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Post by kxj5906 on Nov 12, 2013 0:04:30 GMT -5
Hi guys, I was just wondering how Often valve adjustments should be done. I have a 150cc Chinese scooter that is approaching the 1000 mile mark. What are the symptoms that a valve adjustment needs to be done?
Also, can someone explain to me why a valve adjustment must be done and the purpose of doing a valve adjustment?
Thank you
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Post by Deleted on Nov 12, 2013 0:17:18 GMT -5
In short 900 miles ago! Crated Chinese scooters have been known to have valves that are too tight and that can cause serious damage because of the inability to dissipate heat properly. Proper opening and closing effects vacuum and that also controls fuel flow. Out of spec valves sometimes make it difficult to restart a warmed up engine. Takes 15 minutes to do it. If you can hear a slight tick at the front of your motor thats a good thing. A little tick sound means they are probably set okay. A loud clatter sound and you would have noticed that by now but valves tend to tighten up rather than loosen. Most use .003-.004 on the intake and .004-.005 on the exhaust and they are set when the engine is cold.... There are many videos online showing the procedure.
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Post by millsc on Nov 12, 2013 0:45:46 GMT -5
All my new scoots I bought new which is six the valves where set tight outta the crate set the valves when you get it. Put them both at .004 they will tick some when they stop ticking you know they have tighten up. I don't adjust mine until the bike acts up.
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Post by alleyoop on Nov 12, 2013 0:52:03 GMT -5
The Classic case when valves need to be adjusted is when your riding it and the motor is nice and hot and you come to a stop and it wants to die on you or it dies on you. You will find that you have to goose the throttle when you stoped to keep the motor running. What is causing this is most likely the EXHAUST valve is not sealing and is staying a little open and the motor is loosing compression. You will find that most of the time the INTAKE valve is good but the EXHAUST is tight, the reason is the EXHAUST valve takes the beating with so much heat and nothing to cool it down. The INTAKE valve gets nice cool fuel and cool air all the time so it does not get as hot as the Exhaust valve.
Alleyoop
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Post by yelloscoot on Nov 12, 2013 0:55:33 GMT -5
The way it was explained by Sprocket, from the old forum, is that on a new engine/head, the valves go through quite a pounding. After millions of cycles the valve and head finally seat together. The aluminum head basically takes the form of the valve. Called it "valve head regression". It's not hard to do. One tool that you may not find in a set of metric wrenches is a 9mm. Have one handy, you'll need it. Watch a couple videos,..you'll get.  After the first time, the frequency of adjustments drops. I did my first at about 1K miles, and only a couple times in the last 8K miles. On my first valve adjustment. the exhaust side had 0, zero clearance. Fired right up after afterwards, like a difference between day and night.  |
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Post by yelloscoot on Nov 12, 2013 1:00:59 GMT -5
Yea. what alleyoop said too. You posted as I was typing. You did help me understand now why it's the exhaust side that is all out of whack. Thanks alley.  |
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Post by onewheeldrive on Nov 12, 2013 1:05:04 GMT -5
Usually the symptoms for a valve adjustment are: hard starting and lack of power. Sometimes after it finally starts, the power is just not there as before, and may even die out down the road(probably) like Alley said--- at a stop sign or light. Usually less uphill power, slower acceleration.
The symptoms gradually get worse. Usually it starts off as a hard start or three. Then for a bit it's hard starting(usually when the engine is cold or shut off for a bit) and lack of power. Then, finally, you'll be lucky if it even starts, lol
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Post by alleyoop on Nov 12, 2013 2:01:57 GMT -5
Here is a good example of what happens with the head and or valves and how often they need to be adjusted also depends on the quality of the head and valves.
Alleyoop
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Post by kxj5906 on Nov 12, 2013 17:05:01 GMT -5
Thanks for the help everyone. Since my Scooter is actually starting and idling very well right now, I don't have to do a valve adjustment right now, am i correct?
Should I do a valve adjustment anyways? There are no idling or starting problems
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Post by Deleted on Nov 12, 2013 18:49:06 GMT -5
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Post by alleyoop on Nov 12, 2013 20:23:19 GMT -5
Thanks for the help everyone. Since my Scooter is actually starting and idling very well right now, I don't have to do a valve adjustment right now, am i correct? Should I do a valve adjustment anyways? There are no idling or starting problems If all that is good and when your riding and have the motor nice and hot and you come to stops IT DOES NOT loose RPMS at idle they are still ok. The Classic case when the Valves need to be adjusted is After the motor gets nice and hot while riding it and you come to stops IT DOES NOT want to hold IDLE it drops RPMS and sometimes die and you have to goose the throttle while sitting there to keep the motor running. Most with a tighter Exhaust Valve will start AFTER the motor Cools down but acts up as soon as the motor gets hot. Alleyoop |
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Post by prodigit on Nov 12, 2013 23:28:51 GMT -5
On my ATM50 I have 5500km on it.
I could have gotten away with riding it stock like that, as I only checked up on some things.
Though the electrical circuit is now toast (probably a faulty wire, or a ground short), the valves have never been adjusted, but when cold it does make a ticking sound, not heard when the engine is hot.
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Post by kxj5906 on Nov 13, 2013 13:33:12 GMT -5
I don't think I need to do a valve adjustment. My china scooter is running fine and doesent lose any power at idle.
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Post by scootnwinn on Nov 13, 2013 13:43:22 GMT -5
You may not need to adjust them but you really should check them every oil change (1000 miles or so) You can wait til there is a problem but you can't call it maintenance if you do...
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Post by onewheeldrive on Nov 13, 2013 17:00:11 GMT -5
You'll know if you need a valve adjustment, your scoot won't run right. Period.
If you check the gaps as periodically as scootnwinn suggested (props to anyone that does--nothing wrong with preventive maintenance), then you'll probably never ever have to worry about it. Not sure, a lot can happen between oil changes I suppose?
There really is no exact time that you may need to adjust the valves--- each scoot does vary. I've had an engine that seemed to need it every 3 months, then another engine needed it once over a period of approximately a year.
One thing is for sure, IMO, and that is to always check, and even double check, after a rebuild (BBK..etc) or if/when you ever get a new engine---before starting.
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..BAD TO THE BONE..
