100cc big bore kits? By aaronl8n (Read 2,875 times)

[aaronl8n]

Hey guys im thinking about buying this for my scooter:
www.ebay.com/itm/291020773879?_trksid=p2050601.m570.l4448&_trkparms=gh1g%3DI291020773879.N1.S2.M1211

Would i need to replace anything else if i put this in/would it work on a roketa 50cc scooter?

I noticed there were a lot of you tube videos on installing them so i doubt that would be to hard.

thanks!

[Alleyoop]

If your motor is a 139QMB yes, that is a nice BBK. You would need to up-jet your carb with about a #90-95 main jet.
Alleyoop

[aaronl8n]

^ awesome thank you, incase i dont win that bid is this the same thing:
www.ebay.com/itm/Chinese-Scooter-Big-Bore-Kit-100cc-50mm-Bore-QMB139-23-mm-Intake-Valves-/221239696272?pt=Other_Vehicle_Parts&hash=item3382e9db90&vxp=mtr

it mentions something about 23mm intake valves is that the same? also is qmb139 and 139qmb a diffrent scooter?

[Alleyoop]

Yes, same the other kit puts in a new oil pump and casing gaskets. But just for a bbk you don't need the extra gaskets and oil pump.

Same motor they just mentioned as QMB139 instead of 139QMB

They also include a #90 Main jet which you should put in right away. Do not run it with less than a #90 you may need a bigger one but you won't know until you fire it up and try it after you install the BBK.
Alleyoop

[rob63]

Out of interest Alley, do these kits need the crankcase relieving in the same way the 170 kits do when fitted to a 125/150 engine ?

[aaronl8n]

^ I was doing some searching last night and noticed that. Im thinking the 100cc kit may stress my crank and break it, so maybe an 80cc kit? would that even give me much more boost?

Ill probably stick with the 100cc since 80s the exact same price and I want as much bang for my buck as i can get. Im just wondering how long the bottom end will last lol (4k miles and almost 7 years old)

Would 80cc be cheaper in the long run/give me the same gains?

thanks!

Im almost positive this is my scooter:

[Bashan]

We had a discussion a couple of years ago about how far you can stretch the ccs on a BBK. One guy found a study that showed 80cc to be the limit on a 50cc upgrade. 100cc seemed to be out of the engines limits for handling mechanical stress. I looked for the thread but I can't find it. However, the article cited strong evidence that you can't push a 50cc past 80 without dire consequences, i.e. boom.

[FrankenMech]

The techs in the service department where I purchased my 50cc scooter suggested 80cc as the best option.

[sitticuss]

when i got my bbk i got an aluminum jug to replace my old one... It is so much lighter....less weight more speed every little bit helps... I put an 80cc kit in my 50cc..trust me it does make a difference

[twowheeler]

When chosing a BBK number how is it figured up? Do you add the number of cc's of the BBK to the existing motor to get a total? Is a 50cc BBK make it a 100cc if its already a 50? 80cc BBK make it 130cc's?

[rob63]

Nov 28, 2013 7:19:53 GMT -6 twowheeler said:

When chosing a BBK number how is it figured up? Do you add the number of cc's of the BBK to the existing motor to get a total? Is a 50cc BBK make it a 100cc if its already a 50? 80cc BBK make it 130cc's?

No, an 80cc big bore kit will make the engine 80cc

[bobthetechguy]

Nov 24, 2013 14:11:06 GMT -6 aaronl8n said:

^ I was doin....s my crank and break it, so maybe an 80cc kit? would... much more boost?



Im almost positive this is my scooter:

its the same as a taotao and a peace motorsports too

www.ebay.com/itm/50cc-QMB139-GY6-50mm-100cc-BIG-BORE-KIT-Made-in-Taiwan-NOT-China-US-SELLER-/170948060522?pt=LH_DefaultDomain_0&hash=item27cd4c656a

[aaronl8n]

Nov 24, 2013 17:24:32 GMT -6 Bashan said:

We had a discussion a couple of years ago about how far you can stretch the ccs on a BBK. One guy found a study that showed 80cc to be the limit on a 50cc upgrade. 100cc seemed to be out of the engines limits for handling mechanical stress. I looked for the thread but I can't find it. However, the article cited strong evidence that you can't push a 50cc past 80 without dire consequences, i.e. boom.

Awesome thanks guys! I definitely think im going to go with an 80 I don't want to the boom lol Thanks for letting me know that there are gains on the 80cc I think id like to get an average of 35-40 on flat land to keep up with 35mph traffic.

thanks guys!

[twowheeler]

Mine does 40 easily with no BBK ;D

[FrankenMech]

My 275# 50cc trike will keep up with 35mph speed zone (40mph) traffic with my 210# and 30# of tools. I loose a little on hills but gain it back downhill. For now mine is fast enough. The speedometer says I am doing 30-50mph. I need to get the thing calibrated.