Hitchcocks Forum

Fitted a Carberry vibration reduction plate yesterday - twice! after fitting it for the first time, the engine 'clicked' as it was running. Thinking that I'd done something wrong, I stripped it down again but couldn't find anything amiss.

After much head scratching, I discovered that the 3 'legs' on the new plate were about 0.16mm shorter than the ones on the old plate, so I removed the shims from the ends of the cams. Now running fine with no 'clicking'.

Haven't ridden it yet as it was getting late when I finally got it back together.

Interesting. I fitted mine last Saturday but didn’t have that issue. I replaced the shins on mine. TBH I can’t say it has transformed the engine. It still vibrates though there are now periods of relative smoothness. Worth doing, I feel, if only for the better support of the crank on the timing side. Roger Slater in his series in RealClassic a few issues ago reckons that it’s all down to how accurately the flywheels are fitted to the crank at the factory. The ones on his were miles out. He also balanced his crank to the specified factor using brass plugs in the flywheels. Again, way off design spec from the factory but now accurate. Result: one really smooth engine. Carberry vr plate addresses the symptoms but not the cause in my view.

I fitted it mainly for the extra crank support, if it smooths some of the vibes then that's a bonus.

Rattlebattle. Forgive me please for a slight sidetrack. We don’t get Real Classics out here (South Africa) so I haven't seen the Slater series. Can you tell me what the balance factor was for that engine? I’ve never seen a firm number from RE – they generally range 60-70%. I’m having my 1996 500cc iron barrel crank rebuilt, and I was aiming at 63% as it is quite smooth up to ~4000rpm but maybe this isn’t best.
Cheers
ChrisD

Chris D, RealClassic (note spelling) is available via subscription download. See their website. Highly recommended mag!

REgards, Mark

ChrisD: Sorry, but the articles were about the newer UCE models, not the iron barrel ones but IIRC something around 66% was stated to be the starting point. It was also mentioned that the balance factors for the 500cc UCE, which forms a stressed frame member, and the 535 CGT engine, which is mounted more conventionally in a tubular frame, are different. But, yes, they are typically around 66%.

My 1994 iron barrel was balanced to 63% bored to 535 slight vibes between 100 to 109kph then quite good to 140. Fron near new 273klms all you could ride it for was about 30 min then the fingers went numb, now I can see things in the mirrors.

Thanks for your comments Gents. I too have a 535cc and changed the factor to 63% and it was much better. Originally it was apparently 66% and quite rough. An article by Fritz Egli (British Bike 1994) noted those two numbers. When I put in the steel conrod and didn't balance it, it was awful and destroyed dials, shafts, metal joints etc at ~55%.

Mine too is quite smooth up to around 70mph gps-speed (~110kph) but I was hoping for something even better (at least it was smooth until the inlet valve retainer broke - perhaps a late result of that massive out-of-balance ride)!
Cheers
ChrisD