap fuel filters in the gas lines and it should be easy to check how much crud is flowing through.
Last resort if lots of crud, take off gas tank and thoroughly clean the inside, swish around, pull off petcocks and clean them, reinstall and get ready to rumble......keep us informed,,,,,,,,,,Mike in Sun DIego

[BigRed]

I would check the pick-up coil wires because it's quick, easy, and can sometimes feel like a carb problem. If it runs really well, and then doesn't, that sounds more electrical to me. In my experience, if the carbs aren't working right, it never runs well.

[soccer4m]

ditto the pick up

Big Red has a valuable suggestion also,,,I had the same issue on a MNS, it drove me nuts thinking it was the carbs, it would run fine until warmed up, then run like hardly any fuel is getting to the engine,,,anyway, pull off the cover, pull on the wires while running and see what happens. Also, get those fuel filters to stop future, current problems with crud............keep us informed, Mike in S.D.

[Nederman]

Xs ressurection

Hi y'all. To those who responded to my tech inquiries, I thank you. One of the reasons I bought this bike was because of this website. I've been a vintage Brit and Italian bike owner for 30 plus years so procuring this "high tech" bike put me closer to the 21rst century. I found it on C/L a couple towns away from me in northern Illinois for in the end $250. Petcocks had been removed because he said they leaked. The bike sat like this in his garage since 1998. It sported a Vetter fairing and saddlebags from Vetter also. I'm not a big fan of frame mounts so the first thing was to take it off, what a look without the fairing! To hide ANY part of that power plant would be a shame. I did keep the side bag mounts on even tho they muddle the look of the the back end a little but I've always liked the look of a naked bike with bags.
So the bike sits in my garage for another 14 months staring at me every day. A buddy calls and tells me to meet'm at the BMW national rallye in Sedalia MO, 500 miles away. Time frame was tight to pull it all together for a lengthy ride on an unknown entity but I dove in with great expectations. First, the tank. Some rust and other junk in there so I tried the battery charger anode cathode thing and damned if it didn't do the trick. Should've done it twice tho, I think. Then I did the carbs and slapped it all back together and have since had the bogging problem. Well, thanks to you guys I have been able to identify the problem. The verdict: vacuum! I opened the cap after its most recent bog down and I nearly got sucked into the gas tank. Ah hah! So I blew thru the vent hose that feeds down to the swing arm pivot and it seems to be nearly plugged. I stuck a wd 40 squirt tube up the vent opening at the rear of the tank and it entered without resistance. Maybe the tube is too short. At this point I just wanted to see how it runs so I left the cap open enough to vent. I've ridden around 50 miles with no bogging at all. My first impression of this bike, even with a little below 3000 rpm hesitation is this ain't Kansas folks. I knew my 850 t and commando couldn't match the speed but are you kidding me? I haven't had it past 7 grand but between 3 and 7 there seems to be infinite throttle. 80 mph sweeping curves feel effortless and true. Hard turns at lower speeds feel secure as well. The bike seems smaller in these turns, it leans eagerly without wanting to fall over which I thought it might want to owing to the high up beast motor. But the acceleration is something of a religious experience in my humble opinion. I'm very pleased with it. I did not take it to Sedalia but without that as a motivator I would not have progressed with it at all probably. So I'll examine the vent situation and get that taken care of. Right now it isn't legal because the po had a transfer of title only from the po and never had it transferred over. DMV said no go and I need to go to the original owner who signed the transfer in 98. Well, I found his # only to be speaking to his widow. Understandably, she wasn't too receptive to going down to the DMV with certificate of death in hand...I guess I'll have to figure out another way to get this thing titled. DMV said if I were to fill out transfer of title with plate # and vin, if nothing shows up in their search then I could get a title for it. Finding a title from another bike is possible too. At least I could get a plate for it. In the meantime I'll be eluding the local constable to enjoy the rush of riding this thing. It's somewhat addicting. Thanks again and talk to you soon! Doug

[natemoen]

Glad you found the problem, but that tube you're talking about is not the problem (it is a problem but not what you need to cure your issue, it is just a drain for the recessed cap are). You need to take the cap itself apart and clean out the tiny little hole in there that vents the tank. If you look at the cap there are I think it is 3 screws that you need to remove as well as the seal and that'll gets you into the area that needs to be cleaned.

[DGXSER]

Have a look HERE. I believe that will show you how to clear the vent.

[jwhughes3]

Doug,

That "vent" that pops out of back of tank isnt a vent. Its overflow from the recess in filler area. Doesn't (or shouldn't) connect inside unless the tube is rusted through. Yours is intact or it would act as a vent and you would not need to open cap.

John

[CaptonZap]

Doug,

That "vent" that pops out of back of tank isnt a vent. Its overflow from the recess in filler area. Doesn't (or shouldn't) connect inside unless the tube is rusted through. Yours is intact or it would act as a vent and you would not need to open cap.

John

And, depending on how high up the rust hole is, it would drain gas out the tube when you filled the tank clear up.
Rusted tube can be replaced, but it is not a job for the uninitiated.
CZ

[Nederman]

Xs ressurrection

Thanks again to all of you for direction to the mysteries of my xs. The vent hole in the gas cap was indeed plugged and after a thorough cleaning allowed me to ride with the cap closed. I'll send some pics up when time pemits. More about the bike: it has 14000 miles on it and compression test revealed 175 per cylinder. It's cosmetically challenged a bit with a well chipped original paint job(maroon) which in time I'll address with a black redo. Not a priority at the moment, I want to sort out the essentials first, like the rear master and caliper, the former of which is frozen. The front calipers were sticking when I first picked it up so I disassembled and cleaned 'em and they function but are pretty tepid. Any thoughts on improving this? New lines and pads seem logical, rotors seem sound. The starter button also fell out leaving the contact spring exposed, which I tug out after starting it with my now removeable button/spring security device. It works but a pain it the butt. I'm thinking to machine a new button out of a plastic rod as the old one no longer has the little rim around it that captures it in the throttle assy. The mufflers are rusted out 6 inches from the end on the bottom. I'm a welder by profession so I could cap and wrap for the moment. I'll keep y'all posted. Doug

[bikerphil]

starter button also fell out leaving the contact spring exposed

New ones here, plastic or metal...

http://www.freewebs.com/kibokojoe/

[GLoweVA]

As far as the brakes go, If you had to clean out the front calipers, the I'd suggest cleaning out the master cylinder too. Any crud that was in the calipers is most definitely gonna be found in the master cylinder too.
I've read here that there's a 'spooge' hole in the MC that needs cleaning out to make sure that the fluid travels back into the MC from the calipers.