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Post by milly on Aug 31, 2017 15:03:53 GMT -5
Well got my qmb 139 scoot through mot and on the road today the transmission pulls away fast and seems to drop off accelerating really quickly like its hit a higher gear to soon. Rolls ok when down slight gradiants and on the flat Dont expect miracles from a 49cc with my 196 lb body on it but would like to improve pulling power a bit. Put a new variator on but did not note weight of rollers also a new gates belt. Not done anything elsse to the rest though
Just wondering a ball park sort of for the roller weights to start with and colour/ rpm contra spring.
Many thanks
Milly
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Post by AtariGuy on Aug 31, 2017 15:16:17 GMT -5
In some cases, a new stock contra would fix the shifting too fast issue. It could be that your current one is so heat-faded that even my granny could squeeze the pulley open. So a new stock and a new blue one?
As far as weights go, i believe stock is 5gr. It varies though from scooter to scooter. If you have 5gr now, pick up 4gr and 7gr sets. That plus aluminum foil should have a great series of tuning options.
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Post by milly on Aug 31, 2017 16:03:02 GMT -5
Thanks for that, i have a spare spring or two without size on but colour which I think donates the same as 1000, 1500 and 2000 rpm but not sure which is which. Plus I not sure what the standard size springs are either  Rollers ordered |
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Post by scott7 on Aug 31, 2017 18:11:20 GMT -5
Could be the rear pulley is not operating smoothly ,I would check and clean it and regressed it ifs good .it might be sticking some causing low to high shift change
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Post by AtariGuy on Aug 31, 2017 19:20:36 GMT -5
+1 on scott's comment, but with a new contra (wink)
If its typical chinesium performance, blue is 1k, yellow is 1.5k, red is 2k - my memory mnemonic is cold to hot for the color order. I cant really say for certain what the dimensions are, i do know a blue 150 contra barely shifts in a 50 (its like a 3.5k spring rofl) i had to try it, and it was a beast to get the clutch down on it lolol however i think the extra windings literally prevent the rear pulley from opening fully. So a 150 torque spring won't work in a 50.
Edit- the blue 150 clutch springs are close though, if again on the rather stiff side. They slip through most of the rpm range as the clutch pads arent quite heavy enough.
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Post by 90GTVert on Sept 1, 2017 4:50:19 GMT -5
5g sliders are a popular choice for a stock 139QMB when more pep is desired, but I always recommend actually tuning by trying different weights.
I don't usually go beyond 1K for the contra spring, because stiffer springs can reduce top end because it doesn't seem like the engine is able to compress them as needed in some cases.
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Post by dexameth on Sept 5, 2017 6:54:39 GMT -5
Also pay attention to the ramps inside the clutch! Some stock have curved ramps that hold rpm high for take off and then drop into cruising gear. Some are straight for smooth actuation, with different angles for "shifting speed".
Mine are so worn that it sticks at different speeds, been through 3 different styles and I still can't find one that won't wear grooves or look like a wash board. That's a different discussion...
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Post by uglo on Oct 9, 2017 22:07:50 GMT -5
I think he means ramps inside of your variator. Definitely do as suggested by picking up some 4s and 7s. You can intermix and do the math to find out your average. Acceleration goes to crap higher you go but holding top speed and getting there are pluses with heavier.. lighter gives you much quicker acceleration but makes it tougher getting to top end. Good luck!
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Post by dexameth on Oct 13, 2017 16:28:57 GMT -5
I think he means ramps inside of your variator. Definitely do as suggested by picking up some 4s and 7s. You can intermix and do the math to find out your average. Acceleration goes to crap higher you go but holding top speed and getting there are pluses with heavier.. lighter gives you much quicker acceleration but makes it tougher getting to top end. Good luck! No I mean the actual ramps INSIDE the clutch... the torque driver to be exact. |
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Post by uglo on Oct 14, 2017 13:02:00 GMT -5
Ahhh! Yup
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Post by lostforawhile on Oct 14, 2017 19:03:05 GMT -5
you might need to take your clutch apart and clean and regrease your torque driver and check the slots for wear, if they aren't too bad, you can smooth them out
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Post by lostforawhile on Oct 14, 2017 19:04:25 GMT -5
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Post by dexameth on Oct 17, 2017 15:44:53 GMT -5
you might need to take your clutch apart and clean and regrease your torque driver and check the slots for wear, if they aren't too bad, you can smooth them out I was pondering using a Dremmel to smooth out mine... but I worried about opening up the guides too big. Would this be an issue? There's almost a millimeter of play in stock, so a little bit more play shouldn't hurt anything right? I've seen photos of people opening up the grooves almost an inch and still drove it! weird. |
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Post by hurldem13 on Jan 16, 2018 7:16:35 GMT -5
In some cases, a new stock contra would fix the shifting too fast issue. It could be that your current one is so heat-faded that even my granny could squeeze the pulley open. So a new stock and a new blue one? As far as weights go, i believe stock is 5gr. It varies though from scooter to scooter. If you have 5gr now, pick up 4gr and 7gr sets. That plus aluminum foil should have a great series of tuning options. Aluminum foil? |
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Post by AtariGuy on Jan 16, 2018 7:24:01 GMT -5
Yessir, if you have to super fine tune, you can use partial gram pieces of aluminum foil pressed into the rollers to increase... say a 4 gram weight to 4.5 grams. I recommend using a digital postage scale thats accurate to 0.1 gram or finer to make sure the weights are all equal. Brent has a realky good writeup with pictures on this method of a poor man's fine tuning. I will look for the link when i get home. Edit- 49ccscoot.proboards.com/thread/1199/modding-roller-weights |
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