aka_Gilo Posted May 30, 2021 Report Share Posted May 30, 2021 (edited) Changed the OE levers on my 790 Duke last year for adjustable Puig levers. First ride out the front brake seized on at about 80mph on a dual carriageway, luckily I just made it across onto the hard shoulder where I waited for the fluid to cool down before riding (slowly) home. I like to set the bite point just as I start to pull the lever, figured it was down to me setting it too far out and not allowing enough play for the fluid to heat up. I’ve subsequently changed the OE pads for EBC HH, better initial bite and feel. A few times since the front brake has seized on again, so I’ve had to set the bite point further in than I’d like (with the risk of crushing my fingers - only ever use 1 or 2 on the lever - against the bar under heavy braking), plus always carry Allen keys now I so I can adjust the lever if I feel the brakes starting to seize on. No issues for the last few rides, then last weekend I was out and having done about 120 miles with no issues the brake seized on after a steep descent, though not particularly heavy braking. Pissing me off now, can’t carry on like this and I don’t feel comfortable having the bite point so near the bar. Fitted plenty of aftermarket levers and pads to other bikes and never had any issues. Any suggestions? Edited May 30, 2021 by aka_Gilo 1 Quote Link to comment Share on other sites More sharing options...
chocyboy Posted May 30, 2021 Report Share Posted May 30, 2021 Back to the standard levers? 8 2 Quote Link to comment Share on other sites More sharing options...
srad34 Posted May 30, 2021 Report Share Posted May 30, 2021 Are they genuine Puig levers or possibly knock off as the fault seems like something you can get with cheap aftermarket levers. As Choccy said, put the OEM lever back on and see if that sorts it, once you have re-bled the system.... 3 Quote Link to comment Share on other sites More sharing options...
Alex_H Posted May 31, 2021 Report Share Posted May 31, 2021 4 hours ago, srad34 said: Are they genuine Puig levers or possibly knock off as the fault seems like something you can get with cheap aftermarket levers. As Choccy said, put the OEM lever back on and see if that sorts it, once you have re-bled the system.... This, some of the look alike levers press on the master cylinder piston ever so slightly when fitted causing exactly the issue described. Ask me how I know...😂 3 Quote Link to comment Share on other sites More sharing options...
dansp1 Posted May 31, 2021 Report Share Posted May 31, 2021 Just dress a little material off the lever where it contacts the piston, compare it to the original. if the piston doesn’t fully return it will build up residual pressure in the system 4 Quote Link to comment Share on other sites More sharing options...
lorenzo Posted May 31, 2021 Report Share Posted May 31, 2021 Some folk off here may remember me having this issue around cartagena after I swapped to some new levers. There needs to be a tiny little air gap between your lever (when it's in its resting position) and the plunger on the master cylinder. If the lever itself is resting on the plunger it'll cause just a tiny amount of friction. I guess this all goes into some sort of cyclic feedback loop, the pads get slightly hotter, the fluid & pads expand a bit, which causes them to get a bit hotter, which causes more expansion and then at some point you stop really abruptly. Those who watched me come to a halt at the side of the track, and my own testes from compressing against the tank, will remember this well. I was using iffy knock-off chinese levers, where the bit that pushes the plunger has a cut out in it, a little pocket, that sits against the plunger but shouldn't be in contact with it. On these levers that part with the pocket cut out had rotated so that it was just resting on the plunger, the pocketed area was about 90 degrees from being against the plunger. It didn't feel like my brakes were on much, a tiny bit of drag maybe, but they clearly were. As soon as I rotated the bit that pushes on the plunger and got it in the right place, all was sorted. I suppose a really easy way to test things would be to put your bike up on a front paddock stand, take the lever off altogether, spin the front, and see how much brake drag you have, then fit your new lever and make sure that the drag hasn't increased at all. If it has, you've still got your problem. 2 Quote Link to comment Share on other sites More sharing options...
TLRS Posted May 31, 2021 Report Share Posted May 31, 2021 (edited) Long story short, lever pushes piston, blocks tiny hole that’s there to let the fluid expand into the reservoir when it heats up. Or hole is blocked by dirt. Things that could increase ‘play’: -air in system obvs. Knowing possible air traps in the system helps. Could be in the calipers or in banjo bolts. No bubbles coming out is no guarantee. -bendy lever -bendy installation of the master cilinder. If there’s an arrow and or ‘up’ on the strap, that’s the side you need to tighten up first. There will be support from the whole width of the mc and strap. This reduces flex between mc and bars. Assuming there are no other weird problems. Misalignments etc. Wrong ratio calipers/mc. Pads with more bite ought to help. They will brake as much as original but with less pressure at the lever. Less pressure means less loss (flex). Is my understanding anyway. Edited May 31, 2021 by TLRS 2 Quote Link to comment Share on other sites More sharing options...
Jimmeeh Posted May 31, 2021 Report Share Posted May 31, 2021 18 hours ago, srad34 said: Are they genuine Puig levers or possibly knock off as the fault seems like something you can get with cheap aftermarket levers. As Choccy said, put the OEM lever back on and see if that sorts it, once you have re-bled the system.... Not just knock-offs. A customer at shop I worked got some ASV levers for his ER6. Had brakes jam on. I know PPL were spoken to about it. Don't recall the outcome unfortunately. Think I'd had enough of the bike trade by that point. 1 Quote Link to comment Share on other sites More sharing options...
aka_Gilo Posted May 31, 2021 Author Report Share Posted May 31, 2021 Cheers all. Got the levers from a trusted source I've used before, so pretty confident they are kosher, but then again fakes are very good now. I'll remove the levers and compare them to the OE ones, see if I can work out what is causing the issue. If no joy I'll stick the originals back on. 2 Quote Link to comment Share on other sites More sharing options...
aka_Gilo Posted June 1, 2021 Author Report Share Posted June 1, 2021 7 minutes ago, sev said: Did you bleed the master after you fitted the lever? No, never have when changing levers. How would air get in? Never occurred to me to do so tbh. Quote Link to comment Share on other sites More sharing options...
coombehouse Posted June 3, 2021 Report Share Posted June 3, 2021 When I had my Suzuki master cylinder recall done, the dealer told me of a similar issue with asv levers on 1 bike they had done the recall on. 1 Quote Link to comment Share on other sites More sharing options...
Evilchicken0 Posted June 5, 2021 Report Share Posted June 5, 2021 It probably is the lever but just in case check the caliper pistons are clean and will move back ok. 1 Quote Link to comment Share on other sites More sharing options...
bignige Posted June 6, 2021 Report Share Posted June 6, 2021 I'm hoping you're not dead and have put the original lever back on. 🤞 1 Quote Link to comment Share on other sites More sharing options...
aka_Gilo Posted July 21, 2021 Author Report Share Posted July 21, 2021 So….an update. After posting this I refitted the OE levers. That got rid of the heating up / locking on issue, but the bite point moved right back to just before the lever hit the bar. Usable but a pain as I’ve only used 2 fingers for braking for decades, so felt very odd to have to use 4 to avoid trapping them. I tried to adjust the bite point but the Allen bolt would not budge and I was on the verge of rounding off the head trying (suspect a shitload of thread lock). As I had the annual service due in July I left as was as the bike was rideable and I had a working front brake. Took the bike up for the service a few weeks back (90 mile journey) and there was virtually no pressure at all - reckon I had about 30% of usual braking power as the lever hit the bar. A careful trip to the dealer using engine braking and the rear brake a lot more than usual! Explained all this to the dealer - when I went back to pick the bike up they had replaced the brake fluid and bled the system. They could find no air in the system or any fluid leaks, yet bite point back to just before the bar was as good as they could get it. Their, and my, conclusion was that I must have a faulty master cylinder so they have ordered me a new one under warranty and will pick the bike up to fix it when the part is in. I rode it home as I did have working brakes, albeit not right. So hopefully the new master cylinder will fix it, but it’s a new one on me. With no air in system and no leaks not sure what else can be causing this. 1 Quote Link to comment Share on other sites More sharing options...
426hemi Posted July 21, 2021 Report Share Posted July 21, 2021 (edited) 22 minutes ago, aka_Gilo said: So….an update. After posting this I refitted the OE levers. That got rid of the heating up / locking on issue, but the bite point moved right back to just before the lever hit the bar. Usable but a pain as I’ve only used 2 fingers for braking for decades, so felt very odd to have to use 4 to avoid trapping them. I tried to adjust the bite point but the Allen bolt would not budge and I was on the verge of rounding off the head trying (suspect a shitload of thread lock). As I had the annual service due in July I left as was as the bike was rideable and I had a working front brake. Took the bike up for the service a few weeks back (90 mile journey) and there was virtually no pressure at all - reckon I had about 30% of usual braking power as the lever hit the bar. A careful trip to the dealer using engine braking and the rear brake a lot more than usual! Explained all this to the dealer - when I went back to pick the bike up they had replaced the brake fluid and bled the system. They could find no air in the system or any fluid leaks, yet bite point back to just before the bar was as good as they could get it. Their, and my, conclusion was that I must have a faulty master cylinder so they have ordered me a new one under warranty and will pick the bike up to fix it when the part is in. I rode it home as I did have working brakes, albeit not right. So hopefully the new master cylinder will fix it, but it’s a new one on me. With no air in system and no leaks not sure what else can be causing this. Check that the backing of the pads hasn’t warped as it can cause this, the brake pressure needs to take the flex out of the pads before they work and when you release the brakes the flex pushes the pistons back to far. Take the calipers off and put a solid block between the pistons and try them. Edited July 21, 2021 by 426hemi 2 1 Quote Link to comment Share on other sites More sharing options...
aka_Gilo Posted July 21, 2021 Author Report Share Posted July 21, 2021 13 minutes ago, 426hemi said: Check that the backing of the pads hasn’t warped as it can cause this, the brake pressure needs to take the flex out of the pads before they work and when you release the brakes the flex pushes the pistons back to far. Take the calipers off and put a solid block between the pistons and try them. Interesting - not heard of that before - cheers. Quote Link to comment Share on other sites More sharing options...
426hemi Posted July 21, 2021 Report Share Posted July 21, 2021 15 minutes ago, aka_Gilo said: Interesting - not heard of that before - cheers. I’ve had it on a set of nissin’s, the pads only need to warp a few thou to cause it. 2 Quote Link to comment Share on other sites More sharing options...
TLRS Posted July 23, 2021 Report Share Posted July 23, 2021 That’s a very good point! Maybe ‘dished’ brakediscs could cause this too. Unless pads wear to accommodate.. 1 Quote Link to comment Share on other sites More sharing options...
chancho196 Posted July 30, 2021 Report Share Posted July 30, 2021 With any aftermarket lever, you need to make sure there is slight freeplay between the piston and the rubbing surface of the lever itself. Span adjustment has nothing to do with that basic princicple. If that piston cant go back to its resting position, you can be in for a world of pain - glad to hear you were able to get off the road. Regarding the poor lever feel now, it could be a faulty master cylinder, but I have my doubts. Are your lines fully braided, or are there flexi-rubber sections? If so, you could put a brake pipe clamp on the hoses to check parts of the system. Fitting one close to the master cylinder banjo bolt for instance will soon prove if the issue lies there - a good master cylinder will be absolutely solid with a clamp in place. If they are all braided though, that method doesnt work. Due to the heat induced at the calipers, pads and discs, they could all be causing issues. The rubber seals that go around the pistons themselves pull the pistons back to a certain degree everytime you release the brakes. They may have been damaged when the brakes got excessively hot. Poor feel at the lever is very often down to them sticking to the piston rather than sliding over them. The old method of zip-tieing the lever to the bars overnight ususally helps for the next day because the seals eventually conform to where the piston sits, but as you ride they go back to where they were. Removing, cleaning and lubricating the seals will generally sort that out. As mentioned earlier, the pad material as well as the backing plate of the brake pad itself could be out of shape, it all adds to the effect. The slightest defect down at the wheel has a relatively large effect on the small amount of travel we want to feel at the lever. Quote Link to comment Share on other sites More sharing options...
chancho196 Posted July 30, 2021 Report Share Posted July 30, 2021 Just noticed it's on a 790, I actually got asked about one of these the other day but havent seen the bike as yet. Completely standard, it has started to get air in the system without anything being changed on it. The only reason I know is that when he applies the brake first thing in the morning, air bubbles start to rise in the reservoir. He has flushed and bled the system but it hasn't made any difference. I'll see if he has sorted it out. Quote Link to comment Share on other sites More sharing options...
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