My 2014 owners manual says the clearances have to be checked at 500 miles and every 16,000 miles thereafter. In my experience Hondas retain their clearances very well and need little if any adjustment. This will be an ongoing tutorial. It will not be complete all at once. I plan on checking mine at some point and this instruction will be completed at that time which might not be till spring. Lets get started! Since the gas tank must be removed to access the cylinder head cover its a good idea to have it as empty as possible. Also, the engine must be COLD when checking the clearances. 1) remove the seat by removing the forward most of the four bungee posts. Theres an allen wrench in the "toolbox" to do this. 2) remove the two gas tank shrouds on either side of the gas tank. Three allen bolts each and again the allen wrench is in the tool kit. 3) Remove the wire from the sparkplug and the sparkplug itself. (so turning the engine is easier) Follow the sparkplug wire to the ignition coil and remove that. 4) There are three bolts securing the gastank, two on top and one on the bottom left. Remove them. Lift the tank up and move it to the right and let it hang by the hoses. Im hoping it possible to access the cylinder head cover now without disconnecting the fuel line. This is uncharted territory Ive never done it. Anyways remove whatever is in the way and attached to the cylinderhead cover. Theres the PAIR valve that must be disconnected and some ground wires too. Ive never done it so I don't know exactly what has to come out/be moved aside. 5) Theres two small bolts holding the cylinderhead cover on. Remove them and carefully pry the cover off. You might make use of a rubber mallet. Get the cover off and snake it out of the frame exposing the valve train. 6) Look at the exposed cylinder head. See the two camshafts with a single lobe? See the forked rocker arms that allow the single lobe cam to operate two valves? The exhaust valves are to the FRONT of the head and the intake valves are to the REAR. See where the forked rocker arms contact the valve stems? That's where you've got to get your feeler gauge blades to go. .006 inch for the intakes and .011 inch for the exhaust. Thats + or - .001 inch for both. Thus the clearance for the intakes can be .005, .006, or .007 inch. For the exhaust valves its .010, .011, or .012. Im going to give you an opinion based on years of experience. You can go further than that. I would not change anything is the clearances are + or - .002 inch. 7) But before you can measure anything you have to turn the engine so the lobes of the cams aren't moving the rockers arms or holding them open. Theres a round cover in the center of the side engine case you can remove to access a bolt to turn the engine with using a ratchet, extension, and socket. You can also remove the smaller cover to the side to look at the timing marks and align those. Your choice. 8) If the clearances are within tolerance, youre done! Put everything back together and clean up! 9) If you've determined the clearances need adjusting youre on your own until I take mine apart and do the write up. You could take it to the dealer and have him do it. Or read the online service manual and figure it out yourself. Remember what I said about + or - .002 inch being good enough. Im thinking VERY few engines will need adjusting using .002. But if its more than that you are in for an adjustment. 5)
Good stuff, do you know if they are shims? To be honest I've only ever done the locknut types on a CB250RS and XBR500
Ah - good link to full manual - thanks https://www.crf250l.org/forums/threads/link-to-online-sm.99303/ *shims*
Yes shims but in a novel to me arrangement where the cams dont have to come out to change them, if needed. I invite all to look at the SM and comment. If you have done it, definitely I welcome your input. I have adjusted and checked valves with cam removal system. I believe the most important thing from my reading the SM so far involves the gas tank which must come out to access the cylinder head cover. Its a question of whether you can just unbolt it and lay it aside or whether it needs to be completely disconnected.
With shims I have checked them (on a different bike) but never adjusted. In general shims stay in tolerance far longer. I guess the suggested 500 mile check was just to ensure initial bedding in was good.
Added more to the procedure. Im done with it for now until I actually work on them myself. Any comments from those who have done the work or read the SM please jump in!
Found out the fuel tank main hose to the injector doesn't have to be disconnected and with the available slack in the hose, the tank can be positioned off to the side to access the valve cover.
