Suzuki GT500 brake bleed problem

[Doug_R5C]

Hi, I don't know if anyone's come across this before but when I try to bleed my brakes, all dry following a rebuild, the master cylinder feels like it's hydraulic locked.  As background, the master cylinder was horrible, nearly empty and full of years of gritty debris, so I rebuilt it with a kit that was supplied for a GT500 but was meant for a Tokico, I believe most GT500s use Asco.  The rubber parts of the kit transferred to the existing piston, and it goes through the pumping motion fine when empty.  The brake line appears to be a nearly new replacement rubber hose, as per stock, and the caliper is a barely used Tokico.  I stripped the caliper and red-rubber-greased it, and it appears ok.

As belt and braces I installed a bleed nipple banjo bolt at the master cylinder, the master cylinder pumps ok to the bleed nipple, but when I tighten it and loosen the caliper bleed the master cylinder doesn't work at all, the lever is solid.  I'm left questioning the brake hose, but can't get my head around why it won't pass any fluid at all.  It possibly ingested some of the master cylinder debris, but enough to completely block the line?

Any ideas?

[tore]

Sounds like the bleed nipple banjo bolt does not match the brake hose banjo fitting. Did you get any brake fluid at all  from the caliper or hose towards the caliper?

[Doug_R5C]

The master cylinder works when the top bleed is open, it won't work when the top is closed and the caliper bleed is open.  I've just removed the top third of the rubber hose, and some mahogany-brown fluid dripped out, I managed to get a fine wire through it, and more brown fluid dripped out.  I can blow through it now, which is an improvement, so now I have to prime the system again, which seems to take forever.  I suspect the lower part of the hose is still blocked, I tried reverse filling it with a syringe but it felt solid.

[tore]

Is the hoses old? Split internally is common in old hoses. That causes total blocking. Brake hoses older than 15 years should be replaced to avoid such issues

[Doug_R5C]

The hose and caliper both look new-ish, they are certainly not the original parts, no corrosion on the exterior metal parts at all.  I've ordered a Hel replacent line, but with the three day weekend it will probably be later next week before it arrives.  Annoying really as the bike would have been ready for it's first UK ride.  My last job was to free up the clutch, revving the bike on the mainstand and hitting the rear brake solved that just now. 

I had a GT500 from new back in 1976 and I don't recall the front brake being that effective when it did work, hmmm, I wonder if I could get away with riding it around the block with just a rear brake :-) 

[Doug_R5C]

New brake line solved the problem. 

I took it for it's first spin around the block, it is registered and insured now.  The seat is away being reconditioned, so I was sat on a piece of soft foam, it was like riding a chopper, but it threw up some new issues.  Fuelling was horrible, ok on choke but fighting to keep it running when off choke, until I hit around 5,000 revs and it took off up a hill like a scalded cat, the local joggers club didn't look best pleased at the carpet of white smoke I left behind, I couldn't help but chuckle a bit. 

The vibration is way worse than the one I had in 1976, so I checked the three engine mounts, the lowest one was ok, the front one I could spin the spacer that the spindle goes through, between the rubber mounts, and after taking the sprocket cover off, the rear engine bolt was tight enough but the spacer between the chain runs was loose and rattling around.  I'd say the gap was about the size of the headstock washer.  I don't know if it's the wrong spacer or rattling around has worn it away, it seems a lot lighter than I expected.

Is anyone familiar with this engine?  I don't think the method of mounting to the frame changed from T500 to GT500, and I've read three manuals that are all a bit vague about putting the engine back in, including the genuine Suzuki manual.  The small spacer is obviously wrong, but I'm not sure if the front spacer movement just means the rubber mounts have shrunk.

[tore]

Have you checked this site?
http://www.ozebook.com/compendium/gt500parts/gt500parts25.htm

[Doug_R5C]

I have, thanks.  If you look at item 21, that's the spacer that turns on the front top mount, it sits between the two bushes, parts 25 and 25, with the mounting bolt passing through the centre, I'd expect it to be a tight fit.  Thinking about it, the centre of the bushes is probably metal, so it wouldn't matter if the rubber shrank a little, it would be tight on the metal.

The rear spacer doesn't appear on that diagram, at least not the correct place, I think part 24 is wrongly pictured on the right side.  The engine sits snugly against the frame mount on the right side of the frame, there's no room for a spacer there.

Part 27 I believe is the plastic spacer/cushion for the gearchange, it's missing on my bike.

It's like a detective story, trying to discover what's happened during it's life :-)

[Doug_R5C]

I've just jacked the rear of the engine up and the bolt came out as though it was installed yesterday, virtually no sign of corrosion.  There's two spacers, a solid metal one, and nylon spacer that covers it and presumably deflects the chain if it is loose.  Hopefully the picture will help, the main spacer is loose though, not just the age-hardened nylon one.