86’ Yamaha XJ700-X - Valve Shims

Howdy, plan on pulling valve cover to check clearances this weekend on a new to me 1986 XJ700X - 18k miles - I had an 85 xj700 air head that was very simple to check and shim but I have a feeling I’m not going to be afforded the same luxury with this bike. Is there anything I should study up on before jumping into this if I need to change shims out? Advice? Instructions? Thank you in advance.

 

The cam shafts need to come out to change shims. Make sure you have a manual
You got this!

 

Dont over toque bearing caps or valve cover bolts. There is dowl sleeves on caps, dont drop them down chain gallies or spark plug holes.

 

Have done one of these yrs ago, why I pass them up now for flipping. You will need a manual for sure as stated above. Make sure you do the math and check it a couple of times. You don't want to have to go back and removed the cams until the next service cycle. Good luck.

 

Thanks guys - found this guy on YouTube and is seems like a great resource/visual walkthrough for this specific job. He also has carb rebuild videos for the Mikuni BS33-34s.

www.youtube.com/@dwood2066

 

I’m backkkk - so according to the manual, I should have a TDC marker under the timing cover.. it doesn’t appear to be there. If it is in fact missing and not designed this way, how do I know if I’m at TDC for clearance check?

 

Hmmm, when you took that cover off you didn't find that missing screw or stamped mark tab? Not still behind anything in there? I would take a small straight edge and make a think line through the scew hole for the TDC mark.

You can then put a straw, or something that will not hurt the top of the piston and slowly move the crank until you know TDC is at with ##1 cylinder. There should be a spot that the object you are using stops going up and starts to go down. Judge that with the new line you put through the screw hole.

 

Yeah unfortunately it’s just missing completely. I’m seeing signs that this engine was dismantled and put back together to a certain degree from crank case up. Could be a good thing, could be a bad thing. I’ve run a borescope through every nook and cranny and all looks great so I’ll side with it having a top end rebuild at some point. I’ll try what you mentioned tomorrow. Gotta wait for some tapered feeler gauges to come in since my rounded ones won’t fit.

 

When I my X, I did a new top end on it as well. Man the bike ran great after that.

 

Valve Clearance Check

I checked the valve clearances today — it looks like there may never have been a marker in the normal spot/screw hole as we discussed earlier. I found TDC by aligning the TDC marker with the mark on the top pickup coil sensor (photo attached). I also used a dowel rod that I marked in mm increments and placed it into the sparkplug hole and onto the piston head. Every time that I aligned the TDC marker with the line on the pickup coil sensor, this reflected on the dowel rod as its upper most point before descending when continuing to rotate the engine counterclockwise. @Timbox

I followed this sequence when checking clearances: I rotated the engine counterclockwise one full turn back to TDC each time as needed to get the correct cam lobe positions.

Example:

• Cylinder 1 intake and exhaust lobes were positioned correctly at TDC for measurement.
  
  
• Then I rotated the engine counterclockwise one full turn back to TDC, and cylinder 2 intake lobes were in position.
  
  
• Another full counterclockwise rotation back to TDC and the exhaust lobes for cylinder 2 were correctly positioned.
  
  
• I repeated this process for the rest of the cylinders as needed, following the 1-2-4-3 firing order.
  

Is this the correct method for checking clearances while keeping the firing order in mind?

My concern is that only 3 of the exhaust valves were in spec. This is making me second-guess whether I did everything properly.

Here are my measurements:

Cylinder 1

• Exhaust: 0.20 | 0.20
  
  
• Intake: 0.08 | 0.11 | 0.11
  

Cylinder 2

• Exhaust: 0.18 | 0.20
  
  
• Intake: 0.09 | 0.06 | ~0.01–0.02 (No clearance? — my smallest feeler is 0.03mm and it wouldn’t fit)
  

Cylinder 3

• Exhaust: 0.18 | 0.18
  
  
• Intake: 0.11 | 0.08 | 0.09
  

Cylinder 4

• Exhaust: 0.15 | 0.15
  
  
• Intake: 0.09 | 0.08 | 0.07