Gear Box oils

[sleepy]

I'd use that vmx80 in a Bultaco gearbox and put ATX in the clutch case.
Even though Lozza disagrees with the engineers at castrol this oil is not meant to be used in wet clutches. If it is used in bikes with nominal clutches it will make them slip compared to oil that is made for wet clutch applications.

[Daryl Jones]

I use that same combination in my Bullys.
(VMX80 G-box & ATF Clutch), very happy with it.

cheers, DJ

[Paul552]

Castrol MTX works well.
I started using it when my son raced ktm50's with those 3 shoe clutches. They where horrible. Many guys ran trick shift atf or too cool for the same application.

Mtx was cheap and worked great however it seems to be not so cheap anymore !

[Matador107]

My opinion.Bultaco's  with a chain drive primary from crank to clutch hub should never use ATF as it causes premature wear , causing the chain to break . The chain drive problem under extreme load is the reason the Bandido's , Montadero and TSS road racers are all primary gear drive?
The  only ATF exception is on the Sherpa trials bikes, ie low speed most of the time.

80/90 grade for the gearbox and 30 grade motor oil for the clutch when steel clutch plates are fitted.

[Moto]

I have been using the same combination you recomend for years as well,this is factory spec.
One of the factory bulletins asks dealers to use 30wt instead of autotrans fluid to improve primary chain wear.

[Daryl Jones]

Pretty hard to find a straight 30wt motor oil, without any special additives and friction modifiers, these days.

Friction modifiers and steel on steel clutch plates are not a good combination.

Some of the stock Joresa chains would snap the rollers in half, no matter what oil you used.

I'm not making any "recommendations", just reporting what has worked well for me.

Cheers, Daryl.

[LWC82PE]

Pretty hard to find a straight 30wt motor oil, without any special additives and friction modifiers, these days.

Penrite do a straight 30 weight mineral oil with no friction modifiers. I use it in a lot of primary drives/clutches that are separate to the gearboxes. Its in their 'small engine' range.

http://www.penriteoil.com.au/products.php?id_categ=1&id_subcateg=0&id_products=591

[80-85 husky]

Briggs and Stratton do a straight mineral 30... most mower shops have in 1 and 5 litres..cheap too

[Lozza]

Even though Lozza disagrees with the engineers at castrol this oil is not meant to be used in wet clutches. If it is used in bikes with nominal clutches it will make them slip compared to oil that is made for wet clutch applications.

  Complete Bullshit.  Castrol say it's fine for 2 stroke gearboxes and so do I, wet or dry clutch. Friction modifers are what cause the clutch to slip. VMX80 contains no friction modifiers. A 43hp RS125 superkart engine has no clutch slip with VMX80. 

VMX80 and MTX are one and the same

[sleepy]

Even though Lozza disagrees with the engineers at castrol this oil is not meant to be used in wet clutches. If it is used in bikes with nominal clutches it will make them slip compared to oil that is made for wet clutch applications.

  Complete Bullshit.  Castrol say it's fine for 2 stroke gearboxes and so do I, wet or dry clutch. Friction modifers are what cause the clutch to slip. VMX80 contains no friction modifiers. A 43hp RS125 superkart engine has no clutch slip with VMX80. 

VMX80 and MTX are one and the same

Castrol say it's for 2 strokes with a seperate gearbox. They make no claims that it's good for clutches as they do for the MTX. I've seen CR125's with clutch slip change from VMX80 to ATF and fix the slip.

[Andrew L]

If you read the product data sheet carefully for both , the VMX80 one does say 2 stroke gearboxes which seems to exclude the clutch and the MTX product data sheet says 2 stroke transmissions which would suggest that it incorporates the clutch/gearbox as the whole transmission. Only what I deduce out of the info on Castrol's site might be wrong

[oldfart]

I have run Vmx 80 trans oil for over 6 years without any slippage or abnormal wear. The oil gets changed at the end of each season as part of the maintenance routine.
Each to their won I suppose ....  but it works for me 

[sleepy]

I have run Vmx 80 trans oil for over 6 years without any slippage or abnormal wear. The oil gets changed at the end of each season as part of the maintenance routine.
Each to their won I suppose ....  but it works for me 

I'm sure you are getting away with it, but the piont is that Castrol don't promote it as suitable for wet clutches which is why they make a specific motorcycle transoil. Because of that I don't think it should be recommened as the one to use.
By the way I got your cam back.

[oldfart]

Thanks... will catch up with you Friday.

[chrisdespo]

Back in the seventies all the 2strokes we sold for on road and trail use had castrol XL which was 30w mineral,race bikes on the other hand were lubricated with ATF with no detrimental effects seen.
Out of all of my personal race bikes i only had one that worked better with XL than ATF and that was one of the first six speed suzuki 125s but after a few races that went over to ATF as well it was just a bit tight when it as new i think. ATF is good but you should change it every meeting when you pull down for a freshen up.