Crf50 head gasket....

[qkenuf4u]

Yes I've googled it n everyone says "no can't be the head gasket" ... Lol well it's most certainly the head gasket in this case...Across the whole Top side where the tab sticks out is leaking... Yep new gasket n sealer.. didn't stop the leak ... Cylinder is torqued correctly n it idles ok, starts easy, revs OK but does have a little dead spot , idle hangs a tiny tiny bit.. yep I've played with the air/fuel screw.. likes 2 turns out..

Just seeing if anyone's found a reason for it .... It's a friend's on mine.. he bought it for his kid for Christmas n like a dummy didn't hear it run I guess...

I'm a bike tech for a living but haven't messed w a whole lots of these little bikes... Nothing special about em but doesn't make sense why this one leaks.. everythinis clean n flat from what I can see...

Maybe cylinder/head studs are just stretching instead of taking the torque ??

Edited January 8, 2017 by qkenuf4u

[ohiodrz400sm]

Did you also replace the collar and o-ring on the top of the cylinder?

Are all the dowel pins in? Is the acorn nut and copper washer on the correct stud? Are the studs spinning when torquing the nuts?

Just throwing ideas to think about at you...

Edited January 9, 2017 by ohiodrz400sm

[Go Big Red]

Did you also replace the collar and o-ring on the top of the cylinder?

Are all the dowel pins in? Is the acorn nut and copper washer on the correct stud? Are the studs spinning when torquing the nuts?

Just throwing ideas to think about at you...

this is exactly what I was thinking also.  there is a very specific spot for those nuts and washers and o-rings.  in fact, I'll just call it for all of us.   you either missed the  o-rings or didn't put on the acorn nuts and washers correctly.  I think we all did this once trying to get a top done on these little engines.

[qkenuf4u]

Did you also replace the collar and o-ring on the top of the cylinder?  you mean on the front side of the cylinder ? no i didnt replace the o-ring.. its not leaking on that side. its all along the back side where the tab sticks out.. all good everywhere else..

Are all the dowel pins in?  yep

 

Is the acorn nut and copper washer on the correct stud? studs all looked same length to me and acorn nuts are all the same.. not sure how ya could put em on wrong...

 

Are the studs spinning when torquing the nuts? far as i could tell none where spinning and they are def. tight... started at the 96 in/lb and went up from there slowly after heat cycles... thats why i asked if maybe they are just stretching instead of torquing down...

 

[dirtbkr188]

Quite possibly, the acorn nuts could be bottoming out before snugging the head all the way down. Try replacing the acorn nuts with four conventional 6mm nuts torqued down to 108 in-lbs.

[ohiodrz400sm]

Oil flows around the bottom left stud, the one with the copper washer. If you use a regular nut it will definitely leak.

The studs are stretching, that's how bolts work. It is possible though they were over torqued at some point and have yielded.

Edited January 13, 2017 by ohiodrz400sm

[qkenuf4u]

Oil flows around the bottom left stud, the one with the copper washer. If you use a regular nut it will definitely leak.

The studs are stretching, that's how bolts work. It is possible though they were over torqued at some point and have yielded.

Only leaks on top side where the tab sticks out (carb side)

All 4 studs have a washer n nut.. nothing oil wise leaks anywhere...

Actually it's a little better now that it's SAT for a week without running... Ilthe sealant had a chance to dry so not remotely as bad a leak now..

But yes I would say the studs are probably stretching more than anything else.. have to see if customer wants to replace them..