Forum

[Barry N]

After converting my Sixty5 to a 612, I find that it vibrates more. I am assuming/hoping that the balance factor is right (it's the full Hitchcocks kit) and think it's just an acceptable characteristic of this engine. It's felt mainly through the petrol tank when accelerating through the gears and, although I can live with it, I worry that it might eventually crack a rear tank bracket or even worse, the tank itself. Is there anything I can do to improve matters? I have always thought it was pretty dumb for the head steady to share the same frame attachment as a rigidly mounted petrol tank!

[Riggers]

Hi Barry - like you my first thoughts would be the crankshaft balance and how well it was done. I would assume Hitchcocks make a decent job of it but giving them a call and explaining your problem wouldn't harm. Perhaps you could take the bike to them and get them to road test it to see if it's sgnificantly worse than 'normal' for a 612 conversion. Other secondary causes could be inaccurate ignition timing, loose engine bolts, and even a slack chain (both primary and rear). The only other thing I could suggest is experimenting with some form of rubber mounting for the tank, but I reckon it's not going to be easy.

[Howard 612]

Yup, vibes can be a problem on a 612. As Riggers says make sure your timing etc is spot on and all bolts done up good and tight. Tanks cracking on that rear weld have always been a problem on the Bullet's, even more so with the 612 version.

You can make sure that the weld gets as easy a life as possible by using washers to take up the play so that the mounting tabs are not pulled or stressed when the bolt is tightened up, the tabs should never be bent, always use a spacer to take up the play.

If the worst comes to the worst, the Casswll tank sealant sold by our hosts is very effective, it has stayed intact on my own (hard ridden) 612 for a year now.

Remember LocTite is our friend

[Chris Tindal]

Chaps, whats the 612 like to ride and live with (starting, town manners, cruising etc.)and is it worth doing?

[Barry N]

Thanks for the input. Yes, all the basics are right (mounting bolts, chains, timing, etc) and I wouldn't consider it to be ALL that extreme - it is a single after all so some vibration is inevitable - and I expect the 612 is going to produce more of a "bang" than the standard 500. Hitchcocks (with Alpha) have knocked out enough of these cranks over the years so I doubt there is a problem with the balance. As you recommend Howard, I have already packed the tank tabs with washers so that they are not stressed when the bolt is tightened. As I have only completed 700 miles so far, I have not ventured into the very high rev range yet, so I may well find that its a bit smoother higher up. Best balance, I believe is only achievable at a certain rev band anyway. So Howard, do you find that your 612 vibrates more than standard as well? If other 612 owners are looking in, their experience would be welcome too. I must say that overall I am very pleased with the transformation and if the vibes are normal so be it. Guess I'm looking for some reassurance!

[Barry N]

Chris, mine starts first kick from stone cold every time (on half choke) and if its been stood for a while and is "half warm" it just needs a tickle on the carb and its first kick again! And low speed behaviour is absolutely brilliant - every bit as docile as when it was as a standard 500, with lots of lowdown grunt! Havent cruised much over 60 yet (stil running in).

[Howard 612]

Yes, I do have more vibration than standard, but it is not enough to put me off. The vibration does vary with engine RPM quite a lot more than with the standard set-up... With a 20 tooth gearbox sprocket, in top gear, I find I have smooth running all the way up to a 'sweet spot' around 65-75 MPH where the engine just purrs and runs smoothly, this is ideal for motorway cruising, she will keep this up all day using hardly any oil, just gobbling up the miles. I strongly suspect that there is the vibration band starting at 75 smooths out again by around 85 making 90 MPH cruising quite possible, given the right circumstances.

[Presto]

As daft as it sounds - try slackening off the engine bolts, run the engine at tick-over and re-tighten. Soemtimes the fixings are under stress and this often helps.
Cheers.

[Andy C]

Barry.

As an Ex 612 owner I can honestly say that mine did not vibrate more than the standard 500, if anything it felt like it vibrated less.

Believe me that if the head steady gets loose then it WILL vibrate.......badly. Mine came loose once and I thought that the motor was gonna blow !!

As suggested check for loose bolts / chains. Check timing, carb etc.

The really are great fun to ride and just as easy to manage around town as the standard 500. I only got rid of mine to make way for another Project - and regret doing it.

Definately recommend the Newby clutch, close ratio box and at least a 19 tooth gearbox sprocket.....never did get around to putting a 20 tooth gearbox sprocket on it.

Good luck.