Cold, had sat unused for 3 weeks, with a high compression piston (11.5:1 or so)
Let me stop you right there, mmmm-kay? I can tell by that little intake of breath what’s coming next. Thank you in advance, but I already know that motorcycles are “dangerous.” After nearly twenty years of riding on the streets, I am aware; telling me now will not be a revelation. It is not an insight into my lifestyle that has remained hidden from me until this, the moment of epiphany when you shine the light of outsider wisdom on my foolhardy choices.
Seriously, read the whole thing, hypocritical motherfuckers.
Not sure if this will have any effect, but lane filtering is definitely something that we not be booked for.
I got myself one of the cheap knockoff Brembo radial master cylinders that are coming out of Thailand and going for around AU$60 delivered on ebay. Build quality seems a bit iffy – the handlebar clamp surface isn’t square, and it wasn’t releasing pressure, leading to a seized brake system (not fun!). Since it didn’t cost me much (less than just a Brembo lever!), I wasn’t too upset that it didn’t work. I pulled it apart to see if I could fix it, or at least get an understanding of how they work.
I’m still not 100% certain on the cause of the issue. All the seals appeared ok, and no passages were blocked. I haven’t yet reinstalled and tested. Going by this thread (in particular post 5), I’m pretty sure that the cause of the issue is the piston not retracting fully so that the intake/return port was not uncovered. This would prevent pressure build up from being released. When I first installed the lever, bleeding took ages – no matter how much I pumped the lever the fluid just didn’t seem to be getting through. I had to use a syringe to force fluid up from the caliper out the bleed nipple on the master cylinder. This kind of makes sense if the intake/return port was blocked or not uncovered. Two possible causes for this could be:
- Not enough lever free play preventing the piston from retracting enough to uncover the intake/return port, or
- Construction tolerances out slightly so that piston does not retract far enough to uncover the intake/return port.
It is hard to tell because there’s little light, but it does seem that with the pushrod screwed all the way in, the lip of the first seal is just covering the intake/return port. I’m planning on trying it out as is, in case the cleaning did make a difference. If it still seizes, then I’m going to see about backing off the pushrod cover collar, which should allow the piston to retract slightly more. If this does work, then I’m going to need to make a spacing collar or some such.
As seems to be typical for a bike from the 80s, my 1988 2NX SRX600 has shitty, wooden brakes. This is the result of poor hydraulics, particularly the ratio between the master cylinder size and the total caliper piston area, which dictates the mechanical advantage of the system. The SRX6 has a 15.8mm master cylinder (5/8″, 195.9mm^2 area) and a single four piston caliper acting on a 320 mm floating disc. I wasn’t able to measure the caliper piston sizes at this point. Improving the hydraulic ratio can be done by either using a caliper with a larger piston area, or a master cylinder with a smaller piston bore.
Master cylinder piston size isn’t something that is typically listed, so it took a bit of searching to discover that NSR150 master cylinders are 11mm (piston area is 95mm^2). I got one in decent condition off eBay for around AU$43 delivered. Fitment was fairly straight forward. Due to the increased lever travel I had to rotate the switchblock to give a bit more clearance. Also, there is no mirror mount, so I will use a bar clamp mirror mount. The brakelight switch doesn’t fit, so I will have to find a suitable switch.
Performance is now excellent. Very nice initial bite, and plenty of power for one to two finger use. Lever travel is good – while I could squeeze the lever in enough to get in the way of my fingers during testing, the braking power is good enough that this would only happen if I had some serious brake fade happening, or I was doing a stoppie. I will probably upgrade to braided brake lines at some point, but at the moment it just isn’t really necessary, as there isn’t too much flex apparent.
Overall, A highly recommended and successful upgrade.
If you want to adjust the hydraulic ratio of your brakes to get better feel, then below is a list of possible donor bikes for which I know the master cylinder sizes. Remember, a larger master cylinder will give less power, but require less travel (potentially make the lever feel more wooden), and a smaller master cylinder will give more power, but require more travel (potentially make the lever feel spongy if you go too far). Some master cylinders have the piston size stamped on them (whether it be metric or fractional inch), but a lot don’t.
15.8mm – Very common, especially on 80s bikes, and modern bikes which have twin four piston calipers. Some specific bikes that I know of include: FZR250, FZR400, FZR600, SRX600. It seems to be almost the default size.
14mm – The VFR400 (NC30) uses a 14mm remote reservoir Nissin master cylinder. This is coupled to twin four piston calipers (unsure of the total piston area), and leads to excellent brakes.
12mm – The XT600 (90-2002 at least) uses an integrated reservoir 12mm master cylinder with a two piston sliding type caliper. This gives ok hydraulic performance (although hydraulics can only do so much given the wheel/disc size ratio), but feel is pretty shitty due to the bolt from the lever which acts on the master cylinder piston.
11mm – NSR150 has an integrated reservoir 11mm Nissin master cylinder. The lever is not adjustable for reach. I believe that it is coupled to a two piston sliding type caliper. Unsure of years, but the one I have has piston bore stamped on it.
So, I was riding home, stuck in traffic on when I hear the driver of a bus in the lane next to me start shouting something out his window at me. Being accustomed to Brisbane drivers, I was ready to tell him to go fuck himself, till i heard him say something about Supermoto racing.
Turns out, there’s a supermoto event down at stanthorpe, and seeing the supermoto I was riding he thought he’d do a bit of spruking! Quite awesome really, and I’ll definitely be going. Supermoto racing (or motorcycle racing in general) is one of those things that seems hard to find out about. I’m always keen to go spectate (and participate, if I had the time/money!) but it just seems to hard to find info about when events are being held. Good thing there are friendly supermoto-racing bus drivers out there!
Here’s the details:
I knew that light was there for a reason
I’ve seen a lot of questions relating to filling oil on dry sump engines like those in SRX6’s and XT6’s. In particular, the common issue is overfilling the oil. What happens is that at idle, dry sump engines often “wet sump”. The oil pump doesn’t produce quite enough pressure at idle to get all the oil to return to the oil tank, so it pools in the bottom of the engine cases. There is also a one way valve in the oil tank which prevents it from draining back into the sump. When the bike sits overnight some oil will most likely leak back down into the sump.
So if the oil is checked after the bike has stood for a while, the oil level may show as low due to drainage from the tank back down into the sump. Or, if the engine is started and let idle to circulate the oil, wet sumping means that the oil tank level may show as low. Which then often leads to topping up the oil tank. Sound familiar? Sometimes this can be repeated multiple times leading to excessive overfilling (just ask me how I know this!). The excess oil then flows out the crankcase breather into the airbox.
So, when checking oil, I always do it straight after a ride if I can. After an oil change, I fill the the volume recommended in the service manual, then go for a ride, ensuring that I get the revs up and flick through the gears a bit. This way I know that the oil pump has been working and the oil tank level will indicative of the actual oil level.
I took off from my local bike shop on my SRX6 with a few people watching (probably the kick start…) so I gave it a handful and suddenly the exhaust got very loud (but boy did it sound good!). I pulled over and saw that the muffler/mid pipe had actually fallen off the headers. It seems that the muffler section is only press fit onto the headers, and held in place by two brackets, one of which had snapped. So the back pressure had literally blown the muffler off! I will probably take it to an exhaust shop and get them to weld on some spring hooks and another mount, but in the meantime, I bodgied up a fastening using hose clamps, or, as I will call them from now on, “high temp zipties”
I’ve also got another hose clamp securing the midpipe to the frame, but that’s not all that interesting or easy to photograph.