84' VF750 Low idle, Stuck Brake piston

My 84' interceptor has a really low idle RPM lately, it was running perfectly a week ago and idled at 1100RPM regardless of tempreture and choke. I started her up yesterday and it idles at barely 600RPM, and when I remove choke to about 60% it dies. I do notice the oil light comes on time to time but I have a feeling its not just an oil issue.

Next problem, I've disassembled the rear brake unit but the pistons are completly stuck. I've tried using compressed air but no luck, it seems both piston gaskets are lodged between the piston and the brake unit. If I were to use hydralic pressure to push it out will it push it all the way out?

In addition the cymers manual does not state weather the master/reserve cylinder cap needs to be closed or not when bleeding the braking system.

 

try running some seafoam through the tank. check your oil level , you might need a new oil pump, but you'll have to find out how much oil pressure your bike is putting out now or it could just be a bad oil pressure switch. I'd check that first. easy and quick way is to get another caliper from say E-bay. leave the top off but make sure that it stays full. if not you'll have to start all over (bleeding) if you get air in the line.

 

Hello

Hey

For the first low rpm/low oil simple as that and your rpm can be set right side of the carbuateors I think don´t remember there is a knap you can turn to set the idle.But I would think that you choke is set wrong.And for the bleeding okay to keep the cap on the master cylinder open as long there is enough fluid in the box gotta watch out for that otherwise you will just pump air in.Take a tube from the Brake unit and but into a glass with a brake fluid so the tube is always under then you just pump and the air cannot get in from either sides.If you do the front you have to do the booth brakes unit not just one.Just a reminder.Hope this helps

Best regards

Gunnar

 

Use the hydraulic pressure to push out the pistons.
One piston will come out first. Put a piece of thin wood to keep it from coming all the way out. Continued pressure will push the other one out.

Another method is to hook up a grease gun in place of the bleeder valve and pump it out that way. Makes a mess, but no damage.

 

Oh good news, the low idle was somewhat fixed by letting it warm up for a good 20 mins after an oil change to 10W-30 synthetic Q power. I can play with the choke from rich to low without it stalling out completely so I see a noticable improvement simply from changing the oil. I also followed your advice on bleeding the brake system and I can do it like a pro now. So major thanks for that

Bad news
I've managed to use hydrualic power to pump out ONE piston, the wood method didn't work unfortunately, i guess the piece of shim i had chosen was too thin and it just gave way. I don't think suppose I can re seat the one thats out all the way back and try again since I don't have the proper seals for it yet.

 

You certainly can try it again. Just crack the bleeder when you push piston back in (C-clamp) and make sure that it doesn't go cockeyed on you - I've done it.

Of course, once it's in, you have bleed the system again and start over.

 

Ok so I've finally gotten both out by wrapping my vise grips with a lot of electrical tape, I wiggled them out, took forever but it was well worth it.

From my understanding there are two seals, the two outer ones that are thin about a 1mm thick and one inner one thats about 2-3mm thick. I noticed that the wear between the two smaller rings are very un even, it seems at though one of them was pumped out along with the piston. What steps should I take to reinstall seals?