Problems with my 81 xs400

[menikmati412]

I bought this bike less than a year ago to learn to ride and learn to fix up. Recently I've been spending much more time with the latter. I made a huge mistake and took off my cylinder head assembly (circled), then realized I was taking off the wrong component after it was completely off. I did unscrew one camshaft cover (25), but did not touch anything else and screwed everything right back on.

The next day I went to ride it and after riding for 5 minutes I noticed oil was gushing from the contact breaker cover (highlighted in the next picture)

I've been asking around and have heard two theories of what I did - first is I completely ruined the bike by taking it off and should just try to sell it. Second (which i believe to be true) is that I just need to get the proper gaskets and a torque wrench (for my cylinder head I'm guessing?) and everything will be fine. I don't want to waste more time and money on tools and gaskets if it's not going to fix the problem.

I have not ridden the bike since I noticed this problem, but it was turning on and running fine other than the oil gushing out.

Here are some other problems I have been having with the bike:
1. Will only start with starter fluid.
2. Half the time it loses all its horse power. I can go full throttle and it'll still only go 20mph.
3. The exhaust sounds twice as loud as before.
4. Loud popping noises, mostly when slowing down.

I cleaned my carbs out and cleaned my air filters, and also made sure the carbs were secure on the boots and not sucking up any air.. It has not solved any of the problems.

Thanks for reading! Any help you have to offer will be greatly appreciated!

Here are some images of my bike as it stands today. I know it looks pretty bad - I don't have much money and I got it for cheap, but I am eager to learn to fix it up and clean it up, so I don't want to give up on it now!

The last one shows all the oil that leaked out.

 

[Thedoityourselfguy]

Sounds like a blown motor.....remove spart plugs and place your thumb over the hole on one side.....crank it over while holding you thumb.....it should have enough compression that it is somewhat difficult to hold your thumb tight over the hole.......check both sides.....one will probably have less compression. If your lucky you might just need to do piston and rings..........good luck

 

[BBS360]

That's the valve cover. The head is the next piece down, where the intake and exhaust connect.
Part 25 is a tappet cover.

There's nothing terribly complicated about taking the valve cover off. Mine's on the floor right now waiting for the bolt kit that just arrived in the mail.
No gasket required there. Just and thin layer of yamabond.

Have a look under the points cover. Seems like a lot of oil but it could just be that the seal under the timing plate didn't seal up properly when you reinstalled the valve cover.

Power issues are more complicated but they tend to be carb/ignition related rather than a blown motor.
Sounds like you didn't loosen any of the head nuts under the valve cover so I'd expect everything from the head down to be OK.
Unless you put the cover back on super loose and the valves/camshaft/rockers destroyed themselves I don't think you're looking at anything catastrophic.

Check compression as suggested, visually inspect the cylinders and pistons through the spark plug holes. Manually turn the engine over with the bolt under the generator cover and watch and the pistons go up and down. Any debris inside or other damage would be reason for concern.
You could do a basic visual inspection through the tappet covers but don't be afraid to take the whole valve cover off again.
If you have access to or can buy a compression tester it's always a good idea to check compression. Dry and wet.

We do have the OEM and Haynes manuals available for download. They both do a pretty good job explaining the valve cover removal process.

Edit to add: that much oil in the timing mechanism could interfere with ignition, causing you to randomly lose ignition. Possibly the cause of the power loss right there.

 

[dgoodsy]

Also verify oil level is correct before running the engine again, it looks like lots leaked out.

 

[xschris]

Cam seal, yamabond the valve cover and torque cover to spec and in the proper sequence, make sure rubber rocker plugs are in place and sealing, set valves to spec, make sure the tci pickup is set to correct timing and sync carbs with manometer. This is if all else is clean and in spec. All of these topics are in the manual and in the forum as well. Use search box for more info.

 

[mrdawson]

Cam seal, yamabond the valve cover and torque cover to spec and in the proper sequence, make sure rubber rocker plugs are in place and sealing, set valves to spec, make sure the tci pickup is set to correct timing and sync carbs with manometer. This is if all else is clean and in spec. All of these topics are in the manual and in the forum as well. Use search box for more info.

agreed. and by "cleaned carbs" do you mean completely broke them apart, soaked / boiled, replaced throttle shaft seals? or just a basic "took the bowls off and sprayed carb cleaner around"?

 

[arfstrom]

"I cleaned my carbs out and cleaned my air filters, and also made sure the carbs were secure on the boots and not sucking up any air.. It has not solved any of the problems."

If everything is still oem on this bike, it could still have some serious dry rot. Interim solution tape up the carb intake boots. I would recommend a "self sealing silicone tape" also known as rescue tape http://www.rescuetape.com/ My local store Menards has something similar. It handles up to 500 degrees F. My stores sells it for 10 ft sections, about 4 bucks. its generic, but does everything the brand name says.

I can not tell you how many times, I for got to cap the carb boot vacuum atube when I took off the fuel tank. The one is suppose to plug into the petcock valve. or the side would not be connected. oops.

 

[xschris]

Clean is a full dissemble and cleaning/rebuild with good working non-worn stuff.

 

[mrdawson]

Clean is a full dissemble and cleaning/rebuild with good working non-worn stuff.

exactly

 

[Forward_pack]

I know this thread is old but did you ever find a solution to this problem? I think I have the same issue