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darkshad

Motorcycle not accelerating properly in high RPMs.

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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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Hey,

 

Thanks for the suggestions.  I'll look at the clutch and see what I can find out.

 

Thanks.

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35e59c34ce818133a305c56991b9a743.gif

Sent from my SM-N950U using Tapatalk

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Plan on looking at this tomorrow - Saturday.  Will let you all know what I find out.

 

Thanks.

 

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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

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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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Alright.  Got all of the parts in.  Going to work on the motorcycle this weekend.

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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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