A few XR80 Valve and Cylinder Questions

[92CR500]

A buddy handed off his kids '85 XR80 so I can fix it up for a young relative.

 

I found the timing chain stretched.  Exhaust valve appears to have contacted the piston (slight mark on the piston).  I pulled the valve and its bent.

 

- Has anyone used a non OEM valve?

- Any chance the valve will work w/o machining the seat (maybe some heavy lapping)?

 

I also have a '95 donor motor (head / valve are in worse shape).  I read that some are saying you can get the chain out the side cover so I tried it on the '95 and can get it all out except for the last three links.  So it looks like I'll be splitting the cases.

 

The head was already removed from the'85 when I got it so I don't know what seals were in there.  I was looking through some parts diagrams and see a seal gets placed on one of the head studs between the gasket and head.  I got the seal but the head doesn't seem to bolt down flush with it in place.  In parts diagrams for the '95 I noticed the motor doesn't use that seal.  I examined the heads between my two motors and don't see any difference.

 

- Any idea how to identify which head / cylinder would require that seal (maybe my '85 had something swapped).  Should there be a recess machined in the head for the seal?

 

Thanks for any help!

 

 

 

[Alexxxx]

You have to split the cases to change the timing chain on XR80. On XR100 you could do it without.   

 

They used thicker head gaskets 'till '91, there the square o-ring is needed.

'92 up the head gasket changed in a thin metal gasket without the need for the square ring.

No change in head design, you may interchange them.

 

Give the head to a Honda dealer and let them do a valve job, when you're not satisfied with lapping.

I only use the Honda valves.

[socalxr]

Actually you can pull the chain through on a 80, it's just not as easy. 

[turbo dan]

If the chain is stretched I would expect the cam and crank chain sprockets to show significant wear.

[92CR500]

The head gasket was metal so I guess I'll skip the o-ring!  Thanks for straightening me out on that one!

 

I'll probably go with the OEM valve rather than the el'cheapo off FleBay.  Will check the cost at local dealer for the machining, wonder if they'll do just the single valve.

 

SoCal, I couldn't do it.  Three links still inside the motor and no way they were coming out.  This was on the '95.  I did an internet search and found posts from two people that said they could do it.  Don't know if it was coincidence but both were on 80's motors.  I'll try it before cracking open the '85 but don't expect anything to be different than the '95.

 

I haven't examined the crank sprocket but the cam sprocket does show wear.

 

Thanks!

[socalxr]

Dumb question, but you did pull the seal out right?

[92CR500]

Yup seal was removed!

[92CR500]

Anyone know of a machine shop in the MD / VA area to do the valve seat??

 

I called two:  Heyser said the machine shop they used to use closed and they now send everything out.  I used Battley Cycle to bore the 500 (back in 2000) but they said they don't do the valve seat.

[92CR500]

I got the valve and it lapped in w/o needing any machining.  Temporarily assembled the motor and it has compression.

 

If I roll it over slowly, I can hear the compression leaking into the bottom end.  The cylinder looks good (no scratches).  I don't have a bore gauge so I can't check if its just worn.  Unfortunately my automotive compression tester won't fit the tiny spark plug hole (even with the smallest adapter that came with it).

 

Is it normal to hear it leaking?  Any idea on how to determine if the leak down is excessive?

 

Thanks

[92CR500]

Finally got a chance to play with it a little more today.  Did a leak down test and it seems good (5%).

 

Unfortunately the repair manual I have said not to lap the valves as it may remove a coating from the valve and cause it to wear out fast.  I already lapped the OEM valves, hopefully they'll hold up.

 

I tried pulling the cam chain out the crank seal opening and it came right out!!  There was no way it was coming out of the '95 motor.  Maybe there's a little more clearance on the '85 or perhaps the flexibility of the worn chain let it slip out.

 

So here's the question.  Should I stay with a Honda chain or are the aftermarket chains ok (moose)?  Same question about aftermarket oil seals.

 

Thanks