A-Ha moment and a follow on question

Really enjoying the forums and I am constantly picking up useful information for my new/old bike. Reading one of the topics yesterday I came across advice from BigFitz52 that said "valve clearances: too tight and eventually you will burn a valve". I recently bought an 1982 maxim 650 and I have one cylinder that is dry fouling plugs, is low on compression (125 psi) and get hots to the touch much much quicker than the other cylinders (I use my calibrated finger tips while warming the bike up). I measured the valve clearances incorrectly since I assumed that as the valves wear clearance increases (In the cylinder with lower compression there is no clearance). I figured no clearnace = no problems (this is my first engine without either hydraulic lifters or a 2-stroke...damn I love the simplicity of 2-strokes, lol). So a couple of questions after framing up the situation: I bought the bike for $500 with the intention of putting no more than $500 into it doing the work myself (it has a current inspection, good tires and the only items I thought when looking at the bike that needed attention were fork seals and the improving the brakes)...... so the cylinder with 125 psi is it beyond redemtion or can I adjust the valves and likely improve the situation and if I likely will be successful with the valve adjust should I buy a valve adjust tool on Ebay?
Thanks,
Rich

 

Rich; You've made an incorrect assumption. As the valve "train" wears (it doesn't, the valves do) the clearances get tighter. This is because the valves pound themselves into the head faster than the rest of the stuff wears.

Too tight=bad.

Adjust the valves, re-check compression. You can buy the tool anywhere for generally less than $20; or use the "zip tie" trick ($0.)

CHECK THE BACK BRAKE RIGHT AWAY: http://xjbikes.com/Forums/viewtopic/t=15874.html Don't put that one off it's critical.

That "hot cylinder" could also be running lean for a variety of carburetor-related reasons and can also cause you to burn a valve. Is it by any chance #3? If so then check the vacuum line to the petcock for starters...

Pick up a service manual, and welcome to the wonderful world of the 25+ year old XJ series Yamaha.

Now get ready to learn about carburetors.

 

The low compression cylinder might just need the valves adjusted. If you give it a shot of oil first, then do your compression check on it. If the compression stays the same I'd look at the valves. If compression increases then rings.

 

Thanks for the replies. I've already bought rear brake shoes along with fork seals and I will be buying a new Ebay radial front master cylinder and a rebuild kit for the calipers and new pads. The cylinder with 125 PSI compression is cylinder 1 (closest to the shift lever). Thanks for the heads up on the zip tie method, I searched for it on the forum and I certainly have more zip ties then $ for a custom tool...Nice snowfall here in NH last night so I have until next spring to take advantage of this forum and time in the garage to get the XJ back to being a safe enjoyable bike to enjoy the scenic backroads of my state.

Rich

 

Rich:

If you run down Route-3 and stop-by my place ... I'll let you take my Valve Bucket Tool for the job.

There's a Used Parts Shop in Nashua for Shims.
It's called Drum Hill Cycle, ...
Although, they moved up to Nashua for a warehouse with more room.

 

+1 on the valve adjust, especially if you measured NO clearance.
You should be able to get your bike in pretty good shape for $500, and plenty of time to polish it.

 

Thanks Rick, I would like to take you up on your offer to borrow the valve tool and thanks for the heads up on Drum Hill Cycle for the used shims. I live in Nashua and work in Framingham so I go down route 3 all the time. Time to ride, I cleaned the bike up when I got it as a way to assess it's condition and get to know it (and to have something more presentable to my wife who's first comment was "that is ugly compared to your Buell". After spending a few hours on the bike cleaning it up and getting the rust off the chrome her comment was "wow, that cleaned up nice, but I still like how the Buell looks better....lol)

 

Welcome to the boards and congrats on your new purchase panky.

Ditto on the wife, mine had similar comments but I think the bike has grown on her a bit. She still prefers to ride on my Vulcan though.

I think she doesn't get the vintage thing.. Anyway... When you get the time post some shots of your xj.

Glad to see another Granite Stater on the board. Perhaps we will meet on the road one of these days. I am in the Keene area.

Good luck with your project!
Rob