Engine Knocking - any ideas - Honda Motorcycles - FireBlades.org
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post #1 of 23 Old 04-15-2008, 3:49 PM Thread Starter
 
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Engine Knocking - any ideas

1993 RRP Blade, the bike has done about 30K miles and there is an engine knocking noise that I am worried about. When the bike is in neutral and reved there is no knocking noise and the engine revs fine. If you put the bike into gear and accelerate, if you shut the throttle then there is a knocking noise from somewhere in the engine. I thought it might be the clutch and have checked everything and it seems fine, then I checked the cam chain tensioner and that is ok, and now I am struggling.

The noise is a knock and it is felt through the foot pegs and you can hear it in the engine. The noise can be heard throughout the engine and I am struggling to locate whether it is gearbox or top end etc. The bike revs fine through the gears and the noise only really shows when you shutting off the throttle - it feels like the chain is knackered but it is new and I have replace both sprockets and also the cush drives.

One question, how bad can piston slap get and can it translate into a knocking type noise?

I am now really struggling and last resort will be engine out and strip down but I am still not sure where to focus??

I know that I am clutching at straws but any suggestions would be great.

Thanks

James
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post #2 of 23 Old 04-15-2008, 9:03 PM
 
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Re: Engine Knocking - any ideas

30k...valve adjustment??
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post #3 of 23 Old 04-16-2008, 2:08 AM Thread Starter
 
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Re: Engine Knocking - any ideas

It's strange because when in neutral there is no noise and the engine revs freely, it is only when you put it in gear that the noise starts. I still am hoping it's the clutch but am starting to doubt this.

So:

- engine runs fine in neutral with no knocking when reved and throttle off.
- put bike in gear and rev the bike and then shut the throttle and the knocking starts.
- new clutch plates, new chain and sprockets, new cush drive rubbers, fresh oil.

The last resort will be engine out but I hope not.......

So it has to be something that shows up when it's put in gear. The noise can be heard and felt through the engine and footpegs and is a definite knock.

Any ideas would be really appreciated.

James
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post #4 of 23 Old 04-16-2008, 2:50 AM
 
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Re: Engine Knocking - any ideas

Well, if you dont hear it at all in neutral through the entire RPM range, i would guess its transmission related....Does this happen in all the gears?
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post #5 of 23 Old 04-16-2008, 4:49 AM Thread Starter
 
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Re: Engine Knocking - any ideas

When you are at a standstill and put the bike in gear it is fine, you can rev the engine and shut the throttle off and there is no clunking noise. It is only when you are on the move and seems to be in all gears though I have only run up to third so far.

I am coming to the same conclusion about gearbox but I want to make sure that I cover everything before I start to take the engine out.

Thanks

James
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post #6 of 23 Old 04-16-2008, 5:26 AM
 
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Re: Engine Knocking - any ideas

Quote:
Originally Posted by CBR_954_RR View Post
Well, if you dont hear it at all in neutral through the entire RPM range, i would guess its transmission related....Does this happen in all the gears?
yep
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post #7 of 23 Old 04-16-2008, 5:37 AM
 
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Re: Engine Knocking - any ideas

Do you have another mode of transport you can use whilst the bike is being repaired? The reason im saying this is that i would rather repair the bike before the summer months come in.

I take it you have some mechanical knowledge? If yes, tear the box down and replace what needs replacing - better safe than sorry

"Second is the first of the losers..."
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post #8 of 23 Old 04-16-2008, 6:51 AM
 
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Re: Engine Knocking - any ideas

At the risk of embarrassing myself by asking a stupid question, does anybody know whether this could be a chain or sprockets issue?
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post #9 of 23 Old 04-16-2008, 7:22 AM
 
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Re: Engine Knocking - any ideas

Quote:
Originally Posted by Badgerman View Post
It's strange because when in neutral there is no noise and the engine revs freely, it is only when you put it in gear that the noise starts. I still am hoping it's the clutch but am starting to doubt this.

So:

- engine runs fine in neutral with no knocking when reved and throttle off.
- put bike in gear and rev the bike and then shut the throttle and the knocking starts.
- new clutch plates, new chain and sprockets, new cush drive rubbers, fresh oil.

The last resort will be engine out but I hope not.......

So it has to be something that shows up when it's put in gear. The noise can be heard and felt through the engine and footpegs and is a definite knock.

Any ideas would be really appreciated.

James
Just to clarify. Above you wrote, at least by the sounds of it ,that it will do the knocking when stopped (bike not moving) but running in gear after you rev the engine. Is this correct or does the bike have to be moving down the road and then only when you decel? I'm not splitting hairs but it makes a big difference.
Also was the clutch replaced trying to fix this noise or did the knocking start after doing all this work? Please answer these two questions Badgerman.
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post #10 of 23 Old 04-16-2008, 12:49 PM Thread Starter
 
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Re: Engine Knocking - any ideas

Firstly - thanks for the effort guys!!

To answer the questions, it only makes the noise when the bike is moving - ie, you accelerate and then close the throttle and the nock happens. When moving and accelerating the bike is fine, it is when you shut the throttle that the kock occurs - that is why I changed the cush drives, chain and sprockets because I was sure that it was the type of kocking associated to this.

The kocking occured before I changed the plates but as I have just brought the bike I changed them as a metter of course, and I was sure that the cush drive rubbers would cure the knocking.

I checked all engine mounts today and they seem good an tight and all the shock linkages are likewise.

If it is not a gearbox issue then I still reckon it might be clutch. One strange thing when I took it apart was that on the clutch center where the springs fit over, there was quite bad scoring that looked like the springs had been rubbing or knocking into the clutch center - not sure if this is coincidence or the problem??

Any ideas what could cause this clutch scoring? If you are looking at the clutch (with the plates and pressure plate removed) and grab the clutch outer drum, should there be any movement in the drum or should it be 100% solid? If you take the drum out all together, on the back there are springs set horizontally in the assembly - one of these is tight and does not move and the other rattle and move - should they do this??

Thanks again

James
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post #11 of 23 Old 04-16-2008, 1:45 PM
 
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Re: Engine Knocking - any ideas

You may have stumbled onto your problem James. There should be no movement in the drum at all except rotating of course. A bad bearing in there may be the culprit. How much movement would you say you have? The scoring could be from some pieces floating around in the housing and causing havoc. I'm not familiar with the springs in behind you say are loose. No chance somebody installed a slipper clutch in there is there?
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post #12 of 23 Old 04-16-2008, 3:49 PM Thread Starter
 
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Re: Engine Knocking - any ideas

Thanks Denzee - I have to grip the drum quite hard for any movement to show itself. I would say that there is a good couple of mm each way. If you remove the main clutch nut and then pull the drum off, there is springs on / in the back of the drum (I will try and get a picture for you). I am not sure what could cause the scoring on the clutch center as I would think that there would not be enough movement of the drum to make the springs hit the clutch center spring points.

Thanks

James
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post #13 of 23 Old 04-16-2008, 7:38 PM
 
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Re: Engine Knocking - any ideas

It can be a bearing knock on the crank.
If the bike is in neutral there is not a lot of tension on the pistons, but in gear the pistons gets more force and that knocks on the crank.

Put the bike in first gear. Engage the front and rear brakes, give the engine some revs and leave the clutch slowly, but don't pull the engine dead, just put some strain on it.
If you can hear the knock or it is louder then it might be a bearing knock.
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post #14 of 23 Old 04-17-2008, 7:33 AM
 
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Re: Engine Knocking - any ideas

Difficult without seeing it. The shaft really shouldn't have any movement. If you have a shop manual, it will give you tolerances. A picture of what's behind the drum would be great. I checked the parts layout at Bike Bandit but it's not clear. 1993 Honda Motorcycle Parts for CBR900RR, OEM and Aftermarket at BikeBandit.com
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post #15 of 23 Old 04-17-2008, 8:50 AM
 
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Re: Engine Knocking - any ideas

I put my money on front sprocket issue u feel it vibrate through the left footpeg? and you feel it more on deaccelration coz it puts more load onthe front sprocket take the front sprocket cover off and inspect it should take a min
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