I'm having the same problems as in the post below. I've flushed and filled my system and I've replaced the slave cyclinder with a brand new one from Honda. The posts mention a relief port in the master cylinder being plugged, i have the master cylinder off and i can't find the relief port mentioned. Can anyone identify the location?
New CLutch , Still slipping.....
« on: September 16, 2007, 12:44:49 PM » Quote
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Recently put in new Barnett Clutch and Springs. I get good hard grab when I first start out. After I'm on the highway for about 20-25 miles it starts to slip in 5th and 6th and gets progressively worst, sometimes to the point were I'm barely getting the bike rolling out of first by the time I get off the highway.
Here's how I get home. I pull over, shut it down, and open and shut the bleeder valve for the clutch lever really quickly. It squirts a small amount of fluid. I fire the bike up and it's fine for another 20-30 miles.
I'm at a loss. Any thoughts??
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1982 v45 Magna
Greg Cothern
Super Moderator
Full Throttle Contributor
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New CLutch , Still slipping.....
« Reply #1 on: September 16, 2007, 05:43:38 PM » Quote
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Sounds like the slave cylinder is in need of a rebuild.
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Greg Cothern
00 Valkyrie Interstate
96 Magna project bike
Previously owned:
87 Super
96 Magna
"Pay it forward"
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Posts: 35
New CLutch , Still slipping.....
« Reply #2 on: September 16, 2007, 06:40:19 PM » Quote
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Thanks Greg. I was hoping it would be something simpler. Just my luck. Well this old bike will have a lot of new parts by the time I'm done.
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1982 v45 Magna
Greg Cothern
Super Moderator
Full Throttle Contributor
Posts: 2393
New CLutch , Still slipping.....
« Reply #3 on: September 17, 2007, 04:05:36 AM » Quote
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It will be ready for another 20+ years of fun!
I have seen this same situation happen on the front brake master cylinder on a V65, causing the brakes to progressively grab and not release. There is a very tiny hole in the bottom of the resevour that is virtually a pressure relief for the back side of the piston thus allowing it to return easy.
Good luck, let us know if we can help...
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Greg Cothern
00 Valkyrie Interstate
96 Magna project bike
Previously owned:
87 Super
96 Magna
"Pay it forward"
John Luttrell
1st Gear Contributor
Posts: 201
New CLutch , Still slipping.....
« Reply #4 on: September 17, 2007, 06:53:09 AM » Quote
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The return port in the master cylinder is more than likely clogged with some trash/rust. Flush out the system, refill and bleed and it should be ok. The reason it acts up after warm up is that with the clog, there is no where for the fluid to go during normal heat expansion except torwards the clutch rod, which will slowly disengage the clutch plates.
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John Luttrell
2001 VF750c Magna
http://redneckdrifter.bravehost.com/
What kind of oil are you using? I had the same problem, if I got on full throttle in 5th or 6th gear it would slip. I flushed the fluid in the clutch system and it still happened. I ignorantly was using standard motor oil, which as this site pointed out to me one day, has anti-friction additives. I change to a synthetic specifically for motorcycles and have not had that 5th/6th gear slippage since.
Just a thought since it seems you have gone through the obvious steps already.
I changed the oil in June. Used Golden Spectro Heavy Duty Synthetic 20W50. Problem was existant before oil change. Have rebuilt Master cylinder also. Bike was sitting in climate controlled storage for 10 years before i purchased. Rebuilt brakes, carbs, etc. Runs great except for this problem. Problem is definitely heat related and seems to be related to the expansion of the oil in the slave cylinder. I can ride to work on the cool mornings with no problems, afternoons with a ride up 75 at 65-70 mph, starts to slip. The farther i go the worse it gets. I've had to push to get moving. The bike is not overheating. I can stop and let pressure off of slave cylinder and make it home with no problem. I have noticed that as it gets to the point of slipping all of my free play goes away and clutch does not engage until almost fully released and the clutch gets harder to pull in. After i let the pressure off my free play comes back for awhile and then slowly starts to go away again as the oil expands again. Using Prestone DOT 3 fluid. Can anyone explain how the pressure generated from the heat of the engine is supposed to disapate from the slave cylinder? It has to be able to expand back to the master cylinder but for some reason mine is not. Is there a relief in the master cylinder or is the oil supposed to get back past the piston seals?
Quote from: Rono on October 06, 2008, 07:37:27 PM
I changed the oil in June. Used Golden Spectro Heavy Duty Synthetic 20W50. Problem was existant before oil change. Have rebuilt Master cylinder also. Bike was sitting in climate controlled storage for 10 years before i purchased. Rebuilt brakes, carbs, etc. Runs great except for this problem. Problem is definitely heat related and seems to be related to the expansion of the oil in the slave cylinder. I can ride to work on the cool mornings with no problems, afternoons with a ride up 75 at 65-70 mph, starts to slip. The farther i go the worse it gets. I've had to push to get moving. The bike is not overheating. I can stop and let pressure off of slave cylinder and make it home with no problem. I have noticed that as it gets to the point of slipping all of my free play goes away and clutch does not engage until almost fully released and the clutch gets harder to pull in. After i let the pressure off my free play comes back for awhile and then slowly starts to go away again as the oil expands again. Using Prestone DOT 3 fluid. Can anyone explain how the pressure generated from the heat of the engine is supposed to disapate from the slave cylinder? It has to be able to expand back to the master cylinder but for some reason mine is not. Is there a relief in the master cylinder or is the oil supposed to get back past the piston seals?
Did
you personally rebuild the master cylinder with a kit?
Yes i personally rebuilt it with a kit.
OK.
It's obvious there's back pressure that builds up over time in this system which indicates that there is an intermittant one way restriction in the flow of the brake fluid.
I have a hard time sticking to the philosopy, but the fact is K.I.S.S. (Keep It Simple, Stupid) usually ends up being the answer for me with motorcycle mechanical issues.
Please start back with the hole in the bottom center of the fluid reservoir. It is dead center in the bottom and very small. I know on one or more of my bikes, there is a small metal baffle covering the actual hole so that fluid coming out under pressure when the clutch handle is released will not spray in a stream straight up out of the reservoir. This hole is the gateway for the fluid to flow into and out of the clutch hydraulic system and it must be kept clean of any restriction. Open up your reservoir, find the hole and look at it first to see if there is a metal baffle over it and that the baffle is not blocking the hole. If the hole is exposed, use a fine wire to probe the hole to free up any restriction. Work the clutch lever several times and see if you observe any fluid motion when the lever is relaxed. This is when the fluid should be flowing back into the reservoir because the hole will now be uncovered by the cylinder piston. When working the lever, you should be able to see the piston and cup (seal) moving through the hole in the reservoir. Also, the lever action should be smooth in application and relaxation. If there is any binding in either direction you have to find out why and correct the issue.
The reason I asked about your rebuilding process is that you must be careful to install the piston cup(s) in the right direction on the end of the piston. The concave surface of the cup should face the fluid. If the cup is in backwards or the cup lip rolls over when it is assembled, it could restrict the movement of the piston to its relaxed position which over a period of working the clutch lever could cause a residual level of pressure buildup forcing your clutch to release pressure on the discs and slip when under load in higher gears. This could also exist if you have some piece of trash floating in the fluid in the reservoir cylinder that occasionally backs up and clogs the hole in the reservoir. If anything is causing the piston/seal assembly to not properly seat out of the way of the hole in the reservoir, back pressure will remain in the system and you don't want that unless you are trying to disengage the clutch.
Check the hole first and if you see no issues with clogging, I would recommend disassembly of the master cylinder, examination of the cups and reassembly. Make sure that you coat all of the cup and piston assemblies with new brake fluid and carefully reinstall them in the bore not rolling over the lips of the cups. Bleed the system down one more time with clean brake fluid (DOT4).
Now go ride and see if if behaves as it should.
I agree with you 100% on the back pressure. I rode it to work yesterday. 23 miles 1 way. In the morning i had absolutely no problems. In the afternoon i shoot north on US 75 from 635 in Dallas to Plano parkway. By the time i got about half way to Plano Parkway i went to pass someone and it was slipping. By the time i got home i had no clutch engagement at all, i had to push it into my driveway. I got off the bike with the clutch fully out and the bike in first gear and it would not go at all. I immediately grabbed a wrench and rags and bled the banjo fitting. I then had full clutch action again. So as soon as i release the back pressure things are normal until it build up again. I had taken the master cylinder back apart last weekend. I completely cleaned everything again. The 1 hole in the bottom is clear. I install the guts as in the pictures i can find in my manual and online in microfiche. From the banjo fitting end it starts with the wide end of the spring then the piston cup with the concave toward the banjo fitting, the cup has a nub on it the fits into the small end of the spring to keep it in place, the flat face of the cup buts up to the piston. On the piston on the groove just inside the stop point the secondary cup is installed and it is also concave side to the banjo fitting. You then have the stop washer and circlip the the actuator lever. It does not have the baffle covering the hole in the bottom. I'm certain on the install of the spring and first cup but i don't know for sure about the location of the second cup on the piston.
thanks for all of your inputs
Have you ever removed the line and checked it for obstructions? I have had brake lines disintergrate on the inside, swell and restrict flow. Just a thought..
Very interesting idea! I will check that tonight. Thanks.
When your doing all of this, if you have a way back flush the system with a syringe, if you don't have a syringe pay a visit to your drug store. If the spring is suppose to help push the cup back try stretching the spring and see if that helps.
As you know, both slave and master need to work in unison for this to operate.
When i got home from work i pulled the cover on the master cylinder and verified the hole. It is open. With clutch lever fully released you can see the first convulution of the screw area on the piston. You can never see the cup as it is already past the hole. As you pull the lever in you see the entire length of the piston go by to the point of the second cup that seals the end of the piston close to the lever. I'm thinking this is why i'm getting the back pressure, the cup on the end of the spring never even comes close to the hole to let pressure return. i'm wondering if the aftermarket kit i used may be wrong for my master cylinder? Could i have the wrong piston, too long? does anyone have a length for the correct piston? Should i go to the stealer for a replacement?
There is the tiny'est hole you ever did see in the bottom inline with the piston back further for relief.. Take a very small wire and go poking around should be there.
If you were to better describe where the relief hole is would it closer to the banjo fitting or toward the clutch lever end of the master cylinder? Does it go straight down into the bore?
When i look at my Clymer manuals i see 2 different master cylinders depicted 1 with a banjo fitting that is at 90 degree angle to the bore of the cylinder in the master cylinder and the other the manual claims to for for '87 on bikes with the banjo fitting straight out the end of the cylinder bore. Mine matches the pictures of the 87 on. i've noticed from the parts fiche that an 87 takes a different part number than a 85/86. Same thing for the front brake master cylinder. My bike was built in 11/85 but i'm wondering if it could have gotten some replacement parts in it's life prior to me.
ON the V65 we had a problem with it was a centimeter or so towards the outlet side of the cylinder and in the bore line perpendicular going into the bored chamber that the piston lives in.
Well i think the relief hole has resolved the problem. Cleared out hole with a pin drill. Flushed and filled system with new fluid and rode to work this morning with no problems. i'll know for sure on the ride home.
Thanks to everyone who responded with input. I've learned a lot from this experience.
I have the same problem and I am planning to rebuild my master clutch. I just want to say how awesome this forum is. You can't find this wealth of infomation for a hond magna any where elese. Thanks guys