Seeking some info on 50cc to 83cc upgrades.

[dmartin95]

Hi all, I'm new to the forum and was hoping I could find some advice about engine upgrades.



I recently purchased a Brand New Scooter for my wife that came with an upgrade from the dealership. I was told they had installed an 83cc upgrade kit. I was told the moped would be faster than a normal 49.5/50cc scooter, but it's not. It's not very fast at all. I am 160Lbs and this moped tops out at 32 MPH, level surface. Bogs down on hills to like 15~20MPH and has no more take off power than a low powered 50cc scooter.



When I purchased her scooter, I also purchased one for me. A Bintelli scorch 50cc. I can do 38MPH on level surface and run circles around her 83cc upgraded scooter.



So, I'm getting ready to contact the dealer, however I would like to be armed with a little bit of info.



I see these 83cc big bore kits on the net, but I also see upgraded heads, cams, carbs, exhaust, etc, etc,....



So, In short, here's my question. If you put an 83cc Big Bore kit on a stock 50cc moped, should you also change other parts such as the head, cam, carb and such?



I read a disclaimer on a scooter upgrade site that said to realize the upgrades, other components should be changed as well.



So what happens when you install a Big Bore kit on a 50cc without upgrading anything else? Should there be a gain or loss in performance?



-----------------------------------

UPDATE*

I have started this same thread on a different scooter forum and it has been suggested my carb has not had the jets adjusted/changed properly.


Do the members here have any different recommendations/suggestions? 

[Upgrayedd]

if you did not jet the scooter when you changed out the piston and jug, it is likely pretty far out of tune, and your performance is suffering. the tune is possibly quite lean, which can cause bogging, as well as much hotter running engine temps, and lead to engine damage over time.

i run a 47mm/72cc piston and jug with a stock head, carb (rejetted), and exhaust, and i achieved a good increase in power. top speed around 47mph.

it sounds like you may need to do some tuning.



*edit* i somehow missed the part that said the dealership installed it. yes, it should go faster than it is.

[2TDave]

Welcome! I hate to be a skeptic but I'm not sure the dealer did anything. Have you looked at it? Measured the bore?

[90GTVert]

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The performance you describe sounds like a stock 49cc 139QMB. I'm 300lb and mine does that with the stock bore. IF it's in tune it should be quicker/faster than 32MPH on flat ground and struggling on hills with an avg rider (unless it's a steep grade).

If you can get a look at the carburetor, you can try to see if the mixture screw is capped and if the screws on the bowl have proper heads. If it's capped and the heads are the tamper resistant type, they haven't touched the carb most likely. I've got a vid HERE of the unsealing process so you can see what the screws and cap would look like and where they'd be. Not sure how well you can see this stuff without taking panels off, but it's worth a shot. A flashlight and an inspection mirror can do wonders.

Look at the plug to see if it's running lean. Post a pic if you aren't sure.

There are other possibilities. For example I had a 139QMB with the flywheel machined wrong so the timing was off. It ran around 30-35MPH no matter what I did to it till I got the timing right. Others have reported the flywheel issue as well. Low tire pressure slows them down a lot if it's low enough. CVT out of tune or malfunctioning would hurt performance. Still, in this case I'd suspect there's no big bore first and worry about other possibilities after I knew the bore size was larger than 39mm (stock). It should be 47-52mm if there's a big bore kit on it.

[stevec]

[dmartin95]

HI all and thanks for the replies. The performance issue is now a moot one.

I contacted the dealer and explained the poor performance issues I was experiencing and he had me bring the scooter in. While I was there, I came across a Used Heritage 150cc with only 90 miles on it.

My wife's 83cc Amore was a 2013, this new scooter is a 2011 but it has a way nicer engine. Of course now I have to get a motorcycle endorsement and insure it (I also got a 150cc A Sunny)), but living out here in the country like I do, I needed the extra CC's. I paid $175.00 plus the Amore. I thought it was a great swap seeing as how I would have had trouble unloading her Amore in the condition it was in.




--- 90GTVert. That was an awesome link. I wound up watching like 10 of your videos and feel like I came away with with a wealth of knowledge. You took your time to make those video free of charge and people like you make a difference!

Thank you!

[90GTVert]

Sounds like a good trade. Not likely you'd make the 50/80 run like the 150 for $175. I know there's the expense and effort of licensing and insurance, but at least you'll be totally legal that way.