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Post by lain on Jul 27, 2015 21:46:11 GMT -5
I just got a scooter from my friend who says his cousin installed a 47mm BBK and now it's slower than when it was a stock 50cc. Everything around the engine is correctly installed; #  main jet in CVK carb, idles and tuned up perfectly, foam air filter installed, stock exhaust, and no oil leaks or hard starting and has enough compression to push my thumb off the spark plug hole, and the vales are both at 0.003. Checked for leaks by spraying wd40 all over everything while running, all good. It tops out at about 50, but it stays in the low end on flats and uphill and does not go faster than 20 until going downhill. Seems like there might be blowby since I feel air coming out of the vent on the valve cover, but no sure, maybe the guy installed the rings incorrectly? |
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Post by JoeyBee on Jul 27, 2015 21:57:31 GMT -5
Have you checked the clutch? Maybe some aftermarket "performance" parts were installed.
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Post by lain on Jul 27, 2015 22:47:40 GMT -5
Have you checked the clutch? Maybe some aftermarket "performance" parts were installed. I was told they only changed the variator weights to 7g in the cvt |
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Post by JoeyBee on Jul 27, 2015 22:52:24 GMT -5
7g for a 50cc sounds very light. I thought 9g was the standard, but my experience with 50cc scooters is limited. Either way, just another suggested area to inspect.
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Post by lain on Jul 27, 2015 23:13:14 GMT -5
7g for a 50cc sounds very light. I thought 9g was the standard, but my experience with 50cc scooters is limited. Either way, just another suggested area to inspect. I use 6.5g weights on my 50mm bbk scooter and coast at 40, but on this scoot with 47mm bbk and 7g weights it coasts at 20 if youd call it coasting, its more like stuck at low RPMs, once it hits high RPMs you can hear the difference it is also much faster but it does not get to high RPMs unless going downhill. It is a 139qmb motor, it should definitely be faster, even a 50cc is faster than this 47mm (72cc) kit at least until going downhill, then it just zooms past. Even if the downhill is only very slightly. It seems it needs help to reach higher RPMs and cannot hold high RPMs once on a flat or uphill. |
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Post by JoeyBee on Jul 27, 2015 23:18:46 GMT -5
lain, thanks for the clarification. As I said, 50cc scooters are not my area of expertise. Either way the problem does sound like an issue with the CVT. I have my eye on CL for a cheap 50cc to play around with as a project. A 2 stroke engine is next on my list to learn.
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Post by onewheeldrive on Jul 28, 2015 4:13:59 GMT -5
Improper air/fuel mix (jetting/leaks), bad timing, and poor compression are causes of that. A trashed variator would probably be similar in an extreme case. Not sure if it would run like that with the rollers improperly placed.
If it was me and I was stumped: I'd check the timing, variator, maybe throw a stock airbox on to see if it runs better. Maybe inspect the carb. I tend to do everything ( not replace everything of course, lol) if I'm not sure, and that's limited by whatever tools you have or parts (jets, comp gauge) on hand.
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Post by pistonguy on Jul 28, 2015 7:14:17 GMT -5
I just got a scooter from my friend who says his cousin installed a 47mm BBK and now it's slower than when it was a stock 50cc. Everything around the engine is correctly installed; # main jet in CVK carb, idles and tuned up perfectly, foam air filter installed, stock exhaust, and no oil leaks or hard starting and has enough compression to push my thumb off the spark plug hole, and the vales are both at 0.003. Checked for leaks by spraying wd40 all over everything while running, all good. It tops out at about 50, but it stays in the low end on flats and uphill and does not go faster than 20 until going downhill. Seems like there might be blowby since I feel air coming out of the vent on the valve cover, but no sure, maybe the guy installed the rings incorrectly? Did it have a Cylinder Head installed with the BB Cylinder? You Will be able to feel Some Positive Crank Case Pressure for the Breather, Normal. What RPM is she doing on Straights? RPM on the Down Hills? |
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Post by carasdad on Jul 28, 2015 8:03:29 GMT -5
Have you checked the clutch? Maybe some aftermarket "performance" parts were installed. I was told they only changed the variator weights to 7g in the cvt Bingo! There is your issue.. "I was told they only changed the variator weights to 7g in the cvt" So the stock torque spring 'shifts' too soon because they are weak..and the 7 gram weights cause it to 'shift' too quickly into a higher ratio.. This puts a load on the engine..hence poor performance up hills..and slow take take off. Here is my setup and it works well. JUST a BBK and weights will not improve performance..the whole drive train system needs to be balanced to handle the extra power. here is what I use below.. 2014 TaoTao Thunder 80cc BBK 2k clutch springs 1.5k contra spring 7gram KOSO sliders with KOSO variator Performance exhaust 50-55mph(No not Kph) GPS on a level surface with my skinny butt on it  |
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Post by lain on Jul 28, 2015 9:23:37 GMT -5
I was told they only changed the variator weights to 7g in the cvt Bingo! There is your issue.. "I was told they only changed the variator weights to 7g in the cvt" So the stock torque spring 'shifts' too soon because they are weak..and the 7 gram weights cause it to 'shift' too quickly into a higher ratio.. This puts a load on the engine..hence poor performance up hills..and slow take take off. Here is my setup and it works well. JUST a BBK and weights will not improve performance..the whole drive train system needs to be balanced to handle the extra power. here is what I use below.. 2014 TaoTao Thunder 80cc BBK 2k clutch springs 1.5k contra spring 7gram KOSO sliders with KOSO variator Performance exhaust 50-55mph(No not Kph) GPS on a level surface with my skinny butt on it I swapped the clutch, put in mine which has 1.5k springs and new clutch pads, same outcome. The problem is it is NOT getting to high RPMs until going downhill, and ONLY when going downhill. I also tried switching the weights to 5g and to 8g, still the same issue. It is like it is stuck at low RPMs. I do not have a tach for the scooter otherwise I would give you the numbers. When revving from a stop it slowly climbs up in speed even if I try to give it full throttle. The carb main jet was # , I decided to try fiddling with the carb too so I put i my own #  , it seemed to go slightly faster in the low end but not by much. The needle in the carb is a standard non adjustable needle. I tried installing an adjustable needle but all of the notches 1 to 5 all seemed bad so I put the nonadjustable needle back in. I adjusted the valves to 0.003. I checked and added ground wires. I replaced the spark plug, coil, cdi... Been all over this scooter except inside the engine beyond the valves.... Everything I do only makes small almost unnoticeable changes, it's still about the same as when I started. It goes about 20 on flats, 10 uphill, and 45 downhill and will not hold speed above 20 on flats even when going down a very long downhill first.. |
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Post by lain on Jul 28, 2015 14:27:59 GMT -5
I think I MAY have found the issue, but not entirely sure. The oil seal on the variator side was halfway out and leaking a small amount of oil, which accumulated in the CVT, and ontop of that it looks like there is no oil getting to the topend as well.
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Post by carasdad on Jul 28, 2015 14:55:28 GMT -5
Bingo! There is your issue.. "I was told they only changed the variator weights to 7g in the cvt" So the stock torque spring 'shifts' too soon because they are weak..and the 7 gram weights cause it to 'shift' too quickly into a higher ratio.. This puts a load on the engine..hence poor performance up hills..and slow take take off. Here is my setup and it works well. JUST a BBK and weights will not improve performance..the whole drive train system needs to be balanced to handle the extra power. here is what I use below.. 2014 TaoTao Thunder 80cc BBK 2k clutch springs 1.5k contra spring 7gram KOSO sliders with KOSO variator Performance exhaust 50-55mph(No not Kph) GPS on a level surface with my skinny butt on it I swapped the clutch, put in mine which has 1.5k springs and new clutch pads, same outcome. The problem is it is NOT getting to high RPMs until going downhill, and ONLY when going downhill. I also tried switching the weights to 5g and to 8g, still the same issue. It is like it is stuck at low RPMs. I do not have a tach for the scooter otherwise I would give you the numbers. When revving from a stop it slowly climbs up in speed even if I try to give it full throttle. The carb main jet was # , I decided to try fiddling with the carb too so I put i my own # , it seemed to go slightly faster in the low end but not by much. The needle in the carb is a standard non adjustable needle. I tried installing an adjustable needle but all of the notches 1 to 5 all seemed bad so I put the nonadjustable needle back in. I adjusted the valves to 0.003. I checked and added ground wires. I replaced the spark plug, coil, cdi... Been all over this scooter except inside the engine beyond the valves.... Everything I do only makes small almost unnoticeable changes, it's still about the same as when I started. It goes about 20 on flats, 10 uphill, and 45 downhill and will not hold speed above 20 on flats even when going down a very long downhill first.. Ok..sounds like you did all the right things..but read this below. I copied it from my post in another Scoot forum.. Since that post many have discovered that even their 2-3 year old and older Scoots have the same issue.. So maybe yours does? Below is my snippet and discovery.. --->Discovered a new way they are restricting Scooters. 3 days ago a guy received his new Scoot in the crate. We put it together and I did his PDI. All looked well..with a few minor things like connectors not plugged in all the way. He rode it for 3 days (after we removed the shipping oil) He logged 118k on it and asked me why it would only do 27-28 and just at 30mph on a small slope. Carb was sealed of course so I fixed that and found a #70 main jet and a snow white fresh as new plug. When I rode it there was VERY little power and by a guess I would say the engine never reached 6k rpm. It launched ok..for about 25 feet..then the rpms and speed seemed to drop. Tried a #78 main jet and power was up a hair..but rpms still low. On the center stand it would rev easily to I would guess 9k or better.hmmm..so what was loading it down? I pulled the CVT to weigh the rollers and found 5 gram ones inside. Plenty light for a stock 50cc..yet it would not rev up under a load. THEN..I saw the rear variator pulley half.. The ramps were a whole bunch steeper than any other stock CVT I have seen. I compared it to an old stock CVT I had in the used parts bin..and sure enough..the new CVT was as different as night and day. The ramps were very steep and very short..the area on the outer edge of the pulley(I call it the roller weight stop) That area was about 1/3 taller/higher than the used stock pulley. Using the old pulley I rolled a weight to the end of its travel and it was a few mm above the rim of the pulley. Doing the same with the new stock pulley..I found travel was short and steep..and the weight was stopped from moving by the taller flat area (roller weight stop or whatever its called)In the new pulley the weight was barely even flush with the edge of the rim! I swapped in the used pulley and used the 5 gram weights his scoot came with. Speed was up 6-7 mph with a much less pronounced bog..as before when the engine would hit about 26mph and the rpms would drop...as it barely mushed along forward.. Oh and forget about even a slight incline..cause the scoot just fell on its face. It made it over the hill with the CVT it came with..but at a Turtles pace almost..lol. Then we tried a used DLH brand pulley half I had. rpms were way up and speed was now hitting 36-38mph. So I ordered him a performance variator and things will be resolved then. So if you buy..or work on somebody's new scoot..be on the lookout for this new 'restricting' type variator. I kept his and must say it makes a dandy ashtray in the shop.. 6 people can smoke at once even..because each roller weight track gives them their own personal cig holder..  Below is a pic of the OLD stock type variator and describes the changes I saw as mentioned above. I did not get a pic of the new one..but I will when we dump the cig ashes out of it tomorrow..lol. Enjoy, Glenn  |
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Post by lain on Jul 28, 2015 20:33:59 GMT -5
That's a very interesting post, thanks man I had no idea. Next I will try my own variator and ramp, but not until I replace the oil seal. It is pushed in too far, could I simply pull it back into place or should I get the replacement?
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Post by carasdad on Jul 28, 2015 21:09:19 GMT -5
That's a very interesting post, thanks man I had no idea. Next I will try my own variator and ramp, but not until I replace the oil seal. It is pushed in too far, could I simply pull it back into place or should I get the replacement? If it is a new oil seal..you may get by repositioning it..but seals a year or so old..tend be brittle...and are prone to leaks if tampered with.. |
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Post by lain on Jul 28, 2015 22:35:19 GMT -5
That's a very interesting post, thanks man I had no idea. Next I will try my own variator and ramp, but not until I replace the oil seal. It is pushed in too far, could I simply pull it back into place or should I get the replacement? If it is a new oil seal..you may get by repositioning it..but seals a year or so old..tend be brittle...and are prone to leaks if tampered with.. Hmm... May just replace it then. How do I remove it though? It has been pushed in all the way, a lisle seal remover tool cant really get in there, maybe a paper clip held by pliers? |
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main jet in CVK carb, idles and tuned up perfectly, foam air filter installed, stock exhaust, and no oil leaks or hard starting and has enough compression to push my thumb off the spark plug hole, and the vales are both at 0.003. Checked for leaks by spraying wd40 all over everything while running, all good. 
, it seemed to go slightly faster in the low end but not by much. The needle in the carb is a standard non adjustable needle. I tried installing an adjustable needle but all of the notches 1 to 5 all seemed bad so I put the nonadjustable needle back in.