I'm working on daughters new (to her, 21 year old) Honda motorbike.She would normally do it (under my supervision) but Covid etc etc.I've done the chain and sprockets (un-seizing the rear brake in theprocess) and today replaced the fork seals and dust covers and in theprocess, found the front brake caliper to be pretty stiff (singlesided floating caliper with dual pistons) so currently have it on thebench with some Plus Gas round the pistons.Now in the past I have forced the pistons out with compressed air(restricting their travel with suitable blocks of wood / rag / clampsetc) but feel it would be better to do hydraulically because it wouldbe more predictable and possibly safer.So I might hook it back up to the bikes front brake system this timebut I was wondering about rigging up a general purpose hydraulic handpump for when I need to do such things.It seems they do them fairly cheap on eBay and I'm assuming I coulduse basic hydraulic fluid (less likely to take the paint off?) but I'dneed to make up some fairly high pressure adaptor hoses (25 bar)?Is this something one can do diy and if so, do you need any specialtools for the joints etc?I think the pumps come with a 1/2" male (looks tapered) outlet and soI'd need a mating female to whatever I was working on, in the case ofmost motorbikes, a 'banjo' connection of some sort.Cheers, T i m

Given that you already have a hydraulic pump with all the right fittings and fluid to hand this seems like a lot of work.If you are going to make a general purpose system you have a choice between using mineral oil and "brake fluid". (When you say "hydraulic fluid" earlier it is not quite clear what you mean). I would generally use mineral oil (absorbs less water, gives better lubrication for a stuck or rusted system, and less likely to strip paint). But, you might then worry about compatibility with seals specified for brake fluid. No problem if you are going to replace them once you get the thing apart. In fact in general people worry more than is necessary about compatibility of mineral oil with rubbers other than nitrile and viton. Provided the exposure is short and it is cleaned off well with suitable solvents there should not be a problem. Although mineral oil will cause natural and many other rubbers to swell and become soft the effect is generally reversible.

diy hydraulic fittings?

Oct 25, 2020 Last reply: 5 years ago 21 Replies

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Dave Plowman (News 5 years ago

A mixture of ATF and paraffin makes a decent penetrating oil. Or rather as good as most.

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T i m 5 years ago

I'll see if I have some of each as my Plus Gas spouty (long ally spout and has probably lasted a long time because you can use the spout to apply it just where you want it, not spray it everywhere) tin is nearly empty. ;-(

Cheers, T i m

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