loose black line, fall, engine noise

[wordslinger]

..se the "Additional Options" button in the lower left of the window when you are posting a message..click on it and browse to you pics...


peace

[william13]

I took pictures of the damaged Kymco engine.  The repair suggested is to reposition the gear on the shaft away from the stripped spline. The intentions are to move the gear outwards a few millimeters and to do the same for the starter.  I would appreciate thoughts.  I was told this type of damage is commonly seen when one mods the scooter but it is very uncommon otherwise.

[Areomyst]

I still think that the variator nut wasn't torqued down properly at some point, or the parts weren't assembled properly on the crank. 

An OEM crank from KYMCO is $133.98 from Stadium Yamaha.  That, a starter bendix, and a drive face will get you back on the street parts wise.  I'm actually in the process of rebuilding a very similar engine at the moment.  It's a Chinese QMB139, but a lot of the parts are the same.  I wish you were closer, I'd invite you over to help.

Yes, you can reposition the drive face on the crank, but you'll need a new drive face.  The splines are gone from the inside diameter of the drive face (that's the pulley half with the teeth on it).  Though you could technically get away with doing that, I would advise against it.

The hardest part of rebuilding a 4-stroke engine for a lot of people is understanding the engine timing, and setting it up right.  It's not very hard though, and there are timing marks on the parts to show how they go.  Don't be too intimidated about replacing the crank - we're here to help, and replacing the crank is the correct way to fix the damage.  With the crankshaft being as it is, the trust is gone, and I don't feel like it's a good idea to re-use the parts you have.  Without the splines on the crank, and on the drive face it's going to be very easy to assemble the parts "off center" causing excessive engine vibration, premature belt wear, and things of that nature.

Now, all that said, if you do re-use the old parts, I don't suppose you're going to damage things too much worse than they already are, but I'd grab a spare belt, and get the parts for the job anyway.

~Josh

[Areomyst]

I will post pictures of this build for you.  It may be helpful.

~Josh

[william13]

Thanks for that reply.  That's actually what the Kymco representative said when I showed him the pictures.  He said if I had not modded it then there was something wrong with the factory assembly.  The tech at the shop said the nut on the shaft was very tight when I brought it in and there was no play at all.  Kymco theorized that there was too much play between the splines of the shaft and the spines of that gear when it left the factory.  Kymco offered to devise a fix for it by the method I just mentioned and they are providing a new gear and starter and some spacing devices (don't know what this would be) .  The gentleman at the place where I bought it said it would be a quick job for him and he would do it at no charge.  They said that the gear will only shift by a few millimeters just to place it outside the stripping.  I did ask them if there is any drawbacks at all to the fix and they thought there would not be any.  I am hoping your concerns about that fix are hypothetical in terms of vibration.....early wear...etc.  I did ask them for a whole new motor but they are not making this motor anymore and do not have any in stock.   

[william13]

In regards to being intimidated by the job.  I am actually more mechanically inclined then most but it was a little unsettling to me to hear shop after shop (when I called around for repairs) say to me "that is a big job"  or my shop does not have the tools etc.  So if I seem squeamish and indecisive that is the source of it.

[Areomyst]

Thanks for that reply.  That's actually what the Kymco representative said when I showed him the pictures.  He said if I had not modded it then there was something wrong with the factory assembly.  The tech at the shop said the nut on the shaft was very tight when I brought it in and there was no play at all.  Kymco theorized that there was too much play between the splines of the shaft and the spines of that gear when it left the factory.  Kymco offered to devise a fix for it by the method I just mentioned and they are providing a new gear and starter and some spacing devices (don't know what this would be) .  The gentleman at the place where I bought it said it would be a quick job for him and he would do it at no charge.  They said that the gear will only shift by a few millimeters just to place it outside the stripping.  I did ask them if there is any drawbacks at all to the fix and they thought there would not be any.  I am hoping your concerns about that fix are hypothetical in terms of vibration.....early wear...etc.  I did ask them for a whole new motor but they are not making this motor anymore and do not have any in stock.    

If you shim the variator and install it, it might be okay, but looking at your photos there is an awful lot of damage there on the end of the crank.  I believe you're going to have to space things out more than a couple millimeters.  It looks like the stripped area of the crank is about 3 or 4mm, and then the splines at the end of the crank look a little goobered too.  If you space it out too far, your kickstart gears will be engaged when you put the CVT cover back on (this can actually be countered by adding an additional CVT cover gasket).  I think the shims should go behind the drive plate (all the way in the back of the variator pulley) because if you put them between the drive boss and the drive plate, it will open the variator pulleys too much, and the belt will ride on the drive boss instead of between the pulley halves.

If you can get the drive face (that's the part labled "gear" in your photos) aligned well on the splines then the part will not be mounted off-center, and you won't have that extra vibration.  The vibration and premature wear was mostly referring to if the parts were mounted off center.

I'm nearly done with the crank install I mentioned.  I still have to resize all the photos before I upload them, but I'll be sure to put them up here after I do the write-up on swapping a 4-stroke crank.  If you have air tools the only special tool you really  need is the flywheel puller, which is usually around $15.  If there's no air tools, a universal clutch holding tool does wonders (I'll show photos of one later).

It's good to hear that KYMCO and the dealer are willing to help you out.  The shim thing is doable, and it could work out perfectly fine for you...  I feel like the crank should be replaced, but I understand that the people involved in the situation feel otherwise.  Either way, please keep us posted, and I sincerely hope that you guys reach a resolution that is satisfactory for all involved.

~Josh

[william13]

Josh:  I understood most of this pretty well except for the following line  "I think the shims should go behind the drive plate (all the way in the back of the variator pulley) because if you put them between the drive boss and the drive plate, it will open the variator pulleys too much, and the belt will ride on the drive boss instead of between the pulley halves."

I guess I do not understand the anatomy ie drive boss, drive plate, variator pully and pulley halves.

Thanks:  Sorry for the learning curve

[zombie]

J. You are the best! Here is a utube vid on how easy the cvt work is. Aero is referring to spacing behind the variator assembly. I do agree this is NOT a good fix but something you would expect from a used car dealer. I would pursue Kymco's offer to replace the crank (if I read right) That is the correct fix. OR as I showed you the entire engine w/ carb is only 270.00 delivered. This one I think should be on Kymcooooo. Happy little Ps. I contacted (email) Kymco Global looking for an Asian tail light lens in clear. They told me to contact Kymco Global... (at the same email address...)

[Areomyst]

No need to apologize!  Terminology on these things tends to vary a bit anyway, so it can be confusing

When you pull the CVT cover off of the engine to look at the belt, etc, the front pulley is called the variator, and the pulley in the back (closer to the wheel) is the torque driver.  The torque driver has the clutch attached to it.  

Anyway, if you're looking at the assembled transmission, a nut holds the following parts to the crankshaft, in this order:
1 Nut
2 Washer
3 Kickstarter "ratchet"
4 Plastic CVT cooling fan
5 Drive Face (The drive face acts as a pulley half, as well as a means of the starter bendix to turn the engine over - thus the teeth around the outside of the part)
6 Drive boss (the variator pulley slides open and closed on this boss)
7 Variator Pulley (some OEM's call it the Movable Drive Face... Variator is more common)
8 Roller weights (they go "inside" the variator basically)
9 Drive Plate (also called drive ramp, or ramp plate sometimes)
10 Variator Slides - there are 3 of these that go between the drive plate and the variator.  They're basically little V-shaped plastic dampeners.

~Josh

[william13]

J. You are the best! Here is a utube vid on how easy the cvt work is. MonsterGY6.com Scooter Transmission upgrade Aero is referring to spacing behind the variator assembly.
understand now thanks

I do agree this is NOT a good fix but something you would expect from a used car dealer.
I know I know.  The dealer is actually a decent person who quite honestly told me replacing a crankshaft was something he never did before.  He does minor-mod repairs.  The major emphasis of his business is high end bicycles and he has a few kymcos on his floor he sells or rents.   

I would pursue Kymco's offer to replace the crank (if I read right) That is the correct fix.
Unfortunately they did not feel crank replacement was necessary.  However if the above fix has issues (an I want to know what to look out for), I am guessing they will step to plate.

 OR as I showed you the entire engine w/ carb is only 270.00 delivered. This one I think should be on Kymcooooo.   (can you tell me more about this engine.  How does one compare the two.  Does this mean I have to change the look of my engine also.  The kymco has a nice aluminum engine cover and a sleek look to match the cycle .  The one in photo looked chrome and looked nice but kind of ordinary.  I should not worry about cosmetics but I do not want a mismatch either.

When the problem occurred I asked a few repair shops if they would do an engine substitution for me.  Most places wanted me to tow the bike in.  One person was helpful over the phone but je insinuated to me that the kymco engine was a better engine and that I should do the big repair.
Happy little Ps. I contacted (email) Kymco Global looking for an Asian tail light lens in clear. They told me to contact Kymco Global... (at the same email address...)

[william13]

No need to apologize!  Terminology on these things tends to vary a bit anyway, so it can be confusing

When you pull the CVT cover off of the engine to look at the belt, etc, the front pulley is called the variator, and the pulley in the back (closer to the wheel) is the torque driver.  The torque driver has the clutch attached to it.  

Anyway, if you're looking at the assembled transmission, a nut holds the following parts to the crankshaft, in this order:
1 Nut
2 Washer
3 Kickstarter "ratchet"
4 Plastic CVT cooling fan
5 Drive Face (The drive face acts as a pulley half, as well as a means of the starter bendix to turn the engine over - thus the teeth around the outside of the part)
6 Drive boss (the variator pulley slides open and closed on this boss)
7 Variator Pulley (some OEM's call it the Movable Drive Face... Variator is more common)
8 Roller weights (they go "inside" the variator basically)
9 Drive Plate (also called drive ramp, or ramp plate sometimes)
10 Variator Slides - there are 3 of these that go between the drive plate and the variator.  They're basically little V-shaped plastic dampeners.

~Josh

Thanks:  Its good to know vocabulary.    Now that I understand the situation better my question would be this.  If the starter and drive plate is shimmied outward....and the belt of course moves out also ie the front and rear of belt.......does the rear of the belt also move outward or will it run a little on the slant.

[zombie]

Look at the engine case . It will have an ID plate stamped into it in the middle of the cvt case, bottom. If it is QMB_M 139 or any thing close to that they are the exact same engine. If yours is a ky or ka or anything like that you can swap the cvt covers, and all else is the same. I forget what the Kymco engine codes are but I think you get it. By the way I wasn't meaning to imply the place you are dealing w/ is a "used car lot" or a evil /mechanic?. Just meant shiming is sort'a Rigging. Could I suppose weld/re-shape the bad spot? Maybe even use a square dowel like a "key". Better than shimming cause the belt will be skewed, and wear/perform poorly. JMHO

[zombie]

Or ship it all to J. if he has time?? ?? ??. I'm trying not to make those F'n

[Areomyst]

Yes, the Kymco engine is by far better.  The parts look the same in many cases between the Kymco and the China engines, but believe me, they are VERY different.  

Shimming the variator out will indeed cause the belt to run at a slant.  The misalignment isn't the end of the world, the CVT will still work, but if it was my own new scooter, I wouldn't really want to settle with having a goobered crankshaft and a belt that's misaligned.  I used to work for a Kymco dealership.  The quality, longevity, parts support, and value pricing is what ultimately led me to buying a Kymco.  

Since then, I've rebuilt a LOT of Kymco engines, but not one of those rebuilds was due to KYMCO's quality...  Most often, it was due to negligence.  

I intend no disrespect towards any involved parties, but I've got to be blunt.  If you did not loosen that variator nut at any point in the bike's life, then there is absolutely no reason that you should be having to deal with this.  The crankshaft should be replaced to perform the repair correctly.  In the service manual for that bike it clearly states that the runout limit for the crankshaft is .10mm.  That is about as much play as the thickness of a piece of notebook paper.  If .10mm is unacceptable, then why is this: