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PC800 Clutch Bleed question

11K views 16 replies 7 participants last post by  kaiser_will_1967 
#1 ·
First off, just picked up a cherry 89 PC800. The only thing the previous owner was not fully truthful about was the hydraulic clutch...said he had to bleed the slave cylinder every 2 weeks or so. I have had to bleed it every time I take it for a ride. If I don't either the clutch will not engage until lever fully released or will not engage at all.

I bled out the old fluid and filled the master cylinder with new fluid, using a MightyVac hand vacuum.

Now, cannot get any pressure built up in to engage at all. The clutch lever is loosey goosey.

I am about to trailer it to my Wing mechanic. Suspect the only fix is to rebuild the slave cylinder, like the valve plunger is stuck in la-la land.

Has anyone experienced this common PC800 problem? What has been a working fix for you?
 
#2 ·
Probably the return hole in the master cylinder is plugged. Take the cap off and suck the fluid out, in the bottom should be a little metal cover, take it out. Under it is a little hole with a tiny hole in the bottom of it. Using a piece of very fine wire, like a wire brush bristle, push it down through that tiny hole.
 
#4 ·
How was the old fluid- grey and milky- a decade old? and the rubber cover on master? fits or softened by age and bad fluid?
If it was all new fluid then its been bleed many times while not repairing~

Try burping the system at the master cylinder, the banjo bolt where line to base attaches.
Manual pump a few times then crack open bolt- with rag surrounding- to prevent bad things happening Repeat as needed till lever gets action.
Air likes to get in there, and it will never pump up till thats removed

Buy a slave cyl rebuild kit and pop that thing out.
Worst case = the interior bore is pitted = then you buy a used one and throw that kit on it!

also do the trick with the return hole as noted by others

Once thats all good- Annual clutch line and brake system FLUSH (both use dot4) is recommend. MAX is 2 years between, smart money does it every year.
 
#6 ·
So the bleeder screw was rusted in place? or the cover on master cyl res were frozen? You bled and refilled how?? Pull the slave cyl and inspect.
Buy master and slave cyl rebuild kits,,its couple of orings essentially. Get to work!
This is one of the easier things to do on a bike, my Shadow is similar in many parts to the Coaster...
Honda used few variations of any part across the line!

***Anybody near New Bern NC to lend a hand?
 
#7 ·
I found the master cylinder return port plugged, sure enough (thanks, DaveO430). I flushed the master cyl dry, cleaned out the master cyl return hole with a fine wire, broke the master cyl banjo fitting loose to relieve any air pocket, tightened down, filled master cyl with fresh fluid, vacuum bled from the slave cylinder.

I still see air in the bleeding line and the clutch handle is still loose, no pressure. How long does it take to build clutch pressure back up? I see few small air bubbles in the master cylinder as the clutch handle is moved.

The master cyl screws had been frozen solid. Lubrication and a tap with a hammer on a screwdriver did the trick.
 
#8 ·
make sure that the master cylinder is the highest point when bleeding. If you're burping the banjo bolt, then that has to be the highest point. Turn the handlebars to the right however far to get this to happen. It may take several tries at the banjo bolt to get that air out.
 
#10 ·
yeah thats what I read too- that he tried to burp the banjo with no fluid in the system?!
What was that supposed to do?
The idea is fill res with fluid, allow air to escape at first point- the banjo- then use mighty vac.

Might put a little grease on the bleeder threads, to help them seal while vac is in use

try doing it this way:
fill res, turn bars so res is at high point with bike on centerstand
pump lever 4 times- 1/2 pull in each time then hold halfway in - crack open banjo - Apply rest of pull amount of travel for lever to bar, close banjo.
Tap the res with something GENTLY as air may hide around those ports and cover, tapping will dislodge them so they go to the top
Repeat as needed to get good feel at lever, then proceed to slave cyl
At slave open bleeder 1/4 turn, attach vac hose- apply vac- watch fluid level in res, refill as needed, close bleeder- detach hose.
Never hurt to recheck banjo one more time after slave is good, add fluid to the line inside- when bars are level it will show above half in sight glass
The res contains brake fluid = is why the rag is needed around the bolt during burping = brake fluid squirts out under pressure! Eats our plastic panels!
 
#12 ·
I found the clutch pressure was built back up. It appears all is good for a test. However the PC800 won't start, acts like out of fuel but let it get down to the bottom when dinking with the clutch. Added fresh gas, but no go. Pulled the air filter and shot a bit of ether and she fires up but sputters, eventually. I am thinking the fuel filter is suspect. Previous owner probably let it set due to the clutch pressure issue, letting it get low pulled in the bottom sediment.
 
#14 ·
thats after you make sure there is no air hiding at the banjo bolt to master cyl res. if system was apart or empty for any reason
Cant bleed the system fully until you get rid of trapped air- that wont escape the normal route down thru the line
 
#16 ·
I agree- got my threads confused/crossed...someone was trying to burp banjo with NO fluid in system,,maybe this thread maybe not...hence my caveat

Been years since we discovered this `fix` on my 86 Shadow after slave rebuild,,hidden in the clymer repair book of all places! = if it wont pump up yada-yada banjo
 
#17 ·
After clearing the clutch reservoir return line port, flushing fresh fluid and vacuum bleeding through the bleeder port, it appears I have resolved the issue of air getting (or not coming out) of the hydraulic clutch system.
I couldn't road test the solution, yet, as I let the fuel tank get low and pulled crud into the carbs. After a service trip to the shop, shifting is smooth and problem-free.

Thanks, much, for the input.
 
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