1981 Maxim XJ 650 restore project

I was thinking of taking the starter off this weekend, and cleaning it up, or is there something else I should do first since the bike has sat for so long?

 

Well, I found my old regestration from 1992. That was the last year I rode the bike. Turns out, the bike is an 82, not an 81. I don't think that should change anything with the rebuild.

 

After days of adding lube to the spark plug holes, and putting the bike in gear and manually turning the back wheel to free everything up, I had an old battery that I hooked up to the bike and tried short bursts to see if there was any compression in the cylinders. Low and behold the was!!! The engine isn't seized!

 

So I did a cold compression test, and the readings were
130
130
95
125
Is there anything I should be concerned about?

 

the 95 is a concern could be the rings are still stuck a second treatment of atf/acetone may help for that cylinder.
have you checked the valve clearences? that could be your issue too.

the 125 to 130 cylinders are in spec

 

I haven't tried that yet. What is the mixture for atf/acetone?

 

50/50 works table spoon and let it soak into the rings it will lube and dissolve the crud

to free up the rings if they are stuck

 

just courious what order did you test in? 1 2 4 3 ? battery could have just got weak on you

 

That's a good question. Lol. I think I went 1234, but I might have gone 1243. Brand new battery. I haven't started the bike yet because of a broken float post, and the carbs aren't on the bike. I'll test again tomorrow.

 

from info overload https://www.xjbikes.com/forums/threads/the-information-overload-hour.27544/
d) make sure the battery is FULLY charged, and remains so throughout the course of these tests! It is actually recommended that for purposes of compression testing that the TCI be un-plugged and jumper cables to a large capacity battery (i.e. car battery) be used to make sure that the cranking speed remains pretty constant between each reading. Slow or sluggish cranking speeds will reduce the indicated compression pressure. Yamaha specifies their compression pressures at 300 rpms (which is why the battery needs to be in good shape).


g) Let the starter cool down for a minute or so, then do the next cylinder, etc.).

 

How long does it need to soak for?

 

a few days

 

As far as a new carb body, hit up @chacal

Mine is still repaired with JB weld, but I know it won’t last forever so I bought a spare so I can do a replacement this winter-or whenever it goes TU.

For my 700N it was $130.

 

I picked one up in the wanted section for $55 after postage.

 

While I wait for the new carb to be delivered, and while the cylinder is soaking in ATF/acetone, I was thinking of replacing the throttle shaft seals. Does the carb have to be completely disassembled to do this?

 

Yes and in my experience the butterfly screws will be your main problem. I had at least 1 screw on both sets I have snap off or have head strip out. The screws are very soft metal. The factory peens the tip of the screw on the back side so you have to deal with that to remove the screws. Sometimes they will back right out sometimes they won't.

 

Would heating them up first be ok to loosen them up? I don't think an impact driver would be a good tool there.

 

Heat will help but if you can use a dremel and smooth off the peened end of the screw it should come out a lot easier. I didn't do that.

 

He has Hitachi carbs on his 650 which aren't peened like the mikuni's on your 550. They can still be a bit of a pain but the proper sized JIS screwdriver, the right amount of torque in the right place and they usually come out without too much issue. Penetrating oil or heating may help just dont try to use both or you may end up with a fire. Use some locktite on the screws when you put them back together making sure the throttle blade is aligned properly in the bore

 

I use PB Blaster with a torch all the time. Smells great and gets rid of the gnats in the garage.