Clutch still slipping under heavy accel after bleed, new steels & friction plates

[Cn4366]

Bike is a 2000 with less than 4K on the clock. Bled, new steels & plates (old ones were scorched), lever holds pressure but I put all new fluid in there about 3 months ago and it was super dirty when I bled and filled it today. It doesn't seem like there's air in the hydraulic system. Do these slip bone stock under too much load? Has Sean's muscle kit and a kerker 4-1 with comp but slipped, albeit less, when it was stock. i'm thinking I need a/m spring setup or the dd mod, but any input is appreciated.

 

[Fire-medic]

What oil? That could be it. The Shell Rotella oil is a good compromise in price, lots of guys use it. Using synthetic auto engine oil has caused problems for people, like what you are describing. ZDDP is an additive our engines need in their oil to properly work in a unit-construction crankcase/gearbox. The car oils, with their high-mileage formulas are not suitable for wet clutches.

The VMax clutch will take a lot of abuse before it begins to slip. Dirty brake fluid in such a short time makes me think your lines may be deteriorating internally. Time for replacements, I bet. I don't think dirty brake fluid would make a clutch slip, but it might make it shift poorly, as the hose internal I.D. is expanding rather than moving the clutch pushrod enough to release the clutch pressure plate, and the friction disc pack.

 

[Cn4366]

What oil? That could be it. The Shell Rotella oil is a good compromise in price, lots of guys use it. Using synthetic auto engine oil has caused problems for people, like what you are describing. ZDDP is an additive our engines need in their oil to properly work in a unit-construction crankcase/gearbox. The car oils, with their high-mileage formulas are not suitable for wet clutches.

The VMax clutch will take a lot of abuse before it begins to slip. Dirty brake fluid in such a short time makes me think your lines may be deteriorating internally. Time for replacements, I bet. I don't think dirty brake fluid would make a clutch slip, but it might make it shift poorly, as the hose internal I.D. is expanding rather than moving the clutch pushrod enough to release the clutch pressure plate, and the friction disc pack.

I was actually thinking about oil because it starts off fine when the bikes is cold. After 5 miles it only happens under heavy acceleration, with it being close to unrideable after 20. I was working at a Honda dealer when I changed it last, and put 10-30 honda oil in it. Heated oil being less viscous would explain why it gets worse as it heats up. No problem actually shifting, just slips at everything above 3k or so unless i roll on slowly. I checked when I switched the clutch and it seemed to be pushing it just fine, but if that's the case I'll switch those out as well. Whatever it is probably smoked the old clutch since the bike is such low mileage. I'll start with changing the oil, then lines, then I'll rebuild the slave if it doesn't sort itself out. Any chance it's the spring after 20 years? It barely slipped when I first got it before it gained around 40 bhp.

 

[Fire-medic]

Sean Morley has far-more knowledge than do I about the bike, but oil seems a good place to start. The slave cylinder really only comes into play during gear changes and difficult shifting could be a sign of a leaking slave cylinder, or master cylinder. Air in the lines is probably cause #1, with low fluid a close second. Those are shifting issues. The diaphragm clutch spring usually lasts the life of the bike.

 

[sdt354]

New levers by any chance? There's some built in slip with the 1/2 disk and OEM spring, built in as a precautionary measure. But your slipping could be caused by only partial engagement of the clutch. The Honda oil should be ok. Though not my own first choice.
The previous owner put Mobil 1 oil in my 89, at 12k miles. The clutch slipped until I got rid of the impregnated fibers, went DD and never had an issue again.

 

[Cn4366]

I have new levers but they haven't been installed yet. Bikes has no problems shifting, neutral is easy to find. Slipping over 3k after 20 or 30 mins of riding slower is the only issue. It doesn't slip as bad on highway. Back roads it slips pretty badly, from a dead stop it takes a while to get to speed, like what it should take to do a quarter mile.

 

[MaxMidnight]

It would seen that line pressure is building up either as you use the clutch or as the fluid heats up and expands.
This will cause the clutch to slip.

My first port of call would be the master cylinder to ensure that everything is free and that there hasn't been a build-up of crud which is preventing the fluid returning to the m/c.
As mentioned above this could be from deteriorating lines.
Unless the slave is also crudded up I don't think this would be an issue.

With regard to the half plate mentioned by Steve above, my understanding is that it is to allow space for the spring that acts as a shock absorber when shifting...as always I'm happy to be corrected.

 

[rebeltaz83]

There is a small pin hole in the master, make sure it's not clogged, that releases line pressure. You'll need a sewing needle it's to the right of the bigger hole as your sitting on the bike. I would prolly crack the bleeder so if it does have pressure it doesn't blow brake fluid all over your bike. It's an excellent paint stripper.

 

[sdt354]

It would seen that line pressure is building up either as you use the clutch or as the fluid heats up and expands.
This will cause the clutch to slip.

My first port of call would be the master cylinder to ensure that everything is free and that there hasn't been a build-up of crud which is preventing the fluid returning to the m/c.
As mentioned above this could be from deteriorating lines.
Unless the slave is also crudded up I don't think this would be an issue.

With regard to the half plate mentioned by Steve above, my understanding is that it is to allow space for the spring that acts as a shock absorber when shifting...as always I'm happy to be corrected.

Me too, thank God you're here.

 

[HDH8R]

Fire-medic is right about the oil. I owned a 95 vmax and always used conventional oil with no slipping. I currently own a 2010 gen 2 and the bike shop I had change the oil while installing new tires used synthetic oil and almost immediately my clutch started slipping. It was worse after warming up and when under heavy roll on it would “spool”. I looked it up and in the owners manual Yamaha specifically states not to use synthetic oils. I took the bike back and they replaced the oil and it has improved but will take a few changes to get it all out. The shop acknowledged the mistake after they researched it too.

 

[tmschuller]

Hey all ! Back after a long hiatus , spinal surgery again... I have had the same issue and had given up due to fact I could not ride my bike... NOW that has changed.. My 97 will slip under hi-way speed acceleration.. new clutch and fluids, running a valvoline oil designed for motorcycles. I have not looked to see if there are any other fixes yet but this thread looks to as close as I can get to the same issues.
My other maxes would leave this one due to clutch slipping. My master cylinder seems to be working OK.. The lever has steady pressure even after it had set for a long time.
I can accelerate fine and get to speed ok but sometimes even from a dead stop I have a hard time moving at all. It does not do this often but its nice to apply the throttle and actually go somewhere and not have a bird go faster that I am..
Thanks for help/suggestions. Tim in Indiana

 

[Traumahawk]

Hey all ! Back after a long hiatus , spinal surgery again... I have had the same issue and had given up due to fact I could not ride my bike... NOW that has changed.. My 97 will slip under hi-way speed acceleration.. new clutch and fluids, running a valvoline oil designed for motorcycles. I have not looked to see if there are any other fixes yet but this thread looks to as close as I can get to the same issues.
My other maxes would leave this one due to clutch slipping. My master cylinder seems to be working OK.. The lever has steady pressure even after it had set for a long time.
I can accelerate fine and get to speed ok but sometimes even from a dead stop I have a hard time moving at all. It does not do this often but its nice to apply the throttle and actually go somewhere and not have a bird go faster that I am..
Thanks for help/suggestions. Tim in Indiana

Even if the oil is designed for motorcycles....is it synthetic? The vmax was designed back in the early 80's BEFORE synthetic oils really got going for motorcycles. Rotella for diesels is the way to go.

Are you running aftermarket levers? There was an issue with the levers that i have....after a couple of hours on the bike, the clutch would start slipping. The hole that the push rod fits into wasnt drilled far enough, so the pushrod was always slightly engaged, and the clutch would get hot.

Also is the fluid return hole inside of the MC clear? If not, fluid wont return to the MC and the clutch will start slipping.

Is the MC too full? As the fluid gets warm, it will expand, and put pressure on the clutch itself, and cause it to slip.

 

[Cn4366]

From everything I've seen on that tiny hole, it seems to cause a rock hard clutch, not slipping, but I'll be sure to clear that as well. I think what I'll do is pinhole, rotella, rebuild cylinders(might as well do both anyways, bikes been sitting for who knows how long and seals don't last forever), new lines, and spring conversion, in that order.

 

[HDH8R]

Use what is recommended by manufacturer. Owners manual page explains oil types and clutch slippage for not following.

 

[Tony Strange]

Even if the oil is designed for motorcycles....is it synthetic? The vmax was designed back in the early 80's BEFORE synthetic oils really got going for motorcycles. Rotella for diesels is the way to go.

Are you running aftermarket levers? There was an issue with the levers that i have....after a couple of hours on the bike, the clutch would start slipping. The hole that the push rod fits into wasnt drilled far enough, so the pushrod was always slightly engaged, and the clutch would get hot.

Also is the fluid return hole inside of the MC clear? If not, fluid wont return to the MC and the clutch will start slipping.

Is the MC too full? As the fluid gets warm, it will expand, and put pressure on the clutch itself, and cause it to slip.

I’m with you on the return port, I’ve seen this before.

 

[eric1959]

There is no relation between clutch fluid and slipping.

 

[one2dmax]

There is no relation between clutch fluid and slipping.

This is incorrect. The AMOUNT of fluid in a container designed to allow expansion for fluid as the system heats up can indeed contribute to clutch slippage if the system is overfilled giving no room to expand. This also happens to brakes (and happens more often to brakes). As the system heats up the fluid (which causes expansion not just in the fluid but in the volume requirements of the system) it can start applying pressure. This in turn creates heat which creates a viscous cycle that can cause it to lock up at some point.

 

[Tony Strange]

There is no relation between clutch fluid and slipping.

If the fluid pressure is not allowed to return to the reservoir, it is retained in the line. Therefore it will keep the clutch plates from fully engaging causing it to slip, like I said, I’ve seen it before.

 

[MaxMidnight]

This is incorrect. The AMOUNT of fluid in a container designed to allow expansion for fluid as the system heats up can indeed contribute to clutch slippage if the system is overfilled giving no room to expand. This also happens to brakes (and happens more often to brakes). As the system heats up the fluid (which causes expansion not just in the fluid but in the volume requirements of the system) it can start applying pressure. This in turn creates heat which creates a viscous cycle that can cause it to lock up at some point.

That would be true only if the system is over-filled and that the cap or cover is not vented.

 

[one2dmax]

The cap is vented on the TOP side of the rubber diaphragm to allow expansion as the volume is reduced (helps prevent sloshing). It is sealed from the bottom side of the rubber (and why it will help pull the rubber to expand as fluid volume is used up). The system over filled would be a requirement for this problem to occur.