Author Topic: Sloper S30-13 performance issues  (Read 2776 times)

0 Members and 1 Guest are viewing this topic.

Gadorey

  • Blue Star
  • **
  • Posts: 86
    • View Profile
Sloper S30-13 performance issues
« on: 15 October, 2020, 10:44:35 »
Hello everyone,

I'm new to the forum so a short introduction.  I own a Sloper S30-13 which I restored three years ago. After a catastrophic failure of the old piston, I rebuilt the engine again - I redid the main bearing which was already quite worn, new piston, rings and pin, new small end bush, rebore, new valve guides and springs.  Amazing - after the rebuild she started on the first kick without complaints.

After an initial running in phase, I have now been doing tuning rides to see how she performs at top speed, but the results were somewhat disappointing.  She starts reliably on the first kick and settles in a stable idle, pulls very well, and accelerates up to 70-75km/h without any problems and can cruise at those speeds all day.  Beyond that it's a struggle.  After a very loooong straight at WOT she eventually reaches 80km/h and tops at about 85km/h.  After that there's nothing.

Since there are no signs of an ignition timing problem, I started experimenting with the needle setting on the carburettor. After trying all 5 needle positions, the best performance on mine seems to be on the third notch from the bottom.
However, none of the needle positions made a change on the top speed.  To be noted, at this top speed of 85km/h the engine doesn't seem to be struggling or being tortured - it just seems to not be able to increase the rpms beyond that.  So now I'm out of ideas and hoping for some pointers from the experts here in the forum.

My gearing is for solo work: engine 21t, g’box 19t and final drive 42t. Timing is set at TDC, fully retarded, fag paper just pulling out of the points. Carburetter is an Amal 6/024.  I also double checked that the slider and choke are closing and opening fully, which I can confirm.  After warming up, my choke lever can be anywhere between 3/4 and fully opened. If below that, there is a drop in performance, so the mixture also seems to be OK.

The only other "problem" I have since the rebuild is a somewhat large oil leak from the middle of the pushrod covers, where they telescope into each other. There is no seal there as far as I know.  Is this a known issue? and if so are there are any known cures?

Cheers,
Gui

MDeneve

  • Star
  • *
  • Posts: 1
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #1 on: 15 May, 2021, 07:47:48 »
Dear  Gui,
It seems I'm facing the same trouble ie finding more power  or "nervosity".
Can you tell me how many inch (or mm) did you put before TDC, fully retarded?
Maybe it's a question of ratio before g'box and final drive .
br Michel from Belgium

BEVANC

  • Royal Star
  • ***
  • Posts: 148
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #2 on: 15 May, 2021, 11:16:45 »
Hi Michel, my S29 runs fine with the timing set to points opening at tdc on full retard. This is what the owners manual recommends. I think that equates to 10.7 mm or 35 degrees before tdc if fully advanced. Cheers, Bevan.

Gadorey

  • Blue Star
  • **
  • Posts: 86
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #3 on: 15 May, 2021, 12:25:01 »
Salut Michel,

My timing is set like Bevan said and what the manual recommends - points opening at TDC and full retard.

My gearing is standard for solo work.

Although I have the right and original carburetter, I found that the jetting and slider were wrong. So I got the right jets and slider for it, but this made no change. My top speed is about 90km/h and that‘s it. The engine doesn‘t sound or feel over worked, but she just doesn‘t go beyond that. I really don‘t know what could be the reason at the moment. 

Gui

idie

  • Golden Flash
  • *****
  • Posts: 996
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #4 on: 15 May, 2021, 13:39:31 »
Maybe the valve timing is out.

Gadorey

  • Blue Star
  • **
  • Posts: 86
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #5 on: 15 May, 2021, 13:58:30 »
Idie,

That has crossed my mind. The cam gears are meshed with the timing marks all on their right spots. I‘ve wondered though if due to wear the rocker arms are not opening the valves as they should or something like that. The valve springs are new and the valves were reseated with new guides as well.

Y13 Alan G

  • Royal Star
  • ***
  • Posts: 139
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #6 on: 15 May, 2021, 16:14:56 »
I quote from the 1929 BSA OHV Sloper handbook:
MAGNETO TIMING
To retime the magneto first remove the magneto gear wheel. Remove contact breaker cover and spark plug. Rotate the engine in the forward direction until the inlet valve closes. Then insert a pencil or rod through the sparking plug hole and move the engine still further until the piston is felt to be at the top of its stroke.
Move the ignition control lever (or twist grip) on the left handlebar to the fully-retarded position and turn the magneto shaft in the correct direction (i.e., clockwise from the contact breaker end) until the platinum points P have opened not more than 3/1000in (test with feeler gauges).
Lightly tighten up the magneto gear wheel and check the timing by finding the top of the compression stroke again and examining the position of the points. If correct finally tighten the magneto gear wheel nut.
Hope this helps.

Y13 Alan G

  • Royal Star
  • ***
  • Posts: 139
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #7 on: 15 May, 2021, 16:20:16 »
Further update. 496 CC OHV Sloper 1929/30 should have a top speed of about 70/75 mph. Safe cruising speed 55 mph.

Gadorey

  • Blue Star
  • **
  • Posts: 86
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #8 on: 15 May, 2021, 17:36:13 »
Hi Alan,

Thanks and it‘s what I followed. I really don‘t believe the ignition timing is my problem. The Sloper is also not the only British classic motorcycle I restored and run, so I do have some experience. But always good to check because I don‘t rule out making a mistake somewhere.

My highest ever top speed was 94 km/h which is about 58 mph, and that‘s at WOT on a long straight after about a mile. She cruises all day at 75-80 km/h without any problems, pulls well and starts hot or cold on the first kick. There just doesn‘t seem to be any power above 85kph and it‘s a struggle to get even past 90kph.  So, something is not quite right, but I just can‘t find it.

Gadorey

  • Blue Star
  • **
  • Posts: 86
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #9 on: 15 May, 2021, 18:35:39 »
Here‘s further information on my sloper:

Carb:
Amal 6/024  1 1/16“ with air cleaner canister
New needle 3rd notch from top
New Main jet 160
New 6/4 slider.
New needle jet .106

Gearing:
engine sprocket 21 teeth
Gearbox output sprocket soll 19 teeth
rear wheel chain wheel 42 teeth
Clutch chain wheel 48 teeth

New main bearing rollers
New piston, rings, pin, small end bush and rebore
New valve guides
New valve springs
Valve seats recut and lapped
New clutch plates (doesn‘t slip nor stick)
Magneto and points refurbished.

Mike Farmer

  • Golden Flash
  • *****
  • Posts: 2549
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #10 on: 15 May, 2021, 20:09:29 »
 :) :) :)

Is the engine perhaps a bit tight after all the new work ???

Mike 8) 8) 8)

MGI

  • Silver Star
  • ****
  • Posts: 331
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #11 on: 16 May, 2021, 07:34:29 »
Just a thought...does it rev higher in the intermediate gears, there are very cheap tachos on fleabay (less than £20) which enables comparisons to be made, obviously if it revs significantly higher in (say) 3rd than top it could be the gearing that requires attention.

JohnCH

  • Star
  • *
  • Posts: 5
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #12 on: 16 May, 2021, 09:06:50 »
Have you tried a plug chop after a top speed run? That might give an idea of whether there’s a mixture problem.
Also, is the float level correct?
Finally, is fuel flowing freely to the carb? I once had a performance issue which turned out to be fuel starvation caused by a lump of fluff in the pipe. It would allow enough fuel through to start and run, but not for fast running. Sounds unlikely, but.......

Gadorey

  • Blue Star
  • **
  • Posts: 86
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #13 on: 16 May, 2021, 10:56:39 »
She doesn‘t rev higher on lower gears and accelerates well through the range.

I haven‘t tried a plug chop, but will have to try that one of these days. Same with the float level, although if it‘s low, I really don‘t know how to adjust it on this type 6. I have checked the fuel flow and it‘s free. I might have to adapt a larger fuel hose to see if that makes a difference to my cooper pipe.

Playing with the choke lever doesn‘t give me any indication that the mixture is weak. When I start shutting the choke the performance goes down.

But do keep sending your suggestion and ideas for me to test. Eventually I‘ll find something.

JohnCH

  • Star
  • *
  • Posts: 5
    • View Profile
Re: Sloper S30-13 performance issues
« Reply #14 on: 16 May, 2021, 11:30:47 »
It’s not really a case of adjusting the float, so much as checking it’s OK. Float is not punctured, needle seals on the seat, float is properly clipped to the needle. Just eliminating basic bugs.
A Sloper at WOT will drink at least 110cc of petrol per minute, so that gives a flow rate to aim for.
If the power seems to be rpm limited, could it be the magneto weakening at high revs? I don’t know if this can happen, just a thought. Also, I have in the past had a refurbished magneto come back to me with a dodgy armature.
I would also experiment with ignition timing. Even though you have done it by the book, think about advancing it a tad at static. Mark the lever position where it is correct by the book, set to this position, test your top speed, then carefully advance the ignition. If you gain speed that will show that the engine is capable of operating at higher revs and that you don’t have a breathing or fuel supply problem.