2001 Big bear 400 oil types

[Ironworker709]

I have a 2001 Yamaha Big Bear 400 4x4 i recently bought.

I am going to change all the fluids in it..the gear oil and engine oil.

I already changed the engine with Lucas Motorcycle oil semi synthetic for wet clutches i found at our local Oreillys

Should i use a full synthetic for the gear oil ??

[Gwbarm]

Just my opinion, I think the newer synthetic oils are great, but the older bikes were made when we were not a synthetic world. I have older bikes also, I have a 2000 Big Bear 400, I still use Dino oils in them because that is what was recommended at the time of manufacture, and changing from Dino to synthetic I seem to get leakage where I didn't have a leak before. 

[spock58]

I've used the usual gear oil that's GL5 rated in all quads, old and new without problems. Something like 75W90 is fine on everything except the Polaris front diffs or quads with a wet brake system.

[Mech]

"changing from Dino to synthetic I seem to get leakage where I didn't have a leak before. ".. That's interesting Gw. Is this on oil seals ?

I think the synthetics have their place in modern engines, but in something with a wet clutch, or sharing the oil with the gearbox, I don't really see them being used to their full advantage probably and so something of an extravagance.

[Gwbarm]

Several things I have noticed when changing to synthetic oil, clutch side gasket leaks, shift lever oil seal leaks, now these are older bikes the seals may have needed changing anyway and the sludge from the Dino oil may be all that was keeping it from leaking, my theory was once the clean synthetic oil cleaned the engine the seals started leaking. I also noticed that synthetic oil same weight seems thinner and an engine that is already burning a little oil will burn more when switched to synthetic. Just my observations. 

[Mech]

Ok. There's petroleum product stuff they sell to swell seals to stop leaks, perhaps the synthetic oil doesn't have enough of that in it(whatever it is), and seals shrink after the synthetics put in. Maybe..  Can't say I've noticed oil leaks though, but then I only ever put it in modern, newish, cars.

Oils are so complicated these days.. Agricultural oils especially..  Some machines are really insistent on the right oil too, or they do all sorts of strange things.  

 

 

[Gwbarm]

I completely agree with complicated oils have to research what to put where.