LCGB Forums

Hi folks, wonder if any kind souls can help me here, I used to be able to sort out many problems but this one's got me. I've a 1967 SX200, totally standard, still on points / condenser. Starts up quite well, ticks over fine after a little while, but as soon as I put it into first gear and ride off its immediately got no b-llocks at all, really struggling, almost like 4 stroking if I remember that symptom correctly. Spark is bright and looks very lively, carb been cleaned God knows how many times, exhaust an old 90s one but new when I had it and probably done less than 1K. New plug, fresh petrol, 33:1 ratio. Petrol flow fine. Carb air screw out one turn (tried every concievable position above and below). If I take the air filter out and put elbow / hose back on there's no change and still runs crap, but if I take the whole thing off and ride it without there's a significant improvement indeed.
Any ideas gratefully recieved!
Cheers!

Stuck rings ?

Spark breaking down under load, very common. Try another coil, plug lead and if all fails could be the stator. Few other threads on this recently including my old GP a few months ago. Try the search engine, good luck.

Thanks for those chaps, lead quite a newish one and cap newish also, but I have a spare coil so I'll see if that makes a difference.

From the description, it could well be down to several factors.

If the carb is original, it could have worn. The slide &/or jets may be past their best, not forgetting the float needle which may be the old type & gone hard. Presumably the choke plunger is not allowing any enrichment. Any of the issues stated will cause richness.

The exhaust may be bunged up, despite the low mileage. There is a tendency to over-oil in the pre-mix & your engine was designed to run on 2% of the snake oil available @ the time.

If the air filter bellows are 'new' then they are very likely to collapse inwards as the Indian ones would appear to be made from old, used male contraceptives. Black ones, of course.

What is it like if upon starting, warming up, turning off the fuel, then running it until the carb is empty? If it sounds better/cleaner before it conks out, that would confirm to me problems on the intake side as suggested above.

This is going to be controversial. Don't get too hung up on the need to retard the ignition from the OEM settings. You know the kind of thing: a 'safe' 19 degree BTDC & then some equating to 17 degrees. A mate of mine (stuck in the time warp since last ownership in the 70's) built an engine using the old settings, unaware of the 'advances' in timing (please excuse the reverse psychology pun) & it runs as sweet as a nut.

Just as further advice, (IMHO & experience) do not use a suppressed plug cap with points, though that will not be the likely cause of the running problem. Suppressed caps were originally fitted as a means to suppress radio interference, but technology with home entertainment has moved on, negating that requirement. I hear that Coronation Street is still on the telly, but surely not in colour

Thank you for that interesting answer Warkton, I did actually try another very clean carb off a mate across the road, another SH1/20 albeit off a Pacemaker. Absolutely no change in running or starting at all.
The air filter is an oldish one but looks in good order, as I say the scoot hasn't dsone mega mileage in the last 10 years or so. I did think about the exhaust too.
I'll certainly try some of your suggestions, thanks again!

Warkton Tornado No.1 wrote:From the description, it could well be down to several factors.

The exhaust may be bunged up, despite the low mileage. There is a tendency to over-oil in the pre-mix & your engine was designed to run on 2% of the snake oil available @ the time.

Good shout. Worth spending 10 mins whipping box off and giving it a shake - a baffle could have come loose and is restricting flow.

Thanks for the kind comments, Chaps

Now. Having read through the symptoms again, I have another suggestion. Just between you & me, right (Don't want any of the "Change-to-Electronic-for-reliability' Brigade getting wind of this!)

Your condenser could be on it's way out. If you haven't a spare, AFR knock them out nice & cheap. Worth stocking up on points as well. Double spring, natch. Oh, & whilst I'm emptying your wallet, Champion plugs (N3) & a Champion non suppressed cap.

Now remember. Mum's the word.......