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Lost rear sprocket whle riding.


VFR4Lee

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How does this even happen? I was riding along, everything was going fine today, and then it wasn't.

Felt like the bike jumped out of gear. I fiddled the shift lever and clutch, and only got rattles.

I though maybe something let go in the trans or clutch. Coasted to a stop and found this. Called a tow.

 

Bike just got service 300 or 400 miles ago, valve adjust, fluids change, "major service".

The only thing they might have done with the chain is adjust it.

 

I hope the damage is not too bad. Oil was dripping still when we got it home.  :unsure:

20160821_095223[1].jpg

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Oh. My. God.  Damn are you lucky to not have gone down.  Between the chain flapping around, its a miracle the rear wheel didn't lock.  And then the oil coming out the cases...

 

3d is right though, that's a very bad sign.  I have no idea what would cause such a catastrophic failure of the hub/ sprocket/ cush drive.  I have never seen that before.

 

Glad you are alright though!

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The plastic cover over the front sprocket is cracked into 2 pieces. I got it off and the chain goes around with the sprocket.

But, you can see it busted out chunks of metal case around the sprocket. I pulled that loose grungy piece out

Is that economically fixable? Is that part of the engine case or can it be replaced? Welded up?

Crap. :wacko:

101_3208.JPG

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Oil seems to have stopped dripping more or less.

Bike on centerstand oil is halfway between the lines in the sight glass.

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You need it fully inspected. I've heard of RC51s breaking a chain and taking out the lower engine case. They share the same basic architecture there with the sprocket cover/clutch cylinder area. Best case scenario, the clutch pushrod is bent or the oil seal for the pushrod is damaged.

They must have over tightened the chain and stressed the rear cush drive cover, especially over bumps. 

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They must have over tightened the chain

 

I had that feeling when I picked it up, but figured this shop has been around, they know what they are doing.

 

It looks like I need the piece just right of #4 the gasket, but I see no part number.

 

http://www.servicehonda.com/parts/lookup#/Honda/VFR800FIAC_(98)_MOTORCYCLE%2c_JPN%2c_VIN%23_JH2RC461-WM000001/LEFT_CRANKCASE_COVER/VFR800FI-98-JPN-AC/2Y14MBGWE1AMBG4E0800A

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I'm thinking #15 on the Crankcase Diagram. But, look at the dividing line between the cases in relation to the sprocket cover, which isn't plastic by the way. Too much force into the cover can be transmitted to the cases where it bolts and crack them. Especially because they split right there.

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This oil seal?

  91204-MB0-013 OIL SEAL (8X25X8) (ARAI)

 

On the crankcase diagram, it looks like the part surrounding the sprocket is part of the case and I am probably hosed.

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The metallic cover to the right of the gasket is #3... which includes #22+#23... bearing+seal.

Its part number is 11630-MW4-000 worth about US$80

But like Carver says, you'll have to tear it down and inspect well. Any sideways lashings may have cut into other areas.

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That's what it looks like on the diagram, hard to be 100% sure. You should at the very least clean the entire area as best you can to see where any fresh oil is coming from. I can maybe see a drop of oil on the end of the pushrod in your pic, so maybe just that seal is damaged. Be sure the rod hasn't been bent by rolling it on a flat surface.

Clean it and put it back on the sidestand to see where any oil is dripping. It probably isn't now because you have it on the C stand.

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Like I said #3 is a cover (metallic) and from what I can gather, seeing as it has a gasket, it can be removed and changed. The guide, #2, would also have to be changed, like anything else that might be damaged.

ae3864608c9f57c48d8d4c9a948c66ab.jpg

It can be seen here (in Spanish "tapa" = cover, besides a tasty snack)...

9bf2bd62cbdbbc3759a536e76b254b67.jpg
e7b9027c0e30160a21d23b37a69fa76d.jpg

Here is the same area with #2 & #3 removed...
80d9206a7ed1b0c3cd2eecb28e7cde6b.jpg
db16902939b141443f03713f29a3c888.jpg

Carver could well be right and it may just be a seal. If you're lucky.

Seems pretty difficult the crankcase proper could be damaged actually. Not impossible I guess.



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41 minutes ago, VFR4Lee said:

 

23 minutes ago, Auspanglish said:

The metallic cover to the right of the gasket is #3... which includes #22+#23... bearing+seal.

Its part number is 11630-MW4-000 worth about US$80

But like Carver says, you'll have to tear it down and inspect well. Any sideways lashings may have cut into other areas.
 

I see now what you were asking. That would be a generally positive outcome, versus replacing the whole engine due to cracked cases. 

I've been back and forth in the garage looking at the spare engine out there and your pics and the fiche trying to piece together all the possibilities. The spare engine doesn't have that #3 cover on it. The shift star is behind it, and there is the bearing and seal for the shifter shaft in that cover.

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I see it now. Those diagrams are kinda funny. Thanks for the advice guys.

I'll have to clean it up and get a better look. It's grungy as hell.

Research a bit and see if it's something I feel I can do, or not.

I've never even had that cover off before, so I'm not sure about that.

Def glad to not go down over it.

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The rear axle nut came off and then the hubcover that contains the dampening bits of rubber and the rear sprocket.

 

U lucky man!

 

Past midnight here so i need to log off.

 

 

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2 minutes ago, VFR4Lee said:

And this happens how?

It's "staked" normally, meaning there is a small notch in the axle and you hammer a punch into the sleeve of the nut to "stake" it in place. Plus, the normal rotation of the rear wheel means the very little momentum of the nut would serve to tighten it. If no one has ever taken off the nut to service the cush drive or rear bearings, it would have been done at the factory.

My thought is that the chain was too tight and that broke the cover and it all fell away including the sprocket. But seeing that the nut is gone, it's hard to say the nut didn't come off first. Can you go back and look for parts?

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Can you go back and look for parts?

I just might, but doubt it will pan out. It's out in the sticks in Acton, I was lucky to coast to a KOA and use their phone (no cell service).

Chain and sprockets have been changed more than once, it has 80,000+ miles.

But the last change was thousands of miles ago.

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That's the beauty of the VFR rear hub, the chain and sprockets can be changed without touching the axle nut at all. The only reason to take the axle nut off is to take off the cush cover to get to the rubber dampeners or pull the axle completely out to service the bearing in the hub. I've only had mine apart once in 102k miles to see if the bearings were ok and to change the rubbers.

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 In that case, if the sprocket and cush drive got ripped off by too tight chain,

and it kinda looks like that might be the case

why / how did they take the axle nut along? I am pretty sure it was staked. :unsure:

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I had a chain break on my Y2K FiY back in 2010 and recorded the damage, so here's a few pix of what you might find.

Damaged front sprocket cover and associated bits. Replaced.

Damaged gear selection cover etc.. Cover and rod replaced.

Damaged bolt holes above sprocket. Depth checked and longest possible bolts fitted carefully.

Gear change area underneath was fine.

Also the spacer and bolt between the frame bottom corner and engine was mashed by the flying end. It fits in the gap indicated by the upper arrow.

HTH

Strip 008.jpg

Strip 014.jpg

Strip 015.jpg

Strip 016.jpg

Strip 003.jpg

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Thanks for the pics Steve. Looks bad but fixable for you I guess.

Hope mine is worth fixing.Great bike, but a long way from new.

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I can't recall which direction it is on the 5th gen, it's the opposite on the 6th gen, but if the 17 mm pinch bolt that secures the eccentric on that rear hub is not tightened down properly after adjusting the tension on the chain, riding the bike makes the chain tighten even more on one model and loosens it on the other. Perhaps the mechanic who tightened your chain failed to tighten the pinch bolt adequately... Food for thought?


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