3.40. Top End Reassembly

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Top End Reassembly


By Clayton Lubbers


Tools needed: Sockets/wrenches: 10mm, 12mm, 17mm, torque wrench

Parts needed: I recommend the complete engine gasket kit- this includes all gaskets, copper washers, and o-rings- it’s handy for future work. Otherwise you will need the following:

Head gasket

Base gasket

Possibly o-rings depending on the state of yours- it’s tough to tell until you get into it.

Gasket sealant (Three Bond 1104, Yamabond, or sealer of your choice)

For gasket reassembly the only part that *requires* gasket sealant (Yamabond or ThreeBond or whatever your medicine) is the rocker box (top head) to the head itself, since there is no gasket there. There are varying opinions on the rest from using gasket sealant on both sides of the gaskets to using grease to using nothing.




1. Place the base gasket on top of the engine base.


2. Slide the cylinders on to the pistons. Remember the wire you attached to the cam chain? As you lower on the cylinders, run the wire (and cam chain) back up between the cylinders. You can use piston ring compressors or use a buddy to help compress the rings as you slide the cylinders down on to them. BE CAREFUL on this step that you get the rings in completely before you slide them all the way down.


3. Put in the Cam Chain Guide and attach with the two 10mm bolts.


4. Place the head gasket on the cylinders.


5. Carefully lower the head on to the cylinders, again feeding the cam chain and wire between the cylinders.


6. Put 12mm bolts back in near the spark plug holes, and put in 10mm bolt above the cam chain tensioner. Snug to appropriate torque (7 ft/lbs for the 10mm, 14 ft/lbs for the 12mm bolts).


7. Put in the camshaft, sliding the cam chain over top of it. Line up the camshaft with the marks in your manual and the timing mark on your rotor. Be sure to have the slack at the *rear* of the engine (where the tensioner is).


8. Slide in the camshaft bearings.


9. Put your gasket sealant on all touching surfaces of the rocker box.


10. Lower the rocker box on to the head, put on the washers, and put the 17mm nuts on the studs.


11. Put the four 12mm bolts back into their mounting holes.


12. Begin snugging down the head bolts and nuts in a pattern similar to tightening car lug nuts. Tighten the 12mm bolts to 14 ft/lbs, and the 17mm acorn nuts to 25 ft/lbs. Many suggest a higher torque for the 17mm acorn nuts. Opinions vary.


13. Reattach the top-end oil feeder tube. Be sure to put on the copper washers on each side of the banjo bolts on the head.


14. Attach the bottom end of the oil feeder tube.


15. Put the cam “cups” back on re-using the o-rings (if they are in good shape), using new o-rings, or using the gaskets (as your engine specifies).


16. If you have a 1979 or earlier points ignition or have converted to Boyer-Bransen ignition, you must also re-install the shaft, advance weights and points plates. Adjust them to specs per your manual or instructions.


17. Install the cam covers.


18. Back off the tappet screws from the valves a bit.


19. Rotate the engine using the charging rotor bolt. Adjust the cam chain tensioner until it pops in and out equal amounts.


20. Rotate the engine to the proper points, then adjust the valves.


21. Replace the tappet covers.


22. You are now ready to re-install the engine. After engine is re-installed:


23. Check to make sure all engine mounting bolts are tightened, starting at the bottom of the engine and working forward and around.


24. Install carbs, connect air filter system.


25. Connect electronics and all plugs.


26. Reinstall tank and connect fuel lines.


27. Start engine, give a cheer and enjoy your beverage of choice.


28. If so equipped, adjust points or Boyer timing.

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