Author Topic: Hesitancy  (Read 457 times)

Offline stevejs

  • A's Best Friend
  • ***
  • Join Date: Nov 2017
  • Posts: 40
  • Karma: 0
Hesitancy
« on: 10.10. 2018 17:02 »
Hello. I hope some of the wise heads out there can help with an irritating problem with my 1954 A7SS.

It was rebuilt about ten years ago for a museum. After being on display for a few years, it was later bought by the guy who'd done the engine rebuild. I've spoken to him and he said he rode it a bit, before selling it on. The last owner told me he'd probably done no more than 100 miles on it. In between it spent some time sitting in a dealer's showroom.

I've been driving it through the summer. First impressions suggested that it's probably not yet run in, so I've not been thrashing it. It starts very well, and runs sweetly (cruising comfortably at 50 mph on a gentle throttle). Then, after it's done about four miles, it starts to be hesitant. It won't pull cleanly - it's a matter of finding the spot on the throttle where it's OK and staying there. Too much or too little throttle and it hesitates and it won't rev past 50 mph in top. Initially I put it down to the muck that was blocking the banjo filter on the carb - there was tons. But after several sessions of rinsing the tank, and the fitting of fuel filters, I'm sure that's sorted.

I've checked the points, and the auto advance seems to operate freely. I've also dismantled the carb and blown out all the jets - it's an as new Monobloc. I wondered if perhaps it was nipping up?

Any thoughts would be gratefully accepted.
Good Advice
0
No reactions

Offline Swarfcut

  • Wise & Enlightened
  • *
  • Join Date: Oct 2018
  • Posts: 1229
  • Karma: 18
Re: Hesitancy
« Reply #1 on: 10.10. 2018 17:17 »

   Hi..Try the simple stuff first  Magneto pick ups, slip ring, leads, plugs.  I would be more inclined to make sure the ignition side is OK first.  Fuel system. I would check for air leaks, particularly the  inlet manifold/ carb/ joint.  Dead hot engine after running perfectly points to  the start of possible magneto condenser failure. The sparks usually return as the magneto cools.

     Swarfy
Good Advice
0
No reactions

Online Triton Thrasher

  • Scotland
  • Wise & Enlightened
  • *
  • Join Date: Feb 2009
  • Posts: 1542
  • Karma: 20
Re: Hesitancy
« Reply #2 on: 10.10. 2018 18:17 »
Did you test fuel flow?

Are the plugs getting sooty?
Good Advice
0
No reactions

Offline stevejs

  • A's Best Friend
  • ***
  • Join Date: Nov 2017
  • Posts: 40
  • Karma: 0
Re: Hesitancy
« Reply #3 on: 10.10. 2018 19:25 »
In reply to Swarfy and TT: Many thanks for the quick and helpful replies. Fuel flow and air leaks already checked. Ditto plugs - good colour. The mag has been rebuilt, but the condensor is perhaps a good shout in that it fits the symptoms. I'll check the HT leads etc, but I think if they were the problem the hesitancy would be there from kickover. It's the fact that the problem only manifests itself when the engine's hot is the bit that puzzles me.
Good Advice
0
No reactions

Offline duTch

  • Ricketty Rocketty Golden Flashback
  • Wise & Enlightened
  • *
  • Join Date: Oct 2011
  • Posts: 4540
  • Karma: 41
Re: Hesitancy
« Reply #4 on: 10.10. 2018 20:09 »

 blocked vent holes in the tank/carby ?
Good Advice
0
No reactions
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia

Online Greybeard

  • Jack of all trades; master of none.
  • Wise & Enlightened
  • *
  • Join Date: Feb 2011
  • Posts: 6426
  • Karma: 35
Re: Hesitancy
« Reply #5 on: 10.10. 2018 20:12 »
blocked vent holes in the tank/carby ?
Ooh, yes, I had that problem once, due to me bungying a map in a plastic folder to the top of the tank.
Good Advice
0
No reactions

Online chaterlea25

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 3345
  • Karma: 47
Re: Hesitancy
« Reply #6 on: 10.10. 2018 20:15 »
Hi Stevejs,
New monobloc carbs seem to run lean,
Settings that worked 60 years ago are no longer valid
I would turn in the pilot adjusting in 1/4-1/2 turn and raise the needle a notch,
Then see if that makes a difference
Magneto condensers can fail with heat, and also through time
Remove the points cover when the bike is misbehaving (engine running) and see if there is arcing across the points..
It would also be worthwhile to check the magneto slipring to see if it has been contaminated by too soft brushes being fitted

John
Good Advice
0
No reactions
1961 Super Rocket
1963 RGS (ongoing)

Offline Steverat

  • Valued Contributor
  • ****
  • Join Date: Aug 2018
  • Posts: 251
  • Karma: 1
Re: Hesitancy
« Reply #7 on: 10.10. 2018 22:00 »
You are confident to have fixed the mucky tank. But are you sure? Did you clean it out chemically with some HCl and washing soda? That will remove deposits which are otherwise resistant to swilling out, but can loosen gradually and block your carb.
Good Advice
0
No reactions

1951 BSA A10 - now returned to Germany
1972 Triumph T100R Daytona
1924 B-S SS80
1965 Triumph SH Cub
1960 AJS M18CS

Offline stevejs

  • A's Best Friend
  • ***
  • Join Date: Nov 2017
  • Posts: 40
  • Karma: 0
Re: Hesitancy
« Reply #8 on: 11.10. 2018 07:23 »
Some new ideas there. I'll work through them. Definitely not a blocked tank cap - fell for that one about 40 years ago! Many thanks.
Good Advice
0
No reactions

Offline Klaus

  • Valued Contributor
  • ****
  • Join Date: Jun 2015
  • Posts: 381
  • Karma: 10
Re: Hesitancy
« Reply #9 on: 11.10. 2018 07:40 »
Hi Steve,
please check the valve clearence befor you go back to ignition and carb.
Doing a few miles after a rebuild the valves set down to their seats and  and often the clearence is null.

cheers Klaus
Good Advice
0
No reactions


If you think, everything is under control, you are not fast enought.