Water in Engine

Hmmm, well the head came off with relative ease. One stud was rotted and came off with the nut, and sadly the right cylinder was full of rust. Even the combustion chamber and both valves were rusted up.

 

#4 cylinder is definitely not happy times. I think you will find that the effects of water are widespread. like polock said earlier, "what you have there is a boat anchor".

CN

 

Well, once you realize you need to replace that motor let me know. I have an '85 engine with right around 35k on it. Has a very slight tick on one valve I think it's on the number one cylinder. Shim it and go.

Also, if I'm not mistaken the 700 frame won't hold a 750 the mounts are to different.

 

Oh I'm there, between here and a couple other forums it seems I have reached the limit of this engine. I am going to call some local breakers and see what they have; one not too far from where I work had a good condition 750 a couple months back. No idea what he wants for it, but there are several on eBay in both 700 and 750cc variants that would be between $4-600 shipped.

This from the Information Overload Hour

Not sure why it would point out that one would need to use the 700 frame engine mounts considering that I would be swapping into a 700 frame, unless someone got excited and started cutting them out thinking they wouldn't work.

 

I believe you're getting some years mixed up with the engines.

IF I remember correctly, the 85-86 700 and the 85-86 750(Canadian......was not available in the USA) airheads are the same bike, just diifferent displacements. The 85-86 750 airhead should drop right into the 85-86 700 airhead frame. You may need to swap the TCI.....................

Your swap has nothing to do with the 650, unless you're looking at a 81-83 XJ750 engine. In that case, yeah, you'd run into the 650/750 swap stuff, but again, that would be for the 81-83 years. It seems like I'm reading that you're getting the earlier 750 engine mixed up into the later frame.........

carry on--

dave f
Dave Fox

 

Just going by what was posted, I have no idea.

 

Couple local salvage yards have XJ's in various flavors, I am going to swing by and see if I can get an eye on one this afternoon. If possible, I'd like to get a complete parts bike

 

Last year, my old lady wrecked her '85 700. Amazingly enough I found another one, same color, same year and within 75 miles of the same mileage.
The replacement bike had some carb issues. I swapped the carbs off the wreck onto it and down the road we went.

The wreck destroyed the front whee,l the forks, the handle bars, the tank and the frame. Front brake lever was also broken off. I kept the rest of of the bike. Cut the frame up for scrap.

Shipping the motor from Wisconsin to Texas may be cost prohibitive, but if you need anything else, I sell parts pretty cheap.

 

Shit, as soon as I was ready to toss this engine in the bin, the damn thing made me happy again. Figured I would try and pull the cylinder block, and damn if it didn't pop off with just a few whacks with a wood block. Sure, the pistons and cylinder walls have some rust on them, but I'm seriously encouraged. Had it been a major chore to pull, I'd be more convinced that it was f***ed, but nope.

 

Jeez, you got to believe!

 

I am nothing if not determined.
I did run by a salvage yard that said they had several XJ's in decent shape. They did certainly have several, three 750's, a 650 and a 550 Seca that I really liked. Sadly, "decent shape" is a very subjective term. The 550 was the most complete missing just some body parts, all the others were all missing their starters, only one had carbs, one was completely open much like the engine I already have, none of them looked worth the $200 he was asking for a mill.

 

Hey, maybe you can get the EvapoRust folks to sponsor your rebuild to prove how good their stuff is. At least get them to give you a sample. You can show them this thread and to "before" pics. Still having fun?

 

I wish, at any rate I will photograph the hell out of everything for a reasonable Before:After slideshow.
I would be having fun if I haven't had to work till past 8 the past few nights and still had some time to wrench when I get home. But I am clear this weekend so I am looking forward to removing the pistons, rings, dunk them all in the sonic bath and maybe even get a hone and try to clean up the bores.

 

These are the worst of the pistons

 

Going to back to my local salvage yard engines from earlier; most of the engines he had didn't appear much better than what I've got already, except for the fact that they are 750's. I have searched through a couple dozen different terms trying to find this answer, so I apologize if it has been answered, but the 700 and 750 share the same bore, with the 750 having a longer stroke, thus a different crank, correct? I understand, though, that the cylinder height and pistons are different, as well as compression ratio. So simple crank swap isn't a real consideration.
Thus theoretically, if one had two questionable engines, a 750 and 700, both of which would need work to make them functional, one could take the internals from the 750 and move them to the 700 cases (to keep the VIN matching the frame). This would require the use of the 750 cylinders and pistons and likely the head. Basically the only thing left from the 700 would be the cases themselves. The advantage is a greater parts availability for 750 stuff. Big bore kits and the like.
I am not considering the tranny at this time, although input on that would be helpful for the future.

 

don't worry about VIN #'s the only one that counts is on the frame

 

I know, the title is tied to the frame, I've been around vintage bikes for a while. But if I would have to rebuild a junkyard engine, I may as well keep the VINs together. Meaningless except to me I guess.

 

Pistons turned out well. I'll probably still soda blast them to get the ring lands cleaned out.

 

the thing with swapping cranks is the bearing colors, green, pink, poka-dot who knows, the cams should be kept with the head too