Blown head gasket ?

Hey everyone. New here. I’ve got a 1981 Yamaha xj650 maxim. 13000 miles on the bike. Ran pretty well, needed some carb work. As I took down the bike I noticed what’s in the pictures. Oil looks fresh. Could this be exhaust manifold leak or is it definitely head gasket? Also picture of cam chain tensioner gasket leaking ? I have no doubt I can figure out how to change a head gasket. I just don’t know what other things to look for or to replace if I end up tearing into it. Any input would be much appreciated. Thanks !

 

Welcome to the forum. You should do a compression test first. They usually leak at the cam cover gasket and run down. Make sure the oil is not running down from the cam cover in the spark plug areas and making its way to the head barrel joint. Replacement of the tensioner gasket is easy have you got a Haynes manual? You should not have oil in the heads exhaust ports. I would remove the cam cover and thoroughly check the gasket first. I have not seen an XJ head gasket fail before so eliminate all the easier checks first.

 

Perfect . I do have a Haynes manual. After a bunch, and I mean a bunch of reading, that was the direction I was going to head. Going to put a new valve cover gasket on. Check compression, clean it up. Run it and see if the leak persists. Is it worth backing head bolts a scosh and retorque?

 

I would leave the head bolts. Just find out what compression you have first and checking the valve clearances is wise before stripping the top end of the engine. Low compression doesn't mean head gasket has gone. If the machine was stored for a while the rings can stick. A little 50/50 mix of automatic transmission fluid and acetone frees them up.

 

While staring at the bike, like most novices do while waiting for parts, what is this thing. It connects into main wiring harness with a brown and yellow wire. Mine seems to be broken where it connects to the tab. Thanks again you guys are awesome !

 

Rear brake light switch.

Just looks a little bent to me.

 

When doing the valve clearances if necessary you can crack the head if you turn the cam against the bucket holding tool. Check with us before you do any valve clearance work.

 

Ok, valve gasket comes in tomorrow, work begins this weekend. What do I need to know about checking valve clearances ? Also need to change the o ring on the manual cam chain tensioner, simply unbolt, change o ring and gasket and bolt back on ? Thanks !!

 

Yes unbolt it and change the gasket and o ring.

Valve adjustment information here.

https://xjbikes.com/forums/threads/bigfitzs-airhead-valve-adjustment-with-pics-parts-i-ii.116006/

 

Ok. Valve covers off. Wrong gasket…… dumb

here are my clearances. I believe they are all wrong and I need to start checking what shims are in place now. Is it a one at a time, remove and replace, then onto the next one ? And then do it all over again when I get the correct shim size ? Thank you all again. It’s a process as a rookie for sure

 

Dumb question. I think I have it figured out per the conversion diagram. I decided I want to order the bucket “holder down” thing from chacal first. Will I order shims from chacal or is that something I possibly can get locally ?

 

No, not a dumb question. It would be more efficient if we could take them all out and swap around but you can't do that. Just do one at a time. You WILL do damage to the head or buckets or the cam itself if you take the shim out and turn the engine over without any shim in the bucket. Take out a shim, record what size it is, put it back and move to the next. If you are very, very, very lucky you might be able to swap around what you have to get the right clearances.
Hogfiddles has a shim pool and will trade with you by mail to get the right shims for correct clearances. There might be somebody local to you that will as well. Do you have a friendly, helpful local dealer? Sometimes they will have a stock of used shims and will be reasonable on prices. Good luck. It is not really a hard process, just a bit clumsy if you don't have a few extra shims saved.
Oh, before I forget. It will be easier for you next time if you record the size (number imprinted on the shim) you are putting in to get the correct clearance. That way the next time you will know what size shim you need to go to without taking the old one out to check it while you wait for the new one to arrive.

 

So based on the conversion diagram the exhaust side is .21-.25 and intake side is .11-.15
I know this is like splitting hairs, but since the clearances shrink as time goes on, is it best to get closest to the highest allowable clearance ? I love this stuff. I never thought I’d dig this far into it but with your guys help, the mechanical skill set I have is drastically improved !

 

The intake spec is .11-.15mm, but the exhaust side is .16-.20mm for your engine.

 

Ok guys. Finally after a long delay of ordering parts, I have corrected all of the valve clearances, gaskets on and good to go. I’m getting down to the nitty gritty. There is one thing, that I cannot seem to figure out where to get an extended (by 5”) throttle,clutch, and choke cable. I found this for harley sportster, it appears to be the same, and at 130 mm I really need 120 but, could this work for throttle cable? I’ve searched the web deeply looking for an extended set of xj650 cables but I don’t think such thing exists. Running Murray carbs, so maybe the added 10mm may help

 

Venhill sells cable kits you can customize to any length. Requires a bit of soldering but not a huge hassle.

 

Well guys, I’ve come a long ways since last posting on here. This is her current stance. Valve clearances were done, and everything was put back together. After lubing everything (cables, engine oil, etc) doing all my electrical double checks, I believed I was ready to fire it up. Put the new Murray’s carbs on, connected the fuel lines and vroom, fired right up. after first test ride, I noticed after a few miles after coming to a stop that’s the idle was sort of hanging at 3500 rpm. Back to the board. Changed all the spark plugs, rerouted a few fuel lines and the throttle line and hanging idle is gone. Rode another 6 miles on the bike and now, starting is difficult (but most likely a battery I believe) but the bigger at hand is, when you dump the throttle the bike dies more or less. If you slowly open the throttle bike with throttle up as normal. Same when riding the bike, the initial 2200 rpm range causes a bog. Now, I by all means am mo expert but it would seem as this was a carb problem. But Murray’s carbs swears by there carbs which leads me to think, what did I do? Please someone tell me I’m an idiot and it’s just this simple “this”. A lot of time has been dumped into this thing “joyfully” but I’m hoping this is a simple one. Btw- I just read through the forum “throttle and carb issue” and it seems like this is something simpler. Timing ?
Thanks

 

By the way, I switched the petcock to one with out the vacuum tube , because I assumed it was necessary with the new Murray’s carbs. Did I miss something here? Should I have rebuilt the petcock and attatched one of the 4 breather tubes on the new carbs ?

 

Sounds weak, you need more fuel in the lower range - bigger jet required.

 

The only reason I say it isn’t carburetor is because in any thread speaking of Murray carbs, Murray normally speaks in and says absolutely do not touch the carbs. That they are jetted and synced specifically to the bike. This is why I was hoping it was something else. Would some sort of vacuum leak do something similar ?

 

I don't see how you can "synch carbs" to a particular bike/engine in advance of installation since synch is the process of adjusting the carbs to accommodate differences in the individual power output of each cylinder, and thus individual engines.....due to a variety of reasons (valve shim clearances being the most predominant) .........must have any multi-carb setup (in other words, anything besides a single carb system) an adjustment of individual carb settings in order to create an equality ("synch") of cylinder power output across all of the cylinders.

 

So it doesn't actually die I am assuming. I am also thinking for non CV carbs blipping the throttle is more of an issue in that the engine will typically bog for just a moment, but should recover rather quickly and raise the RPM

Where in Colorado are you located, specifically what elevation - could be quite rich if not jetted for altitude as once again CV carbs kind of self compensate at elevation, whereas the Murray carbs will not

How are the plugs looking as far as color?

 

The plugs I just changed were a little fouled but overall pretty decent. It will die if you stay on the throttle enough. I’m at like 5300 ft in elevation, which I did think about.
But, with that being said, I think because it was my first time every doing valve clearances, I’m going to go back in and re check all clearances now that I have a better understanding and make sure that is not my problem.

does anyone have any input on the original petcock having a breather tube and the aftermarket one installed not having one ?
Thanks everyone, I would have never undertaken something like this without xjbikes forum.

 

The original line to the XJ petcock is to operate the vacuum diaphragm when the bike is running, which then allows fuel to flow in the On or Reserve position. There is no issue going to a manual petcock, but you want to be sure to plug that vacuum line, or just use a cap like the other 3. It would also be good practice with the manual petcock to get in the habit of shutting fuel off when the bike is not running just in case there is seepage and overflow past one of the carburetor needle inlet valves