Damn...

So i just purchased another Yamaha XJ this one being a 750 (my other a 650) Both 82's.. It should be a Wonderful day for me right?? Wrong... So I get home from the 20 mile ride from the sellers house and what do I notice? The screw located to the right of the carb Is spinning in place and leaking oil and seems to be runnning hot (when i turned off it back fired) Im thinking its a blown head gasket!!!! :evil: Does this sound correct to everyone? If so How much is it to replace and how hard is it to do? I have a haynes manual on the way for the bike that should help.

Spent 700.00 on this piece of work... It looks like its it great shape... and ran like it was on test drive... but as soon as I got home it was another story :-/. I hope I can still make it worth my money..

Thank you for your help !

 

Not sure what screw you're talking about. Please post a photo or two.

Backfiring/misfiring on these bikes is usually caused by mixed up ignition wires or incorrect mixture adjustment.

 

The screw just seems to keep spinning in place and oil leaks around it.

 

Its a bolt for the valve/cam cover. If the bolt is snapped off and there is a piece left in the hed, you may have to drill it out if there isnt enough sticking up to grab with plyers when you take the cover off.

Worst case scenario the head is stripped for that hole, and you will need to drill it out and put in a heli-coil. A proper helicoil kit for that is well under $30. Not really that big of a deal.

The good news is you need to get in there and check your valve clearances anyway and you can probably use a new cam cover gasket, but Its certainly not a "blown head gasket".

As for the backfire, Its probably well out of tune and doing the valves and then a carb sync (and probably a colortune or at least a plug chop) is in order anyway. Its all stuff that needs to be attended too ASAP but nothing out of the ordinary.

 

Great picture, it is the eclipse over Greenland isn't it ?

 

PTS has it right. In addition, you'll probably need a new set of the rubber washer/spacers that go around the bolts. These are special bolts that have stops built into them. They are not designed to be torqued down. If the PO was trying to torque them down to hide the oil leak (caused by old washers and an old gasket), he probably stripped its socket. Torque spec for these is only 7.5 lb ft.

 

Lol, sorry about bad quality on the picture . I took it in my garage with poor lighting..

But thank you for You information.. Is this bad to be driving on? Seeing as there is only another month of riding time left I might have to just ride it out until winter. Then fix it.

 

Did you compression test this bike before you bought it?

That would tell you about your head gasket question.

 

Wait whoa stop.

You just bought this bike?

Stop trying to ride it right now, and pull the rear wheel: http://xjbikes.com/Forums/viewtopic/t=15874.html

I wouldn't ride it with a loose/stripped/broken valve cover bolt, it will just pee oil all over everything. The gasket under that cover is the valve cover gasket, not the head gasket. And, as pointed out above, the rubber "donuts" on the bolts are what actually do the work. The bolts have stop collars; something your PO obviously was unaware of. Tightening them too much either breaks or strips something.

Dude, it's not a used car. You can't just start riding it, you're gonna get hurt. You need to check a whole BUNCH of things first, starting with the BRAKES.

 

That "spinning bolt" would have nothing to do with the "backfire"

Can you post a pic of your sparkplugs, laid on brown cardboard, 1-4 ??

 

As far as the backfire, you have to start with the valves. Then make sure your carbs are clean/ok, verify how it is jetted. Proper sync with a YICS tool. Does the bike have the stock airbox and exhaust? You will probably need a new air filter too.

 

Thing has brand new brakes and tires.. I did a minor inspection of everything, Im still new to motorcycles though so I dont know what all to look for.

 

Read "Be the Bunny" and take a MSF course, or maybe a motorcycle shop organizes rides - basically learn to ride safe.
be the bunny clicky

Read "Church of Clean" as most likely your carbs need a good scrub and a proper tune.
carb cleaning

Get a service manual and >"ASSUME"< that no maintenance has ever been done (unless you have written and dated documentation)
Start with brakes and bearings. Good to see you have new tires and new rear brake shoes.