qt50 gear identification

Johnny S /

Sep 28, 2019 08:19PM

I recently picked up a qt50, got it running and had a bad noise in the rear end, (someone had it opened before one of the bearings was missing all together) I replaced all the bearings with new and noise is still there

I tore apart the rear end of my other qt50 and found it has a different sized pinion gear. The ring gears are identical. I pulled out the pinions and put them side by side and one of them is noticeably bigger.

is there anyway to tell what the larger gear is from, maybe someone started a pw50 swap and only had half the parts? I need to buy a stock gear or I can trade this one if I can find out what its from

the one on the right in both photos is the stock qt50 gear

Re: qt50 gear identification

Jack Rutherford /

churioz

Sep 29, 2019 12:20AM

most likely that's a pw50 pinion gear

Re: qt50 gear identification

Bob Naske /

bobqt50

Sep 29, 2019 06:35AM

This doesn't answer the question but by the looks of the roughness of both of them, I'd inspect the ring gear with a magnifying glass for damage that could be the source of further noise if you are going to re-use the ring gear. Just tryin to save ya from another teardown!!!

Re: qt50 gear identification

Johnny S /

92civeg OP

Sep 29, 2019 08:14AM

the large pinion has 11 teeth while the small has 10 anyone have a pw50 gear they can count?

the pinions in the photo still have grease all over them they are in good shape .the ring gears are both fine, I installed both ring gears in one of the housings while the smaller pinion was installed and they are both quiet.

I just want to get this bike on the road, what will be easier to find a pw50 ringear (if that is a pw50 pinion) or a qt50 pinion to match my current ring gear? (edited)

Re: qt50 gear identification

Bob Naske /

bobqt50

Sep 29, 2019 09:23AM

Just my opinion but I see more used QT stuff for sale than PW stuff.

Re: qt50 gear identification

live ɘvil /

themotorhead

Sep 29, 2019 12:55PM

Noise is a common problem with ring and pinion gears in automotive differentials when lash and alignment is not set correctly. Various shims and adjustments are needed to do the job right. I have no idea whats involved with the Yamaha set up. Obviously if the ring and pinion are not a matching set it will never be right. Here is an example link:

ring and pinion set up (edited)

Re: qt50 gear identification

live ɘvil /

themotorhead

Sep 29, 2019 01:33PM

I do remember reading that the pw50 had taller gearing for higher top speed. So, with that in mind, the larger diameter pinion would be from a pw50.

Re: qt50 gear identification

Johnny S /

92civeg OP

Sep 29, 2019 04:25PM

yes looks like from what I've read

qt50 pinion has 10 teeth, ring gear 57 teeth

pw50 pinion has 11 teeth, ring gear 54 teeth

I have a pw pinion and qt ring gear that's why I'm getting all the gear noise.

Re: qt50 gear identification

live ɘvil /

themotorhead

Sep 29, 2019 04:36PM

> Johnny S Wrote:

> -------------------------------------------------------

> yes looks like from what I've read

>

> qt50 pinion has 10 teeth, ring gear 57 teeth

>

> pw50 pinion has 11 teeth, ring gear 54 teeth

>

> I have a pw pinion and qt ring gear that's why I'm getting all the gear

> noise.

Do not mix ring and pinion sets. Go with one set or the other.

Re: qt50 gear identification

live ɘvil /

themotorhead

Sep 29, 2019 05:36PM

These are reed valve engines that have great take off. Go for the top end gearing and find a pw50 ring gear to match that pw50 pinion. (edited)

Re: qt50 gear identification

Johnny S /

92civeg OP

Sep 29, 2019 08:50PM

> live ɘvil Wrote:

> -------------------------------------------------------

> These are reed valve engines that have great take off. Go for the top

> end gearing and find a pw50 ring gear to match that pw50 pinion.

that the plan

Re: qt50 gear identification

live ɘvil /

themotorhead

Sep 29, 2019 09:15PM

And you do know that the drive shaft will need to be pressed out of pw50 ring gear and qt50 shaft pressed in to work?

Re: qt50 gear identification

Jack Rutherford /

churioz

Sep 30, 2019 08:22AM

It's the rear axle that's pressed out and in to the ring gear.

I'd get a new pinion gear too especially if the bikes been ridden a bit in that setup. But chances are you can't get a ring gear without a pinion gear anyway.

And there's really only one pinion gear that could've been. I'm not aware of anything but the 3L6 and 3L5 gears for Yamaha shaft drive bikes.

Re: qt50 gear identification

live ɘvil /

themotorhead

Sep 30, 2019 01:00PM

> Jack Rutherford Wrote:

> -------------------------------------------------------

> It's the rear axle that's pressed out and in to the ring gear.

>

> I'd get a new pinion gear too especially if the bikes been ridden a bit

> in that setup. But chances are you can't get a ring gear without a

> pinion gear anyway.

>

> And there's really only one pinion gear that could've been. I'm not

> aware of anything but the 3L6 and 3L5 gears for Yamaha shaft drive

> bikes.

Yes, Jack is correct. Its the axle and not the propeller shaft.

Re: qt50 gear identification

Mark B****** /

briggslite

Apr 29, 2020 08:47PM

I know it’s an old thread but 3L5 is stamped on the qt50 ring gear. It’s the smaller pinion.

3L6 is on PW50, LC50, and MJ50 ring gears.

MOPED ARMY

Login or Create Account