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Motorcycle not accelerating properly in high RPMs.


darkshad

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Hi all.

 

I have a 2002 Honda VFR 800 non-ABS that I’m having problems with. After first gear, when I get on the throttle, the bike’s RPMs just increase without much increase in speed.  See youtube video below.

 

 

 

 

Do you all have any thoughts what might be wrong or what things I should look at?

 

I had a couple things that I recently fixed on the bike, so not sure if these have something to do with the issue or not.  I had a soft clutch and was unable to shift because I ran out of clutch fluid. I wasn’t sure if my clutch master cylinder or clutch slave cylinder were bad as well, so I replaced those two parts with ebay used parts and bled the clutch with a vacuum bleeder.  My chain was loose, so I also tightened my chain.  After I did these things, the bike ran fine for a week or so, and then started exhibiting the “loss of power at high RPMs.”

 

Appreciate any thoughts you may have.

Thanks.

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It sounds like the clutch is slipping. When this happened to me a couple of years ago, it was a clogged return port in the master cylinder.  There is a small whole in the master cylinder under a small stamped "protector". This a hole allows fluid to return to the reservoir. If it is clogged, then fluid can't return t and the clutch doesn't completely engage.  The other potential problem is to much fluid in the reservoir, if the fluid heats up and there is no room in the reservoir, then the fluid will push on the slave cylinder and disengage the clutch.

.

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Alright....An update.  I looked at the clutch fluid and it was a bit high, so I removed some.  Per the manual, I tuned the handle bars to the right, made sure the master cylinder was level, and with plastics and top on, I see an air bubble at the top of the level.  I also checked the small hole in the master cylinder - as far as I could tell, it looked good.  I stuck an ice pick in the hole to check.  Motorcycle still has the same problem, maybe even a bit worse.  

 

Could a failing water pump have anything to do with it?  It appears that my water pump has seen better days.  See picture below.

 

May look at taking it in to the motorcycle shop for a diagnosis next week.

 

Thanks.

 

 

clutch_fluid.JPG

20200905_095024.jpg

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Did you rebuild the clutch slave and master cylinder when you replaced the parts?

 

It looks like brake fluid may have been dripping down on the outside of the water pump housing..

 

Any seepage from the slave cylinder? And

 

did you rebuild the clutch slave when you replaced it?

 

Sent from my SM-N950U using Tapatalk

 

 

 

 

 

 

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36 minutes ago, jstehman said:

Did you rebuild the clutch slave and master cylinder when you replaced the parts?

No.  Rather than rebuilding, I bought used parts off of ebay.

 

36 minutes ago, jstehman said:

It looks like brake fluid may have been dripping down on the outside of the water pump housing..

 

Any seepage from the slave cylinder? And

 I don't think so.

 

36 minutes ago, jstehman said:

did you rebuild the clutch slave when you replaced it?

No.  Rather than rebuilding, I bought the clutch slave off of ebay.

 

The interesting thing is after I replaced both the master, slave, and added fluid, the motorcycle was running fine for one of my weekly rides.  ie. Saturday weekend 1.  The next weekend I took the motorcycle out and that's when this issue popped up.  ie. weekend 2.  Saturday weekend 2 was fine, but Sunday weekend 2 was when the issue cropped up.  Since it was working properly for weekend 1 and first day of weekend 2, I'm not sure if the issue is a part I replaced, but I guess I could swap one of parts out (ie. slave cylinder) with the old slave cylinder and see if there is any effect.  At least something to try.

 

Thanks.

 

 

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Only other thing I can think of is the return port being blocked.

Fluid heats up and has no where to expand to, pushing on the slave piston causing your slippage.

Hope you get it figured out

Sent from my SM-N950U using Tapatalk

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Or simply worn out or glazed clutch plates. Might pay to have a good look at the clutch slave lifter rod for any scoring, make sure it's dead straight, not bent in any way. But given the age of your clutch and especially after all the slippage in the video, you might be looking at a clutch rebuild.

I'd be very cautious of buying a second hand MC and SC from e-bay unless you were looking at rebuilding them, new seal kits etc. who knows what state they could be in.

Also how does the clutch lever feel? Do you have a small amount of free play? OR does your lever feel loaded from the get go? Is the friction zone roughly where it used to be or is it now virtually at full release of the lever?

 

"Could a failing water pump have anything to do with it?  It appears that my water pump has seen better days."

Water Pump can't effect clutch ops.

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Alright.  Just ordered a MC and SC rebuild kit and also a Barnett Performance Products 303-35-20046 - Complete Clutch Kit.

 

Will rebuild the MC and SC so I have a "known good" set and if I still have the issue, will replace the clutch with Barnett clutch kit.

 

re: clutch lever feel, it's hard to tell.

 

Thanks.

 

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  • 2 weeks later...

I have an old CB650 wich had problems with the clutch not engaging. Lever was very soft and basically not working. Drained it, opened, cleaned, some fine sanding, closed it up again, put new fluid and removed air and it's working like new. Unless you really messed up something putting it together or taking the air out that's probably not the problem and you should notice it in the lever action.

What oil are you running? I don't think the vfr has a dry clutch, so it should be bathed in the engine oil, any problems there and it can start slipping. You can drain the oil and check for water or antifreeze in it. When draining water comes out first as oil is thicker. While the oil is out you can open the side and check the clutch plates, they should be visible without removing the whole assembly and should have grooves like this and not look dark or burnt. Watch the gasket when you remove the cover for the clutch.

If all looks good you just put the cover and oil back on the bike, but I doubt it.

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An Update.

 

Rebuilt the master and slave cylinder.  Was in the process of putting the slave cylinder back on, but couldn't get it back on because the rod was pushed out and couldn't get it pushed back in.

 

Decided to drain the oil and crack open the clutch cover.  Looked at a couple of the rings, but didn't know what I was looking at and had the replacement ones at my house and not where I was working on my motorcycle.

 

I hadn't looked at the manual yet on replacing the clutch (replacing the clutch was going to be the second phase after the MC/SC), so I looked at it and also ordered a replacement gasket for the clutch cover.  

 

Need to wait for the replacement gasket to arrive before I can continue on this project.

 

Thanks.

 

 

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Well, gasket would be needed to put stuff back together.

 

For now, you can at least measure thickness of individual clutch discs and plates along with thickness of entire stack.

Also measure clutch-springs if you have tension-measuring devices. Otherwise, free-height will do.

I usually replace springs with stiffer Barnett ones while I'm there.

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An update:

 

I was able to get the new clutch plates put in. The one problem I have now is that if I put the slave cylinder back on, the plate where the springs are sticks out about 1/4 of an inch.  If I tighten down the bolts and get the plate flush to where it should be, then the rod sticks out too much for the slave cylinder to be flush.

 

It's almost as if the rod is a hair bit too big, but it's the same rod.  See pictures - this with the slave cylinder bolted in, as  you can see there is a gap between the clutch plates and the plate where the springs are.

 

Appreciate any thoughts.

 

Thanks.

 

 

clutch-small.jpg

slave_cylinder-small.jpg

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With situations like that, it's usually best to double check the work,  both on the slave and clutch.  It's a lot of work to take it all back apart,  but it's the only way to be sure it's assembled correctly. 

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Are you sure the push rod is not bent in any way? You need to make sure the pushrod is properly seated into both the slave piston and clutch lifter piece. Are you sure the slave piston is not jammed in the extended state?

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I would suggest there is something wrong in your clutch pack rebuild as even when built correctly I have never seen that much space between the end plate and friction plate even with a squeezed in clutch lever.
 

Strip the clutch pack again and check your work. Are there any missing plates both friction and solid metal? Are the slots aligned correctly on the spring seats and where the bolt screws in? Is the central release bearing mounted in the end plate seated correctly?

 

Good luck and let us know how you get on.

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What did the old plates look like? Did you measure them or take pictures, compare them to the old ones? The springs as well? If your springs were bad changing the clutch pack will not solve the problem as the new clutch plates will wear out quick due to low pressure and high friction.

Just throwing new parts at it untill the problem gets solved is an expensive way of fixing it...

Did you check the manual, it's pretty detailed for the clutch and it's a pretty easy pease job.

Did you also check the lifter rod, it should have mooved freely with the master out. It's basically a stick that pushes the clutch pack from one side of the bike to the other with hydraulic pressure.

installation.PNG

limits.PNG

 

This video might help you understand how it works:
 

 

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On 9/24/2020 at 10:11 PM, Grum said:

Are you sure the push rod is not bent in any way? You need to make sure the pushrod is properly seated into both the slave piston and clutch lifter piece. Are you sure the slave piston is not jammed in the extended state?

 

The push rod doesn't look bent and the slave piston isn't jammed in the extended state.  See youtube video at the end of this message.

 

 

On 9/25/2020 at 1:08 AM, Marooncobra said:

I would suggest there is something wrong in your clutch pack rebuild as even when built correctly I have never seen that much space between the end plate and friction plate even with a squeezed in clutch lever.
 

 

Strip the clutch pack again and check your work. Are there any missing plates both friction and solid metal? Are the slots aligned correctly on the spring seats and where the bolt screws in? Is the central release bearing mounted in the end plate seated correctly?

 

 

Yah.  I removed the clutch pack rebuild and still have the same issue.  It's not the clutch pack piece.  The central bearing is mounted on the end plate and seated correctly.  See youtube video.

 

 

I checked the lifter piece, and the hole is clean.  The rod properly seats in it.

 

It's probably something simple, but I'm at a loss as to what it could be.  There are only a handful of parts that actually connect directly to the lifter rod.

 

Other thoughts/ideas to look at?

 

Thanks.

 

 

 

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Your Slave Cylinder assembly doesn't look correct! Are you showing the Slave with the spring removed for demonstration? The spring should be internal! Is the piston in the correct orientation?

 

Can only suggest you check your disc pack for the correct number of steel discs and friction discs, along with the spring seat and friction spring.

 

Whenever I've replaced a drive chain I've noticed a certain amount of pre-load tension with the Clutch Slave as I remount the sprocket cover and slave assembly.

 

Clutch_Slave.JPG

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I agree with Grum, your slave cylinder has been put together back to front. You need to disassemble and put the spring in first followed by the piston. Make sure you put the piston into the slave assembly seal first as well. From looking at your video the piston currently is round the wrong way hence having a large gap at the clutch plates. The spring will always try and push the piston out especially as you have removed the hydraulic supply from the clutch master cylinder.
 

I would rebuild the slave cylinder correctly, refit on the bike and then rebuild your clutch pack ensuring the push rod is fitted.

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  • 2 weeks later...

All:

 

An update - I got the motorcycle back up and running and the "motorcycle not accelerating properly is fixed."  I installed a new clutch and that fixed the issue.

 

Clutch I used:  Barnett Performance Products 303-35-20046 - Complete Clutch Kit

https://www.amazon.com/gp/product/B0031BJGM8/ref=ppx_yo_dt_b_asin_title_o05_s00?ie=UTF8&psc=1

 

Repair Steps:

--Make sure the slave cylinder is rebuilt correctly - put the spring in first followed by the piston. 

--Put gasket sealer on slave cylinder gasket and put on slave cylinder.

--Put oil on clutch plates

--Put clutch plates in - make sure they are in the correct order.

--Put on lifter plate with lifter bearing

--Put in springs and bolts.- make sure to tighten them in correctly. 9 lbf-ft

--Put gasket sealer on clutch cover gasket.

--Put clutch cover gasket on clutch cover and put in all of the bolts.

--Wait 24 hours for gasket sealant to setup

 

Next day -

--Add oil filter and oil to the motorcycle.

--Bleed the clutch.

--Motorcycle should start back up.  Make sure you have added enough oil and take the motorcycle out for a test to see if the issue been resolved.

 

If the motorcycle doesn't want to start, or if the bike is in neutral, but you don't see the neutral light on the dash, look and see if you have any lose wires that might have came disconnected - ie. neutral switch (around the left side of the clutch cover) or ignition pulse generator (on the top side of the clutch cover).

 

Appreciate all of your help and ideas in helping me get the VFR back up and running.  Sometimes one just needs another set of eyes.

 

Have a good one.

 

Thanks.

 

 

 

 

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