It should not be there!!!!!!

[BigBoreSwede]

Hey.

I´m about to pull the head and cylinder of my engine this winter. First time ever!! I did´nt come very far before I found this behind the camchain adjustment assembly......a worn and twisted nut

I have been running my bike all summer with no problems so I guess I´m lucky......but where does it come from? I don´t belive in God so that´s not an option


/BigBoreSwede

 

[Tech7]

It should become apparent as you remove the head.

 

[BigBoreSwede]

Yeah, I guess.

I´m planning to pull the cylinder to change the base gasket but if I don´t find anything suspicious should I assume someone forgot it there??

/BigBoreSwede

 

[5twins]

What wrench size fits it? If it's 12mm, it may be a valve adjuster screw lock nut that came loose and fell off sometime in the past. That's about the only nut I'm aware of in the top end.

 

[XSLeo]

I can't think of where else it could have come from. Some years had a 13 mm nut as a lock nut. My 75 has 13 mm, the 81 and 82 are 12 mm.

 

[BigBoreSwede]

Ok.....now a have an answer to this mystic nut

As you can see it´s most likely that some braindead son of a b...... has left or forgot a valve adjuster locknut in the head since all the rocker has locknut mounted. It´s have been grinded by the camknock but have cracked the "wall" between the cam and the valvespring.

When I pulled the engine out of the frame and put it on my workbench the nut problably falled down to the camchain adjuster were I found it later!!

The cam has some pitting on one knock but not on the one grinding the nut and besides that the cam seems to be in good shape......so I guess I´m kind of a lucky guy

Now I´m wondering what I should do with the cracked "wall". What´s the function?? At least I need to weld it so that it´s not cracking anymore but maybe I need to straigthen it to??



/BigBoreSwede

 

[gggGary]

I would go with "do nothing, or maybe a dab of JB weld". real welding is likely to create more problems then it solves warping, stress? No real knowledge just shooting from the hip. because of the thinness of the wall it might just be there to help direct oil back to the sump.

 

[TwoJugs]

I would pull the piece out so I didn't have to worry about it breaking off and doing more damage. Like gggggggggggGray said, welding might cause a new round of problems.

 

[BigBoreSwede]

Hmmm....ok.

First.....what´s JB weld?? Some sort of compound??

The problems that might occur...would that be that the head will bend?


I have no experiance what´s so ever in this but with this "wall" gone, would not that result in a valve flooded in oil?

/BigBoreSwede

 

[TwoJugs]

It looks like it might be a dam to slow down oil being slung by the cam lobes? Not sure if it will put too much oil back there to start a leak or allow it to suck through the seal easier? That hole area is full of flying oil anyway when running. I would be worried about the welding upsetting the machined surfaces close by. They are pretty critical beig a metal to mteal seal with only liquid sealant in between. Maybe a couple of small spot welds to stabilize it? JB weld is an epoxy type glue that is tough as steel and holds up to most anything. I would just be worried about how well it grabs the metal being so oil soaked and it might come lose from vibration or different expansion rates then the metal itis on.

 

[xjwmx]

I would wonder if welding it could misalign the machined places any more than they already are from the hit that cracked it.

 

[XSLeo]

JB Weld is an epoxy that is reinforced with steel or aluminum. don't recall which.
You may have something over there that is the same just with a different name.
I would clean it vey well. Sanding it a bit with 100 grit sand paper will give it something for the epoxy to bite. Apply 1 or 2 thin coats. Once its cured, it will be fine.

 

[BigBoreSwede]

Yeah, we have someting like JB weld here in Sweden. We usally call in chemical steel, an epoxy compound.
Maybe I could lower the ridge on the "wall" a bit so I´ll be alble to put the JB on 3 sides of the damage. By that it should be stronger if the compund gets shapet like a "claw" around it, right??

But........what´s the purpose of this "wall"?


/BigBoreSwede

 

[Tech7]

JUst a guess, but I'd say given that it's on the back of the head it'is to keep the oil toward the center. It also could just be for strength, like an I-beam. I'd leave it, unless it feels very weak. I wouldn't trust any epoxy for fear of it coming loose... That must have made a pretty noise for a while, you think?

 

[XSLeo]

There was some discussion on the old 650 Rider forum about this. As the cam spins it throws oil. The wall was there to keep to much oil being thrown around the intake valves. If too much oil gets thrown there it may not drain fast enough and get pulled past the valve seals and into the cylinder.
If you prep the area well the JB Weld will hold. I've not had any fail if properly prepped. My sump filter patch is holding fine. I've even patched the water jacket on an old truck I had. It's probably still running with it on there, that was in 86.

 

[BigBoreSwede]

Okay.

Tech7.......this is my first XS but as I understand there is some amount of "noice" from this engine but I don´t think the enginenoice has been "wrong" in any way.

But this summer I was riding the bike at low speed/5th gear when the engine suddenly backfired and died. I pulled the clutch for a while, put in 4th gear and started the engine again with the clutch and it work fine after that. That´s the ONLY time the engine has been acting weird since I bought it.
Maybe the nut changed it´s location at that time??

When it comes to the JB I´m a big fan of it......BUT I´m worried about the vibrations and the amount of movment in the head since the head gets pretty warm when running I guess. Hope you guys know what I mean here?! The JB is really "stiff" and I´m unsure it will follow the movement due to the heat.....am I right??


/BigBoreSwede

 

[xjwmx]

What would you do if, say, it was your airplane motor? Or better yet, your daughter's airplane motor.

 

[pyroman]

Wow! In Aviation We call that FOD. Foreign Object Damage. It can bring down a Honda 50, or a Space Shuttle. someone had their head up their ass. I would spray out the cracks repeatedly with carb cleaner, then follow up with compressed air, to dry the fractures. Then a 2 part application of JB WELD first filling the cracks only, like a weld bead. Cure. Then, a second application, feathered at the edges to reinforce the repair. I don't think Thermal Expansion will be adverse enough to cause a problem. IMO.

 

[BigBoreSwede]

Alright!

Thanks alot all of you!!! It´s really helpful when you can´t figure it out by yourself.

I´ll give this JB some time to think over it and I´ll surely return with some pics of I go for the JB alternativ.

Now I´m down to the garage to clean up the cylinder and a little bit of this and that


/BigBoreSwede

 

[nj1639]

JB Weld is an epoxy that is reinforced with steel or aluminum. don't recall which.
You may have something over there that is the same just with a different name.
I would clean it vey well. Sanding it a bit with 100 grit sand paper will give it something for the epoxy to bite. Apply 1 or 2 thin coats. Once its cured, it will be fine.

It's steel, as it has a magnetic attraction.

Looking at the pics it appears that the piece is just about broken through. IF it wiggled at all, I'd break it free and jb weld it back in place, of course after a good cleaning.....acetone?