2 Stroke MX bike Gearbox Oil change frequency?

[jdmboy]

I am going to send off oil from my MX bik. It is 2 stroke. I am a few weekd from doing the UOA. I have never done it on anythig but my car. should be intisting. The oill is i the gearbox only since it is 2 stroke. The piston and crank oil is in the fuel. It is a wet clutch system and the motor oil is just gearbox oil. Like a manual gear box in a car. I run a 10W-30 or 40 oil in the gear box by the way.

Here is the question. People say change the oil every ride, or every 3 hours or every 2 rides. I just don't get that. A 5MT in a car lasts a long time and so does the gear oil in a street bike. I can not see how it needs to be changed so frequently. Since the oil does not lubricate the rod bearings I would suspect even less wear.

Can anybody shed some light here or has anyone done a UOA on a 2 stroke dirt bike? How cann the gears need to oil chnges every few hours? I'll post my results in th UOA when I get them?

 

[Master ACiD]

it needs to be changed more frequently because a 2 stroke bike has a wet clutch which SHEDS clutch fibres right into the oil. mx bikes and atv's are really really hard on clutches. every single time you take off from a stop, even if its an easy take off, you have to slip that clutch and overcome the large ammount of drag created by the dirt and youre knobby tyres. if you like to ride hard (as most do) slipping the clutch in the corners, rev-n-dumps, etc abuse that clutch.

ever notice how when you drain the oil, its darker then the oil which goes in? thats youre clutch fibres darkening the oil and contaminating it. the oil its self is not going to wear out in 3 hours or 30 hours. its a contamination via clutch issue.
you probably dont need to change it every 3 hours unless you are really super hard on the clutch. but then youd be replacing the clutch every 2 hours and so you would naturally drain the oil in order to get the side cover off, so thats a non issue.
i have a 2 stroke yamaha banshee and i change the oil every 10-20 hours. really it depends on how hard i am riding and how much i am using or abusing the clutch.
if i am drag racing all day and doing 2nd or 3rd gear full thottle launches then ill change it earlier. if its some relaxed trail riding i might double the interval. if its REALLY easy stuff like ferrying around 6 year old relatives where i dont even shift for an hour at a time i might just triple the interval.

on the flip side, these 2 strokes dont take much oil at all. i think my 250cc twin cylinder takes 1.5 quarts. i bet yours takes less sence its probably not as wide as a twin. most people can afford to be a little wastefull and change it more often sence these 2 stroke engines take such little oil.
if you drop $5 every 10-20 hours on some oil, who cares right? youre gas costs hundred times more than that.

 

[Master ACiD]

correction thats a 350cc twin cylinder not a 250!
heres a pic of me at the drag strip.

 

[ccdhowell]

Hey Master, what oil are you using in your banshee transmission? I've been running Silkolene Light Gear Oil in my Tecate 3wheeler, but recently bought some Royal Purple Syncromax. Haven't put it in yet, but hoping for good results. Chris

Nice pic too.

 

[wileyE]

Used dextron atf in many of my bikes. Also used motor oil. Not sure about atv's but with the bikes it was mostly finding the fluid that gave the best clutch feel. Any kind of gear oil I ever tried would big time drag the clutch.

 

[Jaybird]

I have used ATF for years in 2T dirt bike engines.
But, I only use Type F ATF. It's frictional charactoristics are more suited for the dirtbike clutch than Dexron/Mercon type ATF's. Especially racing bikes.
Type F's friction increases with RPM's, where as Dexron is the opposite.

 

[Jaybird]

Oh, and I change out fluid in a 2T after every other ride or so. No matter what the fluid is.
Easy to do with $1 qt. ATF. And I have much more piece of mind than if I were to use a high-dollar boutique oil and try to make it last.

 

[Master ACiD]

Quote:

---

Hey Master, what oil are you using in your banshee transmission? I've been running Silkolene Light Gear Oil in my Tecate 3wheeler, but recently bought some Royal Purple Syncromax. Haven't put it in yet, but hoping for good results. Chris

Nice pic too.

---

like jaybird i am using type f atf. but now that i scored 25 gallons of 15w40 diesel oil for nearly free , ill probably end up using that.

 

[wileyE]

The type f vs dextron debate has been going since day 1. Bottomline, IMO, there is no rule, use what works best for the application. At one time I had 3 race bikes that all liked something different. A husky that didn't like atf, a ktm that did, and a Maico that worked best with 10w30. The husky held at least twice the oil of the others so didn't get changed as often.

 

[ccdhowell]

I've never known anyone to use Dexron ATF, and assumed it wasn't appropriate, but I have several gallons of DexIII that's just sitting there doing nothing. I may try it just to see how it works. It would be nice to use up all the DexIII I have.

 

[Panzerman]

I used type F and it seemed to work great. I wouldnt change it out alot unless you really abuse it, it all depends on the application.

 

[jdmboy]

Ok so it is the clutch fibers that makes the mess. Ok then, Devlis advocate, what is the problem with that. The gear teeth should chew it up.

Does the older oil affect the gears or the clutch then?
cost is not an issue, I am just tryig to understand why the oil that is not even close to shearing neds to be changd.

The issue is not gear box damage the issue is clutch performance?

 

[Master ACiD]

thats the million dollar question. just how much contamination is acceptable? with most 2 strokes holding a quart or less, its not worth argueing about. just change the oil once in a while and be done with it.

most 4 stroke wet clutch bikes have oil filters or screens or centrifuges. my old honda 125cc enduro 4 stroke has a screen, magnet, and a centrifuge.
my 1969 honda ct 70 (70cc's) has a oil mesh screen and a centrifuge. (i still have this bike!)
my old kawasaki kl250 enduro had a paper filter and screen.

it would seem that 4 strokes would naturally be MORE susecptible than a 2 stroke sence that contaminated gearbox oil also lubes the engine. and you dont want nasty clutch fibres going round and round youre crank. but on the other hand you dont zing the throttle as hard on takeoff with a 4 stroke as you do a 2 stroke.

so maybe sence a 2 stroke clutch gets abused a bit harder than a 4 stroke , and the fact that no 2 strokes that i know of have an oil screen or filter or centrifuge, maybe they do need to be changed more often.

 

[beanoil]

On a 2t, I run an 80w90 gear oil (basically a 10-30) and change it every 4 hours. The oil isn't worn out by any stretch, but it is full of clutch fibers, and metals from the clutch plates, basket, hub, and gears. No the gears won't chew up the debris. Do some research on oil film thickness vs debris size... In a 4t, that stuff is out of there pronto... every couple of hours. Most modern 4t dirt bikes have sump screens before the pump. Clutch fibers clog the screens, even at very short OCI intervals, and then the top end starves. I just reassembled a KX250F. M1 did fine at 3 hour intervals for 50 hours. The cases were split every 10 hours, and the screens were clean. A sponsor switch to Motorex, and the screen clogged within 3 hours. Analysis and autopsy of the oil and engine showed an abnormally high percentage of solids in the virgin oil. The cams were flat, the buckets had grooves in them, the piston was toast (no oil squirting up to cool the bottom of the piston.) The cylinder was OK. (IMO: I was running Race Cool- I think that sved my keister on the cylinder) Total cost, right at 600.00 for the parts and If I were charging myself labor, another 360 on top of that. I'm back to a steady diet of M1.