Latest topics
» 2t Villiers Electronic Ignition etc
Yesterday at 9:10 pm by stuart elkes

» Cruiser 39 Dynamo
Yesterday at 6:29 pm by piston 197

» Cruiser piston rings needed please
Tue Oct 16, 2018 10:40 am by kerabo

» WIRING HARNESS WANTED
Tue Oct 16, 2018 10:38 am by kerabo

» Stafford Show
Mon Oct 15, 2018 6:39 pm by stuart elkes

» What's this?
Sun Oct 14, 2018 8:34 pm by piston 197

» head bolts 8e
Sun Oct 14, 2018 12:55 pm by alan67

» Copdock and Scotland
Sat Oct 13, 2018 7:21 am by alan67

» 2 7/8" tank badges
Fri Oct 12, 2018 10:00 pm by FrankG


Villiers S25/7

Go down

Villiers S25/7

Post  Bigjim on Sat Oct 21, 2017 6:17 pm

Hello
Does anyone know the thread for the throttle stop screw, as used on the Villiers S25/7. Someone on FBook wants to modify their S25 carb, to have a throttle stop. The boss is there, but nothing else.
BJ
https://www.facebook.com/photo.php?fbid=401228333628119&set=p.401228333628119&type=3&ifg=1


Last edited by Bigjim on Sat Oct 21, 2017 9:56 pm; edited 2 times in total
avatar
Bigjim

Posts : 167
Join date : 2016-06-13

Back to top Go down

Throttle stop

Post  kerabo on Sat Oct 21, 2017 6:32 pm

Hi Jim

Any chance of posting a picture of this carb. I find it's the one thing I don't like about Villiers carbs is the fact the idle has to be set on the cable.
Thanks Ken
avatar
kerabo

Posts : 2439
Join date : 2008-02-11
Age : 68
Location : Falcon 87..1936 Cruiser 39. Falcon 81 Green Lane bitsa. Sunbeam S8. Honda Deuville.

Back to top Go down

Throttle stop screw

Post  piston 197 on Sat Oct 21, 2017 6:45 pm

The slide on all S25 carbs have a cut-out for a throttle stop screw, but only the late S25 bodies have the boss to fit a stop screw, the ones used on the micro/invalid cars were fitted with a stop screw to set tickover. whereas the motorcycle ones generally had an untapped boss, early model s25 carbs did not have this boss. Generally speaking the air mixture screw will double as a throttle stop screw if you have a spare mixture screw, if the boss is untapped, it needs to be tapped out to the same thread as the stop screw.
JH
avatar
piston 197
Moderator

Posts : 4066
Join date : 2008-08-17
Location : ross-on-wye

Back to top Go down

carb..

Post  john87 on Sat Oct 21, 2017 7:42 pm

Asuming no-one else posts first, i will have a look tomorrow and tell you what thread it is..

john..

john87

Posts : 224
Join date : 2015-10-24

Back to top Go down

2 stroke carburettors

Post  FB vincent on Sun Oct 22, 2017 9:03 am

kerabo wrote:Hi Jim

Any chance of posting a picture of this carb. I find it's the one thing I don't like about Villiers carbs is the fact the idle has to be set on the cable.
Thanks Ken


Ken,

Although it may be a problem for trials riders or Bond minicar (etc) drivers, for traditional two stroke road machines the throttle should shut completely and the idle speed set by the rider when required. This is to avoid a build up of mixture and 4 stroking on the overrun.

It was not just Villiers who did not provide a throttle stop, Amal carburettors (but not the Monobloc) fitted to other makes of small two strokes were the same.

The later AMC engines with an Amal Monobloc were of course originally designed for 4 stroke engines, which have different characteristics to our 2 strokes. I have always run my 20T engine with the throttle stop out of use, but with the twist grip friction control set correctly.

Sandy

FB vincent

Posts : 663
Join date : 2009-01-20
Location : Hertfordshire

Back to top Go down

Throttle stop for the Villiers S25/7

Post  Bigjim on Sun Oct 22, 2017 10:25 am


Amal did make 2 stroke monobloc carburettors. Though they were dedicated 4 or 2 stroke versions. the concentric can be adapted from 4 strokes to 2 strokes, by changing the main jet & jet holder and the needle, plus the jet block angled spray can be swapped in.
AMAL made 2 other different spray versions, one for Norton & one for Triumph, that each had differing angles, to suit the needs of the two companies.

http://amalcarb.co.uk/carbspec/carburettor/spares/id/5143/ On the Amal web site, for a early 60s FB they have an ASK on the jet block where you would put quantity. They are asking if it 4 or 2 stroke
avatar
Bigjim

Posts : 167
Join date : 2016-06-13

Back to top Go down

carbs..

Post  john87 on Sun Oct 22, 2017 12:02 pm

Hi all,

Having had a quick look, the thread is EITHER 3/16 BSF or 2BA. the thread form is completely different though, so you need to try a mixture screw in a 3/16 BSF nut to find out. i will try to have a proper look later!!

john..

john87

Posts : 224
Join date : 2015-10-24

Back to top Go down

thread pitch etc

Post  Bigjim on Sun Oct 22, 2017 12:53 pm

john87 wrote:Hi all,

Having had a quick look, the thread is EITHER 3/16 BSF or 2BA. the thread form is completely different though, so you need to try a mixture screw in a 3/16 BSF nut to find out. I will try to have a proper look later!!

john..
3/16" BSF is 32tpi
2BA is 31.35 tpi a gnat's whisker different
great web site for thread data
https://mdmetric.com/tech/thddat8.htm#bsf
avatar
Bigjim

Posts : 167
Join date : 2016-06-13

Back to top Go down

carb

Post  john87 on Sun Oct 22, 2017 1:58 pm

Yes, the pitch is close, but the threadform is different. One is 47 1/2 degrees, the other 55, both have rounded roots and crests, but as to the proportions, they will be different. They are close, but with threads, there is no such thing as close, it is either right or wrong.

Likewise, Whitworth and UNC are most definitely NOT the same, no matter what the local bike shop might tell you.

Very importantly for bikes, BSP and NPT are different, so when you buy cheapo petrol taps from china, they will not fit your tank.... [unless you just force it in...]

john..

john87

Posts : 224
Join date : 2015-10-24

Back to top Go down

threads

Post  Bigjim on Sun Oct 22, 2017 2:49 pm

john87 wrote:Yes, the pitch is close, but the thread form is different. One is 47 1/2 degrees, the other 55, both have rounded roots and crests, but as to the proportions, they will be different. They are close, but with threads, there is no such thing as close, it is either right or wrong.

Likewise, Whitworth and UNC are most definitely NOT the same, no matter what the local bike shop might tell you.

Very importantly for bikes, BSP and NPT are different, so when you buy cheapo petrol taps from China, they will not fit your tank.... [unless you just force it in...]

john..
What I was saying; is that even with a thread gauge, it would hard to spot 32tpi or 31.25tpi. At this mall diameter, even 47.5 and 55 is hard to spot. But any nut, given a big enough spanner can be made to fit. Bodge job though.
avatar
Bigjim

Posts : 167
Join date : 2016-06-13

Back to top Go down

Carbs

Post  john87 on Sun Oct 22, 2017 4:14 pm

Yes, i agree!! I Will get out the thread gauges leter and a loupe and have a proper look.

What you think though?? BSF i would imagine??

Buzzing at the second as about 10 minutes ago i got my falcon 81 running for the first time since 1975. It has been in bits in boxes ever since!! Started first time too!!!

john..

john87

Posts : 224
Join date : 2015-10-24

Back to top Go down

thread

Post  Bigjim on Sun Oct 22, 2017 6:19 pm

john87 wrote:Yes, I agree!! I Will get out the thread gauges later and a loupe and have a proper look.

What you think though?? BSF I would imagine??

Buzzing at the second as about 10 minutes ago I got my falcon 81 running for the first time since 1975. It has been in bits in boxes ever since!! Started first time too!!!

john..
Great news, but what is a loupe?
avatar
Bigjim

Posts : 167
Join date : 2016-06-13

Back to top Go down

carbs

Post  john87 on Sun Oct 22, 2017 6:38 pm

The sort of thing that jewellers look through when examining diamonds!!

They are well worth having. You can put two bolts together, say a whit and a unc, and look at where they meet. You can see the HUGE difference and how the threads only touch at the tips VERY clearly. They do not cost much, i have a few, a 30X and a 40x and one mounted on a glasses frame.

If you see one for sale, get it, they really are very useful.


john87

Posts : 224
Join date : 2015-10-24

Back to top Go down

loupe

Post  Bigjim on Sun Oct 22, 2017 7:05 pm

john87 wrote:The sort of thing that jewellers look through when examining diamonds!!

They are well worth having. You can put two bolts together, say a whit and a unc, and look at where they meet. You can see the HUGE difference and how the threads only touch at the tips VERY clearly. They do not cost much, i have a few, a 30X and a 40x and one mounted on a glasses frame.

If you see one for sale, get it, they really are very useful.

My other half has one, she used for her geology work. Now I know its proper name
avatar
Bigjim

Posts : 167
Join date : 2016-06-13

Back to top Go down

Carbs..

Post  john87 on Sun Oct 22, 2017 7:34 pm

See what i meant about useful though!! I am well pleased with mine!!

john..

john87

Posts : 224
Join date : 2015-10-24

Back to top Go down

Re: Villiers S25/7

Post  Sponsored content


Sponsored content


Back to top Go down

Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum