Forum

[John Turner]

Creaky, an alloy barrel will always sound more rattly than an iron barrel. Looking back at some old instructions for the same piston I have which are about 10 years old so not sure if anything has changed, the bore is listed as 87.00-87.01mm and the clearance 0.135-0.145mm measuring at the front to back 15mm from the bottom. JT

[Lone Wolf]

Wotcha. I fitted an Accralite piston to my alloy barrel Bullet back in 2007. It has horrendous piston slap - but it's still running as good now as the day I fitted it.

[Creaky45]

Lone Wolf, That's what I wanted to hear. Sounds a bit like my mate, Rick's bike. So maybe I should not worry. John T, yes I got those dimensions with the piston. Alan R, I am presuming you are the Alan from our host. Correct me if I'm wrong. But if you are, I did send you photos of the original holey piston to which you replied the obvious, too lean or too advanced which I was sure was not the problem. Someone may suggest my valve timing was out so I will beat you to it. Blind Freddy could line up those dots on the cam wheels. Ignition timing was spot on, static and full advance. Yes, it was a 200074C. I can't blame you for not replacing it, or at least giving me a pensioner's discount (joke) on another as you could presume I knew nothing about tuning and it was all my fault. However the motor was assembled and tuned by a competent RE mechanic well known to yourselves whose name I won't mention to protect the innocent. So, no I never did find out why it blew but that was two years ago. My latest operation is this new piston 90020 and I am using my standard head, standard silencer, free flowing air filter, and 125 main jet. It runs well, so well in fact I now have to attend to my slipping clutch problem and the plug looks good, a bit rich if anything. I have yet to do a plug chop at WOT but that can wait till it's run in. Beware, I may start a thread on slipping clutches next.

[papasmurf]

"They all do that Sir"

[Revband]

I think you have the wrong Alan?, But I think he will let you know?.
There are a couple of things which case a piston to melt a hole and and the piston itself is rarely the cause?.

[Wayne]

That sounds awful and I would suggest more than piston slap - take it apart again and check everything !

[papasmurf]

Wayne, that is a video I found on YouTube, it is not Creaky45's Enfield.
(It just sounds like a loose silencer baffle to me.)

[Barry N]

I bought my 535 alloy barrel and the Accralite piston as a matched pair from Hitchcocks as part of my 612 kit. I measured the total clearance (front to back) at the bottom of the skirt with a feeler guage, and it was per their specification at around 5.5 thou (of an inch) - approx 0.140mm. About 5000 miles on and I have very noticable piston slap (a metallic tapping sound) when I blip the throttle lightly, just off idle (even when warm). However, I don't hear it when riding and it doesn't bother me. The alloy barrel of course "rings like a bell" and magnifies a lot of mechanical noise that the iron barrel muffles. A forged piston (like the Accralite) expands more than a standard cast piston, so needs a generous clearance. I wouldn't worry Creaky, unless of course you've got way over the 6 thou!

[Revband]

The sentence, "my brand new piston was well over that", is a bit indistinct, it would be interesting to know how much over it is?.

[Creaky45]

Revband, Its in the bike now but I think for memory it was .21mm the way I measured it which could have been wrong as I was just using a digital vernier. I don't think I'll worry about it any more. I'll just keep the earplugs in. What I can't hear won't hurt me.