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Post by humanshield on Sept 12, 2016 21:38:11 GMT -5
Received my 150cc A9 cam today.
Installed it and.......lost a bunch of power.
Checked the cam timing...yep perfect.
Sometimes the manufacturer has already put a cam with the best lift, duration, valve timing and overlap for the engine.
Looks to my eye that the stock cam has VERY high duration compared to the A9. Not much more lift.
I was recently told by a performance scooter builder that my 150 was exceptionally quick. He even said I might lose power changing the cam. He was right. My 150 with A9 cam feels much slower like what he told me about most 150cc scooters.
Odd since the A9 does wonders for the 49cc scoots.
Tomorrow I'm removing the A9 and going back to the stock cam. Disappointing. On my 83cc scoot the A9 cam made a YUGE difference. I was hoping for that on the 150 but nooooooooo.
Also, others who installed the A9 on the 150 reported a lot of valve noise. I got the same thing. These cams appear to be regrinds of stock cams where they take a stock cam and grind down the lobes and lobe shafts decreasing the overall height but altering the lift and duration. I think this smaller diameter is causing the noise.
I may get my dial indicator out before I remove it and measure the actual lift vs the stock cam.
Not sure I have a degree wheel to check the difference in duration but I sure would be interested to know.
So for me...no go on the 150cc A9 cam. Bummer. Wasted $30.00
My recommendation? Avoid the A9 cam on 150cc scooters.
They REALLY need to start providing the lift and duration numbers for these aftermarket cams.
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Post by humanshield on Sept 12, 2016 22:09:28 GMT -5
A very good read about how cams work...... link |
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Post by dan50 on Sept 13, 2016 0:09:38 GMT -5
Shouldn't a 150cc have an a12 cam? I also think there is an a15 cam.
I thought the 19 cam was for a 50cc BBK.
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Post by humanshield on Sept 13, 2016 7:34:42 GMT -5
Shouldn't a 150cc have an a12 cam? I also think there is an a15 cam. I thought the 19 cam was for a 50cc BBK. A9 is available for both the QMB139 50cc based motors and 150cc scoots. The 150cc cams are physically longer so you cannot interchange a 50cc cam with a 150cc cam. It's hard to find actual lift and duration numbers for scooter cams but from what I've read, as the numbers go higher, top end is sacrificed for low end. So if you needed tons of low end torque you'd go with an A15 etc. |
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Post by dan50 on Sept 13, 2016 22:06:20 GMT -5
I didn't know they make an A9 cam for the 150cc. I learn something new every day on 49ccScoot.com. That's the great thing about this forum.
Thanks for informing me, as in the near future I want to put a 47mm BBK on my Dongfang, but the cam is the most confusing part of the process.
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Post by 90GTVert on Sept 14, 2016 11:02:19 GMT -5
I profiled my A9 cam from Hoca and it's definitely got more lift and duration than my stock cam. Maybe some of the difference lies in what your stock cam is or maybe how much compression you have. Chinese scoots aren't known for their uniformity. Here's a bunch of info from my A9 swap that ended up in compression changes, cutting pistons, degreeing and all sorts of fun stuff. The specs are in there, but mine killed dynamic compression numbers, so that's why I went to the trouble to get a bit more compression out of the engine before bothering to try the cam. 49ccscoot.proboards.com/thread/14563/2006-roketa-cayman-150-mc?page=5&scrollTo=228887 |
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Post by humanshield on Sept 14, 2016 12:39:26 GMT -5
Your write up on 150cc A9 cam knocked it out of the park !!! DAMN good job!  |
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Post by visthum on Oct 6, 2016 21:02:18 GMT -5
Just can confirm this that A9 cam is useless on 150cc... Lost top speed and acceleration. What a waste. My original cam is 26mm and the A9 was 27mm (Yes both In and Out has same size, oddly).
Don't waste your time on camshafts, at least if your are running 150cc. I ruined my timing somehow too so now no ride.
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Post by humanshield on Oct 6, 2016 21:38:42 GMT -5
Just can confirm this that A9 cam is useless on 150cc... Lost top speed and acceleration. What a waste. My original cam is 26mm and the A9 was 27mm (Yes both In and Out has same size, oddly). Don't waste your time on camshafts, at least if your are running 150cc. I ruined my timing somehow too so now no ride. Brent says it's due to loss of dynamic compression and to make it work, you'd need to boost compression I believe. I didn't check the compression after I installed mine but that is EXACTLY what it "felt" like. No compression, so I believe him. I think I'm just going to make sure my compression is up around 180 - 190psi for best results and leave it at that. I have a friend with a 150cc scoot that has compression of about 205psi and that thing is a monster. Mine is around 150psi right now. Compression makes a world of difference. |
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Post by visthum on Oct 7, 2016 2:44:43 GMT -5
Yeah i guess he's right. Not sure if you can tell by the electric starter turning easier or not but it did turn much easier with the A9 cam. Now i have to figure out how the hell i time that damn chain correctly, somehow i am about 100degrees off even though i'm using same teeth on the chain that i marked  By the way, it might then work better on 190cc (180cc and stroker). I will try it out after winter when i build mine to 190cc. My original cam is like A8, so in theory if lower = faster top speed, my original cam should also give me highest top speed hm |
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Post by humanshield on Oct 7, 2016 7:25:24 GMT -5
The stock cam isn't bad. I did some experimenting with my cam's timing to see what effect it would have. Lots of work but I rolled the cam two teeth forward (no good at all), then just one tooth forward (better but still less power) and finally put it back to where it's supposed to be. It ran best set where it's supposed to be.
I did not try rolling it BACK one tooth although I suspect it runs best set exactly where it's supposed to be in relation to TDC.
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Post by visthum on Oct 7, 2016 14:27:12 GMT -5
Humanshield, do you have any ideas how to set the cam timing chain? I tried to get mine to work again after trying out the A9 like i said.. I lined up the T mark and set the cam and it worked... kinda. Very hard to start. Then i tried another location after the T-mark and it worked also, but hard to start too.. I am completely lost now. Can i remove the head and just set it to TDC, mark the flywheel with an pen? How accurately would this be? Sorry for going off topic on this thread. PM if you want.
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Post by 90GTVert on Oct 9, 2016 8:11:59 GMT -5
The stock cam isn't bad. I did some experimenting with my cam's timing to see what effect it would have. Lots of work but I rolled the cam two teeth forward (no good at all), then just one tooth forward (better but still less power) and finally put it back to where it's supposed to be. It ran best set where it's supposed to be. I did not try rolling it BACK one tooth although I suspect it runs best set exactly where it's supposed to be in relation to TDC. If you want to do that, get yourself an adjustable gear to swap onto the cam and break out the degree wheel. It takes a very small movement to make a few degrees of change. Also, it's a bad idea to play with cam timing if you aren't monitoring piston to valve clearances. |
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Post by 90GTVert on Oct 9, 2016 8:14:49 GMT -5
Humanshield, do you have any ideas how to set the cam timing chain? I tried to get mine to work again after trying out the A9 like i said.. I lined up the T mark and set the cam and it worked... kinda. Very hard to start. Then i tried another location after the T-mark and it worked also, but hard to start too.. I am completely lost now. Can i remove the head and just set it to TDC, mark the flywheel with an pen? How accurately would this be? Sorry for going off topic on this thread. PM if you want. Is hard starting the only issue? Did you redo the valve clearances afterward? If it runs OK other than hard starting and the marks are aligned, timing should be OK. There are some flywheels machined wrong, so it doesn't hurt to see if you're really at TDC when it says you are. If that's the case, it throws off ignition timing too. |
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Post by visthum on Oct 9, 2016 8:50:00 GMT -5
Is hard starting the only issue? Did you redo the valve clearances afterward? If it runs OK other than hard starting and the marks are aligned, timing should be OK. There are some flywheels machined wrong, so it doesn't hurt to see if you're really at TDC when it says you are. If that's the case, it throws off ignition timing too. You can check my thread over at Troubleshooting, i wrote about the problem in there instead, not to get too off topic here  But now it starts super fast, i just tap the button and it fires up right away. Only problem now is that it bogs the first 1-2 seconds and then it's fine after that. I am using air filter as well now but it did the same without air filter. Haven't done anything in the carburetor but i know for sure that my exhaust valve clearance is WAY off, i think i set it to about 0.008" or more because i was so mad at that point lol, and to adjust it i have to remove saddle and fuel tank so right now... i don't feel like changing it until i get my 190cc kit  Winter in about 1 month too so |
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Winter in about 1 month too so