Leaking Oil from Transmission? Loose nut

[spikebites]

Hi,

So I've been having this problem I guess for awhile, but I never noticed it until now.  This has been happening for 2 years.  Next to my fill nut on my transmission, a black powder keeps forming.  I have included photos.  If you wipe it off with a paper towel, it just flakes off.  I'm assuming this is the transmission oil.

I didn't think much of it, until there was a heavy smell of transmission oil after a ride one day.  I went to loosen the nut, and I noticed that it is no longer tightened.  The nut remains in but it has maybe a cm of give.  If i twist it left, it will not unscrew unless I twist left while pulling.  Then I am able to remove the nut.  When I turn right to tighten, the nut just keeps spinning. 

How difficult is this repair?  And what would you recommend I do?  I feel like I've lost a lot of transmission oil the past 2-3 years riding along not even noticing this has happened.  How much would a repair like this cost at a shop?  Should I drain my transmission oil, and refill it in order to drive to a shop?

Thank you,

[Ruffus]

@spikebites welcome here!
Your assumption this being gear oil COULD be right (judging pics). COULD (since the whole gearbox is oilcovered) also be too much oil in there and it blew out through this breather hose.
Check this before further steps.

If there is NO oil oozing out when you remove the drain plug, there is already emergency happening in your gear box.

The transmission oil check and drain bolt on the Kymco Downtown 300i uses a 12 mm socket size with an 8 mm (standart) thread diameter.
Key Specifications:
• Socket / Wrench size: 12 mm
• Thread size (diameter): 8 mm
• Tightening torque: 1.8 – 2.2 kgf-m (19.7 N-m)
• Recommended oil: SAE 90 gear oil
• Transmission oil capacity: 0.23 liters (at disassembly) or 0.21 liters (at change)

So, seen this specs there are three possibilities, depending on your skills:

A) pull the fill plug out and set an stainless steel thread, called HELICOIL or similars.
Inexpensive, professional and secure (see pic).

B) fill up oil and drive to a dealer who does the same.
Depending on where you located at it will cost between €20,- and €100,- without further complications.

C) take a tap and tie set, cut a 10mm thread, put a short 10mm bolt with a gasket in it.
Costs € 2,- and having a tap and tie set.
Driving w/o gear oil costs you a whole engine!
Come back for Qs.

[spikebites]

Hi Ruffus,

Thank you for your response.  I finally had the chance to drain my transmission oil today and only 150ml was collected.  I didn't get a chance to examine the oil before I drained it into a larger container. 

I imagine I was riding on 150ml oil for perhaps the last 2-3k miles or the past year .  Do you believe there is any damage to the transmission?

[Ruffus]

Well done. No, this 150ml are enough being splashed around and lubricate gears innerts.

[spikebites]

I spoke to a friend who is an automobile mechanic.  He said doing a heli-coil requires removing the whole transmission case, so that way the shavings don't get stuck inside.

Is that true or should I find a shop that can do it without removing the entire thing?  Also, there was no washer under the bolt.  Is this missing? or did this never have one?

Also he recommend using teflon or silicon for the time being so it doesn't leak.  Those are temporary fixes because I am debating whether I should keep my 2014 Downtown 300i, or upgrade to the 2026 Downtown 350i .  I will call a few shops in the area to ask for quotes.  My friend quoted me around $500 for the service, roughly 4 hours of work.  I imagine shops will be more expensive here in the US.

[Ruffus]

Your friend is wrong and not a friend for $500,- for such a minor thing!

It can be done without removing the gearcase from the scooter. Of course needs some wits.

Doing:
- plug out
- drain oil
- put/push a long cut of fabric into gearcase (2cm wide and 200cm long)
- go with a thin wire from the drainhole to catch the fabric, pull it out a few cm
- make sure you can fish it out with a hook afterwards (drainhole is possible too)
- drill required hole (grease on the drill)
- use strong vacuum cleaner now
- tap the thread (grease on the tap)
- use strong vacuum cleaner again
- set the helicoil or similar insert
- pull the long fabric out with a thin wire hook (99% of shavings are out now)
- take a liter of diesel, rinse the gear two times
- fill oil
The few small alu shavings remaining there will not harm anything, my word for it.
- put a new or cleaned plug in.
Labor = half an hour
Material = €3,-

Even removing the gearcase would not take more than one hour.
-muffler, wheelcarrier, wheel off, open gearbox, cut thread, fine festa!

This method with teflon or silicon is done only by ignorants and backyard tinkerers.