Adding a throttle stop to a S25 carb

[akendall1966]

Hi All,

I have read some threads where it has been said people have added a throttle stop to the S25 to mimic the version used on mini cars.

Can any one share the specifics of this mod, I would like to be able to not have choose between turning left without accelerating or the engine ticking over without holding the throttle!!

With only the S25 that is on the bike availiable, and that it seems to be working quite well I would like to follow some proven guidence. I have the kit and knowledge how to drill and tap OK.

Thanks
Adrian

[John Wakefield]

S25 idle screw

Look at this thread all details on how to fit an idle screw are in there http://www.greeves-riders.org.uk/for...ead.php?t=4524

[akendall1966]

Cheers John,

My membership isn't done yet so can't see that one yet. Probably why I didn't find anything on my searches.

Good to know the info is there, thank for you help.

Adrian

[akendall1966]

Full member now

So had a look at that thread but my s25 doesn't have the boss to drill and tap

No other option than a different carb I guess?

[Andy Z]

Full member now

So had a look at that thread but my s25 doesn't have the boss to drill and tap

No other option than a different carb I guess?

There are S25 carbs with the boss on ebay quite frequently. Since you only need the body, an incomplete one will suffice, and be a fair bit cheaper.

[John Wakefield]

S25 carb for sale

I was talking to Dave Pink tonight at the Cambridge Group meeting & he has a complete S25 carb for sale with air filter & throttle cable. Price £65 tel Dave on 01223 880525

[akendall1966]

Wot I did......

So I have a throttle stop now

To overcome the lack of a cast in boss on my MkIII S25 I...

Drilled a 2mm pilot through the carb wall, drilled some brass rod with the same pilot drill and parted off approx 4~5mm piece. Spot grit blasted the card and boss to roughen. Epoxied the 2 togeather using the drill as a locating dowel, remebering to carefully pull the drill out before fully hard.

Epoxy used was jb weld, is reputed fuel reistant, high working temperature, low viscosity and wets out nicely to give a broad fillet to support the boss. Once fully hard (at least 24hrs) drill and tap, I did M4 becuase I had that tap on hand. Screw is a bodge until some M4 grub screws arrive. Was hoping to use a locknut but its too close to the pilot air screw for that, so will likely dab some silicone gasket once I an happy with the setting to stop it moving.



I think with the colour of the epoxy it wont look too obvious. Just hope it proves durable.

[John Wakefield]

Rather than mess about with thread sealant on a grub screw, use a conventional headed screw with a spring. Not sure that the JB Weld will hold once the ethanol gets to it, its epoxy resin after all & ethanol softens it.

[akendall1966]

Rather than mess about with thread sealant on a grub screw, use a conventional headed screw with a spring. Not sure that the JB Weld will hold once the ethanol gets to it, its epoxy resin after all & ethanol softens it.

I didn't want to have to try and drill tangentally to the round carb body, so the tick over screw is angled towards the pilot air screw and would interfere witht it if it had a head and enough length for a spring. A reduced hex thin lock nut if such a thing exists in M3 would do. Bit more of a faf as you need a spanner and driver to adjust tick over, but not something you have to do to often.

Hopefull apart from an spalash of fuel from the tickler it wont see much where it is and cause it to debond. I'll keep a look out if a body comes up with the boss cast in at the right price, I can swap later.