1st post: just acquired XS400

[Lemonysword]

Actually, could it be the valves? I attempted a valve adjustment today but was unsuccessful. It seems for one that the flywheel wants to rotate whenever the cylinder is near reaching TDC. I managed to get it to lock into place, but couldn't get a feeler gauge into the valve. I tried bending mine, because I read a 45 degree gauge works well, but just broke it. I also couldnt get a wrench on the adjustment nut well enough to loosen it.

I will go grab a set of 45 degree gauges and try again fresh tomorrow, when I'm less stressed out after all the other stuff.

 

[xschris]

3 turn out is a good starting point for pilot screws. Removing the plugs helps with setting the valves. Sync the carbs with a manometer after you set valves. It's one of the most important things to getting these bike to run well. Avoid excessive idle time as this will cause the plugs to get carbon fouled. If the bike is running well enough take it out for a good 50 mile run at highway speeds. This is the best way to free up and clean the motor out. Make sure the chain is clean lubed and adjusted to spec. If it's rusty replace it. If you don't know the age or miles of the sprockets it's a good idea to replace all of it. All of which should be done at the same time anyways. There are threads on all of these things in the forum and manual.

 

[Lemonysword]

I’ll pull the tank today and back them out some more, thanks.

I did have the plugs out, my issue was I couldn’t get the feeler gauge to go between the valve, and when I tried loosening the adjustment but I didn’t have a good enough angle with my short wrench to loosen it. I’ll give it another go today.

By synch, do you mean using the adjustment screw to ensure both butterfly valves open at the same time, or adjusting the pilot screws so each carb is creating the same amount of vacuum? I did adjust the butterfly valves when I put the carbs back together, so visually they open at the same time.

 

[xschris]

You need to sync the with a manometer. This ensures the vacuum is the same for each cylinder. Lots of threads on this in the forum. Makes sure the valve you are doing is at tdc and the correct stroke or your adjustment will be wrong. Left to right cylinder and with the motor completely cold. Always turn the motor in one direction to hit your marks and never turn it back to catch it. If you go past turn it all the way around and start over. Otherwise it puts slack in the cam chain giving you a bad adjustment. Search the forum for this also.

 

[Specdog]

A couple of thoughts on your progress. I too had gasoline in my crankcase. After draining I did a flush with cheap oil to be sure of getting all that gassy oil removed from the engine. Sometimes oil will remain in the cam hollows and other crevices so you want that out of there. I use a breaker bar when turning my engine for timing alignment, this way I can control movement better. You're making good steps forward.

 

[Lemonysword]

A couple of thoughts on your progress. I too had gasoline in my crankcase. After draining I did a flush with cheap oil to be sure of getting all that gassy oil removed from the engine. Sometimes oil will remain in the cam hollows and other crevices so you want that out of there. I use a breaker bar when turning my engine for timing alignment, this way I can control movement better. You're making good steps forward.

I've ordered a new oil filter bolt. I'm going to ride it sparingly until it arrives to mix any remaining gasoline with the oil, then do another complete oil change. Kinda sucks that I spent $30 on oil. The breaker bar is a great idea; I was using a standard socket wrench, and whenever it got close to being TDC, the flywheel would spin back, and since the socket was set to go forward I would lose it. I was going to use a box end 17mm wrench but a breaker bar should work much better.

 

[Lemonysword]

Welp. Bike has been running well and has been my daily to work the last week. I’ve got a new chain (non O ring), sprockets, and fork seals coming.

Yesterday my wife tried to move my XS400 and immediately dropped it. It didn’t hit the ground since it landed on the engine of my ural, but it laid tipped over like that for about 4 hours until I got home. It’s been leaking gas out the air box for about 27 hours now. I figured that was gas from the float bowls that was able to roll back to the air box while it was tipped over, but i feel like it’s leaked way more gas than the float bowls hold. So I guess tomorrow I get to take it all back apart.

 

[markmakeitso]

Welp. Bike has been running well and has been my daily to work the last week. I’ve got a new chain (non O ring), sprockets, and fork seals coming.

Yesterday my wife tried to move my XS400 and immediately dropped it. It didn’t hit the ground since it landed on the engine of my ural, but it laid tipped over like that for about 4 hours until I got home. It’s been leaking gas out the air box for about 27 hours now. I figured that was gas from the float bowls that was able to roll back to the air box while it was tipped over, but i feel like it’s leaked way more gas than the float bowls hold. So I guess tomorrow I get to take it all back apart.

Ahhh, always something. Hope the XS and the Ural are relatively okay after that mishap.

 

[Lemonysword]

Ahhh, always something. Hope the XS and the Ural are relatively okay after that mishap.

It ripped the spark plug boot out of the brand new spark plug cables I made on my ural, but I just cut a half inch off the end and screwed it back in, works fine. I’m about to go pull the carbs out of the xs400 to drain the air boxes and make sure the floats didn’t get damaged or something.

 

[markmakeitso]

It ripped the spark plug boot out of the brand new spark plug cables I made on my ural, but I just cut a half inch off the end and screwed it back in, works fine. I’m about to go pull the carbs out of the xs400 to drain the air boxes and make sure the floats didn’t get damaged or something.

When the carbs are out and the floats have been causing problems I like to try to try the "flop test" just before putting them in. Attach some clean vinyl tubing to the fuel inlet and then blow into the tubing. Simultaneously turn the carbs upside down so gravity pushes the float valves shut. Air flow through the carbs should stop completely. I usually do it several times, and it only takes 45 seconds to perform the whole thing. Obviously it's not a comprehensive float valve system check, but it requires no disassembly or reassembly and is easy to do right before mounting them on the bike.

 

[xschris]

Make sure the filters are ok as gas can destroy them.

 

[Lemonysword]

Make sure the filters are ok as gas can destroy them.

they look OK, but the glue holding the foam filter element to the box is failing on one side now. I’m gonna hit it with some superglue and see if it holds up before putting the filters back together. Currently I have them both airing out outside.

 

[Lemonysword]

I didn't have time to work on this until a few days ago. Carbs appeared to be OK from all visual indications. While I was working on it I decided to do a valve adjustment per the manual. I used a 17mm box end wrench on the rotor nut. Whenever it reached TDC on the compression stroke, it wanted to spin. I wound up holding it in place using the heads of the hex bolts that hold the rotor on. I used a set of allen wrenches as spacers between the wrench and the bold heads to make sure it was lined up perfectly. Rocker arms had a little bit of wriggle so I am confident it was on the compression stroke.

Last week I drove all over town looking for 45 degree feeler gauges and found none, so I had to use straight ones. The method I use on my Ural, which has far more accessible valves, is to loosen the adjustment nut until I can easily slip a gauge of the widest clearance in, then tighten the adjustment down until I can just barely pull that gauge out. On my Ural, that typically will let a gauge in the middle of the clearance range in, but it is tight enough to hold that gauge. I did that for the XS400 because even the thinnest gauge wouldn't slip in unless the adjustment nut was backed off a lot due to the angle the gauge has to come in at.

I fired the bike up today and it runs like shit. There is a pretty noticeable lag between when I apply throttle and when the engine revs up, and when riding it has a hanging idle when the throttle is released. Like 5-6 seconds before the RPMs come down. I'm not sure what exactly happened but it was pretty disappointing. Any ideas?

 

[markmakeitso]

I'd guess you have excessive valve lash from using straight feelers. Probably a decent part of your poor running. You could bend just a couple of individual feelers to the correct angle and then not put them back in the stack, which is what I've done after a couple times through that job. Straight feeler sets are impressively cheap on eBay, but angled ones always seem to carry a premium.

 

[motoTrooper]

Yup, bend those feelers!

 

[Lemonysword]

I tried bending feelers a few weeks ago when I first tried the valve adjustment and it just wound up breaking the feeler! I guess I need to order some online.

 

[GuyS]

The four big (8 or 10mm) screws holding the bracket that attaches the carbs were the most seized screws I’ve ever encountered. I think they actually glued them in place; there was white residue in the screws hole. Two of them I was able to get out, after much heat and banging, with an impact driver. They were so seized that I had to use to impact driver til they were a quarter of the way out before I could use a screwdriver. This one I actually gave up on and was trying to cut the head off to just leave it, I was so mad. This cut goes to almost the bottom of the screw, when I decided to give it one more shot with my big flathead. Muscles popping and straining, finally it turned

Exactly my experience with those same screws too! I cannot understand what they used or why they used what they did to cement the screws in. Of course any movement in the bracket could have consequences to the sync, but glueing them in!

 

[Lemonysword]

Well this thread is five years old but I am finally picking up where I left off, so I might as well continue using it (after my brief hiatus here)

Last night I found a box of parts I'd ordered for this bike in 2020. Chain, sprockets, front brake pads, shaft seals, and some fork gaiters. My plan today was just to give the very dirty bike a thorough scrubbing, but I found myself with more time so I went about the task of replacing the chain and sprockets. I ran out of daylight and had to put the wheel on and attach the chain in the dark. Tomorrow I'll adjust the chain setting and the back should be good.

The pads on the rear drums seemed pretty thin but i don't feel like dealing with that right now. Tomorrow if i have the time, I'm going to tear into the front wheel and forks. I will have to go find a cheap measuring cup to get an accurate 142ml for the forks.

 

[GuyS]

Keep us posted. It’s very interesting and informative for sure!

 

[Lemonysword]

adjusted the chain and tightened up the sprocket and axle today. Seat and side covers went back on. I started it up in hopes of letting it run long enough to get warm so I can adjust the idle, but i ran out of gas. I rolled it into the garage to put it on the trickle charger since the battery is so low that the electric start won't turn over, but when I tried to take the seat back off the left side wouldn't release. Not sure what's going on there but I decided not to mess with it anymore.

Yesterday's bath was probably the first one this bike has had in a decade and revealed a lot of the little defects one would expect on a 45 year old bike. Most of the chrome is speckled lightly with rust, the rubber grommets are decayed, the boots on the clutch and throttle cable are cracked, and unfortunately the paint on the tank has some decent scratches and swirls. Most of the little rust I think can be cleaned up with wet aluminum foil or fine steel wool, but I am concerned about the rust on the front fender. Might need to replace it. Additionally, all of the washers under pretty much every nut on the bike are rusted. Eventually I'd like to replace all the hardware on the bike with stainless steel, and while I'm on that I might as well replace the rubber bits too. That's stuff for later though.