• Welcome to the Online Forum and Website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Hon. Editor and Online Forum Webmaster by calling 07977 001 025 or by clicking this link.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this Club website.

    If you have previously registered to use this forum, you should log in now.

    If you have never registered to use this website before, you can do so now by following this link.

Misc Back Fire Comet

brian gains

Well Known and Active Forum User
Non-VOC Member
#1
Hard deceleration produces backfire, no leak around exhaust, inlet manifold all snug. Only change recently was oiling and consequently adjusting throttle cable. The throttle slide has quite some play within the carb body, would I be right in thinking that on deceleration with throttle closed air is being sucked around the slide producing excessively lean mix and then backfire?

Thanks
 

oexing

Well Known and Active Forum User
VOC Member
#3
The slide was clapped out for many thousands of miles, why would that be a cause suddenly ? How can you know the exhaust side does not draw air in, this is difficult to find and stop ? I say the exhaust is your problem, a sloppy slide would just produce a weaker mixture, no banging in the silencer.

Vic
 
Last edited:

timetraveller

Well Known and Active Forum User
VOC Member
#4
To seal any leaks in the exhaust system you can use clear silicon sealant as sold for many domestic purposes and it withstands the heat with no problems. Don't just put it on the outside. Put it where the tubes pass into each other and where the top flange of the exhaust pipe is held into the cylinder head. Leave it for a day to fully set before you go for a blast down the road.
 

Bill Thomas

Well Known and Active Forum User
VOC Member
#5
Just been out on my Twin, With New/ Old Mk2 s Banging on over run, Not too bad, Checked the plugs, A little rich ,Weakened them off a nats and turned the tick over up a touch = A lot better. Cheers Bill.
 

brian gains

Well Known and Active Forum User
Non-VOC Member
#6
As I say problem appeared after the cable was oiled so looked at carb' first.
I thought it was possibly a lean mixture caused by throttle slide although this conflicts with Bill's scenario where the problem appears to be too rich a mixture on over run.

I'll check exhaust fit again but am satisfied that's all ship shape.
 

timetraveller

Well Known and Active Forum User
VOC Member
#9
Don't bother to pay extra for a special. Believe me the normal mastic works but I would always use the translucent, not one with a pigment. Should be about £2 for a full sized tube, trade.
 
Top