1972 Kawasaki H1B - Gearbox Oil Question

[Syd]

Hello,

I would be keen to know if anyone has found using synthetic oil rather than mineral oil in the transmission has helped reduce gearbox noise or whine etc. My gearbox is 100% original with the new clutch pack which has done around 800 miles.

I am using Penrite brand mineral oil which is available in New Zealand and Australia in my H1. Penrite MCGO (Gear oil, API GL-4, SAE 10W-40) is designed for 2 stroke motorcycles with a wet clutch which goes really well but the gearbox is a bit noisy. I contacted Penrite and asked for their thoughts about changing over to a synthetic wet clutch oil to see if this would help reduced the transmission whine and they suggested the following:

The only product we consider worth trying is our MC4-ST 10W-40, www.penriteoil.com.au/applications/motocycle/4-stroke-engine-oils/mc-4st-10w-40-100-pao-ester#/.

It is slightly thicker for 4 stroke motorcycles with a wet clutch; not a huge amount in it but it may be worth trying.

[autofobe]

Trouble with synthetic is the fact that it attracts moisture.
So if sitting for long periods the trans could rust.

Brad

[kawonda750]

I use 80/90 gear oil with good results in both H1 and H2

[Curtis]

Feb 14, 2019 15:14:19 GMT -5 autofobe said:

Trouble with synthetic is the fact that it attracts moisture.
So if sitting for long periods the trans could rust.

Brad

Synthetic is not hygroscopic
However synthetic does not stick to a parent metal.
The nail test proves that mineral is far superior to sticking to the parent metal.

Gear whine is generally associated with improper clearance between the gear sets. Unfortunately for our “cliche” of motorcycles they are NLA I like Harley Davidson where you can measure the root of each gear set and determine if you need a +/- oversize/undersize ear to remove said noise....

Does it shift okay ?

[Syd]

Thanks for the info.

The gear shift is really good and the whine is only noticeable when riding in top gear which just may be an H1 thing. The oil I am using is fine but I just wanted to know if using synthetic oil was a magic bullet.

[tankie]

No , I've tried it, use gear oil or mineral oil

[daffey1]

I’ve been using Honda HP Trans oil, 80/85 weight with out any issues

[H2 Dude]

Me I'm still using 10w30 motor oil

[Syd]

All good, I think I'll stick to what I have been using and forget about the synthetic oil option suggested by a friend.