Gear Oil for CR125

Sam Zavaglia · Posted: Thu Jan 17, 2013 4:12 pm Post subject: Gear Oil for CR125

Just to start another comedy of information on these forums, I use Castrol MTX which is very cost effective in Australia. Not sure if this is available in the USA.
http://www.castrolmoto.com/au/our_oils_new/mtx_gear_oil.php
I only change my gear oil at least 1-2 years apart.

Anyway, I put Castrol MTX into my very first CR125 kart engine. Over six months later, the Redline rep said...."mate you gotta try this blah blah blah....and more horsepower.

So since there is a drop in HP through the gearbox and I got the stuff for free for testing and feedback, thought I'd test it proper. I went to a "rolling road" dynojet dyno with my gearbox still with original Castrol MTX and got a read out. Drained the gear oil while still warm and dropped this exact Redline stuff in.
http://www.redlineoil.com/product.aspx?pid=112&pcid=26
The next dyno read out was exactly the same .......could not spot a single difference......what a load of crap I said to myself.

This Redline stuff now stayed in the engine for a further 2 years....never changed. So after the engine was 3000miles and nearly 3 years old, I've had Castrol MTX for over six months (at least 6 race meetings) and then 2 years without a change on the Redline stuff, I decided time to change the crankshaft as preventative maintenance.

After opening the crankcases, the gears/dogs all looked virtually perfect, the shift forks like brand new.
I also did another engine rebuild with over 2 years on Castrol MTX never changed, very similar results, maybe not quite as perfect as Redline but still very remarkable and worthwhile staying with Castrol MTX.

Both engines, no magnetic drain plug, no notable bits of metal in the gear oil.

This is the engine with over 2 years on a single fill of Redline, over 2000miles on that gear oil, I know you can't see the dogs but imagine it looks as good as the rest of it.

Has everyone else got the same results? I imagine so since I do not read any bitchin about CR125 gearboxs on here.

Has anyone got notable differences between different brands of gear oil that are specific to motorcycle/wet clutch use?
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Jeff DeMello · Posted: Thu Jan 17, 2013 4:41 pm Post subject:

I only used Mobil 1 synthetic oil with no gear box problems. I would change after every season of racing..
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Ken Schilling · Joined: 01 Dec 2005 Posts: 1340

Wow, you guys change your transmission oil very infrequently compared to me... I change mine every race and use TransOil 2T 10W30. The CR-125 trannys are considered to be bulletproof and I do it this frequently as a relatively inexpensive preventative measure as well as trying to extend the life as much as possible. I'm on a shoestring racing budget and don't want to open the bottom end unless absolutely necessary.

http://www.corseracing.com/Motul-TransOil-Petroleum-Gear-Oil-1L-One-Liter-Bottle-10W30-p3568.html?gclid=CMX42YLY8LQCFayPPAodq2QATA
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Mike Goebel · Posted: Thu Jan 17, 2013 6:35 pm Post subject:

Sam you have to change it more offten Laughing

It "Will" never last as long as it already did!

Mike G.
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Sam Zavaglia · Posted: Thu Jan 17, 2013 6:58 pm Post subject:

Jim McMahon · Posted: Thu Jan 17, 2013 7:13 pm Post subject:

Do you still have the oil Sam? You should send it off for analysis.
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marc-andre hubert · Joined: 10 Apr 2012 Posts: 174

i use honda racing oil 75w90 shift great and offers great protection

Sam Zavaglia · Posted: Thu Jan 17, 2013 7:24 pm Post subject:

Jim McMahon · Posted: Thu Jan 17, 2013 8:58 pm Post subject:

Michael Taksa · Posted: Fri Jan 18, 2013 10:15 am Post subject:

The consensus is that the tranny on that motor is bulletproof, so it will run on whatever you put in it. I use mobil1 syntetic 5W30, used 10W30 in the past, but now my car wants 5W30, so my kart gets the same oil I already have.