Hydraulic clutch fluid ?

[Haychip]

Once you have brake fluid in the system you need to stick to it. If you want to change to Mineral oil you will need ao buy a rebuild kit for the master cylinder and o-rings for the slave. Same goes if you want to switch from Mineral oil to Brake fluid or ATF or Suspension fluid. The rubber parts won't hold up once you change fliud type.

[offworlder]

Chip,

Really appreciate this info.
So, is one fluid type better than another ? ie: will the clutch feel any difference using mineral oil vs. brake fluid ? And are the wearable parts (rubber) able to handle either ? Considering mineral oil is not corrosive (and brake fluid is), I'd imagine using brake fluid will shorten the life of these components....

Thanks.

[Orangeshirtdude]

I have the same problem. It's difficult to get into neutral even when not running so I attribute this to the personality of the KTM RFS engine.

[Haychip]

I use Maxima SYN DOT 4 Hi-Temp. The rubber parts seen to last the same with either fluid. I'd typicaly expect to get 4-5 years out of your replaceable items in the master and slave. The Maxima SYN DOT 4 Hi-Temp has a boiling temp of only about 35-40 degrees higher than their regular DOT 4 but it seems to make a difference. Works for me, that is what I put in all my racers bikes as well.

[offworlder]

OK, ever since I replaced the fluid with Dot 4 brake fluid, the clutch has never been the same. I'm going back to mineral oil. Chip, you mentioned I'll have to replace all the seals ?
And is it just me, or is the clutch bleeder valve abnormally short ? Its so short, I cant get a wrench and a tube around it at the same time ! Makes it pretty dang hard to bleed...

[betamax]

If the master says dot4 I personally would stick with it. Rebuild it with a kit but stick to dot4.imho The older KTMs used mineral oil (Magura)but don't anymore(Brembo). It's not really a KTM(engine) thing but a master cylinder thing.Beta=AJP and now, I think, Brembo also.Better to just have to keep one fluid for everything, no? Remove the rubber cover lanyard helps bleeding,it pops right off. Good Luck,Steve

[terboed]

Ive got a 05 and thus a AJP master. I use generic baby oil from the grocery store (baby oil is mineral oil with fragrance).... and have for years and its never let me down. I flush the system twice a year, along with the front and rear brakes (Dot 4 for the brakes). It gets dark colored pretty quick compared to dot 4 but I will keep running it. 4 years running the stuff and no issues whatsoever. Same clutch pull at 20 and 100 degrees F.

[ChasM]

Ive got a 05 and thus a AJP master. I use generic baby oil from the grocery store (baby oil is mineral oil with fragrance).... and have for years and its never let me down. I flush the system twice a year, along with the front and rear brakes (Dot 4 for the brakes). It gets dark colored pretty quick compared to dot 4 but I will keep running it. 4 years running the stuff and no issues whatsoever. Same clutch pull at 20 and 100 degrees F.

Why did you use mineral oil when the AJP MC calls for DOT 4 brake fluid??

[terboed]

Why did you use mineral oil when the AJP MC calls for DOT 4 brake fluid??

The 05 Beta 250RR - 525RR Manual specifies ARAL VITAM LS (mineral oil) as the required clutch fluid.

Quote from page 43 of the user manual -

"CHECKING THE OIL LEVEL IN THE HYDRAULIC
CLUTCH
To check the oil level in the clutch pump,
first remove cover 2.
Remove the two screws 1 and take off
cover 2 together with the rubber bellows.
With the clutch pump in a horizontal position,
the level of the oil should be 4 mm
below the upper rim.
If necessary top up with ARAL VITAM LS
hydraulic oil, which is available from your
BETAMOTOR dealer."

[Haychip]

Do not go by the manual on the master cylinder. AJP Master cylinders on Betas from 2005-2011 use DOT4 brake fluid. IF you flushed the system, yes mineral oil will work. However if the brake fluid has been in there a while, I'm guessing that changing to mineral oil will make the o-rings fail.