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Post by Moat on Sept 13, 2014 0:49:18 GMT -5
The problem is, that by the time you may have noticed some degradation in performance due to a too-tight valve, the damage (i.e. - burned/eroded exhaust valve face/seat/sealing surfaces) is quite likely to have already begun. Sure, if caught in time, any further "damage" will likely be prevented - but that effortless starting and idle you mentioned will be among the first things to go.
Yes - there is some risk involved in doing the work yourself, as a first-timer - but you've gotta jump in at some point, right? Just take your time, follow the directions, be as clean as possible, and make especially sure the adjustment screw's lock nuts are appropriately tight before buttoning things up.
At least you'll know exactly what's been done in there... something you can't say if you have someone else (noob? hack?) do it for you. And that in itself is quite satisfying and re-assuring. If you have the time and general mechanical competence... well worth it, IMO.
Bob
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Post by onewheeldrive on Sept 13, 2014 1:01:57 GMT -5
If a motor does not start on the 1st or 2nd SHORT hit of the start button something is not right. If you have to crank and crank the motor to start it needs some TLC.  Alleyoop You got that right!! The first year I had this scooter, 2007(?) I think, my scooter was very hard starting and then died out about 200 feet down the road. Again, very hard to start back up and seemed to make it a bit further before it died again. That starter was toast after about a week. This was way back when I was in a Yahoo Group for my scooter. I posted my issues on that group, and guess who brought up the valves? JR. Lol. So glad those days are over! |
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Post by onewheeldrive on Sept 13, 2014 1:04:43 GMT -5
Every now and then I think about that---- adjusting the valves before any symptoms start of the gap(s) being too tight. If my scoot is running fine, I'll change the oil and that's pretty much it. I guess I'm curious as to what we'd benefit from by adjusting the valves before symptoms start, besides just avoiding poor/hard starting, lack of power...etc...etc. I think Rockynv posted something about that at one time, not too long ago. Sometimes, it's the frog in the boiling water syndrom. You don't think you have lost any performance, but you have. It has just happened over a long period of time. When you finally adjust the valves you notice a huge difference in MPG or acceleration is better etc. Good point! |
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Post by rockynv on Sept 13, 2014 10:30:56 GMT -5
Every now and then I think about that---- adjusting the valves before any symptoms start of the gap(s) being too tight. If my scoot is running fine, I'll change the oil and that's pretty much it. I guess I'm curious as to what we'd benefit from by adjusting the valves before symptoms start, besides just avoiding poor/hard starting, lack of power...etc...etc. I think Rockynv posted something about that at one time, not too long ago. Sometimes, it's the frog in the boiling water syndrom. You don't think you have lost any performance, but you have. It has just happened over a long period of time. When you finally adjust the valves you notice a huge difference in MPG or acceleration is better etc. By the time you notice you may already have an exhaust valve starting to burn up on you. You go in per schedule at first and if you keep finding that they don't need adjustment then you can extend it. I was needing to do the adjust on my Lance every month and sometimes twice a month until I started using premium or mid grade gas finally going with the mid grade and found I could go two months between valve adjustments on the middle grade gasoline. I sometimes put over 1,000 miles on in a month so I found out pretty quickly what works in the Tropical heat/weather we have here in Tampa Bay. |
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Post by JerryScript on Sept 13, 2014 22:05:19 GMT -5
I have the BN139QMB, Znen short case 50cc. When valves are adjusted properly, it's like you say, no cranking, it just starts. I have had to adjust my valves several times, but I have also installed a BBK, which puts more strain on the valve system.
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Post by dmartin95 on Sept 14, 2014 0:06:08 GMT -5
I have the BN139QMB, Znen short case 50cc. When valves are adjusted properly, it's like you say, no cranking, it just starts. I have had to adjust my valves several times, but I have also installed a BBK, which puts more strain on the valve system. Yeah, I actually had to adjust the way I start my scooters because of the ZNEN engines.  My first "Chinese scooter" I purchased was a 50cc, Bintelli, Scorch. It also had the BN139QMB and it just started as well. What I mean by "adjust the way I start" is almost every other scooter I've owned, I would have to give it a little throttle in conjunction with starting. On all of the Bintelli's i've owned, if I give it the gas while I'm starting, is the only time I will actually have to "crank" the starter to get them to start. However, If I do not give it any gas, it "just starts". ZNEN makes some really good GY6's in my opinion! What do you set your valves to? My Manual for the Scorch was very in depth and it suggest setting them to .003in on both the int and ex...... My 150cc Havoc came with exact same manual which to me suggest they want me set the Valves the same...... However, the GY6 manuals published here and other sources say .004 on the int and .005 on the ex..... I think what I'm going to do is set it to .003 on both and see how she runs. But I am going to wait until I hit 1500 miles. I'm only at 1025...... |
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Post by JerryScript on Sept 14, 2014 0:58:40 GMT -5
While this is my first scooter, I have helped relatives wrench on theirs for years, and I'm very pleased with the quality of my Znen in comparison to some others I worked on. However, I have also read some bad reports from a few Znen owners. Did a little research, and found that Znen makes a subset of "patent models" of which mine is the Q model. The complaints I've read never mentioned any of the patent models, so I assume Znen has paid a bit more attention to the details on them. I set my intake to .003, and exhaust to .004, however for a 150cc it's usually recommended by forum members to set .004 intake and .004-5 exhaust. The manufacturer's plate on mine says to set them to .06-8mm, which is a tight .003".  One issue I've had since installing my BBK is I get a bit of valve float around 40mph. I plan on installing one of scrappy's performance heads soon, hoping the springs are stiffer on it. |
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Post by dmartin95 on Sept 14, 2014 1:16:23 GMT -5
Hey, that's awesome! Mine has the exact same tag except it has the Bentilli logo in place of the ZNEN one. The tag on mine says to set the valves at 0.06mm~0.08mm. I've seen that rivet plate 1000's times, but never thought of actually reading it...  |
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Post by urbanmadness on Sept 14, 2014 9:21:24 GMT -5
The problem is, that by the time you may have noticed some degradation in performance due to a too-tight valve, the damage (i.e. - burned/eroded exhaust valve face/seat/sealing surfaces) is quite likely to have already begun. Sure, if caught in time, any further "damage" will likely be prevented - but that effortless starting and idle you mentioned will be among the first things to go. Yes - there is some risk involved in doing the work yourself, as a first-timer - but you've gotta jump in at some point, right? Just take your time, follow the directions, be as clean as possible, and make especially sure the adjustment screw's lock nuts are appropriately tight before buttoning things up. At least you'll know exactly what's been done in there... something you can't say if you have someone else (noob? hack?) do it for you. And that in itself is quite satisfying and re-assuring. If you have the time and general mechanical competence... well worth it, IMO. Bob It doesn't seem to be an issue with GY-6's. I'm not saying it doesn't happen, but usually if you have hard starts and bad idle, a valve adjustments will fix them right up. The changes in lift, duration and overlap as the valve tightens up seems to be what will make them idle bad, or start hard. Only in extreme cases, will it keep the exhaust valve open. |
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Post by dmartin95 on Sept 14, 2014 11:49:51 GMT -5
Yes - there is some risk involved in doing the work yourself, as a first-timer - but you've gotta jump in at some point, right? Just take your time, follow the directions, be as clean as possible, and make especially sure the adjustment screw's lock nuts are appropriately tight before buttoning things up. At least you'll know exactly what's been done in there... something you can't say if you have someone else (noob? hack?) do it for you. And that in itself is quite satisfying and re-assuring. If you have the time and general mechanical competence... well worth it, IMO. Bob You should be a coach! You're absolutely right....I do have to jump in there at some point because irregardless if she's running right, right now, I will at some point have to adjust the valves. I also have a 150cc Jonway (DongFang) Sunny.... It's a P.O.S.. It has had issue after issue and it's under 500 miles... That one for sure needs the valves adjusted. I can practice on that one I suppose... I actually own 3 (4 if I count my wife's) scooters at the moment... All are 150cc's so I'm going to have to expand my wrenching abilities sooner or later. |
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