Author Topic: Rattle  (Read 3543 times)

Offline alanp

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Rattle
« on: 23.07. 2010 19:19 »
My RGS engine has developed a rattle like loud tappets. A few days back it started, so I adjusted the tappets a small amount. On a subsequent ride it got worse amd worse until arriving back home my wife asked what the noise was!
I took off the timing side covers and turning the engine over slowly it seemed that the metallic click happened at the same point in the rotation and corresponded to when both exhaust valves started to return.
I've stripped off the head and turning the engine over again there was no click noise at all.
I took off the barrel to get to the cam followers in case they were at fault, and only causing the noise when loaded with the valve system springs. I couldn't find any fault with the cam followers, which were renewed 950 miles ago.
There doesn't appear to be any problem with the pistons/barrel since they were new (standard) 1000miles ago.
The big and small ends were renewed by SRM when they rebuilt the bottom end 950 miles ago.
The valves don't look like they are sticking in the guides and there is no evidence that the guides are moving in the head.
I'm stumped.
Any ideas?
Thanks
Alan  
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Offline MG

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Re: Rattle
« Reply #1 on: 23.07. 2010 19:44 »
Alan,
have you checked the teeth of the timing gears and the fit of the camshaft pinion on the shaft? Maybe the nut came loose and the keyway is damaged now?

If the small ends are okay, no further ideas at the moment, sorry.
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Online RichardL

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Re: Rattle
« Reply #2 on: 23.07. 2010 20:53 »
Alan,

I'm a bit confused here as to the order in which things came apart. You say you took off the "timing side covers". By this, do you mean the three- corner timing cover, or do you mean you removed the valve adjustment covers. I was thinking, maybe, interference between vavle cover(s) and adjusters, if the adjusters got loose or were replaced with too-long aftermarket parts. However, with the clicking at low RPM, my next thought was a sticky valve guide that, somehow, let the valve snap back after a short bit of time. Having taken the engine apart to the extent you have, it seems not that big a leap to release the vavle springs and feel the valves in their guides. Maybe all that would be needed is Molyslip Oil Additive or some other top-end lubricant.

Also, check your pushrod ends to be sure they are tight in the tubes and not hopping about. I'm not sure if I can logically connect that to the clicking noise, but as long as you are in the vicinity, may as well check it.

All this said, I would check out what Markus (MG) said as well, and hope for yet more ideas.

Richard L.
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Offline muskrat

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Re: Rattle
« Reply #3 on: 23.07. 2010 22:07 »
G'day Alan,
                  sounds like backlash in the timing gears. When turning over by hand the tension of the valve springs tends to force the cam backwards. This gives you a click click sound. Both my A's do it but I can't hear it at running speeds (loud exhaust  *smile*)
Cheers
PS as MG said check the key & fit of the pinion.
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Offline trevinoz

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Re: Rattle
« Reply #4 on: 23.07. 2010 23:51 »
Alan,
         When you say the guides don't seem loose, have you stripped the head and made sure?
Possibly you have one coming loose when the head heats up.
Did you let the engine cool and start again after you found the problem?
Trev.

Offline alanp

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Re: Rattle
« Reply #5 on: 24.07. 2010 10:10 »
Thanks everyone. Once I get through some kitchen worktop DIY I'll get back in the garage. The engine is currently stripped down to the crankcase tops and valves are out.
Some answers to questions -
Yes, I ran the engine the following day and the noise was still there when cold.
The covers I took off were the outer and inner timing side covers.
There are no marks on the tappet adjusters or inside the valve covers.
However, I did notice that the cam followers are clearly worn where they ride on the cams in a way that indicates that they are not central on the cam surface i.e. two of them are showing side ridges where the follower is off the side of the cam. Also there is clear end to end movement of the cam shaft and gear. So, that's an area for a more detailed check. I'll post photos when I get a spare minute or three.
Thanks again
Alan
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Offline muskrat

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Re: Rattle
« Reply #6 on: 24.07. 2010 12:56 »
G'day Alan,
                  the followers do wear like that. The size of the ridge is a measure of how far they have worn (20 thou max). The cam end float is taken up by the cork for the timed breather.
Cheers
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Online RichardL

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Re: Rattle
« Reply #7 on: 24.07. 2010 13:13 »
Alan,

Addressing self regarding "covers", "Duh!" I guess I was expecting you to mean valve covers, so I missed the obvious.

If the clicking is in the timing gears or rocker box, I would think it could have been localized, either with unaided ears or with some type of stehoscopic probe. Did you have any success in localizing the sound?

Richard L.
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Offline alanp

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Re: Rattle
« Reply #8 on: 24.07. 2010 15:12 »
So far I've grabbed enough time to check out the timing side parts. No obvious problem with gear teeth/keys.
Yes Muskrat, I had a look at the cams/followers and you're right, the cam followers are bound to ridge up since each inlet and exhaust cam follower slides against the other and the cams have a gap between them. Great piece of design, not.
Fitting the inner timing side cover has confirmed that the breather cork does take up the end to end movement of the camshaft. 
I'm not happy with the cam follower wear after being new only 950 miles ago so will try to get a set from SRM.
Back to the kitchen!!
Alan
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Online bsa-bill

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Re: Rattle
« Reply #9 on: 24.07. 2010 15:25 »
interesting - all the cam followers I've seen ( all three sets ! ) have been good but respective camshafts have been worn with a ridge on some of the cams but not all
All the best - Bill
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Offline Goldy

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Re: Rattle
« Reply #10 on: 24.07. 2010 16:31 »
Just to add another thought, I had a clicking noise on my A10. It was due to the use of alloy push rods which were flexing and causing them to bind on the edge of the barrel/head at the push rod tunnel.
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Offline alanp

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Re: Rattle
« Reply #11 on: 24.07. 2010 19:03 »
Goldy, funny you should mention that. One of my aluminium push rods was bent a bit. I've been back to take another look and the two long push rods, exhausts, have scuff marks on them. It seems as if they have been touching the rocker box casting at the point where they enter the base of the rocker box. They are quite easy to bend, even by hand, so I'll straighten the bent one and relieve part of the casting. Anyone know if the originals were aluminium? If not, I should get some originals if possible.
Concerning worn cams or followers, I expect it depends on which is harder on which wears away.
Alan  
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Offline MG

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Re: Rattle
« Reply #12 on: 24.07. 2010 19:13 »
Alan,
the original ones are made of thin-walled steel tubings.

As you've ruled out everything else, this very probably was the source of the noise.
When you have the whole stuff re-assembled, check the valve springs, some pattern ones are known to become coil-bound when the valve is fully open, thus causing the push rod to flex. This would also explain the pre-mature wear on the followers.
The 67-357 cam also requires different springs afaik.

I assume the aluminium ones also wouldn't flex under normal load, unless they are repro-crap of course.

You are right, the hardness values of the cams and followers have to match, that's why SRM recommends the stellite tipped followers for their cams and vice versa.
I am using a good original 356 cam and home-refaced followers in the Flash, had them both nitrided and now after 2000 miles there's zero wear (had a chance to check them recently  *smile*). The base circles on each lobe even still show the greyish colour caused by the nitriding process.

Cheers, Markus
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1961 Matchless G12 CSR

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Online bsa-bill

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Re: Rattle
« Reply #13 on: 24.07. 2010 21:02 »
Quote
It seems as if they have been touching the rocker box casting at the point where they enter the base of the rocker box

Two of my pushrods are marked like this (exhaust I think) but it's not due to a bend as the mark is all the way around the pushrod like a ring
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline chaterlea25

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Re: Rattle
« Reply #14 on: 24.07. 2010 23:22 »
Hi Alan and All,
Where did the cam and followers come from? there have been lots of "soft" ones around

In addition to what has been said it is VERY IMPORTANT that the cam is pulled out towards the timing side by the gear
there should be only a very small amount of end float when the gear nut is tightened, Check the cam bushes for wear on the faces
Make sure the key does not get displaced when fitting the gear, Fit the gear BEFORE the barrels that way you can wedge a piece of alloy or copper at the far end of the cam to prevent the key digging into the bush *eek* *eek*
The cam is then held against the thrust face of the bush/gear by the breather
If the cam has / had moved over it can make a noise as a cam  lobe will start touching another follower

Throw away the alloy pushrods and get some originals or lash out on SRM's high tensile ones, the alloy ones spring and rub on the head /barrel joint, they rotate as they run so the rub appears all around

When you reassemble the engine make sure to check for coil bound springds as others have said, fit say a 0.030 feeler between the tappet and valve and adjust this tightish carefully wind the engine over with a spanner on the crank and see if it goes tight when the valve spring is fully compressed, (do one at a time so you can compare)

HTH
John O R
1961 Super Rocket
1963 RGS (ongoing)