1987 NSR 250 MC16 Front Brakes

[simo]

Anyone know how to bleed the front brakes on an NSR250 MC16, have tried the obvious, can't get any pressure at all, is there a trick or two here to sort it?

[k14]

Try cracking the top banjo bolt by the master cylinder. There can sometimes be a bit of air trapped there.

[simo]

Try cracking the top banjo bolt by the master cylinder. There can sometimes be a bit of air trapped there.

Thanks mate, worked a treat, now got some brakes, still spongy though, don't know what to do next, have run two lines up to master cylinder and run fluid through, no bubbles showing, still really spongy, then cracked the banjo bolt and pull lever in, then tightened bolt, a little better, but not the stopping power that it should be. Any suggestions?

[F5 Dave]

Japas claim you should replace the lines every 2 year [insert Tui add] but they have a point, yours are approaching 20yrs old.

But for stopping power the spongyness is almost a red herring (although removing a bunch is nice for feel & helps weak brakes). But there should be enough power that it doesn’t matter. This sounds contradictory but never mind that.

Lets start with the basics. What do the discs look like? Are they shagged & bent? Are they discoloured? Can clean up with sandpaper & clean off with brake clean. Don’t handle with greasy fingers.

OK the callipers are next to explore. Remove the pads & inspect. Maybe in a past life they had a leaking fork bleed on them. They would never recover. They may be a cruddy brand or touring model suited to heavier bike. Consider replacing with decent pads.

Then the pistons. Pump them out a ways & make sure all are moving. If they stick they will be soddin useless. Also being a Honda they may have those sliding calliper models. If so take out clean & regrease with Hi Temp copper grease. Check the pins are ok.

I would also consider pumping the pistons out & cleaning the callipers on such an old bike. Crud accumulates at the bottom of the system & a clean out & new fluid will help. It is easy as long as you are not ham fisted & use the noggin. Write if you need more info.

[simo]

Japas claim you should replace the lines every 2 year [insert Tui add] but they have a point, yours are approaching 20yrs old.

But for stopping power the spongyness is almost a red herring (although removing a bunch is nice for feel & helps weak brakes). But there should be enough power that it doesn’t matter. This sounds contradictory but never mind that.

Lets start with the basics. What do the discs look like? Are they shagged & bent? Are they discoloured? Can clean up with sandpaper & clean off with brake clean. Don’t handle with greasy fingers.

OK the callipers are next to explore. Remove the pads & inspect. Maybe in a past life they had a leaking fork bleed on them. They would never recover. They may be a cruddy brand or touring model suited to heavier bike. Consider replacing with decent pads.

Then the pistons. Pump them out a ways & make sure all are moving. If they stick they will be soddin useless. Also being a Honda they may have those sliding calliper models. If so take out clean & regrease with Hi Temp copper grease. Check the pins are ok.

I would also consider pumping the pistons out & cleaning the callipers on such an old bike. Crud accumulates at the bottom of the system & a clean out & new fluid will help. It is easy as long as you are not ham fisted & use the noggin. Write if you need more info.

Thanks mate, have replaced pads, checked and freed up pistons, came with braided lines, so dont probably need to replace those....replace fluid obviously, cracking the bolt behind the lever is what got the show on the road, its just getting a bit more pressure would be good

[F5 Dave]

Might be master cylinder needs a rebuild.

Hmm, NSR with a 600 Honda huh? A friend sold one of those a year or two back. Was to the SI though. Got some serious power from it too.

[ahug030]

Go to www.nsr-world.com, I think they might have a section on this in the 'technical' area. Otherwise the responses in the forum there are usually very good.

[imdying]

You could take the master and splitter off, and make them below the calipers. Rebleed. The air will rise to the calipers, instead of fighting your attempts to get it down the lines. Works a treat :)

[Pussy]

Many years ago I had a bugger of a job getting pressure in a 650 Yam front brake, and ended up pumping fluid from the bleeders back up. Worked perfect

[simo]

Might be master cylinder needs a rebuild.

Hmm, NSR with a 600 Honda huh? A friend sold one of those a year or two back. Was to the SI though. Got some serious power from it too.

I was thinking that the master cylinder might be the next port of call. This bike smoked the oppostion on more than one occassion with Laurie Love as the pilot back in 1990-1992, it has some toe with a high compression piston and hot cams, it weighs stuff all being a total loss system, its really just a chassis and an engine. I've finished the rebuild, just the vital bits like the brakes to do!!!! - by the way she's a bitch to start...funny that!?!?!?!?

[simo]

You could take the master and splitter off, and make them below the calipers. Rebleed. The air will rise to the calipers, instead of fighting your attempts to get it down the lines. Works a treat :)

Will try this before the master cylinder reincarnation

[F5 Dave]

Ahh, different bike. My friends one had been seriously stuffed with by Pete Sales (Total motorcycles in Palmy north) silly big carbs & new inlets welded on at steep angle. Pity he sold it but it bit him (that whole close the throttle on a big single thing) & he lost interest.

[simo]

Ahh, different bike. My friends one had been seriously stuffed with by Pete Sales (Total motorcycles in Palmy north) silly big carbs & new inlets welded on at steep angle. Pity he sold it but it bit him (that whole close the throttle on a big single thing) & he lost interest.

Whats the "Close the throttle on a big single" scenario? I know V-Twins are no problem, but do singles have a twitch when you do this?

[F5 Dave]

If you're a bit ham fisted with a high compression single. In the same manner that they can come on power abruptly. Plenty of people race singles with no probs. They just make sure they don't change down a bunch of gears & let go of the clutch with reckless abandon.