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Post by bigkahuna427 on Feb 23, 2011 7:14:38 GMT -5
If youy didn't find that there was a BB floating around somewhere and there certainly would have been evidence of that you should probably get it back together again and be sure you do not have detonation preignition issues. Get it to someone who can make sure it is not running too lean at any time while driving.
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Post by motorhead on Mar 1, 2011 22:22:55 GMT -5
Well, I got my replacement piston kit from autotech / ebay. It's a 1 ring piston but the ring turned out to only be 1mm thick. The ring my bike came with was 1.5mm thick. And although gudgeon pin is in the right place this ebay piston is 1mm shorter than the ruined piston. I ran it in the bike anyhow and the bike could only 20mph. I chock it up to less compression and less sealing. I have a new 47mm 2 ring piston which is the exact size of the ruined piston but I used it's rings to fix another scoot. This piston's ring grooves are 1.15mm wide. I was thinking of using this piston with wiseco piston rings to repair my aprilia. This set here: cgi.ebay.com/ebaymotors/WISECO-PISTON-RING-SET-47MM-1850CD-KAW-KX80-YAM-PW80-/180586417765?pt=Motorcycles_Parts_Accessories&hash=item2a0bca0e65I've spent the day searching for the exact piston that came from the 70cc top cylinder kit and could not find anyone that just sold the piston set. The wiseco dimensions are perfect. So, should I try the wiseco rings with the 2 ring piston in my aprilia? |
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Post by 2strokd on Mar 1, 2011 22:38:47 GMT -5
If you try a two ring piston in a cylinder with a port layout for a single ring piston you will probably have the same results or worse than you got from the piston Autotech sold you.
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Post by motorhead on Mar 1, 2011 22:53:11 GMT -5
I took the 2 ring piston and I etched marks the piston top and inserted the piston into the cylinder. Arrow pointing at exhaust and the ring gaps will miss the intake port holes by about 1 or 2mm. The original piston's gap also misses the port by 1 or 2mm.
Does this just come down to don't use 2 rings because the jug came with a 1 ring piston? Or because fitting wiseco rings in a scoot with a non wiseco piston is totally uncharted?
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Post by 190mech on Mar 2, 2011 5:17:44 GMT -5
If the right rings are fitted,2 rings will run fine,not as well as the 1ring with proper deck height though.Email autotech,he's likely got some rings that would fit,heck he may even cut you a deal on the right deck hight piston set.He's helped out a bunch of people here before! :thumb:
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Post by motorhead on Mar 2, 2011 8:35:43 GMT -5
I set the engine on a table and put in all 3 pistons on the crank and in the cylinder to check if the gaps are in relation to the ports. The original piston misses the ports by 2mm. but both the ebay and my 2 ring piston come 1mm next to a port if not right at the edge of a port. This is too close for comfort.
Mounted on the crank and in the cylinder, the 2 ring piston and the original both have the same amount of dome and deck height. Now here is the really controversial part. If I point the arrow away from the exhaust on the 2 ring piston its ring gaps hug the exhaust port but sit 2mm away on both sides of the port. So here we go I have found the best alternative solution. 2 ring piston, 180 out!
note: I will not be using wiseco rings because they are not compatible with chrome plated cylinders.
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Post by 90GTVert on Mar 2, 2011 9:08:22 GMT -5
What about the ports in the piston? Or is this just a symmetrical cut piston?
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Post by motorhead on Mar 2, 2011 10:09:57 GMT -5
The broken piston has square ports. On the 2 ring piston the ports in the same area but are 2mm taller and 2mm narrower. What I am hoping here is that the two 1mm rings can work better or as good as the one 1.5mm ring. Other than that both pistons are very identical.
The reason I believe this will work is because long ago I bought a Trac moped with a seized piston. I bought a new piston set for it and the rings were really hard to get on. So I got 1 ring on and said "lets see if it runs with 1." It did run, but it ran poorly and smoked a lot. Later when I put in both rings the bike ran 2x better with much less smoke.
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Post by 190mech on Mar 2, 2011 12:22:47 GMT -5
If you 180 the 2 ringer,are the piston windows open to the case at TDC?
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Post by motorhead on Mar 2, 2011 13:08:12 GMT -5
Shoot! I forgot about that. Should I just cut the skirt open to match the port?
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Post by 190mech on Mar 2, 2011 14:22:11 GMT -5
I'm asking will the windows open into the exhaust port at TDC?If so the bottom end will not pressurize properly,thus barely run..
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Post by motorhead on Mar 2, 2011 14:30:51 GMT -5
Wow! You are absolutely correct. I didn't think about that. Good thing I didn't buy any rings yet. Okay, back to the drawing board.
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Post by motorhead on Mar 2, 2011 20:30:01 GMT -5
I guess I just need to give in and spend the money to fix my scoot properly. And after giving up on my mad scientist repair I sat down to seek out the correct piston. finally after hours of serious searching I have found the piston I need. On this continent! Check out a pic of it. Its a heat treated ceramic looking concoction, any one seen something like this before?
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Post by 190mech on Mar 2, 2011 21:36:05 GMT -5
I'd shop some more..Did you email Carlos(autotech355) yet?
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Post by motorhead on Mar 2, 2011 21:58:03 GMT -5
Yeah I talked to autotech. Unfortunately he doesn't carry a piston with the dimensions my scoot uses. Attachments:
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