Valve adjust and questions By bobf (Read 794 times)

[bobf]

My scoot is the vertical 250 engine. 2008 250cc Model: MC-54-250B

OK, I have 250 miles on my machine so I decided to do the valve adjust routine.

I watched several films about the valve adjust. One was way too detailed and required a near complete tear down. To do the marks on the flywheel and feeler gages. So I decided to follow the other routine that just seems to apply the ear to any sounds from the engine.

So I did remove the rear covers, meaning the seat, the box, the side panels. OK. Well later I found I did not need to do all that as the adjust was done through the removable cover over the engine and the battery cover. I will know better next time I try the valve adjust routine. If I decide to do it again I will likely take a hack saw and make a much bigger hole on the side where the removable cover is. It is way too small for my hands and tools to feel free to move or do something. Only the rear most valve is visible and reachable. The front valve I could not get to so I tightened it back up where it was.

Now for the rear valve I was able to loosen it till the arm fell down. Then I started the engine and tried to hold the arm up and then get in there with my wrench to tighten the nut on the arm. I could not do that. Too many fingers in the way. So I just looked down on the valve as I moved the arm till it first got quiet. Tried to remember that position and with the engine shut off, using a tool with a right angle end on it, pried the arm back to that position. No second set of fingers in there so I could tightened the nut. Sure hope it is correct.

Now my first question is, does this sound good? I watched a film of this technique but the sound isn't good. Too me a loud clicking sound means it is hitting the valve stem hard. When I moved the arm I was closing the gap till it just cleared the valve stem. And then the clicking sound stops.

My next question is about the access area. It is so offset and small that I was thinking of cutting just back of the removable cover, from behind the valves forward till ahead of the front valve. Then go toward the left side and down till below the valve adjuster area. That should give me plenty of room to get in there to move the valve plates and also have my number 8 socket size in place to tighten as things quiet down.

Am I nuts? I hope not. But I was not satisfied with what the designer thought was a good access area for adjusting valves. I spent hours trying to do that with no luck at all. It is running pretty good for now but will likely want to go back and redo the valves again.

[ellpee]

FWIW, on my Magnum trike I was also annoyed at the difficulty of getting at the carb and other stuff, so I cut away a lot, probably 75%, of the plastic comprising the floor of the under-seat compartment. Then I cut a piece of somewhat flexible plastic material to cover the hole, and used velcro to hold it in place. Storage area is uncompromised, but when I need to fiddle with the engine, I just pull off the home-made cover and have lots of room to get in there with tools. I considered whether I was harming anything structurally, but could see no reason that would be the case.

[crwford]

I did about the same thing on my Zodiac but I put it back together by adding a ledge under made opening of trunk laying cut section on top and screwing self tapping screws. Kinda looks like it was there all the time.

[bobf]

Thanks to both of you. So my idea of cut and patch for better access has taken place with no problems. On a slow day I will attempt that solution myself.

Was hoping for some comments about my adjustment. Am I to adjust for no clicking at all, or just to lighten the noise to just before it ends. What I did seems to be OK as the engine starts immediately and runs pretty smoothly when warmed up. So maybe I got lucky.

[pmatulew]

Whoa! Time out! Please don't burn your valves. Exhaust valve clearance is critical to the life of your motor.

You absolutely must use feeler gauges to set the valve clearance!

The engine designers are very specific about valve clearance for a reason. Too much gap and the valves are really noisy and don't open fully. Too little gap and the valve may not close completely or get enough dwell time when closed to dissipate the combustion heat. If that happens you can burn a hole in the edge of the valve or the valve seat. That would be bad. If you have them set so that they are not making any noise then they are too tight. Ticking valves are happy valves. Only engines with hydraulic lifters that adjust automatically don't have ticking valves. Scooter engines don't have those.

If getting to the flywheel marks is a problem on your machine you can skip those steps just by making sure that the rocker arm you are adjusting is resting on the low part of the cam rather than up on the bump. The cam lobes are egg shaped. Half of it is short round, the other half is the tall bump. Just blip the starter button until the cam rotates to where you want it. (or use the kick start if you have one to gently rotate the engine)

Also you need to make these adjustment when the engine is cold (room temperature). Depending on the particular engine design the valve clearance could get tighter or looser when the engine is hot. The only valid reference point you have is to work on the engine when it is cold.

As far as access to the motor under the body plastic you're on your own. Every machine is different and you just have to deal with it as best you can.

[cyborg]

Pmlew speaks the truth,,, the only time the valves ( especially the exhaust ) get to shed heat is when it's resting on the seat and the head takes the heat away,,, hot spots will indeed hurt the valve and or seat

[ellpee]

So (I've never done valves on either of my scooters yet, not particularly looking forward to it) the correct solution is the least amount of click you can get, but not no click at all? Presumably using feeler gauges would give that result, just wanting to delve a little deeper into the click-or-no-click thing.

[pmatulew]

Every engine type has it's own voice. Valve tick is just part of the symphony.

Theoretically speaking, if the designer has done his testing properly, and the oil viscosity is correct, and the RPM, and operating temperature is within design parameters, and the stars and planets align on the second Monday of the week, the valve train will have a miniscule amount of clearance when running. (Running hard under load. Not necessarily when loafing at idle.)

The clearance measurement in the service manual is extrapolated backward from that perfect world scenario, (with maybe an extra "0.001" thrown in for good luck.) A little loose is better than a little tight.

Also the valves and valve seats in Chinese GY6 motors tend toward the soft side. After a few hundred miles they can bed themselves deeper (recede) and the clearance can shrink to nothing. Hello burnt valve.

Usually you can tell when it's time for an adjustment because the motor is hard to start and not performing like it used to.

[pmatulew]

Oh, and be glad you don't have shims and buckets to deal with!

[bobf]

Thanks to all that have answered. One thing before I go back in there is to make a much better path for adjustments. I will cut the top off my motor cover and then use the provided running method. Sure need a better description of how and what to do for that method.

Now I think I know better about the adjustment system I had used. Very light tapping is what I want. I went to completely solid and no tapping. Thanks for that clarification.

Will I tear my scoot down and strip the engine? Not likely. My scoot seems to be set up for the running method and that is what I will do.

If I was running a racing bike or going long miles cross country I might pay someone to do it the tear down way. But see no reason otherwise.

Thanks to all for the input to my question. I feel I learned a lot from these inputs.

Here is the method I tried but will redo for some tapping noise.

[pmatulew]

Now that's a completely different animal. I can honestly say I've never seen an engine with external valve adjusters like that. Clean and simple. Now I'm going to have to look it up to find out how that is arranged inside. And also what the intended adjustment procedure is.

Doing what he does in the video will probably get you very close. Doing it with the engine warmed up to operating temperature will be best.

Remember, ticking valves are happy valves.

[JR]

Remember this engine is a copy of the long time Honda Helix engine and part 1 of the manual shows the cold method and gap clearances for adjusting the valves on page 25

thescooterprofessor.proboards.com/thread/277/244cc-helix-cfmoto-service-manual

Later on there was a update to the original manual that was put together because the service techs found it easier and more accurate to adjust the valves with the engine warm and with it running. We have that video in the video tech section also.

thescooterprofessor.proboards.com/thread/373/valve-adjustment-helix-cfmoto-engine

JR