1st post: just acquired XS400

I’m dunking them, so I wanted to remove and replace the 40 year old center hose so I’m starting completely fresh.
 
Ok, so I drilled out the brass plug on the pilot screws today. Drilling went fine on both carbs, and on one, the pilot screw assembly came right out. Keeping in the trend of this fucking bike though, the other stripped out. I drilled into it and used the small size 1 extractor I use on pilot jets. It grabbed onto it for a fraction of a second, turned it once, then ate through the brass and just spun in the hole. So tomorrow I am off to grab the next size up extractor. If that doesn't work, I really have no idea how to get it out. I think what happened is some of the brass debris from the drilling got stuck in the sides and gummed it up, so when i twisted my screwdriver it got stuck.
 
Success! I went up an extractor size and it pulled right out. Carbs are now 100% disassembled, both have been dunked for 24 hours in cleaner, had cleaner sprayed through the ports, so I’m just waiting for my rebuild kits to arrive. Then I’ll throw it back together, a quick oil change, and see how she runs. I put new air cleaners in their pods the other day and replaced the brake fluid.
 

Attachments

  • 582643A1-CB61-4927-954E-55559730E1C6.jpeg
    582643A1-CB61-4927-954E-55559730E1C6.jpeg
    123.6 KB · Views: 269
  • ABFDD443-09F8-4241-B207-B103A951D3AB.jpeg
    ABFDD443-09F8-4241-B207-B103A951D3AB.jpeg
    217.7 KB · Views: 271
If you dip them they will need new shaft seals.
Well. Looks like I need to buy shaft seals. Cursory glance seems like it’s going to be a huge PITA to replace them. It never ends, does it? These needed to be dipped though, they were pretty dirty.

This may be why my GN400 is having issues. It’s got a BS36 carb that was dunked.
 
You need four. One for each side of the shaft. 256-14997-00 This is the OEM part number. Make sure you still have the plastic washer covers for the outer ones. Those are very fragile and no one makes them that I am aware of.
 
Shaft seals are on the way, but I managed to get the butterfly off tonight. I'd tried before with the carb sitting on my bench and the screws started to strip, so I got a long wooden dowel and shoved it down the carb to support the butterfly, and set the other end on the floor. Screws came right out.

Once the seals come in, I can throw the carbs back together. The ONLY thing that concerns me is that missing brass piece that holds the needle jet in place. I don't really know what to do about that other than make a replacement out of like JBweld, but that feels incredibly bubba to me.

https://imgur.com/a/YZfhjFJ
 
Mikesxs sell new screws I think and I have seen stainless ones also for sale. If you search 80-84 xs650 carbs you can usually find them. I would use some lock tight to keep them in place as they were peened at the ends from the factory. I would try to find a small rod for that carb as it also keeps the needle jet from turning when you screw in the main jet.
 
I misspoke slightly. The screws did not strip, but before I used the dowel I knew if I turned any harder they would. The dowel allowed me to exert more downward pressure and they came out unharmed, so I am going to reuse them.

Do you think cutting the middle out of a nail and Jbwelding it in place would be effective enough? Short of going to a machine shop, I don’t think I’ll find anything precise enough to have a press-in fit.
 
I cut the end off a small drill bit and it was almost a perfect fit. Put it in there with some JB weld steel stick to seal the hole up. Now I'm just (still) waiting for my shaft seals. I ordered an air filter for my other bike, and it turns out its backordered and they keep pushing the in stock date back further and further. About to cancel the whole order and get the seals somewhere else because I'd like to get this bike rolling.

https://imgur.com/a/kOikRC7
 
Wow. My shaft seals finally arrived yesterday. Only took a month. Carbs were rebuilt, all with brand new stainless steel hex bolts. I also replaced the butterfly screws with new ones since they'd stripped a little being removed. The butterfly screws, as well as the 8 bolts holding the two carbs together, all received a dose of loctite, then moved the adjustment screw until both butterfly valves moved at the same time from the same spot. I reinstalled the carbs and air filters onto the bike to wait 24 hours for the loctite to cure. Unfortunately, I worked all day today so I didn't get to test it, but I decided I am going to check/adjust the valves and do a thorough oil change first, as the oil seems to be contaminated with gas. I'm guessing my buddy flooded it pretty badly when he kicked it for 10+ minutes trying to get it started.

Oh, I also replaced all the seized and rusting hex bolts holding the crankcase and chain cover on with new stainless steel ones. Hopefully if someone has to do a rebuild or something down the road, this will make the job less painful. Do these need loctite too, or should I just crank hard on them with my hex key?
 

Attachments

  • o6fGwms.jpg
    o6fGwms.jpg
    202.2 KB · Views: 217
I would have used the loctite Only on the butterfly screws. Aluminum and that stuff can be a bad thing. It can cause the bolt to crack the metal if you turn it too hard when you remove them. Did you use the blue type?
 
I would have used the loctite Only on the butterfly screws. Aluminum and that stuff can be a bad thing. It can cause the bolt to crack the metal if you turn it too hard when you remove them. Did you use the blue type?

I couldn’t find my blue loctite, so unfortunately I used red. However, as to the bolts holding the carb brackets in place, I can’t see any way that loctite would be harder to remove than that glue that was holding them in before. I’m doing this rebuild so that hopefully nobody will have to do this for another 40 years (and that person won’t be me).

Ill guess that’s a no for loctiting the crankcase covers in place?
 
Oh no!! That is a permanent sealer. It has like 3000 psi of holding power. The only bolts that had any type of stuff from the factory was the bottom link bar and that was a blue loctite equivalent. Lets hope you never have to pull them apart again. I actually never use any type of loctite on any of the link bars as they don't really see any stress or twisting. A lock washer would do just fine.
 
That’s alright, it’s now the next owners problem. Which may be sooner than expected. I changed the oil just now, well, tried to.

first off, a flood of gasoline came out of the drain plug. Like, at least a gallon. It flooded my drain pan and spilled all over my garage.

Then the bolt holding the oil filter assembly was super rusted and degraded. Plus, the engine guard bar was in the way so I had to take that off. All the bolts are seized, but thankfully a few snapped off and I was able to move it out of the way. I’m going to cut the rest of them off with my dremel as soon as I move the bike somewhere not filled with gasoline fumes. I had to use a very aggressive extractor socket to get it off. I changed the filter and O rings, then used a less aggressive extractor to put it back on, lol.

finally, I cleaned the little filter on the bottom. It’s strange because none of my other bikes have one. Well of course putting it back on, two of the fucking little bolts snapped. I used an inch pound torque wrench set to 60 inch pounds to go for the factory spec of 4.5-6 ft pounds. I’m about to take this thing to the junkyard.. I was planning on attempting to start it right now, not having to figure out how to remove these broken bolts. I’m hoping that they didn’t break flush with the bottom of the crankcase and I can just grab them with pliers.
 

Attachments

  • 6A422AA2-F2FD-4EB3-9E5B-AB8D4FBFDE58.jpeg
    6A422AA2-F2FD-4EB3-9E5B-AB8D4FBFDE58.jpeg
    88.5 KB · Views: 224
Good news, all 3 broke above the crankcase, and two were loose enough to be grabbed by hand. The 3rd needed some persuading with pliers but came out. I discovered a 4th bolt that likely almost snapped; there is a section 3 threads deep in the middle that looked stretched. The gap between the threads was longer and the bolt was skinnier there.
I’m running to the store to replace all 6 of these chintzy potmetal bolts with new ones.
 

Attachments

  • 34E0D61A-5FD1-4F6F-83CF-7DFF7268A772.jpeg
    34E0D61A-5FD1-4F6F-83CF-7DFF7268A772.jpeg
    175.5 KB · Views: 196
I have never had one snap before but have seen others with this issue. I just snug them just some the gasket doesn't leak. In 81 they changed the design of that screen to a solid metal one as the ones with the rubber feet don't stay tight in place over time. Also a baffle in the direction of the oil sling from the crank. I believe. I have one on all my bikes.
s-l1600.jpg
 
Yeah, I replaced them with six hex head bolts and just snugged them up by hand. I got it all together and it fired right up, as long as I was just barely twisting the throttle. I couldn't get it to idle past 1000 RPM, even with the idle screw all the way in. My guess is probably the pilot screws need adjusting. I think I set mine to 1.5 screws out, but thats only because thats stock on my other bike. I haven't had a chance to dig through the manual to see what the recommended setting is.

I rode it around a bit, and it seemed to be struggling a little. After about 10 minutes, it still took off slow from a stop, but would radically jump in power once I passed 10 or 15mph and got up a gear or two. Tomorrow I am going to lube and adjust the throttle and clutch cables. The throttle cable feels like it's got a bit of slack which might explain the lag when twisting from a stop. I should also adjust and lube the chain. Anything else I should do or adjust to get it running smoothly? It fires up nicely and has a nice steady idle.

video of it running (well) for the first time in years.
https://imgur.com/SACqpVs
 
Back
Top