hesitation when accelerating

[Len Matthews]

Hesitation

I'm sure all the foregoing advice is valid but one other possibility has occured to me. If using a pattern spiral baffle silencer (muffler), it has been known for the baffle assembly to break free inside and obstruct the free flow from the tailpipe as Peter Sprot will confirm!

 

[SteveW]

Hesitation Problem

It seems the hesitation problem was due to a bad magneto after all. Last summer when the hesitation showed up I sent the mag back to where I had it rebuilt (Mainely Magnetos) to have it checked under warrenty and it was given a clean bill of health. After rebuilding the carbs and going down many expensive blind alleys the mag was switched out w/ a known good one and the bike worked perfectly. The mag must of been failing under a higher compression. I am waiting for a competent rebuild to be completed now to find out what was wrong w/ it.
Mainely Mags would not refund any money but did offer to look at it again (this would be the third time). I declined w/ a some not to kind observasions about Mainely Mags.*
*I got the mag back originaly, after the rebuild w/ the cam side end bell off 180 degrees. After trying to time it for a day and a half, I luckily found the problem before breaking my leg from a kick back or doing any other damage, that along w/ the next problem and Mainely Magnetos not finding a problem when I sent it back to them to check it, I personnely would not trust them w/ fixing a flashlight (torch).

 

[Tom Gaynor]

Sounds as though you've solved your problem. Next time get Doug Wood (in Pennsylvania) to rebuild it for you, contact through jtan. Doug has a solid reputation for building Vincent magnetos that work. And for KHS - knowing his sh*t.
Another possible cause is the Lucas ATD. These were built down to a price that BSA et al were prepared to pay, and, consequently, at about 30,000 miles, need to be replaced. I personally don't believe they can be overhauled, then work. Roy Price, advertises in MPH, will oblige.
What happens is that they are fully retarded at starting, so the bike starts, then instead of gradually advancing ignition as one accelerates, stick, then go straight to full advance. The bike starts and ticks over, the bike runs, but between the two...
In my box of Vincent bits I have FIVE alloy idlers, all one tooth short, and SEVEN Lucas ATD's, all useless. Go figure.
My Roy Price ATD works very, very well: better still must be the Pazon solid state system, apparently available for Vincent, but only for a coil-based system.
Choices, choices...the tyranny of choice...

Tom

 

[SteveW]

Funny you should mention Doug, since that's who I sent it to. I had one rebuilt by him years ago and can't remember "now" why I didn't send it to him again. While going through the bike looking for the hesitation problem a few other issues were found. The ATD's gear was found lacking in testicular foritude and just the gear was changed out w/ a new one (not an easy task). The timing idler gear was found to be one size to small and replaced with a new one and the cams were found to have been ground poorly at one time, causing a late closing of the valves. Once I get the mag back from Doug it should be a nice running bike. Thanks for the feed back, Steve