76 XS650 won't start after carb rebuild

[Vivianthebarbarian]

First of all, Hi folks, I'm new here! I have a 76 XS650 that I used to ride all the time...but got a Goldwing in 2007 and parked it. I have had a urge to ride it again and pulled it out of the shed. The tank was a mess, the petcocks trashed (plugged and fuel uptakes rusted off). I cleaned the tank with vinegar and replaced the petcocks then cleaned the carbs. Everything was standard in there except the needle clips were on the bottom setting. There was some carbon showing so I put the clips on the middle position, and set the float heights to 25 mm. I wasn't getting spark on one side so I cleaned the points...no effect. Checked the coils and one was shorted out. Replaced it with another old one I had and got spark. (BTW, all the coils were reading about 5.2 ohms when tested...a bit higher than they should be if I understand correctly...could be causing weak spark?)

So, after all this I got it put back together today and tried it.....cranked a long time...didn't seem to matter if I used the choke lever or not. A couple of time it did fire and run for a few seconds, but when I tried to rev it up it immediately died. I put it on the battery charger for a few hours, but the results were the same. I'm not sure where to go from here...suggestions?

 

[Kevin Werner]

Pull the plugs after cranking. If they are wet you have a spark problem. If they are dry you have a carb problem.

 

[grizld1]

Exactly what did you do to "rebuild" the carburetors? Are the OE air boxes in place? If so the filter foam has probably degraded. The best and cheapest fix is to clean off the OE filter foam and wrap the core with a layer of new aftermarket filter foam. If the OE breaker point ignition is still in place, did you service the points and check gap and timing? All kinds of defects can and will develop when a vehicle is parked with no service for 25 years, and while we may be able to help you troubleshoot and suggest things to try and things that need to be done, nobody is going to be able to pinpoint your problem, especially from very sketchy information.

 

[5twins]

When you cleaned the carbs, you may have missed the choke jet. If plugged, the choke won't work and the bike will be very difficult to start cold. Here's it's location and how to check it .....

Your coils are testing a little high but did you touch the meter leads together first and subtract any reading you got from your test reading? If you didn't, that may explain the higher result.

 

[Vivianthebarbarian]

Perhaps I should have used the word "clean" instead of "rebuild". I am happy to provide any needed information. I don't expect anyone to pinpoint my problem...I only asked for suggestions.

The carbs were disassembled and cleaned with carb cleaner and a toothbrush. All the small holes and passages were flushed with carb cleaner and compressed air multiple times. The jets were removed and cleaned with carb cleaner, brush and compressed air and checked for the size against the table of standard sizes for each year from this site. The needle clips were at the bottom setting as I mentioned and I moved them to the center as I was seeing black streaking in the carb body around the butterfly valves (on both carbs) and I took that to mean that it was running rich and the table indicated the standard position was in the middle. The valve seat assembly was inspected for damage and confirmed that the spring still worked. The diaphragms were cleaned and inspected for damage. When they were reinstalled they were checked that they held a vacuum by pushing them up and holding a thumb over the air inlet and seeing if they stayed up. Both did. The float heights were adjusted to 25 mm (without a gasket in place). Old hardened fuel overflow hose were replace with new. Carbs were reassembled and roughly balanced. Mixture screws were set at 1 1/2 turns out. I'm not sure they really needed cleaning...they were pretty clean inside, but I did it anyway.

Original air boxes were gone when I got the bike. I put some Mike's XS pods on it. They are from 20 years ago so they may need replacing.

I cleaned the points but have not gapped or timed them. I remember that it was done shortly before I parked it...but it goes on the list of things to check.

The battery is new, but as it has been being used for testing I have been charging it periodically.

Thanks for your help,
Vivian

 

[Vivianthebarbarian]

When you cleaned the carbs, you may have missed the choke jet. If plugged, the choke won't work and the bike will be very difficult to start cold. Here's it's location and how to check it .....

View attachment 218490

View attachment 218491

Your coils are testing a little high but did you touch the meter leads together first and subtract any reading you got from your test reading? If you didn't, that may explain the higher result.

Thank you 5twins. While I'm pretty sure I blew carb cleaner and compressed air through there...it it certainly going on the list of things to check. Also I didn't know about touching the leads together and subtracting the results, so you might be right there.
Viv

 

[grizld1]

The Mike's XS tapered oval pods are a known source of trouble. 5twins attributes their bad behavior to the pleats disrupting air flow and I think the problem is the small volume of the filters, but we're agreed that they're stinkers. The raised needle was probably an attempt to tune for them. If you must use pods, Uni foam filters do a good job for a good price if they don't get wet. You'll need to move the mix screws to a richer position at the very least. If you get to 3 turns out and the motor is asking for more, you'll need to increase pilot jet size by 1 step.

 

[Vivianthebarbarian]

The Mike's XS tapered oval pods are a known source of trouble. 5twins attributes their bad behavior to the pleats disrupting air flow and I think the problem is the small volume of the filters, but we're agreed that they're stinkers. The raised needle was probably an attempt to tune for them. If you must use pods, Uni foam filters do a good job for a good price if they don't get wet. You'll need to move the mix screws to a richer position at the very least. If you get to 3 turns out and the motor is asking for more, you'll need to increase pilot jet size by 1 step.

Thank you for these suggestions grizld1.

 

[Vivianthebarbarian]

Well, after charging up the battery again, I turned the mixture screws out half a turn and put on the choke...and after a couple of tries it started and I was able to rev it up. After a minute I took it off choke and it idled at about 1500 rpm. I let it run for a few minutes then shut it off. After a few minutes I was able to start it again without choke but it wasn't running as good...maybe not hitting on both cylinders every time...I don't know. Seems like I was hearing more mechanical metal noises that I expected to. I noticed that when I would rev it up the handlebars wanted to pull to the right for some reason. Also when I reved it up it looked like fine rust would come out of the exhaust. It seemed like the hotter it got the worse it ran. In what is probably a separate problem the started button stopped working, but I was able to start if by jumping the relay. I researched the button thing and it sounds like it is often the ground that causes that...but the horn is working and they are supposed to use the same ground so idk.

 

[jpdevol]

Most everything you describe may be normal. Rust out the exhaust certainly is given circumstance. Handlebar movement may be normal - if they're on the centerstand, they'll back across the floor with a little throttle. Mechanical noises, compared to a Wing, yep. It would still pay to check valve and cam chain adjustment soon. The running when warm issue may well be fouled spark plugs at the present point in rehab.

Starter button: hopefully corrosion on switch contacts or wire terminals.

I think you've done well so far

 

[Vivianthebarbarian]

Most everything you describe may be normal. Rust out the exhaust certainly is given circumstance. Handlebar movement may be normal - if they're on the centerstand, they'll back across the floor with a little throttle. Mechanical noises, compared to a Wing, yep. It would still pay to check valve and cam chain adjustment soon. The running when warm issue may well be fouled spark plugs at the present point in rehab.

Starter button: hopefully corrosion on switch contacts or wire terminals.

I think you've done well so far

Thanks jpdevol! And thanks for addressing my concerns. I hope that it is normal noise, but will check valve clearances and cam chain soon. I will try new plugs and I'm still not sure that the old coils are working the best. Mike's XS is out of stock but Ebay has them...tempted to get new ones. I took a short video where you can hear what it sounds like, but so far haven't been able to upload it. My internet is poor in the country. Maybe try it on Monday at work.

 

[Kevin Werner]

My XS jumps on the sidestand and gets me nervous often...

 

[Vivianthebarbarian]

Today I'm back to not being able to start it. Did the same thing as yesterday...mixture screws at 2 turns out...put choke on and cranked it (bypassing the relay) but no start. It did stumble a couple of times. Put the battery back on the charger and adjusted the cam chain tensioner which was a good bit out. Later checked the valve clearances...very little adjustment needed there. Took the plugs out and they were pretty black. Cleaned them up a bit and put back in. The battery had been charging for several hours at this point so I tried it again. This time I couldn't even get a stumble out of it. Pulled the plugs again and they seemed dry. Also double checked for spark and I am getting spark. Guess I'm pulling the carbs again. Definitely going the check the choke jet. Maybe I should put the needle clip back on the richest setting where it was before? Or the spot in between..idk, it used to run pretty good when it was at the riches setting, but was put there by the previous owner. When I got it it didn't have any air cleaners on it at all, and I put the Mike's XS pods on it. Hmmm.

 

[jpdevol]

It's getting back at you for previous neglect - lol. You know it's not going to be that easy. Perhaps rig a fuel-bottle IV to eliminate tank and petcocks. Try it that way before you go back into carbs. Will start with needle clip either place (maybe not run right). If you put the pods back on the grizzly bear will bite you

 

[grizld1]

The handle refers to greying hair, not the critter--anyway, those Mike's XS pods are better than nothing at this stage, they won't cause trouble when you're working on starting/idle tuning. Don't fixate on a particular mixture screw setting. With pod filters you'll need #27.5 pilot jets, type VM22/210. The motor ran at idle previously because in BS series carbs there are strong interactions between needle position and idle mixture. That isn't a good way to tune, the PO knew just enough to make a mess. I wrote the idle tuning procedures in the Carb Guide, and the section on tuning for modifications is 5twins' work. I can't offer you any more recommendations than we covered in the Carb Guide. Good luck to you.

 

[Vivianthebarbarian]

It's getting back at you for previous neglect - lol. You know it's not going to be that easy. Perhaps rig a fuel-bottle IV to eliminate tank and petcocks. Try it that way before you go back into carbs. Will start with needle clip either place (maybe not run right). If you put the pods back on the grizzly bear will bite you

Using a fuel bottle is a good idea, but not needed in this case I think. I took the fuel lines off and ran some gas out into a cup from the petcocks. Both are flowing freely when open.

 

[Vivianthebarbarian]

The handle refers to greying hair, not the critter--anyway, those Mike's XS pods are better than nothing at this stage, they won't cause trouble when you're working on starting/idle tuning. Don't fixate on a particular mixture screw setting. With pod filters you'll need #27.5 pilot jets, type VM22/210. The motor ran at idle previously because in BS series carbs there are strong interactions between needle position and idle mixture. That isn't a good way to tune, the PO knew just enough to make a mess. I wrote the idle tuning procedures in the Carb Guide, and the section on tuning for modifications is 5twins' work. I can't offer you any more recommendations than we covered in the Carb Guide. Good luck to you.

Thanks grizld1, I'm ordering the 27.5 pilot jets and will be doing a deep dive into the Carb Guide. Also on my list is points gap and timing...to be sure there isn't a problem there.

 

[grizld1]

If points gap and timing are unknowns, that's a problem in itself. Don't forget to replace those Mike's XS Chiwanese clones of K&N tapered oval filters with a pair of 4" Uni filters. To keep them dry, send the dimensions to Outerwears for a pair of their rain covers.

 

[Jim]

Also on my list is points gap and timing...to be sure there isn't a problem there.

If points gap and timing are unknowns, that's a problem in itself.

Ain't that the truth!
Timing can affect mixture needs.
Mixture can affect timing needs.
If you're tuning the carbs to an unknown ignition system... well, to put it bluntly... you're pissin' in the wind.

... or as Griz is fond of saying about carb tuning.... "everything else first."
My saying is "never underestimate an ignitions ability to fool you into blaming the carbs.

 

[Vivianthebarbarian]

Ain't that the truth!
Timing can affect mixture needs.
Mixture can affect timing needs.
If you're tuning the carbs to an unknown ignition system... well, to put it bluntly... you're pissin' in the wind.

... or as Griz is fond of saying about carb tuning.... "everything else first."
My saying is "never underestimate an ignitions ability to fool you into blaming the carbs.

Ok.....I guess that better be first on the list. I was pretty sure it was done shortly before I parked it...but that was 15 years ago, so better check it. Hope I can find the light I used last time.