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Old 07-18-2015, 06:25 PM   #1
B-rad   B-rad is offline
 
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9" stretch ruined my engine, how to prevent??

So, i have a 2011 taotao vip gy6 150. The scooter had 10k on it when i got it and was bone stock. Ive added a few things, most recently i did a 9" stretch. I did not use a kit, i did some research and decided to build it myself. I measured twice cut once etc etc, made extra sure alignment was correct and no binding/ rubbing. Got about 100 miles with no unusual tire wear, handling issues except for more vibration. Well, my mount bushings went bad, and it was like it happened all at once it felt like i was riding a fish. I went ahead and tore it apart to do the new bushings, and then... I saw a nightmare no scooter owner never wants to ever see. The rear of the case, just in front of the clutch/transmission unit SNAPPED OFF!! I was planning on doing the swingarm delete with shorter axle later, but thank God i didnt because that steel swingarm was the only thing holding it together!! So now, i am shoppi g for an engine, but how can i prevent this? As far as i know i have kept every measurement, mount height, geometry etc the same, but something must have caused this . what step did i miss? I have searched for similar stories but found none, so if any1 knos better advice would be golden about now!!
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Old 07-21-2015, 11:40 PM   #2
Dodgeme   Dodgeme is offline
 
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Location: schofield, wi
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You may have had a bad casting I've seen bad castings do the same in cars, trucks (BIG TRUCKS gross weights around 80k) where all it takes is one flaw and some time and/or mileage and suddenly the dreaded crack forms, cast parts are most prone to this. From what I can tell from your pictures this looks like this may be the case good news is you can get case halves from numerous parts dealers examples partsforscooters.com, scrappydogscooter.com,scoot-tuning.com to name a few. and a new case half and a little elbow grease is a whole lot less expensive than a new engine.
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Old 07-22-2015, 12:02 AM   #3
Dodgeme   Dodgeme is offline
 
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Location: schofield, wi
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pics of how you stretched it would be very helpful to determine if the stretch actually had any effect on it. I would look into getting the tire and wheel balanced as well especially when stretching, but I've bought pretty poorly balanced tires and there was a lot of vibration before I had them balanced, just something to look into/ think about.
Usually when you see a break like this if it stress cracked along a flaw you will see areas that almost look old or different or even crystallized along where the part failed the old/ dirty looking areas are usually where its been cracked for a while and on a few occasions I've even seen where the cracks weren't even visible prior to the failure but looked dirty, corroded, or discolored along the failure with a clean looking break in a few areas of the failure



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Old 07-22-2015, 09:31 PM   #4
GaScooter23   GaScooter23 is offline
 
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I was just thinking about stretching mines but I don't know anymore. I was going to cut and weld
couldn't really find a kit for the Chinese peds
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Old 07-23-2015, 08:22 AM   #5
bandito2   bandito2 is offline
 
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I would think it broke because of a flaw as well. A small flaw in cast aluminum allowing a small crack is kind of like a small tear in paper. Under under repeated cycles of compression and tension the crack will open up very easily. Much like how a sheet of paper is so much easier to tear once a very small rip has been started.

Nicks on an edge, irregular or acute (sharp) angle edges like a square opening present areas for stress cracks to appear and propagate. Cleaning up burrs and mold flashing, rounding the sharp edges of cuts and drill holes, smoothing surfaces and making bends with some radiusing rather than sharp angle bends are ways to help cracks from starting in the first place or to prevent a crack from getting larger.

Like Dodgeme said, some flaws are too small see initially or may be in a hidden area. Like inside of a drive-line case for example. The broken case you experienced may not even be your fault.
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Old 07-23-2015, 12:30 PM   #6
B-rad   B-rad is offline
 
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Thanks for all your replys very helpful. We did get to looking at it sry no pics at the moment but it IS dirty along the top edge! I have checked my angles and still no binding, case flaw is what i now believe as well
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