about to buy 92 cc kit do i need to buy new valves as well?

[Kimcofan]

I am about to buy a 92 cc kit for my gy6 agility 50 I was wondering if it is absolutly nessecary to install anything else when putting this kit on my scooter? Unfortunatly my crankshaft blew out and busted a hole in my oil pan which i have already recieved parts for but while i have my motor apart i figure may as well go ahead and upgrade so where looking for any input!!! Thanks

[scootermike]

Really no use in installing a new larger cylinder kit without larger head with larger valves, when piston comes up to met head there will be nothing there no new air or fuel so there is a huge lack of performance, you are doing this to push more air to get more power those little tiny valves will not let this happen. Where you are buying a 92cc kit which to me is bigger than 52mm and how thats possible would be new to me and I have been doing it 7 years to your engine, why someone sells the kit without a head is just plain wrong, then there is all other aspects like exhaust variator weights clutch CDI springs and quality of parts matters as well as belt. This is all opinion I have only due to my knowledge through experience. I can help and know what parts to use.

[zombie]

Hey Kymcomike (pun Interned), It's an Ebay jug right? Listen to "been there done that". Buy a proper kit, and reap the rewards, But a junk kit, and post back when you are ready to give your scoot away! Sct.mike sells parts and is willing to share what he knows (hopefully making a buck), and everything I have learned says, If spend the extra $'s, you will get what you want. Find the best kit by looking around the web/ Look for the best price on the parts you want/ Post here to keep getting advice! You can destroy your scoot or you can have a machine to "play with" for quite awhile! Search wordslinger on this forum(top right) read ALL his posts (if you have a few hours) and you can follow his progression on an ag/50. Ps. Don't stop half way through because you will have a scoot that doesn't run right!   

[scootermike]

Thats the whole thing, I have had many calls from people who buy a kit from ebay and then call me and say nothing happen or my piston is hitting head after they tell me what a great deal they got on a kit and when I ask did you get correct head no I am using stock, think about where is the piston which is huge compared to stock going to go on a stock head, well it will bang right into it , try putting a 52mm piston into a 39mm head do I need to say more, its all about pushing air, I have killer parts that goes with my experience, if its cheap how can it be that good besides skip cam shaft and you are really missing the boat, complete is what I say not a piece here and there till scoot does not even run, please be careful there are plenty of 139QMB engines that do not accept any kits like SYM engines and Tomos, Kymco I have no problem but I have not seen all of them plus I have special kits for SYM

[wordslinger]

...from what i've read here, i think a 72cc kit is about all the crank / bearings will stand up to over time..

..what happened to cause you to lose a crankshaft....that's kinda unheard of around here...

peace


Search wordslinger on this forum(top right) read ALL his posts (if you have a few hours) and you can follow his progression on an ag/50

...cpl of hours, huh...lol...

[Kimcofan]

Here is the description of what the kit comes with:
92cc High Performance Cylinder Kit for 50cc GY6 139QMB Scooter Engines, by manufacturer NCY. A high quality kit that can be used to upgrade a 50cc 139QMB scooter engine to 92cc that is ideal for modern city and highway riding.

Upgrading your 50cc 139QMB has never been more convenient with this easy to install upgrade kit. This scooter upgrade kit increases your engine bore size to 92cc, or 59mm. Includes an aluminum cylinder with piston, and rings plus gaskets. You will see a direct increase in performance after installation with both enhanced low end acceleration and improved top speed.

Combine this kit with a high performance carburetor and exhaust for an even larger boost in performance

It doesnt come with new valves but if I need them i should buy them I just need to know what size valves to put on it

[Kimcofan]

My crank bearings went out!!! How I have no idea, but the warrenty wouldnt cover it because some one made an attempt to steal my scooter and popped out my ignition and so the dealer said your SOL.  So now i have my motor in a bunch of peices and figure I may as well do any mod's while its apart Not as hard to take apart as i would have thought.  I do think the crank bearings were a manufactuar defect and they should have fixed it.  I even called the manufactuar and they said take it up with the dealer so around the merry go round I go.

[zombie]

Agreed NOW is the time! The Best advice I can give is keep reading everything you can find on your engine, and choose the best parts you can find. Scooter mike has a very good Idea of what you need, and Scooter Invasion has a lot of tuners you can listen to as well. Listen to everyone, and choose what comes up the most as the best.  Search wordslinger for trans. set up for a few more ideas. Bearings will only fail if there is no oil/ over rev/ age/ or defect. A "poped" ign. tells the Dealer "over rev". Now you have a clean slate to work from though. Please keep posting w/ your progress. I would like to see how your project turns out!

[wordslinger]

It doesnt come with new valves but if I need them i should buy them I just need to know what size valves to put on it

..I believe you would need a larger head...can't just change valves, as they are sized to fit the head...


...well, good luck with your project...I hope it all turns out well for you...

..just let me add one thing...I've seen a BUNCH of guys pop in here all fired up gonna upgrade to a big-bore kit...

..they rush into it and for whatever reasons...after a few weeks of.."what happened??" posts, we never hear from them again...

..take your time, and as everybody says, buy only compatible, top quality parts...

..I wish you the best!!!..(sure you don't wanna consider the 72cc??)..

peace

[Shaka]

It was my understanding that anything bigger than about a 72cc and the case will need to be machined with a larger opening.  If you do any size BB kit, you will almost certainly have to upgrade your intake, exhaust, and re-tune the transmission minimum!  Otherwise, you will end up with a scoot that doesn't run very well, if at all, and will have a very short lifespan!