I did a search...this topic has come up at least one million times before...but.....

Is a special tool needed move the tappets? On these engines, they're square...I don't have anything in my tool box that would fit these tappets. On my old ATC, Honda kindly used tappets that could be adjusted with a small screw driver...but access to the valves was somewhat of a PITA. Yamaha has nice access to the valves...but an odd tappet.

So...what do you guys used to move the square head for these things? They look small....3mm or 4mm?

 

Yeah I know it's kinda odd, they do that so you buy the tool from Yamaha, I just use a small adjustable wrench, then use my torque wrench to tighten the jam nut.

 

Gotcha. So your able to tighten the jam nut without moving the tappet?

 

I have a rap 350 i just use a small socket...

 

You may not need all this but it may help some... when searching


How to check and maintain:
You will need:
17mm socket and ratchet set.
10 mm socket.
5mm allen wrech.
feeler guage set that has stock sizes (6-8 thousandths on the exhaust, 4-6 on the intake valve)(different if you have aftermarket cam, i set mine to what my engine builder says .003 intake and .004 on the exhaust)
BIG flat head screwdriver
4mm wrench
now youre ready.

Take off the crankcase timing mark cap, cam sprocket engine sidecover thing(on head), and valve covers.

Now while you have the socket on the bolt that is holding the cam sprocket on, spin the engine over with that while looking in the timing check hole on the crank. wait till the T (tdc) mark on the mag. lines up with the line on the case. The look up at youre cam sprocket and make sure that lines up with the line on the head. (make sure its a compression stroke).

Now while everythings lined up, take the 10mm and loosen the jamnuts on the tappits on the rocker arms. This will allow you to adjust the tappits up or down.
take youre feeler guage (stock specification clearance) and put it between the tappit and valve stem. then tighten the tappit down with the 4mm wrench and tighten the jamnut. Once done with both intake and exhaust valves, make sure jamnuts are TIGHT, and make sure you can fit the feeler guage you used back under the tappit but noting smaller or bigger.
Then put the valve covers, head side cover, case timing plug, and the tank back on and fire it up.

Unknown terms you might like to know (nooBs):
Tappit-called something else by yamaha....the bolt that is in the end of youre rocker arm once the valve cover is off....when engine is running it pushes down on valve stem...not hard to find.

Jamnut- the locknut that holds the tappit in place when tightened.

Feeler guages-like diff. thickness little paperlike stainless steel things used for measuring small clearances....will get pics of stuff next time i do mine.

Engine tdc: TDC means TOP DEAD CENTER. Its when youre piston is at the highest point in the combustion chamber it will ever get.

As for just checking them and possibly not having to adjust them:
Instead of loosening jamnut so you can adjust the tappit, just line all the markings up so the engine is tdc and then stick the specified thickness feeler guage between tappit and valve stem. make sure the right one fits. then see if a size bigger or smaller fits. if not, then youre in the clear.

 

Thanks guys. Looks like the special tool isn't needed after all.