Hitchcocks Forum

Hi guys
My 1996 Classic 535 is getting closer to running OK, but I have a noise from the cam area which is, I think, backlash on the cam spindles. There are two “clacks” from each of the performance cams, one just before the follower reaches top lobe and the other just after the follower passes top of lobe. I have posted a video on my Photobucket page (ChrisD200) and shall attempt to post it here. Is it backlash and should I replace the original spindles with the adjustable ones?

Video here (I hope)

You’ll also notice the twin-plugging and centre-located decompressor – works just fine except the engine won’t stop if the decompressor is opened as the hole in the head is just 2mm diameter, but it saves my foot!
Cheers, ChrisD

No video that I can see, try again! My AVL/classic hybrid engine was originally built with adjustable spindles, which allowed me to minimise camshaft backlash, but only at the expense of increasing the backlash noticeably to the rest of the timing gear train to the ignition - I got Bullet Whisperer to replace them with fixed spindles when he did some tuning work. Bullets ran happily - if noisily - without adjustble spindles for years. I still have the adjustable spindles on my Electra-X though, which being a proper AVL engine has no contact breaker pinion or idler pinions to worry about. A.

Adrian - that's a good point. So I might be able to remove the "clacks" with the adjustable spindles, only to shift the noise to "clonks" elsewhere?
About the video - when I open this thread, I see the video but it takes ~10 seconds to load. I followed Exile's guidance from this forum (January 2014) and loaded the html version from Photobucket - don't know any other way to load it but you can get to see the video in my Photobucket library (full of other engine problem shots too).
Cheers, ChrisD

How much back-lash do you have? But that is not the source of the noise I could hear...




Did you check that your rockers are not binding after tightening the nuts, and the nuts were tightened evenly?


Any distortion to the base of the alloy rocker blocks or dirt on the surface of the head will cause binding between the rocker and the alloy block, and clacking...


Dont fret about adjustable pinnions and the points-drive train having potentially excessive back last, the point drive has a steady constant load and is not subject to directional load variation as is the case with both cams. If you end up with excess backlash at the idler to inlet cam, then in all probability the lash was adjusted on the ex cam in the opposite direction.


Reset the ex pinion but on the other side of the eccentric.

Oops, A paragraph seems to have got deleted?


What piston are you running?


What compression? Anything shaved off the head or barrel?


What is the inlet valve to piston clearance @ TDC?

This might be of some help.

http://www.nandanmotors.com/camgear.html

Tim (and others), I have our hosts 8.5:1 535cc conversion in their alloy barrel with Samrat rockers.

The clacking noise is, I believe, evident from the video as each follower reaches, and then goes over, the highest point of each cam lobe. Yes, Gurunandan’s lengthy and excellent discussions were my first Bullet reading (even before I discovered Hitchcocks) and this does sound like the common cam backlash. But it has become louder over the past ~1000km, hence my concern - so what is getting worse, and should I worry?

The head had ~1.5mm removed to (a) remove the Indian tilt-and-leak, (b) up the compression from the original 6 and-a-bit (as it was) and (c) allow for a gasket-free joint. With the new barrel and piston (and roller bigend) and with a 3mm compression plate, the separation between valve and piston cutaways was ~60thou on inlet and ~75 thou on the exhaust valve (measured with “play-dough” inserts in the piston). Currently I have 2 x 2mm compression plates fitted so the actual static compression is ~7.5:1. I originally had just one 2mm plate (which even so did not result in contact between valve and piston) but found issues with ignition timing and detonation. So to avoid that I added another 2mm plate – maybe when this mechanical issue is resolved, I’ll go back to the 3mm plate and try again.

The rockers are quite free when fitted to the head and usually bolted down at 7ft-lb but today at 9ft-lb to see if there is a difference (no, there isn't) - all nuts being routinely tightened diagonally in sequence and to matching tension.
Cheers, ChrisD

i can’t view the video, but i once found one of the pushrod adjusters that sheared over the time space you are talking.



i made a clacking sound which became gradually louder till it broke.

it was an engine with the performance cams mounted.

it broke just inside the pushrod itself.

First you say it is getting closer to running, then you add that the noise has been there for over 1000km...


You fit a hi comp piston, then you add spacer plates to lower it??


The first prerequisite for running a Hi comp piston is Super petrol; then set and adjust the timing...


The only real advantage of the 535 piston over the std item is the HIGHER compression...


The first step in setting the cam backlash is selecting the optimum size crank pinnion. (1 dot 2 dot or 3 dot(


The second step is doing so BEFORE the timing pinions have worn and taken a set...


It is a bit late now as you cam pinnions will be worn eccentrically and have taken a set.

I got talked into fitting Samrat rockers to my Bullet. They didn`t sound any quieter to me. It developed a clacking noise soon after. My mechanic found it was coming from the exhaust rocker. He refitted the original rockers and the noise stopped. Make of this what you will.