T250 motor oil.

[alanr]

Rebuilt motor.what is the best oil for the gearbox thanks

[Alan H]

20w50.

[daxman]

Clean oil. Most anything will do from ATF to 20/50. JASO approved for wet clutches if you really must.

[ConnerVT]

OIL THREAD! Excellent!

[argo1974]

There is SAE specification for gearbox lubricants, the API GL.
Best suitable oil for T250 gearbox with wet clutch is transmission oil of GL 4/5 spec.
Viscosity 80w90 works fine.

Engine oils, ATF, YASO M1 or M2 etc. oils are missing API GL specs. Use at own risk.

[daxman]

There is SAE specification for gearbox lubricants, the API GL.
Best suitable oil for T250 gearbox with wet clutch is transmission oil of GL 4/5 spec.
Viscosity 80w90 works fine.

Engine oils, ATF, YASO M1 or M2 etc. oils are missing API GL specs. Use at own risk.

That sounds like bollocks... Clutch/Gearbox on a 2T bike is no different to 4T so just use 4T bike oil
it will also suffer less from combustion contaminants. I'm certainly not going to start crapping myself over
GL specs, which appears to be related to transaxles and hypoid gears in the main.

There we go.. pointless oil thread arguments started!

[alanr]

we can end it here.ended up putting 20w 50 in.

[dollydog]

sorry argo, you are very wrong. 20/50 has always been fine in gt gearboxes, and always will be
cheers, dd.

[argo1974]

Those "always been fine" oils destroyed lots of engines and gearboxes in the history. Some oils did it immediately, others slowly but steadily.
Because they didn't meet the specs.
Of course, everybody is free to go by belief or by specs.

On the other hand, if those 20W-50 or JASO MA oils were so great in lubricating transmissions, why nobody is using them in their cars?

[joethebike]

I have used 20-50 motor oil in my T350 gearbox from new and it went through 2 Castrol 6Hour road races and associated practice plus many years of road use, clocking up over 160,00km and the gearbox is still original and working perfectly so forget your gear oils.

[jabcb]

Those "always been fine" oils destroyed lots of engines and gearboxes in the history. Some oils did it immediately, others slowly but steadily.
Because they didn't meet the specs.
Of course, everybody is free to go by belief or by specs.

On the other hand, if those 20W-50 or JASO MA oils were so great in lubricating transmissions, why nobody is using them in their cars?

How many modern Japanese 4 stroke bikes with wet clutches separate the engine & transmission so that they can use motor oil for the engine & tranny oil for the transmission?

[dollydog]

i've stripped and rebuilt god knows how many suzuki 250 engines - it easily runs into many times 3 figures - including t250, gt250, t10, ts250 and rg250. both gt250 ramair and later engines. in that time i've only ever rebuilt 2 engines with anything wrong with the gearboxes. one was lack of oil, due to the neutral light switch weeping, but the oil not topped up, so the gears at the very top of the gearbox were fkt, to put it bluntly, as was the middle bearing on the crank. on the ramair engine the gearbox oil feeds the centre bearing. on the 250a it feeds the right hand main bearing. have a look inside a crankcase and see how oil gets from gearbox to main bearing - very tortuous. thick hypoid oil would make it worse. plus, of course, it's got to return to the gearbox. the second gt250 i had problems with kept wearing out the double gear that the kickstart and oilpump uses. these things need a million miles before they are totally worn out, but he went through 2 in as many months. i asked him on the offchance what oil he used in the gearbox? it was hypoid 90. i told him to use 20/50, just normal good old 20/50. and despite several thousands of miles on the road and track days, he's not had ANY problems since. he changes his 20/50 'gearbox' oil every 3 years. kickstart never slips and it never jumps out of gear. oh yes, all the other engines i stripped down had what us old gits call normal engine oil in them - i.e 20/50 - so argo, listen to the voice of experience and learn from it
cheers, dd.
p.s. i've used the same oil in all my gt suzuki's and i've ridden and thrashed everything from a 185 up to and including a couple of 750's. if you read the manual, 20/50 was recommended for these gearboxes - and that was 45 years ago - look how much better modern oil is. and that is my very last word on something that's been discussed and agreed on far too many times before

20/50

[daxman]

Those "always been fine" oils destroyed lots of engines and gearboxes in the history. Some oils did it immediately, others slowly but steadily.
Because they didn't meet the specs.

Got any examples..

On the other hand, if those 20W-50 or JASO MA oils were so great in lubricating transmissions, why nobody is using them in their cars?

Ever heard of the Mini?


PS Oil threads are the best aren't they?

[Alan H]

PS Oil threads are the best aren't they?

Yup, see my post at the top of the thread!!

[argo1974]

Kevin Cameron about Yamaha TZ500/750 development:
Did I mention a gearbox oil pump? Why yes. Rather than just accept the drag of a gearbox up to its hips in oil, Yamaha engineer Noriyuki Hata in 1959 eliminated most oil drag by directing a small jet of pumped gear oil onto each meshing gear pair, with the gearbox oil level far below. Although four-stroke production bikes share the same oil between engine and gearbox, today’s low viscosity engine oils make poor gear lubricants. To make such sharing possible, gears are made larger in diameter and given wider teeth to reduce the pressure to something lo-vis oil can handle. Now I hear that one or more new designs in MotoGP use separate gear oil, whose greater load capacity makes it possible for smaller, lighter gears to survive.

// He's talking about JASO MA oils and the need of over-dimensioned gearboxes vs regular gear oils (API GL).

Kevin Cameron about ATF, 20-50 etc and highly effective gear oils (GL):
https://www.bilder-hochladen.net/i/bfqr-q4-0315.jpg" onclick="window.open(this.href);return false;

// You pay the same or even more for ATF, 20-50 or JASO MA specs. oil but receive inferior product (for lubricating transmission gears) compared to simple 80W90 GL4 gear oil.