Modern Buddy

So I stripped the splined on the crankshaft(?) where the variator goes because my impact driver sucks and it was my first time changing the rollers last week. I guess it didn't tighten the nut enough.



How difficult is it to replace this? Or should I just take it in to scooterworks and have them fix it?

Thanks

Unfortunately, that's the end of the crankshaft, so it's a complete engine teardown to replace it.

That's exactly how I wound up creating the Iron Buddy. The engine case has the be split to change that. The part itself isn't too expensive but it's about 4 hours labor, i think. Multiply that times your shop's labor rate.

It's a major bummer.

Howard

I've nearly done this also, but managed to catch the play in the pulley before I went any further. I got lucky.

For me, I've found the steps help to avoid this:

1. Make sure the belt is really loose (down in the rear driven pulley) so you can be sure the outer half of the drive pulley is the whole way in toward the motor

2. Hold the outer variator plate in when installing the spline washer, and make sure the splined washer is on the splines properly. If it isn't, the nut can be tightened and the splined washer won't press against the pulley, leaving it loose.

3. Hand tighten the nut while holding the whole assembly, including the splined washer, tightly toward the motor. Make sure the belt is loose again and not pinched between the variator plates.

4. Tighten the nut with a wrench a little bit and make sure there is absolutely NO play in the outer plate of the pulley.

5. If OK, torque the nut to spec. Check the pully plate again for play just to make sure.

never ever tighten things with an impact wrench i have seen more destroyed cranks because of this

its not that it didnt get it tight enough it over tightened the dang thing and started to rip the threads off

impacts are only for taking things apart never putting them togehter on a scooter

but yes it is time to split the case and replace the crank

you should be tightening down and using some sort of stop to prevent the crank from turning when you are torqueing down the nuts

i personaly like to feed an old lawn mower chord down the spark plug hole and fill the bore up with it then when you turn the crank just a bit it comes into contact with the rope and cant turn the engine over farther

jmkjr72 wrote:never ever tighten things with an impact wrench i have seen more destroyed cranks because of this

its not that it didnt get it tight enough it over tightened the dang thing and started to rip the threads off

impacts are only for taking things apart never putting them togehter on a scooter

but yes it is time to split the case and replace the crank

you should be tightening down and using some sort of stop to prevent the crank from turning when you are torqueing down the nuts

i personaly like to feed an old lawn mower chord down the spark plug hole and fill the bore up with it then when you turn the crank just a bit it comes into contact with the rope and cant turn the engine over farther

when I did my weights I used an oil strap wrech to hold the variator in plave. It took a bit to get the damn thing to stay in place but it did the job. I'm a firm believer in using a torque wrench to put bolts back on, figure they give you torque values for a reason.

Thanks for the replies and advice, guys. Looks like I'm going to learn a lot about the engine over the next couple days.

You will.

I feel your pain though. I gave my Buddy the Steve Austin treatment over the last couple months after undertightening the oil filter, which subsequently came loose and siezed the engine. My heart hit the ground when I pulled over and saw what had happend. Everyone makes mistakes.

The good news - there are lots of performance parts out there, and neither the stock nor performance parts are very expensive (relative to cars, motorcycles, etc.).

Sorry to hear about your crankshaft woes. I'm currently in the middle of replacing mine due to a seized connecting rod bearing. One thing to keep in mind when shopping for a new crankshaft, PGO engines have a lot of unique details when compared to a "standard" GY6 engine. Does your engine use a kickstart coupler on the variator shaft? It's a washer like thing with tabs sticking up (see post topic5444.html). If it does, then you'll have to use a stock PGO crankshaft if you want to keep your kickstarter because the splines on the PGO are longer by about 4mm compared to a "standard" GY6. The longer splines are to accomodate that coupler. If you want to increase your engine's displacement by going with a longer stroke, then you won't be able to use the coupler which means you'll no longer have a kickstarter. For my engine, I'm using a +4 or 4mm longer stroke crankshaft. The slines are too short to accomodate the kickstart coupler so instead of doing away with the kickstarter, I've pinned the coupler to the variator plate with hardened dowel pins. I'll be posting pics on my thread in the Blur forums (topic16629.html)
Also, with a longer stroke, you may have to install a shim between the cylinder and the crankcase to make-up for the increased stroke length. The thickness of this shim should be half the length of the amount of increase in stroke - in other words, if your stroke is increased 2mm over stock, then the shim should be 1mm thick.
Good luck with your engine.

babblefish wrote:Sorry to hear about your crankshaft woes. I'm currently in the middle of replacing mine due to a seized connecting rod bearing. One thing to keep in mind when shopping for a new crankshaft, PGO engines have a lot of unique details when compared to a "standard" GY6 engine. Does your engine use a kickstart coupler on the variator shaft? It's a washer like thing with tabs sticking up (see post topic5444.html). If it does, then you'll have to use a stock PGO crankshaft if you want to keep your kickstarter because the splines on the PGO are longer by about 4mm compared to a "standard" GY6. The longer splines are to accomodate that coupler. If you want to increase your engine's displacement by going with a longer stroke, then you won't be able to use the coupler which means you'll no longer have a kickstarter. For my engine, I'm using a +4 or 4mm longer stroke crankshaft. The slines are too short to accomodate the kickstart coupler so instead of doing away with the kickstarter, I've pinned the coupler to the variator plate with hardened dowel pins. I'll be posting pics on my thread in the Blur forums (topic16629.html)
Also, with a longer stroke, you may have to install a shim between the cylinder and the crankcase to make-up for the increased stroke length. The thickness of this shim should be half the length of the amount of increase in stroke - in other words, if your stroke is increased 2mm over stock, then the shim should be 1mm thick.
Good luck with your engine.

Also keep in mind that the Buddy 125 crankshaft is UNIQUE. Its the only 2mm stroker crank with a 13mm wrist pin out there. If you choose to upgrade(and you can if you like!) You'll end up with a crank that has a 15mm wrist pin(The same as the Buddy 150's) which means you'll also HAVE to get a new piston.

There are also a couple of long spline stroker cranks out there, but they're quite uncommon.

Thanks for the heads-up regarding the spline length and other measurements.

This is the GY6 125/150cc crankshaft sold on scooterworks: http://www.scooterworks.com/Crankshaft- ... 1C483.aspx. Is that the same as the stock one, or do I need a new piston and 15mm wrist pin?

goldscott wrote:Thanks for the heads-up regarding the spline length and other measurements.

This is the GY6 125/150cc crankshaft sold on scooterworks: http://www.scooterworks.com/Crankshaft- ... 1C483.aspx. Is that the same as the stock one, or do I need a new piston and 15mm wrist pin?

That is for a standard GY6. To get that to work you will need:

Piston
camshaft
gasket set
Have a machine shop modify your variator to allow your kickstarter to work.

Unless you are looking to go crazy with performance. Just get an OEM replacement.

I used the stock Buddy 125 crankshaft from Genuine/Scooterworks (ordered through my local dealer). Unfortunatley, it's more expensive than a generic GY6 crank. I think it was around $180.

Bcon wrote:I used the stock Buddy 125 crankshaft from Genuine/Scooterworks (ordered through my local dealer). Unfortunatley, it's more expensive than a generic GY6 crank. I think it was around $180.

Thats because the stock Buddy 125 crank is actually a 2mm stroker performance crank.

Sorry, should have been more clear. I used the stock 125 crank from Genuine because it is different than a "standard" GY6 crank (as Kaos points out). Different usually means more expensive when it comes to parts.

For me, there were just too many other modifications required if I had used a different crank.

In the end, there are so many variations on GY6 engines that it was much easier to just get everyting I needed from Genuine/Scooterworks. Every time I looked for a more economical part option, I found that in some slight way it wouldn't work.

Thanks for your expertise, guys. Greatly appreciated.

Bcon wrote: 5. If OK, torque the nut to spec. Check the pully plate again for play just to make sure.

What is spec for this nut?

According to the service manual, it's 5.0-6.0 kg.m, which is 36-43 lb.ft.

Same for the rear (driven) pulley nuts.

Thank you

So I reassessed the situation and realized that the splines weren't as bad as I thought.

I took a Dremel to them to smooth them out a bit and reshape them. I rode to and from work (50 miles round trip) yesterday, and made it to work today. Cheap & easy fix: let's hope it holds up.

Great! I found some posts where others mentioned they were able to do some careful file work to get it usable again.

At this point, you have nothing to lose. I guess the variator pulley could strip, or it could weld itself to the shaft. It's unlikely either of those would leave you stranded.

So, no voodoo?

No voodoo yet.

I got the scooter in April 2010, and I'd like to maintain the 2 year warranty on it (assuming it's still valid). I do all of my own mechanical work on it, i.e. change motor and gear oil, change tires, and just recently changed the rollers - which caused this problem. I was going to change the belt at the same time as the rollers, but the belt width was fine. How long do belts last, anyway?

great! at least you dont have to tear the motor apart. Also, you can delete the kick start completely if you want to go with a more common crank with 15mm wrist pin that has shorter splines on the variator side.

Another tip in this situation sometimes you can grind down the solid pulley washer that slides over the crank to reveal more splines on the crank that have not been shifted or striped. You must have a broke in belt to do this and put up with starting off slower due to the belt being higher up on the drive face after retightening