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The (BMW) master cylinder has provison for an O ring - this should seal nicely against the Marlin supplied adapter plate.
The Metro servo has no provision for anything (no surprise there then). The Marlin adapter plate rocks very slightly when offered up and so it will definitly need some sort of gasket.
I guess all the instant gasket gloop you can buy will fail as the air from the manifold is laden with fuel which is an excellent solvent. So what it needs is some form of solid gasket - The sort of material used for inlet manifold gaskets would be best - anyone any idea where to get a sheet of that sort of material from?
I think you can get that universal gasket stuff a bit like cork or cardboard. You just mark up what you want and cut it out. Im sure ive seen that used before on a TV proggy.
Hi guys,
I asked Mark some time ago about a gasket between the adaptor plate and the servo and he advised me to use silicon sealer.
I have used Wurth Super RTV Silicone. It seemed to work really well but I have not had a chance to run my engine yet. I used an 'o' ring between the BMW master cylinder and the adapter plate which seemed to seal nicely.
Patrick,
where exaclty is your gap/gash? I think you should send it back to Marlin? They seem to have used that version of the master cylinder on their purple demo car, so there must be a solution.
BM master cylinders are not cheap!
I would check your servo, it may have a leaky diaphragm. The master cylinder does not normally seal to servo, with the master cylinder totally removed it should not leak vacuum, ask your fellow builders to confirm it on there builds, it might save you some wasted time and cash.
I would check your servo, it may have a leaky diaphragm. The master cylinder does not normally seal to servo, with the master cylinder totally removed it should not leak vacuum, ask your fellow builders to confirm it on there builds, it might save you some wasted time and cash.
Brian
Just checked mine and the vacuum does pull on the master cylinder side on the Metro servo (has to when u think about it to amplify the force applied to the other side by the brake pedal which is open to the atmosphere). So that means the master cylinder has to seal to the servo or you will get unmetred air leaking into the manifold upsetting the mixture.
The BMW master is not too bad from GSF, bit much from motormec. I feel that the brakes are the most important system in a car, therefore I dont mind having to spend a little bit more money to get things working in an optimal way - makes me feel better driving the car
I have noticed looking through the ETK that ABS cars use only two pipes out of the master cylinder to the ABS unit, but cars without use three, one to the back and one to each of the front wheels. I notice there is a bung in the "ABS" master cylinder in one of the two holes for the front. You can buy these as different parts form GSF but they are probably one at the same just the ABS one with a bung.
I'm going to get some new calipers too, I just cant decide if I want to splash out of wilwoods at the front (if it even needs it)
Mine came from GSF and it is an ATE one - the same as fitted by BMW as original equipment. I am with you Patrick on the brakes - most important bit of the car. Why dont you rebuild your old calipers? It's not difficult and no different to the reconditioned ones that you buy from places like GSF (except much cheaper to DIY) The bits are readily available from BMW.
In my view after market calipers won't be a big benefit because of the lower weight of the Sportster (look good mind you). The biggest problem is the Metro servo which is tiny compared to the BMW one which means much more effort is required on the brake pedal. I think a better upgrade would be a bigger servo if anyone could find one that would fit the bill.
I'll get the ATE one from GSF! As for rebuilding yeah that sounds like the best idea, they are very grotty though!
I do like the look of those wilwoods - perhapse a future upgrade once I put bigger wheels on so the stock ones dont look so ikle
Thanks on the millstone front too, i've left a bit of budgt aside for the Sportster, its just finding the time now. Luckly I'm only 10mins away from my parents to its easy to pop over at work on it!
