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General Discussion / Re: ABS
« Last post by Borsig on Today at 09:53:18 AM »I got a message to say that FabioQ has asked whether I sorted the brake problem on my Stelvio, well yes and no. I took it to my Guzzi dealer who ran through he brakes with Navigator and cycled the ABS several times, prior to the visit I did some research, studied the Guzzi ABS diagram and came to my conclusion. The ABS cycled as expected but always returned to a spongy brake so I discussed my findings with them and they agreed as there was no real other option.
I hope you are ready for this as its a bit technical. Basically there are 2 solenoid valves in the ABS, the first is normally open and the second closed, after this is a spring loaded buffer chamber then the pump. The fluid is normally stopped by the closed valve when ABS is not activated, when it is the valve opens, the fluid to the pump is pressurised and escapes into the buffer chamber, ABS shuts the first valve and pumps a small amount from the buffer back into the brake line, causing a long pull in on the lever followed by it being pushed back out. This happens rapidly as long as the lever is held and the wheel slips. In my case the second valve is not closing so fluid passes into the part that should only be in use when ABS is activated, the buffer chamber fills causing the long pull on the lever then the brake works as normal.
The cure is a new ABS unit. As the rear ABS is a second circuit and unaffected and I don't like ABS anyway, I opted to have hoses made and bypassed the ABS for the front only. The brake now works better than it ever has, I do not have warped rotors or air in the system, I was let down by technology. If this happens to you and you choose to bypass it, be glad that the bike does not have sensors in the ABS unit and is totally unaware that I have bypassed it, the light comes on as normal and goes out after the wheels have turned, so no issues at all, and the rear still has ABS.
Unfortunately I seized the engine not long after fixing the brakes, the oil pump gear in theses engines is plastic on a metal center, mine came loose on the center, twisted and had its teeth stripped causing a big end seizure. I did not notice the warning on the display as its a red triangle with a picture of an oil can that is just not visible on a bright morning, the first I knew was the engine feeling rough. This cost me a used crankshaft from Germany, a seal and a few gaskets, and a new gear of course. I did it myself and its been running fine ever since. As a precaution I will be replacing this gear if I still own the bike in 2026, 5 years is probably as long as I want to trust a plastic gear running in hot oil all the time. I spent the next 2 months of riding watching the display like a hawk, a glance every 10 seconds or so, then I gave myself a good talking to and now treaty it normally and don't look for warnings. If anything nasty happens I can fix it.
I hope this helps anyone with strange brakes, I seem to have become a bit of an expert on the Guzzi system, message me if you want to know anything.
I hope you are ready for this as its a bit technical. Basically there are 2 solenoid valves in the ABS, the first is normally open and the second closed, after this is a spring loaded buffer chamber then the pump. The fluid is normally stopped by the closed valve when ABS is not activated, when it is the valve opens, the fluid to the pump is pressurised and escapes into the buffer chamber, ABS shuts the first valve and pumps a small amount from the buffer back into the brake line, causing a long pull in on the lever followed by it being pushed back out. This happens rapidly as long as the lever is held and the wheel slips. In my case the second valve is not closing so fluid passes into the part that should only be in use when ABS is activated, the buffer chamber fills causing the long pull on the lever then the brake works as normal.
The cure is a new ABS unit. As the rear ABS is a second circuit and unaffected and I don't like ABS anyway, I opted to have hoses made and bypassed the ABS for the front only. The brake now works better than it ever has, I do not have warped rotors or air in the system, I was let down by technology. If this happens to you and you choose to bypass it, be glad that the bike does not have sensors in the ABS unit and is totally unaware that I have bypassed it, the light comes on as normal and goes out after the wheels have turned, so no issues at all, and the rear still has ABS.
Unfortunately I seized the engine not long after fixing the brakes, the oil pump gear in theses engines is plastic on a metal center, mine came loose on the center, twisted and had its teeth stripped causing a big end seizure. I did not notice the warning on the display as its a red triangle with a picture of an oil can that is just not visible on a bright morning, the first I knew was the engine feeling rough. This cost me a used crankshaft from Germany, a seal and a few gaskets, and a new gear of course. I did it myself and its been running fine ever since. As a precaution I will be replacing this gear if I still own the bike in 2026, 5 years is probably as long as I want to trust a plastic gear running in hot oil all the time. I spent the next 2 months of riding watching the display like a hawk, a glance every 10 seconds or so, then I gave myself a good talking to and now treaty it normally and don't look for warnings. If anything nasty happens I can fix it.
I hope this helps anyone with strange brakes, I seem to have become a bit of an expert on the Guzzi system, message me if you want to know anything.
