Bought an XJ, to fix or not to fix?

First post, Hi.

So I got a pretty good deal in an 83 Midnight Maxim 750, for $50.00.

Apparently the shop the owner had it at closed down, and she tried to finish assembling it herself, and somehow or another broke both the cams, in the same spot. All I can figure is maybe the started tightening down one end instead of doing it evenly with all the caps. It wasn't running when they broke. So it needs cams for sure.

They also left the sparkplugs out, some visible dirt down in there, need to pull the head and clean it up in there before it turns over.

The big thing, sorta, is there was in the box three, count em three, new in package Yamaha ring sets. I wonder what happened to the fourth one, if it's MIA or been installed for some reason and not the others. I believe the shop that had it removed the cylinders for something, I suppose the wise thing would be to procure a fourth ring set and do em all while I have it apart.

If it's worth fixing anyway. Been sitting two years, I imagine all the standard stuff, fork seals, hoses, carbs, tires, will need attention.
Like I said, I spent jack on the bike, so I have some room for parts and such. What do you guys think, fix or part out?

 

even if you put 500 dollars into the bike and get it running you still got a good deal.

 

worst comes to worst: you have to buy an engine. $300 or so. If you have the title, it's worth it.

 

I do have the title.

I thought about the complete engine route. I can handle the fixing on this one, just not sure which way to go at this point.

I suppose *new* pistons cylinder and head are cost prohibitive?
I'm still learning where to find parts for this thing.

 

I don't know how far you are from me but I'll give twice what you paid for it if you decide not to rebuild. Cams come up on ebay a lot and sometimes complete heads. The engine had to be miss timed to break the cams. Otherwise they are only compressing valve springs to seat. Valve springs couldn't break the cams so there must have been a valve against a piston it tried to compress. So a bent valve is also most likely to be there.

 

I'm in agreement, you have a great opportunity in your hands. Run with it. I've purchased complete heads off Flea-Bay for $40, you can too. One thought, if the cams are broken and the boobs let the dirt in, I'd be pulling the engine and splitting the case to clean it out. No telling what all they did or didn't do to it. Be sure to replace the starter chain guide and rebuild the starter clutch while your at it.

 

If we knew where you were at... someone was offering up a 700 motor for cheap in the PA area... There was a 750 motor on CL in my area within the last 2 weeks for $250....


Steve

 

I'm in N.C.

The owner swears the motor was never turned over, they broke installing them, I think after looking it over it might have been installed miss-timed with a lobe pushing down on the valve, and into the piston, and cracked it that way. I don't guess it matters anyway, need to pull the head and look at the cylinder bore, see how they look.

I don't think I'd object to replacing the motor, the bike is worth fixing in my general old vehicle estimation, I'm not a bike guy, yet, but I do a lot with old European cars. I don't really want to split the case to be honest, I've done such before but it's been a decade ago.

 

You can vacuum out the Cylinders right through the Spark Plug Holes with a hose that will snake down into the Spark Plug hole and Duct-taped to a HOUSEHOLD Vacuum Cleaner.

You need the Cams, though ... because you have to have the Valves opened to get the swirl and Vacuum to pull-out dust in the hole.

I vacuum out the Cylinder after putting-in a Spark Plug Thread Insert Bushing.

 

Quick question, are the head/cams on an XJ650 the same as the 750? I assume the 750 is just bored out to get it's displacement?

 

I just checked the Yamaha Parts Site.

Aside from the Model Number ... they share the same part number.

That could mean that they are the same Cams.

If they are broken clean .... you could box them up and sent them to Cam Company ... like Delta Cams and see what they could do to repair them.

http://www.deltacam.com/services.php

 

heres a set of cams for $15 plus $10 for shipping...

yeah its on the flea...


flea-bay 750 xj cams


JEEZ! was i off...starting now at $7.99 and $15.95 for shipping...

 

Yeah, there is a head on ebay, near me too. Think I might buy it.
It's not much more than the cams.



Cheap as it is, be the best way I guess.

 

I didn't think it would be that easy finding both cams. Looks like you're in business.

You'll be happy to know that the Motorcycle Press gave the XJ Engine some pretty high marks back when they were writing about them

Their words were: "Hard to Kill" and "Bulletproof" ... so, I guess it's going to be another XJ saved from being parted-out and on-the-road sometime soon ... huh?.

 

Yeah, guess I'll see if I can bring the old critter back to life.

So, I can pull the cams and find out if the valves are sealing, or if they are bent. Do I really chance just using a shopvac to clean out the chambers and not pull the head? Is a compression test going to be meaningful on a motor that hasn't been run in ages? I can add some ATF and do a wet test, but I usually like to see what a given cylinder reads when hot from normal running, but otherwise "dry" first.

 

Without the Camsm in there you should be able to move the crank without valves crashing ... they're all closed.

Vacuum as best as you can ... unless you can actually see crape in there that would be bad.
I remember a Post that we had awhile back where somebody found sheet metal screws shoved down in through the Spark Plug Hole.

You have to jack it over wet.
Marvel Mystery Oil
Don't let the Cam Chain bunch-up.
Put some Marvel in the Holes and take the Engine through a few full revolutions after clearing out the chambers with some makeshift vacuum.

I hope you don't need to do a Head removal. I hope she'll be OK as she sits. But, you never know until Show-time.

You hope that there's nothing serious to deal with. Just time-off!

 

Man, Aren't we sentimental. I am in agreeance with everyone else. Put her back on the road.

 

That's good news, WW. The Midnights were kinda rare and special, IMHO.

Would love to have a Midnight like yours (said with no disrespect to the reliable old girl outside). Good thing I live too far away; might be tempted to come pester you to sell that one.

Congratulations. I think you'll be glad you revived the bike.

 

Well I scored a complete 14K mile head on ebay for $20, haha..

Maybe I'll get to tinkering with it this weekend.

 

I had a Midnight Max. The Black was dull and lifeless. The gold layed-on the aluminum was flaking-off everywhere.

So, ... I de-Blacked the whole Bike and sanded off all the gold plate.

One less Midnight Maxim.
One more 750 saved and running good!

 

This one is actually in decent cosmetic shape. Needs more cleaning. The gold is intact, but I think it's going to go bye-bye. The black is pretty much there seems like. I'll get some pics eventually, we all know what they look like though I suppose.

 

No braggin... but my sig says it all... excluding the 550 part

 

True that.

Our household consists of an 87 740 wagon and 83 240 sedan, Volvo's, and a 77 Buick wagon.
Payments suck.

My head is due in tomorrow!

 

Well my $20 ebay head came in today. The cam's look usable.
The head has a pretty bent over exh stud, and just past the cylinder wall on one there is a good little gauge in the sealing surface of the head. Eyeballing I think it's deeper than one can shave that head, but I"ll have to clean it up and see. Maybe I"ll get luck and my valves aren't bent.

Anyone want to bet my OCD self ends up rebuilding this motor's top end?

Find out this weekend I guess.

 

If you do ...

I want you to Port and Polish-up the Exhaust and Intake Ports. (It won't take much work because they actually do a decent job during the build.

Ckean to bare metal the Combustion Chamber. (Do a number on the Head Chambers. You'll love the idea that Polished Chambers mean less places for Carbon Build-up)

Sand and Polish the Piston Crowns.
This is Hard Core.
Race Prepping. The Engine will run cooler and there will be no place for a Hot Spot of Carbon to Build up.

 

Can do, been there done that on cars. Are these motors prone to carbon deposits/hot spots and/or pinging?

Know off hand how much one can shave one of these heads? I'm ok with premium fuel, an air cooled motor with high comp seems cause for some though though. I'm going to clean up that gouge in the replacement head and see if I can get a depth measurement tomorrow. Might be fixable.
I guess somebody could weld that spot if I really wanted.