Float height question s25

[akendall1966]

Tried a search but couldn't see an answer

Had set to 3/16 " based on info gleaned from the web. Its Running rich, adjustment of the pilot air screw don't produce the expected rise I revs to tune its position. But note if I turn off the fuel as the float bowl empties rev rise until it stalls.

So I have set it to about 3/8" running leaner now but too lean as the revs hang after closing the throttle. So I guess somewhere in between is right? Or is the pi!of jet wrong can't see any numbers on it to tell.

[John Wakefield]

You dont say what type of engine you have the carb fitted to. The settings are:
Singles 31A - 37A
Main Jet 130 or 140
Pilot Jet 35
Taper 3 1/2
Needle set out 1.85 inches
Throttle slide 3 or 4

Twins 2T 4T
Main Jet 180
Pilot Jet 35
Taper 3 1/2
Needle set out 1.94 inches
Throttle slide 3

There is a thread on the FB Owners Club forum on this topic, http://fboc.niceboards.org/t1017-s25-carb 3/16 inch appears to be normal float hight

[akendall1966]

Hi John,

Sorry 250 single no engine plate so assumed a 32a.

Currently has
No 3 slide
Needle is 3 1/2
Can't see any marking on the pilot jet
Needle set to 1.9"
Main in 140

That thread is the same place I got 3/16 for the float height which seems to make mine run too rich, settled on 1/4 as 3/8 was too lean. Just need to get some main jets to try as 140 is too rich at WOT lots of smoke 😷

[John Pattinson]

S 25 Float Height

Correct measurement for s22 and s25 is 1/4 inch measured between float and seating area for large fibre washer...John P.

[Dick F]

John, nice to hear your reports mate, i was wondering if you use a s25 on your Anglian as a lot of riders do in preference to the Amal concentric, Terry Sewell i know does and i think Dave Spurgeon used to as well they are supposed to be simpler to set up, i was thinking of trying the one odd my TFS as my concentric is 15 years old and getting a smooth take up at low revs is proving difficult also 4 stroking as it wont rev out, it used to be ok but since an engine overhaul it is noticeable , what are your views !!

[akendall1966]

Correct measurement for s22 and s25 is 1/4 inch measured between float and seating area for large fibre washer...John P.

Thanks John P - confirms what I have found empirically the 3/16" quoted on the FBOC forum is wrong. I'll stick with 1/4" and try and dial in the jetting now.

[John Pattinson]

S25 Float Height

Hi Dick, I have a TES not an Anglian but do not ride much these days (knees). I do use a S25 Villiers carb. When engines are overhauled your once perfect setup for your carb no longer is right. You could switch to Villiers or try fiddling with your Amal settings, if it were me I would go back to Villiers, a better carb, easier to work on and fine tune. John P.

[Dick F]

Thanks Marcelle, and John, you are both right in what you say. Yes John i was told that the set up would change ie new crank seals and worn bits and need adjustments .
I wish i could put a Mikuni on, but in the pre 70 scene in scrambles they did ban them! not sure about classic trials though? apart from electronic ignition and modern shocks you cant alter a lot, not like last weeks new Bantam with a fresh stamp on a new fangled frame etc, still i wont go down that road today.

Thanks again Dicky

[John Wakefield]

The Villiers S25 carb is a very simple device as far as carburetors go, & it was designed for two stroke engines by Villiers.
The point to remember when trying to sort out problems is to start from basic settings with a carb that is in good condition. As carbs go the Villiers S25 (and for that matter other Villiers carbs) have a good resistance to wear and apart from worn float needles or punctured floats will still work ok.
My advice before replacing it with a Mikuni, Amal or some other make of carb, is to get the engine sorted with a correctly set up S25. If problems still exist you need to look further into other things & the condition of the engine itself.

[350biker]

Villiers S25 problems

Have found this thread and wonder if anyone can help with the problems I am having getting my 32A engined 24TD Scottish to run properly with the S25 carb?
It's marked as an S25/6 with no choke slide but does have a throttle stop screw. The bike starts easily enough (electronic ignition) when the carb is tickled but I cant get it to idle smoothly and it seems to be running weak. The new exhaust pipe has turned a nice shade of blue on the first bend out of the barrel. Took the carb off to clean it all up, changed the fibre washers and reassembled it. Started the engine up and it seemed a bit better, got it to idle sort of, kept stalling then when it seemed to be idling for 30 seconds or so the revs went skyward and I had to make a dash for the kill button.

I am loath to spend any money on an old carb unless there is an expert out there who can point me in the right direction and dont want to spend a lot of money on a new Amal carb and adapter unnecessarily! Help please, all the Pre65 trials Villiers motors I see when observing just seem to burble along when kicked off - mine sounds to have a very sharp edge to the exhaust note but maybe that is just the pattern exhaust and silencer!

[John Wakefield]

Have you checked that the pilot jet is clear, this being a long tube with the actual jet at the top can get blocked by debris being sucked up the tube.
Try passing a piece of fuse wire through the jet to make sure there is no blockage. Other than that try to borrow another S25 carb and try that so as to eliminate the carb from the problem. Dont go changing carb to an Amal until you have established the problem. The Villiers S25 is a very simple carb and rarely gives problems other than blocked jets or a punctured float.

[350biker]

S25 carb problems

Thanks John, will try this next.

[Brian Thompson]

Villiers Carb Servicing Article.....

Hi Ian,

Sorry for late response on this one.....meant to post this link for you in case you hadn't seen the thread before, but forgot....!

http://greeves-riders.org.uk/forums/showthread.php?t=4136

Don't know if it'll help solve your problem but handy to have for a bit of extra background info, if nothing else....

Good luck, and hope you get to the bottom of it.

Brian.

[350biker]

S25 carb problems

Thanks John and Brian for the help and advice. Took the carb apart and cleared the pilot jet but that made no difference to the problem of the engine revs screaming skywards after the throttle has been closed after being "blipped". Rang Villiers Services to see if they could offer some advice if they had come across this before. Difficult to fault find at a hundred miles away but air leak into the system suspected - from where who knows! I have put a wanted ad on the forum to see if anyone has an S25 surplus to requirements to try to fault find ie carb or engine? Next stage is to send the carb to VS for strip down, ultrasonic clean and fettle as found necessary.
The link to the article was most useful - would like to get a copy for my workshop file somehow, cant print from the thumbnails unfortunately.

[Brian Thompson]

Article download etc......

Hi Ian,

Regarding copying the article, as a check I've just downloaded the first page and tried a 'print to pdf' preview to see how it comes out, and have to say it looked OK on my screen.

It was a little smaller than full A4 'portrait' size, but still perfectly readable.

My printer/scanner is off the road sadly at the moment so I couldn't go any further with it.

I assume you tried downloading it to your computer first? If not, open up the pic, then click on it...it should get a bit bigger.....then click on the image again...it will now be at maximum size, then right click on the image and 'save as' etc....Once you have it stored on your system, open it up and try a print preview and see if it get's you the same result as I got. You many have to check/change settings a bit, i.e. 'fill page', 'set boarders' etc, but if you play around a bit, if needed, it should work fine. It will certainly be OK to view on screen regardless, so at least you'll have a copy on file in your computer, but let me know how you get on producing a 'hard copy'.....

I've always had to be careful with images sizes due to forum bandwidth etc, otherwise the forum software just rejects the upload......old issue from day one, but we've had to do our best with it and resize certain images as required in order to get them on here.

Finally, here's another extremely useful link with some crucial info on Villiers carb specs and applications from Peter Rotherham, one of the GRA's founder members....http://www.greeves-riders.org.uk/for...ead.php?t=1188

Brian.