This question is for my project bike that belongs to a family friend.
He dropped it down hard over a year ago and it was left as it was
until I received it from him about six weeks ago. It is a 1990
CBR1000F. With thanks from this forum the alt damper has been
replaced and now starts quickly. I have adjusted valves, the compression
increased on three of four cylinders. Cleaned carbs adjusted two of
four floats. Just replaced tires and took it on it's first ride since it was
dropped. Everything seems fine except beginning at around 3000 rpm
till 5000rpm a noise/rattle occurs. It is a faint noise at 3000 rpm
and is the loudest between 4000 and 5000 rpm. Once beyond
5000 rpm it's totally gone, almost like a switch was thrown to
the off position. It is a top end noise and is the same in all gears.
I've done a search and did not find anyone with this same noise.
It has 58000 on the odometer and no idea if cam chain or tensioner
has been replaced. First time working on this model engine.
Any info would be helpful. Don't know if normal, or start of a problem.
Also has standard cold engine rattle when cold but when warm
rattle goes away.


Take Care

Tim

 

Does it make the noise standing still or only under load whilst riding? If it can be replicated standing still, make a vid from all around so one of the resident 'brains trust' can have a listen.

 

Ahh Tim , have the same thing on the 93 I have ..... and it's slight and like you goes away
around 5 k........ don't think it's anything terminal though and I'd put it down to slightly
worn cam lobes and I think (although I have not pulled the cover yet to do it) but it could
be "treated" by adjusting the valves just a lil' bit more than usual .... just a bit mind you.
The fact it is gone around 5k to me anyways ....says one thing ........valves

And yeah ....it's a bit irritating

 

Thanks Guys: It just makes the noise under load. Also have the valve
cover off again. Seems to be coming from the front, when I went through
clearance adjustment the first time I found two of the exhaust valves
a little loose and left them. Honda book chapter 21 indicates exhaust
valve clearance at .18 mm. I believe Haynes has .16mm. Could one
of you please verify which is correct, I tend to side with Honda.
Found the two exhaust valves a very easy .18 mm. Might set them at
.17 mm if .18 mm is correct.

Take Care

Tim

 

Inlet should be 0.10 (+/- 0.02mm)
Exhaust should be 0.18 (+/- 0.02mm)

What I go by

so yeah set 'em at .17 and see


Plus USEFUL THREAD on valve adjustment

courtesy of one "malbojah"

 

Thanks Sprock, Those are the tolerances I went by the first time I checked and adjusted clearances. But given your thoughts on slight
cam wear I'm thinking of adjusting all to the tighter side of the tolerance
instead of the wider, both intake and exhaust.

Thanks

Tim

 

I wouldn't do that - a slight mistake and you'll have REAL problems
Slightly loose is better on these bikes.........a little noise is a small price to pay.

 

One of these years I'll finish that post

 

Well...let me tell you what I've done, and the changes it has made. One reply for narrowing the valve clearance, one for don't do it. I can see the point of both. Please feel free to comment, I'm by far not a pro. Just want to do the best I can with what I've got. Spent about three hours reducing the clearance to the lower limit, checked each about four or five times go/ no go. Reset carb sync. and took for a ride this morning. The following is before and after results. Before noise/rattle became noticeable at 3k got louder between 4k and 5k. Then all quiet from 5k on. Was the same under light/ moderate/ heavy load. After results are, nothing noticeable under light/moderate loads. Under heavy load noise / rattle is reduced about 70%, sounds like just one valve?? Before noise rattle would begin at 3k and end at 5k. After result, begins at aprox. 3600 rpm and ends at between 46k and 48k, narrower band where noise occurs. As soon as I got home preformed compression test found all between 170 to 175 with no fuel in carbs. About 20 psi greater per cylinder than when checked cold just after clearance adjustment. Checked compression hot, (taken about five min after shutdown). Thought being, if I had gotten sloppy and had adjusted any too narrow I would show a decrease in compression or, one not the same as the others.

What do you think??
Like I said, comments welcome. Just looking for best result for our friends limited budget.

Take Care

Tim

 

Since all that checks out ....adjusting the valves & taking up "slack" as it were ,
which then produces a quieter / lesser noise

.... I'm more beginning to wonder how the actual camshafts themselves are ?

Wonder if one of the exhaust cams itself is worn !.....or the cct and or chain is
also at issue

might be a few factors at play here

Just thinking out loud

Ya know what though since it's 70% reduced as you say .....I'd say at this
point ......screw everything and just ride it like there's no tomorrow

I think that motor may have got a good bit of hard running in the past !