Rear brake pedal fade

[Wobbly]

Ok, so here's an interesting one ... my rear brake pedal seems to have decided to start fading quite badly ... by that I mean step on the rear brake, then let off but the pedal stays down, then comes back up slowly ... or I press on it lightly and then feel it drop away from my foot :?

The master cylinder reservoir looks a bit bowed, so I'm wondering if its letting air in ... but that shouldn't cause this sort of problem as the system isn't pressurised there. I've run some new fluid through it a couple of times and its better to begin with but then becomes bad quite quickly (more so recently). It's also got new pads in it which didn't make any difference.

I ran my finger over the disc while spinning the rear wheel and I can't feel any movement that would force the brake piston back into the caliper, and can't feel any pulsing from the brake. I tried the same putting pressure on the brake pad in the caliper itself and same result. Haven't run it around with a dial guage though.

Seal kit needed for the m/c?

Thoughts?

:-k

[Flash]

That would be my first guess.

[Muzzard]

Certainly would seem hydraulic, and the bow in the master cylinder is a legacy of single cylinder vibes on the pedal and transferred into the piston by distal offload of the shaft between.
Caliper may also need looking at Neil as for every action there is equal reaction.
Up for an overhaul I suggest, not expensive, but a day off the road and some fiddling around. :roll:

[Wobbly]

and the bow in the master cylinder is a legacy of single cylinder vibes on the pedal and transferred into the piston by distal offload of the shaft between.
Who did what to then where now?
Up for an overhaul I suggest, not expensive, but a day off the road and some fiddling around. :roll:
Yeah, its looking like a new seal kit for caliper and master cyl then and a replacement reservoir. Which begs the question whether I should replace it with a CRF one which is supposedly better :-k

Looks like bike will be off the road for a week or so when I do the big bore, so I'm going to organise some holiday time off work (since i've got over 5 weeks up atm) and sort that out, plus pull the water pump off, do a bit of a reject, drill some holes in random locations, etc etc :D

[Flash]

When you say drill some holes is that the technical term for boring it out to 440?? If so Finally!! If not then Steve is going to leave you behind :( His is not far away from being big.

[Muzzard]

Everyone is entitled to do as they please, but for my money, I would have ridden the 400 for 2 years like my WRF and then when things actually need replacing then get it done...
There is a shitload more things to improve the performance on a stock motor that can be done with the money over the next 2 years...
Makes better financial sense to me, but just my 2 bobs worth.

Frequency vibration of single cylinder motorcycles/engines and harmonics play major roles when designing for radial and distal off loading of resonance. This in real terms means the angles that components fit together at and the structure/integrity of the joint can actually limit horsepower being produced and certainly affects frame dynamics...
Some early 40/50 bikes particularly English, (sorry John) riders with fast machines like TT racers, removed/cut off the alloy rear mudguards as the vibration going to the tip of the guard accentuated by distal offload of resonant harmonics would see the bikes uncontrollable over certain MPH, purely through excess vibration.
This is why motards flog tyres, full floating brake buttons and alloy components that have either movement as part of its function or are just plain loose...
(Enter Talon full-floating Brake Rotor, fitted to WRF flogged out twice in 2 years) :roll:
And of course your master cylinder Neil, understand now, who did what to who with,.. a tuning fork? :lol:

[Flash]

Everyone is entitled to do as they please, but for my money, I would have ridden the 400 for 2 years like my WRF and then when things actually need replacing then get it done...
There is a shitload more things to improve the performance on a stock motor that can be done with the money over the next 2 years...
Makes better financial sense to me, but just my 2 bobs worth.
:lol:


So what your saying is that he should put cams, exhaust and perhaps a rejet?
He is going to have that too!!! :D
After all this there will be some head work
Oh yeah it's going on a diet as well soon and I know that he has been looking around at rm forks.
:twisted:

[Muzzard]

If he is that keen for some performance, why buy the DRZ?
They are for rider enjoyment/longevity of machine. Could have just bought an LC4 and had the grunt, or a DR650 with the same mods.
RM forks, I would have thought for this sort of modding a 55mm set of Marzocchi Shivers would be more the ticket. :twisted:

[dicky]

mmm... LC4...

dicky.

[Wobbly]

Yep, the big bore is going in since the poor thing needs some new rings anyways. Got the cams waiting to go in already.

By holes I actually meant cutting up the airbox more and drilling some big holes in the side. Might also do some drilling for weight reduction, like headstock, frame, forks, crankcases, etc :lol2:

As for steve passing me engine wise, I've already got the cams and have the full tapered-header yoshi exhaust on the bike which also gives you a good boost in juice :fucku:

Just jokes :lol: