25DC Sports Twin problems

[grahamyoung1942]

Just joined the GRA having been bought a 1961 250 Sports Twin by my wife for my 70th birthday.
It's been beautifully restored including a complete engine rebuild by Villiers Engineering Services in 2011. Looks lovely, but just won't run properly. Starts fine, ticks over fine, revs up if you only open the throttle a wee bit, but dies completely as soon as you open the throttle wider. Often oils up the LH plug and runs on one cylinder.
So far I've changed the plugs, emptied and flushed the tank and refilled with fresh fuel, stripped and cleaned the carburettor (which was clean as a whistle anyway), checked and cleaned the points (which look like new). Did notice one set of points arcs a lot, the other doesn't (?condenser)
Now run out of ideas.
Had hoped to ride the bike, but looks like I've got a very expensive ornament at the moment.
Any ideas would be very welcome.

[John Wakefield]

Sorry to hear of your troubles Graham, but this seems a common problem with restored bikes these days. Some restorations are not what they are claimed to be. You dont say whether you bought it from a dealer or private seller, but I think the first call should be to the sellor. If its a dealer then he sould put it right, as under the trades description act it is clearly not fit for purpose. The same applies to a private sellor although it might be more difficult to get him to sort it, that is if he has the expertise to do it.
From what you have said it looks like it could be a condenser, or carburettor settings, but without actually seeing the bike its difficult to say.
You could check the carb settings which for a 1961 25DC would be as follows:-
Carb: Villiers S22/2
Main jet: 180
Pilot jet: 35
Needle: 3 1/2
Groove: 3
Throttle slide: 3
Best of luck

[grahamyoung1942]

Thanks John. The carb and it's settings were all correct, I checked when I had it stripped down. I did buy it privately and I'm sure the gentleman I bought it from is genuine. He spent a fortune on it and it seemed ok when I took it off his trailer and drove it the 20 yards to my garage. So I am sure it can't be anything too serious, but it's niggling me that I can't solve it. If all else fails I'm going to trailer it to Villiers Engineering Services and pay for an expert to have a go.

[John Wakefield]

I would speak to the seller first as if as you say he is genuine (may even be a GRA member) he would be only too pleased to sort it out.

[John Pattinson]

2T problems

Hi Graham you may as well fit a condenser as they cost little (to the points set that is sparking) As it is very cold at the moment it may not run much better until warmed up, may be at least 2-5 minutes. You need loads of choke and tickling just to start at the moment and maybe to keep it running until warmed up! Also good clean plugs and check the crankcase drain plugs are fitted and tight. Hope that is some use...John P.

[grahamyoung1942]

Thanks John. All advice very much welcomed. I didn't mention it but I did drain the crankcases and replaced the plugs. Starting it is not a problem, it runs and warms up easily as long as you keep the throttle closed or nearly closed, it's only when you open up the throttle (as if to drive away) that the engine dies.
Will try a new condenser anyway as you suggest.

[John Pattinson]

2T problems

Hi Graham why not raise the needle to the highest position and see if it improves ...John

[Colin Sparrow]

Fifty year old ignition systems do have a problem coping with modern fuels, it might simply be starting technique. The position of the choke shutter can be critical, it can be a fine balance between too weak a mixture to start it and a rich mixture causing oiling. Try experimenting with the choke position when you start it from cold, it might not like full choke.

Also, what proportion of oil are you using? With modern premix oils 30:1 is fine for a 2T, in fact some get away with 40:1.

Congratulations on acquiring an underrated but thoroughly worthwhile little bike. Very suitable for those of us "of a certain age"...

[bryan]

25DC sports twin problems

Hello Graham,I bought a 25dc a couple of years ago,that also is a 1961 model,and had quite a few problems with it,please see 25dc trouble shooting under road bikes.However I had loads of help and am happy to say that the bike now runs really well.So stick with it and do change that condenser cos it cured a similar problem for me.

[grahamyoung1942]

Thanks everyone. New condenser ordered. To answer some points:
Refilled with new fuel and mixed at 30:1 using Villiers Engineering 2t suitable for classics.
Ref choke position, the bike starts up first kick with the choke full on, warms up so you can let the choke off, then dies when you open the throttle. Can't make it actually go (drive it) with the choke in any position.
I did read the whole of Bryan's thread, interesting.
Keep taking the tablets!

[John Wakefield]

Have you checked if the fuel is running freely to the carb ie blocked tap or filter.
Also make sure the tank cap is venting, if not it will cause a vaccume & fuel will not flow.

[grahamyoung1942]

I did check the flow of fuel from the tank (with the cap on) to check the tap and filter were clear, but I have not yet checked the banjo union at the carb end, which I think also contains a filter. I'll do that next, when it's not quite so perishing cold in the garage.
Thanks again for all the help.

[grahamyoung1942]

Just took the banjo union off to check for blocked filter. Certainly wasn't blocked, there was no filter.
Took the carb off again and noticed the needle has no retaining clip so falls right down. Don't know why I didn't see it before, or maybe it fell off when I had it apart before. Can't find it anywhere though despite fingertip search. New one (and a filter) ordered from VES - they do provide a good parts service I must say.
Fingers crossed I'm getting closer to actually riding.

[Colin Sparrow]

Fingers crossed I'm getting closer to actually riding.

Nice when you find something though, isn't it? That's what I hate about electrical gremlins - you can't see 'em.

Bedfordshire - not too far from Cambs group meetings at Barton near Cambridge then...

[grahamyoung1942]

Less than an hour away from Cambridge. What's the general format? Is anyone welcome?