Stroker crank information please

[2010iron883]

I have a 2007 kymco agility 125 that has been a very very dependable bike and still is. I messed up the drive plate on the crankshaft becasue i didnt know WTF i was doing. I know now and im am a pro withit but the damage is already done. My question is can i just go with a stroker crank only? Would i have to change anything else? A good stroker crank isnt anymore than a oem crank from kymco. I know the case will have to be bored to fit but im having the job done professionally so no worrie there. My engine is a kdu 125cc. No from the outside it looks no diff than a short case gy6 but from what im understnding there is a diff inside. Does anybody have any ideas on a stroker crank. Can i just go with the stroker crank alone? Would i have to rejet or change anything else at all. My engine is far from worn out though it does have 17,000 k but it never uses a drop of oil and ive kept tedious record of the services ive done. Thanks for your time and help.
Justin

[noday]

replacing a stock crank with a stroker will increase the compression ratio and require a higher Octane gasoline.

you will get maybe 5% to 10% increase in engine HP, if that

overall change in scooter performance will be small

[Rebel]

Welcome to the forum,

Since you are having the job done in the shop, I would hope the mechanic would know if the stroker has enough room. You are going to have a bit more compression, that will depend on how much more stroke you are going for. Again, since you are having it done professionally I'd ask the mechanic about the proper octane fuel to use. Longer strokes will probably improve bottom end torque.

How much are you planning on increasing the stroke?

I think the stoke bore and stroke on a 125 is 52X57, I'd be more tempted to go with a stock stroke and a big bore kit to bring it up to square at 57X57, or a 150cc

[2010iron883]

I dont know if a stroker is even what i want. Im really looking for more low end torque than i am speed. What kinda crank would you go with if i where to just go back stock and maybe go with a bbk. Yeah the mechanic said he would have to bore the crank case. I knew it wasnt an easy job by no means. What would you do just get a crank from kymco or and aftermarket. I run 93 non ethanol fuel in everything i own. I just like the clean burn and the fuel miles i get plus no ping. So what would be a good bran crank and bbk. i want good stuff that will last. This little scoot has 17000 on it now and runs awesome. If i hadnt screwed it up. Again im not trying to tell my mechanic how to do his job , i just gotta figure out what i want to put in this thng so he can do his job. I just wander what the diff in the gy6 and this kdu engine really is? It uses alot of gy6 parts but i dont know about inside. By golly it looks dang close though.

[Rocketdog]

I'm afraid I can't tell you if your Kymco is the spittin' image of a GY6. I have a Kymco Filly that has a 139QMB in it, 49cc. It's just like a Chinese model except the parts are better quality.

I would ask Carlos in Taiwan About your model. Here's his store stores.ebay.com/Autotech355-Performance-Parts . E-Mail him and tell him what your thinking about doing. I have my doubts that a 125 crank is any different than a 150, except for the rod length. Personally I would say that if you used a good quality 150cc <57.8mm> it would fit. For production reasons you wouldn't change the diameter of the flywheel, you would shave weight off the sides in order to balance it. Here's one- cgi.ebay.com/ebaymotors/GY6-152QMI-crankshaft-57-8mm-genuine-Honda-SYM-/230665300869?pt=Motorcycles_Parts_Accessories&hash=item35b4b92b85#ht_1710wt_939 Then I would put a 59mm bore kit on it. They are relatively inexpensive and they will fit a GY6 with no boring of the cases. That will give you 157cc. A lot more torque than a 125. My China scoot will do over 60 with this setup and has descent acceleration.

One bad thing is that it takes 2 weeks from Tiawan.

RD

[xs650]

Aug 29, 2011 19:11:27 GMT -5 Rocketdog said:

I. I have my doubts that a 125 crank is any different than a 150, except for the rod length.

RD

RD, Kymco 125cc and 150cc engines both have the same stroke. I would expect the crank and rods to be the same.

[2010iron883]

Thanks everybody!

[Rocketdog]

Aug 29, 2011 21:23:00 GMT -5 xs650 said:

Aug 29, 2011 19:11:27 GMT -5 Rocketdog said:

I. I have my doubts that a 125 crank is any different than a 150, except for the rod length.

RD

RD, Kymco 125cc and 150cc engines both have the same stroke. I would expect the crank and rods to be the same.

Thanks XS makes sense.

[Rebel]

I have a link to a manual for the 125 in the help area, double checked and the stroke and bore for the 125 gy6 is what I posted above.

[2010iron883]

Well i got an estimate and its only gonna be $120 more for a stroker crank on the labor and part so i thnk i may just go ahead an have a ncy stroker installed. He also gave me an estimate with a ncy , cam, cam tensioner, chain, head and bbk, gasket set, and of course the stroker crank. With labor and parts its gonna run me about $1023.00. Now i know this is alot but the chinese scooter my buddy has is a 150 and is doesnt compare to my 125cc. I dont know why but it just has more speed and power , plus i just like the quality of my scooter alot better than his . Im not knocking chinese scooter cause ive saw some that are really nice so please dont take me wrong. I dont thnk this is a bad price for a whole new engine that will be 183cc. Ill keep you guys posted.

[Rebel]

That should make a big difference in the get up and go.

[jmkjr72]

well as long as the shop does the work right
when it comes to mods a lot of the shops realy dont do every thing right for scooters
i dont know how many i have seen that were sent out with oem cabs and jets and lean as can be
so as long as they can tune it properly its not a bad deal

[Rocketdog]

So 210Iron, how much are you going over standard on the stroke? 2mm? 4mm? And what's the bore going to be? Seems that I recall a 2mm stroke and a 59mm bore is real close the a 183. It will be a nice setup. If I might mention one small item. I would suggest a manual fuel petcock. The vacuum ones leave a lot to be desired.

RD

[2010iron883]

Yeah thats a good idea about the fuel petcock. I will have to check the estimate to see how big he was goin. I didnt want to go hugh on the crank though. I can promise you this , Josh at The Scooter Garage knows what he is doing , and he does thngs right. Check out the website he has too. This guy is the best around me and im still driving 2 and 1/2 hrs to get to him. if he wasnt worth every penny i would get it done closer. Ill get back to you on the size of the stroker. I would be discussing everything with him a little more when i take the scooter to him in person.

[2010iron883]

Sept 1, 2011 18:25:53 GMT -5 Rocketdog said:

So 210Iron, how much are you going over standard on the stroke? 2mm? 4mm? And what's the bore going to be? Seems that I recall a 2mm stroke and a 59mm bore is real close the a 183. It will be a nice setup. If I might mention one small item. I would suggest a manual fuel petcock. The vacuum ones leave a lot to be desired.

RD

Hi its says 62mm NCY cylinder kit and performance crank. Im gonna give him a call and see which crank it is. Im type person that he will have to take my old parts and put them back into the new part packageing because i will be bringing them home. He is a heck of a mechanic too. He is honest about his work. Im ready to get the jet kit installed and put my stainless exhaust system on. This little scooter is gonna be bad for what it is. I thnk it is anyhow.