Valve Adjustment Tutorial
 

Several members have asked for a tutorial on adjusting the valves on these 163fml type motors, so here goes.

OK, first and foremost it is critical that the engine be completely COLD for setting the valve clearance. Not just "a couple hours since running cold", but like "sat OVERNIGHT" cold. You'll need to strip the bike down to the motor, so the side panels, seat and gas tank need to come off. The Roketa motor is OHC, so locate the valve covers (caps) as seen highlighted in this pic:

http://www.chinariders.net/gallery2/...serialNumber=2


Remove the valve caps with a 24mm wrench. NOTE: On the pushrod style motors, there are no valve caps, so the entire valve cover needs to be removed. Several members have reported that this will require dropping the motor down to get the cover off on some model bikes. Under the caps, or cover, the rocker arm assembly looks like this:

http://www.chinariders.net/gallery2/...serialNumber=2


Next, you'll need to locate the timing cover which is located on the left side engine cover. Different bikes will have this cap either on top of the engine cover or on the side, but it will look something like this:

http://www.chinariders.net/gallery2/...serialNumber=2


Remove this cap to uncover the flywheel. Make sure the ignition switch is in the OFF position!! You will use the kickstarter to rotate the engine until a "T" mark appears and lines up with the mark on the engine case. There will more then likely be several marks and lines on the flywheel, make sure you find the "T". The "T" stands for top dead center which is the point in the engines rotation where the piston is at it's highest point in the cylinder. NOTE, the engine is at top dead center TWICE during the 4 strokes of revolution; once on the exhaust stroke and once on the compression stroke. You need to be on the COMPRESSION stroke to set the valves, so you need to determine which stroke you are locating top dead center for. The easiest way to do this is to remove the sparkplug and stick your finger in the plug hole to plug it off. Rotate the engine on the kickstarter until your finger is forced out by the compression, you are now on the compression stroke, look for the "T" and you're ready to adjust the valves. It isn't very far around the flywheel so go REAL easy on the kickstarter. Dropping the kickstarter about an inch moves the flywheel half way around, so you gotta be careful. Think ittsy bittsy taps. If you accidently go past the "T", you'll have to go back around TWICE and you'll be back on the compression stroke again. If you have found the right "T", you should be able to wiggle both the rocker arms ever so slightly. If they are fully tight, you are on the wrong stroke. The"T" mark will look like this:

http://www.chinariders.net/gallery2/...serialNumber=2


Now, using a feeler guage of .05 mm, we'll adjust the intake valve (the one next to the carb.) To do this you'll need a 10 mm wrench. Loosen the jam nut on the valve stud (the stud on the rocker arm assembly from the above pic). Back the stud out enough to slide the feeler guage between the stud bottom (underneith the stud you just loosened the nut on) and the valve tip. Now turn the stud down BY HAND until it just bottoms on the feeler guage and holds it sandwiched between the stud and valve tip. Snug down the jam nut and if you did it correctly the feeler guage should slide out with a little resistance. If it falls right out easily, you have the valve too loose, if you can't smoothly pull it out, it is too tight. I have been adjusting valves for many, many years and it took me 4 shots on the intake valve to get it just right, so don't get frustrated if you don't get it on the first try. You more then likely wont. Once you feel like you have it, tighten down the jam nut fully. I'm sure the nut has a torque spec, but there is realistically no way to get a torque wrench in there so just get it good and tight, but don't kill it. Now repeat this process for the exhaust valve except with a .08 mm feeler guage. Congratulations, you are done. Re-assemble the bike and forget about it for 1000 miles!!!

Thanks Red

You are very welcome. :D

Excellent Post..
Very detailed and good pics!
Makes me want to do mine just cause.

where did you get the specs from?

wonder what the max and min are? i know on my Honda civic my intake and exhaust i go .002 under what the book says. it kinda acts like a cam and gives more lift and duration. i wonder if the valve springs in these motors could take it?

Wow, thats got to be the easiest valve adjustment I've ever seen. I didn't even realize thats what those bolts were for. I'm still waiting for my china bike...

Red you da man!! Nice, clear, concise directions.

Jason

The specs are directly from my Roketa manual that came with the bike. No max or min, valve lash IS what it is. Running the valve clearance tighter then spec is a bad idea. It is set to factory specs for a reason. If you set it too tight, the valves will be held open when the motor heats up and you will LOSE performance. Setting the clearance tighter might get you a little more valve lift safely, but it would have nothing to do with the duration. Cam lift duration is a function of the cam lobe profile, and that can only be changed with a different camshaft.

I was going to write this exactly! Thanks Red, great pics. N2r.

No problem guys. FROSTBITE, maybe you could make this a sticky? I'm afraid it's gonna get burried quickly. I've been able to put some miles on the bike since I adjusted the valves. It definately runs smoother, especially at higher revs. It sounds like the valvetrain is actually a little LOUDER now. I think they might have been set tight from the factory and leaking by a little, which would make sense if they assume they will "wear in" to spec. I highly suggest if you feel confident in your mechanical skills, you adjust the valves after engine break-in. I did mine at 500 miles, I will again at 1000, then once a year after that.

I was going to adjust mine a month ago and got all the stuff off and out of the way, but found it difficult to get a feeler guage in there from the intake side. How were you able to do it??

Yup, it is a tremendous PITA to get it in there with the frame in the way. I bent the feeler guage into a 90 about 1/2 in from the end so the guage would slide down and under the rocker stud. Be careful, if you bend it a little too far, you'll snap it off :( . I had to loosen the jam nut, back the stud out until I could wiggle the guage in between then run the stud down by hand (well by fingers, which is also a PITA) until the guage is "stuck in between" Once you tighten the jam nut, you either got it and you can pull the guage out with slight resistance OR , if not, then you gotta start the process all over again. Like I said it took several tries on the intake valve to get it right. I got the exhaust valve first try. So, you have like 7000 miles and haven't adjusted the valves yet? Man, that is amazing! These engines are pretty incredible.

Yes, 7100 now. I have a little valve and/or cam chain chatter when it's cold. If I keep the revs low, they go away by the time the engine is warm. However, I still need to figure out the cam chain adjustment. After 1000miles, I should have adjusted the tensioner. Any idea how this can be done with the starter still in? Or for that matter if there is a "standard" procedure for this adjustment?

It was my understanding that these motors have a NON-adjustable cam chain tensioner. They are made just like the 83 XR200R motor though, so maybe OB1 or someone else with Honda knowledge can tell us or look it up in a book somewhere.

Anyone else tried it yet???