Valve Clatter

Glen Jordan

Glen Jordan

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I'm getting obvious valve clatter on the left exhaust. Others are making the usual racket. Overall the bike runs strong. I replaced the top end on this '70 engine when I developed a serious left valve guide oil leak. The '70 replacement rocker assembly has essentially new valve rockers, bushings, and after-market elephant-feet tappets that I removed from the previous engine rocker assembly. I wasn't getting this clatter in the previous engine, so it's something peculiar to this replacement assembly. I'm sure my valve clearance is set correctly. Ditto can chain tension. Seems my left engine side is jinxed. Your thoughts/suggestions would be appreciated.

IMG_0165.jpeg
 
Yes, running the large clearances - 15 and 30. I'll reduce those by half and see what develops. But, I've been using the larger clearances for years, without obvious clatter.
 
Did you check the valve guides when you built it? Badly worn guides (and/or valve stems) will clatter a fair bit more than tight ones.
 
As you can see in the chart above, the intake spec for my '78 is .004". When I tried to use that, the intakes clattered like crazy. I reduced it just .001", to the .003" spec many other years use, and they quieted right down. So, it seems a small change can make a big difference. You may not have to go all the way down to 3 and 6, maybe just slightly smaller will help.

I now have the elephant foot adjusters on my '78. They allow larger clearances but only to a certain point. Get too big and they'll clatter too. But, I am able to go slightly larger with no noise, so I use about 4 to 5 on the intakes and 6 to 7 on the exhausts. Larger clearances let more oil get in between the moving parts. I was never too concerned about the exhausts normally set at 6, but it was nice to be able to open the intakes up a little from that rather tight 3.
 
Hope you don’t mind but rather than start a new thread I thought I would ask here, when I start my 78 from cold the tappets sound VERY loud for about 30seconds and then goes quite is this the time it takes for the oil to reach the tappets or the time for them to heat and expand?
 
londoncabby said:
Hope you don’t mind but rather than start a new thread I thought I would ask here, when I start my 78 from cold the tappets sound VERY loud for about 30seconds and then goes quite is this the time it takes for the oil to reach the tappets or the time for them to heat and expand?
Click to expand...
Since this is a low volume/low pressure system, oil doesn't move anywhere very quickly. If I had to guess, I'd say 15-30 seconds is about right for the oil to make it's way back into the head. There's no check valve to prevent oil drain-back so the only thing limiting that is the pump. The more worn the pump is, the easier it will be for the oil to drain back into the sump.
 
You may have a different issue. My '78 used to do that. When I tore into the topend, I found the front cam chain guide failing. The rubber strip was loose for about 2/3 of it's length .....

w1FmGEX.jpg


My theory is when cold starting, this loose rubber strip was slapping against the guide's aluminum base and making the racket, until oil got splashed up and quieted it down. With a new front guide installed, that 30 seconds or so of loud ticking on cold starts has gone away.
 
Re-adjusted the exhaust valves to 15 mm as suggested. I couldn't detect less clatter in the left valve, but got my ears down close and tried to compare valve noise left versus right. Nice and quiet on the right but left still making a godawful noise. I eventually figured out was was causing the noise - leaking exhaust. I tightened the left engine exhaust nuts and low and behold the noise disappeared. It sounded like valve clatter for all the world. Now I'm embarrassed. Always learning. Always learning.
 
Last edited:
5twins said:
You may have a different issue. My '78 used to do that. When I tore into the topend, I found the front cam chain guide failing. The rubber strip was loose for about 2/3 of it's length .....

w1FmGEX.jpg


My theory is when cold starting, this loose rubber strip was slapping against the guide's aluminum base and making the racket, until oil got splashed up and quieted it down. With a new front guide installed, that 30 seconds or so of loud ticking on cold starts has gone away.
Click to expand...
Is there any way I can find out weather it's the cam chain guide that's causing the tappet noise on start up on my bike it only lasts for 30/40 secs then goes really quiet, the bikes running fine and I don't want to tear it down for no reason but I'm paranoid if it is the chain guide it could cause more damage if left.
 
Unfortunately, there's really no way to tell the condition of that front guide without tearing it down. There's no way to look in there and see it with the motor assembled. The guide failing is a very common problem on these now due to it's age. It's not really a bad part, it's just that it's so old now. But that being said, I wish Yamaha would have made the guide base out of steel instead of aluminum. The SR500 has a similar guide set-up using a steel guide base and you never hear about any of them failing. Apparently attaching a rubber strip to steel holds up better than trying to attach it to aluminum, lol.
 
Replacing that front guide is just something that needs doing on these old bikes. I put two seasons on mine before I tore into it. It didn't start making the noise until sometime in the second season. So, I started making plans (and acquiring parts) to tear into it over the coming winter. What with having to take the motor out of the frame, it is a lot of work getting into one of these. For that reason, it's best you do all that needs doing while in there.
 

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