Aftermarket top end issues

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Mbiggs3124
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Aftermarket top end issues

Post by Mbiggs3124 » Mon Mar 11, 2019 6:07 pm

I recently purchased a 86 Honda spree. When I bought it it was not running, after some inspections I found the ring lands were broken and the cylinder wall was badly scored.
I am a mechanic by trade so I figured the repair would be easy, but after sourcing the aftermarket parks new from eBay I relived the repair would be harder than I thought. I rebuilt the top end of my scooter a total of 4 different times all with new parts. The first time it was running fineafter start up but on my first run I went full throttle and it stalled, I tore it down and discovered the rings broke and destroyed the jug so I ordered new pars and repaired it. Afterward I thought the damage was caused by improper break in. The second time I took it easy on the scooter and drove about 15 miles at no more than 1/2 throttle when I thought I was good I hit full speed and again it blew up. The third time I rebuilt it I was sure I had a air fuel problem the was causing the scooter to run lean so I rebuilt the carb and adjusted it properly and cleared the carbon from the exhaust with a torch. When I was done I thought there was no possible way the engine could be damaged but still I took it easy, I never went over 20 mph I babied the throttle and never fully opened it up for 60 miles but sure enough as soon as I hit full throttle the engine blew once again. It was at that point I knew there was a problem with the aftermarket ring so I order a new set properly gapped them and put them square in the jug, I used a torch to bring the jug up to operating temperature of 250 degrees checking the temp with a infrared thermometer and unsurprisingly the rings expanded so much the end touched. So I opened up the gap until the ring lands wouldn’t touch but at that point the ring gas was so big the cylinder would only make 15 psi of pressure. So my solution was to buy genuine Honda parts of eBay I tested them the same way I did with the aftermarket rings and the results showed very little movement so I reassembled my scooter and it worked fine for over 300 miles now with compression holding strong at 165 psi. In ending cheap eBay scooter rings are junk that are made very poorly and do not handle any thermal expansion

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Meatball
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Re: Aftermarket top end issues

Post by Meatball » Mon Mar 11, 2019 6:43 pm

Let me start by saying 165psi is way too high...needs to be in the 120 range.

The cheap Ebay bores are actually hit n miss. Theres a small portion of them that are good quality but the majority are total junk.

As your mechanic background has likely educated you, running lean is a recipe for overheating. As with these old air-cooled motors, youre not going to get steam from a radiator cap or a bunch of OBD codes....they simply melt metal. Not suggesting your issue isnt carb related but I would take measures to ensure you dont have any air leaks....like base gasket, head gasket, intake and carb connection, crank seals (both sides) etc...

Sometimes even an old dry and cracked vacuum line can be sneaking in air. Check everything.
I need to find some new haters...the ones I have are starting to like me.

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benji
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Re: Aftermarket top end issues

Post by benji » Tue Mar 12, 2019 3:18 am

The crank seals can leak on these old motors, especially at full throttle.

Also, it's a spree. You're not really supposed to be going Full Throttle haha. The bike was designed as a small run around vehicle, something to be used to ride down to the mailbox and back. I believe it came with two horsepower from the factory, and cost like $350 new.

165 psi could be high. Watch your sparkplug for detonation. If none, enjoy the extra power I guess.

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eclark5483
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Re: Aftermarket top end issues

Post by eclark5483 » Thu Mar 14, 2019 2:18 pm

That's pretty much every top end kit for the Spree found on eBay and Amazon. Rings are always junk. For future reference, you can still buy the rings from your Honda dealer locally or online. Part number is: 13011-GAB-305
Should run you around $20 or so. Plus shipping and taxes of course.
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3SPDX
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Re: Aftermarket top end issues

Post by 3SPDX » Fri Mar 15, 2019 11:19 pm

You need to put your oem cylinder back on. THose chinese bores have a 75% fail rate. And yes meatball, I'm back :)

figured why not.

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