Ive got a weepy clutch MC which is mineral oil. Question is can I fit a DOT type MC or do I need to stick to mineral? What is the reason for using mineral oil over DOT fluid?

 Why don`t you just get the proper rebuild kit for the m/c? Or did you try that already?

5 hours ago, iank said:

Ive got a weepy clutch MC which is mineral oil. Question is can I fit a DOT type MC or do I need to stick to mineral? What is the reason for using mineral oil over DOT fluid?

@iank The use of mineral oil is to stop the contamination by Dot4 of the gearbox oil and the possibility of any nitrile seals/ clutch parts being damaged in there if the O rings in the slave fail  , the clutch slave cylinder sits in the clutch casing and its a wet clutch so it is best to use mineral oil, I just converted an old DOT4 setup to mineral oil on a Gas Gas pro for that very reason.

Edited November 7, 20232 yr by Tr1AL

15 minutes ago, Tr1AL said:

@iank The use of mineral oil is to stop the contamination of the gearbox oil and the possibility of any nitrile seals/ clutch parts being damaged in there , the clutch slave cylinder sits in the clutch casing and its a wet clutch so it is best to use mineral oil, I just converted an old DOT4 setup to mineral oil on a Gas Gas pro for that very reason.

Just an add on , if you use DOT4 in a clutch or brake M/C the seals and any feed tubing will normally be made of EPDM ,  if you want to use mineral oil the seals will normally be FKM more commonly known as Viton.

Look at it the other way around, they use ethyl glycol in brake applications so a failure does not result in oiled brakes, if it was not for that fact they would most likely be using mineral oil in all the hydraulics.  

2 hours ago, lemur said:

Look at it the other way around, they use ethyl glycol in brake applications so a failure does not result in oiled brakes, if it was not for that fact they would most likely be using mineral oil in all the hydraulics.  

That is not why brake fluid was developed. Its hygroscopic nature, while also a disadvantage is one of the main reasons for its use

Thanks guys, I did wonder if it was because the slave was in the clutch casing and possible leakages would be an issue. I haven't tried a seal kit yeti can't really work out what size mine is. Ive seen kits for large and small MC's. I'll look at either a seal kit or another mineral MC. 

2 hours ago, iank said:

Thanks guys, I did wonder if it was because the slave was in the clutch casing and possible leakages would be an issue. I haven't tried a seal kit yeti can't really work out what size mine is. Ive seen kits for large and small MC's. I'll look at either a seal kit or another mineral MC. 

This may help https://youtu.be/tB_bFTSqaBk?feature=shared  Jim Snell Trials parts USA MKII.

Edited November 8, 20232 yr by Tr1AL

Thanks Tr1AL I’ll have look at that 👍 the clutch drags slightly too so may have to have the plates out as well and check all them 🙄 

Gas Gas clutches do drag a bit.