When I restored my SS90 I started with original points (dist) and carb (Monobloc).
It idled fine but pick up and higher speed running was poor and got worse as the engine warmed up.
First I installed Pazon EE which helped a bit.
Then I switched the carb to a new concentric with spec: 28mm Premier, 170cc Main Jet, .106" Needle Jet, 19 Pilot Jet and a 3 1/2 Throttle Valve as recommended by Burlen. This helped a bit more.
However the problem is still there - idle is fine cold and warm, pick up is fine when cold, rough when warm as is running at 1/2+ throttle.
I've just ordered some new HT lead and a plug cap. Coil will be next if they don't fix it.
Any other suggestions please?
Thanks,
Bernie
I presume you have a tufnell/heat insulating spacer to the manifold to prevent the carb-overheating?
Yes, tufnol spacer fitted.
Cheers,
Bernie
:) :) :) :)
Any untoward deposits in the exhaust pipe??
Mike 8) 8) 8)
How long do you have to let it cool down before it is useable again?
Have you checked the valve clearances?
Does sound like something is breaking down when hot in the ignition system. Have you tried putting some choke on when running to see if it improves or gets worse to see if it is running weak or rich?
I note Burlen advised on the best setup, but am still wondering if perhaps the fuel is a bit rich. Does it start easily in the cold ?
I realise you have a SS90, but when I asked Dave Smith on concentric set up for my B40 Star ( although I asked specifically RE a 626 setup, and did not query on a 928) he suggested starting with:
pilot jet 20 ( I understand the premier 17 equates to 23cc/min so bigger than a old style 20)
Main jet 160
throttle slide 3
needle jet .106
wondering if the pilot jet is too large and possibly the main jet.
Thanks all. I haven't noticed anything in the exhaust - though not removed pipe to check. Choke makes the running rougher so maybe rich if anything.
HT cable and cap should be here in a day or two so will try those. Valve clearances next and then maybe experimenting with carb components.
Will post back with developments.
Cheers,
Bernie
as you have said, coil will be after.. its a possibility that the coil is breaking down
I take my comments back. Having just checked the original monoblocs & settings for an SS90 and B40 I see why Burlen suggested the settings they did ( it's just possible they know better than me ;D)
So, have now changed carb, switched to EE, also replaced coil, HT lead and plug - same problem.
Start fine and idles nicely. Picks up pretty well when cold. As soon as warm, after a mile or so, it loses power, won't pick up, struggles on even the slightest incline and misfires on pickup.
Still idles fine. Lowering airslide doesn't help, tank vent is clear (can suck through OK).
I don't have my RR book with me at present - could you please advise on valve clearances and any other checks I can make before pulling the top end please?
Thanks,
Bernie
inlet 0.008 exhaust 0.010
just wondering if you have the correct ring/piston clearances as could be nipping up if too close
This might be daft idea but has it been standing over the winter? I had a similar problem with my B40 and it was due to bad fuel that had been in the tank for year or so. Emptied the tank, swilled it out and put fresh fuel in and it ran well.
As usual I didn't think of this until I'd had the carb off twice, completely stripped and cleaned plus checked the timing on full advance and full retard and spent a couple of weeks thinking about all the disastrous scenarios that it could be.
If it has been running ok it is often the simplest things that go wrong.
Thanks, will check the valve clearances and rings if I have to pull the top.
The fuel is the first fill into a newly lined tank (2 part epoxy) and has been standing since about last October so I'll try draining and refilling with fresh before getting the spanners out!
Cheers,
Bernie
Bernie, fuel is a good place to start probably messed up the high speed part of the carb.
when I stripped the Triumph before its rebuild, I had to buy new carbs as the brass insides were eaten away and green from corrosion yet it had been running the season before. got pictures somewhere but not on this laptop.
may be a timely time to mention to all to check carbs after the winter break and refer back to the Ethanol threads. Just came back from France and pumps there have E10 on them, its the Ethanol that is hydrascopic and absorbs water that corrodes the insides, on the A10 its actually eaten away the brass gauze and pipes in the fuel tap and the rubber fuel pipe to the carb.
the fact you said it was running may well be because of the larger jets that are fed and have bigger holes, I would probably have thought there would be some pinking due to water in the fuel BUT always a good test is to smell the fuel being used, decent fuel still smells like petrol, old ( a few months old) looses its smell.
I fired the Laverda up a couple of weeks ago, first time for 2 or 3 years and it ran straight away, no fuel tank on and new fuel apart from what was in the carbs, the little cb250 wouldnt start yet it was MOTd last year and did 30 miles in the year, carb off and clean and it ran ok to test again.....now sold.
I had similar problem with my ss90 on a wassell concentric the previous owner had put on because it wasn't running right on the monobloc. It was breaking up at about 55mph in top and I was convinced it was electrical. I tried plugs , lead, cap, coil, new wiring harness, new magnets on the boyer, still the same. I then decided to try the original monobloc supplied with the bike which it allegedly didn't run right. I did notice the flange was distorted so put a thicker o ring to compensate . What do you know it runs great now. So I think my point is , sure try the electrical stuff but if no joy may very well be the carb. thicker o ring maybe ?