transmission/final reduction noise and oil discoloration

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linguine
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transmission/final reduction noise and oil discoloration

Post by linguine »

Hello, I've been lurking for awhile and with the knowledge I have gained here and from the manual, I finally got a 1986 Honda Spree I had running again after five years of sitting in my parents garage while I was away at college. It took awhile, but I got it to start thea few days ago and ripped around for a bit! Stopped so I could marvel at my accomplishment and then went to eat some dinner. However, I took it for a spin around the neighborhood again the next day and lost power around 15 - 20 MPH. Got it back, thought the carb needed adjusting. Put the scoot on a stand, I adjusted the carb screws trying to get the wheel to spin but it did not seem to want to. Gave it some throttle, a weird low grinding noise came from the final reduction/transmission cover at lower RPMs. Opened the drain plug to make sure there was oil in the final reduction, gray oil came out. I looked at it with a light on my fingers but it did not seem to have any metallic flakes, as the manual suggests that there could be gear wearing or damage based on my observations. Took the kickstarter cover off to see if there was anything going on in there, noticed that the driven pulley/clutch had a fraction of a millimeter of axial play in it, enough to make a clunking metal on metal sound when moved side to side. Additionally, I spun the rear wheel by hand and the driven pulley/clutch moved outward and inward as the wheel rotated.

I assume the transmission cover bearing is probably shot. I have not started it again since then, I am looking for advice from the community about what I should do next or ideas on what the problem could be. Thank you for your time!
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Meatball
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Re: transmission/final reduction noise and oil discoloration

Post by Meatball »

Gray oil in there is normal from gear wear. Every single stock trans Ive ever opened had grey oil in it. From scoots with 500mi to well over 8000. The fact that theres no glitter in it is a good sign your issue hasnt become a terminal illness.

If it were me, Id remove the muffler, rear wheel, airbox and clutch/belt assembly. Then remove the trans cover to inspect. Id be sure to have a catch pan in place for the dripping gear oil. I would take note on where the thrust washers go. Maybe even take pictures with my phone. I’d Spin each bearing with my finger gently while looking for any sticky spots in the rotation. Also checking for ANY lateral play in the center race. Bearings should be tight with ZERO play in all directions and spin quiet and effortlessly. If theres ANY suspect bearings, I would replace them. My OCD would take over and if I found ONE bad bearing, Id replace them all....but thats just me.

After all bearings are checked, Id move on to the gear teeth. Looking closely for any chipped teeth or unusal wear. I know the contact points of each gear will have SOME wear and would look different that non-contact areas but thats normal.

Once all bearings and gears are deemed to be in good working order, I begin reassembly process. I’d scrape the old gasket from the mating surfaces of the motor and gear cover. I would thoroughly clean the gear cavity and cover to remove all old grey oil and bits of gasket I scraped off. I use generous amounts of Brakleen followed with a shot of compressed air. I Install gears and DONT forget the thrust washers! I use a NEW gasket and torque bolts to spec. Fill with 3oz of 10w40 of choice.

Bet hey, thats just me....do what you want.
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linguine
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Re: transmission/final reduction noise and oil discoloration

Post by linguine »

Hey thanks for the help Meatball, I went ahead and did everything you recommended. I did not see anything wrong with the gears in the transmission case nor did I see much wrong with the bearing the final gear passes through. However, the transmission cover bearing will probably have to be replaced because it seems noisy and does not spin as easily as the final gear bearing. I did find some damage to the thrust washer that the drive shaft butts up against in the transmission case. The drive shaft essentially wore a groove into the thrust washer where the teeth and the washer meet. The thrust washer is probably going to need to be replaced as well, do you think the drive shaft needs replacing as well or is that normal wear for a 30 year old scoot? I assume it probably is fairly normal wear.
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Meatball
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Re: transmission/final reduction noise and oil discoloration

Post by Meatball »

If it aint broke (or bent) dont fix it. Drive shaft failure would wreak havoc and show its’ ugly face in ways that nightmares are made of. If theres no obvious vibration when running at speeds or shiny bits of glitter in the oil than Id leave it be. However, Replacing any suspect bearings is certainly insurance worth buying.

Side note: a small bit of lateral play in the axel (with wheel removed) is normal. Once wheel is installed and torqued to spec, the axel stays put. The final drive shaft should have no play at any time. Any movement in this shaft would mean a bad cover bearing.
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