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Post by sailracer on Jul 21, 2013 19:02:32 GMT -5
I recently built a 50cc with a bbk,and a new bigger carb, variator and gear upgrades. My question is:Are these engines dependable? Or are they super high maintenance, breaking down at the least opportune times, and requiring almost constant attention?
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Post by JR on Jul 21, 2013 19:59:34 GMT -5
The faster they go, the faster they blow!
Really, now if you don't go all out all the time they will last longer. If you have to go faster all the time, get a bigger bike. The 50cc is made to be a 30 - 35mhp scooter not a 50 mph scooter. Kind of like buying a cheap tool and expecting to use it to make a living on, not a good idea.
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Post by scootnwinn on Jul 21, 2013 20:02:56 GMT -5
Run the crap out of it and tell us I've never built a 50. We will know pretty fast, maybe.
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Post by sailracer on Jul 21, 2013 20:11:50 GMT -5
The reason I ask this is that i am very happy with the overall performance of my 50cc . It goes 37-40 on flat ground. the only thing that kind of bothers me is like all 50cc scooters, lousy uphill and against the wind. My desire is to be able to do 40 without WOT all the time, and better uphill performance. I do not want a race bike.And i dont much care for the loud mufflers and uni filters. i have the 2 stroke style exhaust with the expansion chamber and a few 3/8" holes on the bottom of the stock airbox.The motor is a Qmb139 with a BBK,A9 Cam 20mm carb koso variator with 5 gram sliders and 16/50 gears. If it" going to be a maintenance hog, I just as soon not use it as a daily driver. I have another scooter I can put it in if it's going to be more of a toy than a dependable motor. What do you think?BTW, I already installed it, and had overheat problems because of a lean mix. So I took it out and put the original back in  my scooter is a 2012 with 750 miles on it. I dont want to ruin it,just improve it ;D |
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Post by ramblinman on Jul 21, 2013 20:42:37 GMT -5
I already installed it, and had overheat problems because of a lean mix. So I took it out and put the original back in my scooter is a 2012 with 750 miles on it. I dont want to ruin it,just improve it ;D i can't answer from experience but from all the reading i have done it seems like this is the biggest problem with BBK's. if you can install the right jet then i would assume you would be fine. everyone says adjusting your carb is easy. nothing to it. childs play... but they have been working with carbs for years, perhaps decades.  i wouldn't trust myself to tune it properly so EFI will be my solution in the future. |
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Post by spandi on Jul 21, 2013 21:22:25 GMT -5
When discussing Chinese scooters (and their power-plants) size would also play a role as to reliability. The bigger the engine the less strain on it when going faster or uphill. I have also noticed the parts on the larger machines tend to be made heavier and are less prone to breakage.
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Post by jerseyboy on Jul 21, 2013 22:25:34 GMT -5
I read somewhere that a 50 runs cooler than a 150 cause it was originally designed from a bigger motor like an 80cc,,and the 150 is from a 125cc,,I take that with a grain of salt cause i read it online. I would say run the heck outta it with plenty of fresh oil and see what happens,,they are cheap to fix/replace  |
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Post by millsc on Jul 21, 2013 23:10:57 GMT -5
It should be fine if you have a quality bbk, i ride around town at 30-35 mph at 1/4 throttle motor barely working with the mods i have only have to wot on steep hills,make sure its jetted correctly and keep clean oil in it and all will be good  |
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Post by sailracer on Jul 22, 2013 4:36:29 GMT -5
what size jet would be a good starting point ?  is the biggest ive got |
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Post by millsc on Jul 22, 2013 7:58:25 GMT -5
what size carb?
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Post by sailracer on Jul 22, 2013 8:12:06 GMT -5
20mm and I also have the stock , 17 or 18mm
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Post by millsc on Jul 22, 2013 10:16:37 GMT -5
jet with the 20mm carb should be plenty big enough.I've never had to go past 98 on a 20mm carb or smaller. I ran a 98 on my scoot with the 20mm because of the big valve head |
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Post by sailracer on Jul 22, 2013 10:32:06 GMT -5
Thats great info :Dthanks I got the 20 mm from scrappys, but couldnt figure the jet (not marked), So I put in an  And Adjusted, and went for a ride. She overheated and wouldnt re start. I pulled the head, and no damage ? i dunno, Maybe valves. I got the head from scrappy also and A9 cam, but the valves are short, so I had to put the lock nuts under the adjuster. Anyway, Im Thinking of getting a Buford head now whadda you think? Im buttoning up the plastics now. I put the original motor back. I can fool around with the hy-perf.while its out BTW, It ran so hot. It wore down the tiny tip of the iridium plug! |
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And Adjusted, and went for a ride. She overheated and wouldnt re start. I pulled the head, and no damage ? i dunno, Maybe valves. I got the head from scrappy also and A9 cam, but the valves are short, so I had to put the lock nuts under the adjuster. Anyway, Im Thinking of getting a Buford head now whadda you think? Im buttoning up the plastics now. I put the original motor back. I can fool around with the hy-perf.while its out BTW, It ran so hot. It wore down the tiny tip of the iridium plug!