My son owns a 1985 XR80 and runs terrible. I replaced the rings because of the black plug and smoking exhaust (its a 4 stroke)
Can the timing be adjusted ? My be the jets replaced? I'm getting frustrated into why it wont idle smoothly. Can anyone help ? Thanks for reading. Bob

 

Did you clean the carb and check the spark plug? If so, try adjusting the pilot screw to get a smoother idle. Fresh gas may also help.

 

when replacing the rings did you hone the cylinders? what year XR? are you sure your timing is correct(eg chain/tooth position)? ws ti running proper prior to you opening it up and doing the rings?

 

check the ignition points my XR80 needed them cleaned all the time but it was a bit older so i do now know, but a guess anyways.

 

For sure... if its a points system your going to get sh*tty running if the gap is not correct. but one step at a time

 

valves need adjusted?

 

Sounds like all good stuff to check. The cylinder was honed, new spark plug, I had to get the timing chain back in position. My bigger question is the timing. Can the timing be off by a link or two positions ? How do you adjust for timing ?

 

yes you can be off... you can be off by a tooth +/- or you can be off by 180 degrees. I mean to be honest I dont have hands on experience with an xr, but I do know about mechanical issues. Also if the bike is already together, check points gap and points condition before removing the valve cover to look at tooth position. Have you cleaned the fuel system (lines, filter, carbs)?

 

Yes, I cleaned the carb. I know the timing is close and not off 180 degrees. Also I'm using new gas. And yes it ran the same way before I changed the rings. How can the timing be slightly adjusted ?

 

on the xr I am not sure about the cams... but usually it's on or it's off, unless you have adjustible gear up there... other than that the gap/rotation issue at the points is the only other method of control. is your cam chain tension adjusted properly?

 

ya might wanna check your cam chain for stretch as well as your valves, seats, and guides.
the cam chains really like to stretch, and the guides and valves like to get loose and leak.
look at your cam lobes for gaulding, and check your valve springs for pressure and make sure theyre not broken.
might perform a leak down test and save yourself some diagnostic time.
thumpertalk.com, xrsonly.com are a couple good sources for info....service manual and such.
hope this helps.
by the way im lookin for a 70-90 xr/crf block if anyone has one cheap.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ktmoffroad72901 &raquo;</TD></TR><TR><TD CLASS="quote"> ya might wanna check your cam chain for stretch as well as your valves, seats, and guides.
the cam chains really like to stretch, and the guides and valves like to get loose and leak.
look at your cam lobes for gaulding, and check your valve springs for pressure and make sure theyre not broken.
might perform a leak down test and save yourself some diagnostic time.
thumpertalk.com, xrsonly.com are a couple good sources for info....service manual and such.
hope this helps.
by the way im lookin for a 70-90 xr/crf block if anyone has one cheap.</TD></TR></TABLE>