Question
Is it nescesary to position the brake fluid
reservoir above the brake calipers?
(reservoir is above the master cilinder.
In my opinion it is not but problems with bleeding the system makes me doubt.

Cor

A qualified no!

You need to ensure that the fluid doesn't flow back from the calipers to the master cylinder which it will if the calipers are above the level of the reservoir.

You can either raise your reservoir or fit a very low pressure non-return valve into the brake lines. I can't remember the poundage of the valve you need but I think it was something 2 lb/sqin. Someone else will no doubt comfirm this.

If you don't fit this valve then the fluid will slowly run back to the m/c and increase the amount of brake pedal travel required to activate the brakes because the slave pistons will back off from the disc/drum as the fluid runs away from them.

HTH,
Craig.

you can have the res lower than the callipers just means a real bitch when you have to bleed them.
If you don't believe me ask anyone that has ever owned a race Kart with a gearbox.

Viper,
I used to have a Villiers 210 kart with gearbox and disc brakes all round but the reservoir consisted of one of the tubes up the steering column and it was well above the level of the calipers.

Here is a quote from the wilwood website @ www.wilwood.com:

Q: Do I need to use a Residual Pressure Valve?

A: Residual pressure valves maintain a nominal amount of pressure in the brake system to alleviate fluid from draining back towards the master cylinder and causing excessive pedal travel. Use 2lb. RPV's when the master cylinder is mounted below the level of the disc brake calipers to prevent brake fluid from draining back down into the master cylinder. Use 10 lb. RPV's with all drum brake applications to offset return spring tension.

These RPV's can be used even in a conventional system and help to maintain a firm pedal but shouldn't be used to correct an otherwise defective system (eg. a defective master cylinder)

HTH,
Craig.

My formula E and 125 open both had Kelgate brakes (the best at the time) the resovoirs were lower than the calipers and they worked fine.

Fair enough but for all the cost of an RPV I'd stick one in when I was making up the brake pipes.

Formula E? Those are seriously mad machines!!
Did you race them?
My Villiers was just for fun but used to owned by the Scottish karting champion before he retired so it was pretty well set up. It's not up to Formula E standards but was bloody good fun all the same!

I was actually going to take up karting and built my garage for that purpose mainly. However, after reading the RC book which I picked up one day in Halfords I decided I'd be better off building a Locost. The rest is history...

Cheers,
Craig.

Perhaps the Kelgate master cyls had an rpv built in , spose it would make sense seeing as the manufacturers would know where it was going to located on the chassis.
Yeah i did race them both, with a little succses too, but the re mortgage money ran out, and my sponsor vanished over night leaving me with a big engine rebuild bill so that was that, forced into retirement...
Got myself a rotax max for a bit of fun now though, cheap and reliable...

Not heard anyone mention this on the MK indy's,my reservoir is lower than all 4 calipers and i dont seem to have had a problem bleeding the brakes.

There are also plenty indy's on the road too.

Hope this helps

Viper,
I was thinking of getting a Rotax Max but wasn't sure if this was the right way to go or not and they are a lot more expensive than the TKM. How do you think they compare in terms of performance with the likes of the TKM and even the 125 open. I know the 125 open has a gearbox but in terms of fun factor and basic speed/cornering, does the Rotax Max represent good value? What sort of money would I have to spend to get a workable Rotax Max bearing in mind that I am interested in fun more than serious racing? My local track is Larkhall near Glasgow and I have seen the Rotax Max racing there but they don't look as fast from the outside as I'm sure they are from the drivers seat...
They should be about the same "speed" as my old Villiers 210 I'd expect (Yes/No?)

Cheers,
Craig.

The max has a lot going for it, cheap and reliable, electric start is an excelent idea, i have only played in mine at whilton mill and granted it's not a 125 open but bloody good fun, the last time out there were a bunch of opens there and only a couple were quicker, if memory serves, the only 100's quicker were intercontinental A's (mega expensive)
why not try to blag a go in one...