Ariel Owners Motorcycle Club

Hi
Although I have not owned my bike for long (and never ridden it yet), I have noticed that very occasionally when turning it over using the kickstart, the engine would lock up to the point where the only way I could turn it over would be to engage a gear, and rotate the wheel backwards; this freed it up. Once running I also get the occasional mechanical knock, which has puzzled me - I thought it was the exhaust lifter, but no.

This happened today, so I decided it was time to track it down. Having got it into the locked up state, I carefully removed the inlet rocker box; still locked up. So then I removed the exhaust rocker box, that released the engine to rotate again.

Looking carefully at the rocker levers I note that the exhaust cup sits a lot further back in the box, compared to the inlet lever. See pictures.

I think the shoulder on the lower part of the exhaust pushrod is becoming jammed against the bottom of the push rod tube, or something else down at the lower end. I can actually make this happen by inserting the pushrod, biasing the top end and clunk, lock up.

So, looking at the pictures, should the cups be roughly a similar distance from the end of the box?

Also, looking in detail at the distance collar, I note that on the inlet there is a distance collar and a small washer. On the exhaust, just the distance washer.

If I am right in my diagnosis, then I need to bring the exhaust lever spindle back towards the screw.

I hope I am on the way track.

Cheers

Steve

Somewhere around 1949 Ariel changed the arrangement for the rocker spindles
adding a thackery spring in place of one of the spacers. The rockers remained
unchanged.

I've posted an image comparing the two spindle types in another thread some while
ago, long enough ago for me to forget quite where. When and if I remember I'll
post the location.

Thanks Will. Do you think that both the inlet and exhaust cups should be in the same place front/back?

I'll say yes simply because I've never noticed them being obviously different.

I just measured the distance collars. On the inlet, the distance collar is 0.120" plus a shim of 0.040", so 0.160".
On the exhaust which just has the distance collar, its 0.120".
According to Drags site, the distance collars should be 0.160". I wonder if the undersized exhaust distance collar is the problem in that the top of the pushrod is not quite in the right position to avoid an occasional lock/clunk up at the lower end?

I don't know if it's just my old eyes but is there an additional thin washer on your inlet rocker? Below is a picture of a pair of rockers from my NH and they both appear to be the same distance. The hardened steel washer between the rocker (on the pushrod end) and the aluminium rockerbox dictates this spacing. The washers appear to be 1/8".
Pete

Hi Pete, your old eyes are functioning perfectly, unlike my Ariel!
There is an additional shim, making the total thickness 0.160", which is correct. The exhaust side is undersized by 0.040", and I am thinking that is the problem.

Just a silly thought - are you sure it is the engine that is locking not just the kickstart quadrant jamming (which they do very easily)? Can you get the engine to lock by turning the back wheel in gear or only with the kickstart?

Pete

I don't know Pete. Its a very occasional problem when starting, but a real nasty clang when running.

As a very, very long shot, long ago a bike had a similar problem. It would lock up for no apparent reason. All possible options were explored and dismantled / re-assembled to no avail. The problem finally went away. Some time later, the crankcases were split. The problem then became evident and was the big end nut catching on the crankcase strengthening webs due to the spacer between flywheel and main bearing being omitted.

Ever after, the bike ran with very streamlined pushrod ends, amongst other un-necessary modifications.