Villiers Mk25 – What Carb?

[vhgmcbuddy]

Hello All. I would really appreciate help on identifying what carb I have on my Mk25 Villiers, and then point me to a manual or something to tell me how to tune it up?

I have cleaned it thoroughly inside but it is still running quite rough, engine missing and a fair few puffs of black smoke.

Picture attached. It only has one adjustment screw on it, as well as a tickler and strangler and is a Villiers own carb, not a Zenith etc. Thanks in advance!

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[andyfrost]

I’m fairly certain that is a variant of the 4/5 Carb , which was unique to Atco(I’m not 100% on that , but have never seen it on any other machine)
It’s a very simple carb to work on and get clean , which leads me to suspect you have an ignition problem , either timing , or coil/condenser failure.

Andy.

[vhgmcbuddy]

Here is a link to a video of it running today – maybe it’s not the carb, maybe the coil is on the way out?

https://we.tl/t-aL0rbuhk4v

Points and timing are all correct.

[vhgmcbuddy]

Thanks Andy. I reckon it must be the coil, I’ve just taken it for a spin on the lawn and once the engine is hot it has lost power and died. Let it cool down and its okish for a while then died again.

[andyfrost]

Couldn’t get that link to work , first and foremost would be to get the coil and condenser PROPERLY tested , and by that I don’t mean wasting ones time with a multimeter.

Andy.

[mickwhitt]

Hi all.
I seem to be having similar problems with my machine.
It will start after 4 or five pulls from cold. It runs for a few minutes then dies and will not run till it cools down.
Been playing with the carb but that doesn’t seem to make much difference.
How would I get the coil tested?
Villiers parts show it as a £75 part which is a bit much just to try.
Mick

[bill-c]

I know it might sound strange but have you changed the plug. Not had much to do with Villiers but I do know Hondas are prone to cutting out when hot if the plug is old.

[mickwhitt]

Curiously I bought a Denso version of the plug that was in when I got it. And that might well be wrong as it was a garden ornament not a runner.
I swapped back to the old plug and it runs, bit of popping back through the carb but it recovers and runs ok.
Shakes like a tin outhouse which I guess is the cutter head, i took off the spring drive bar to cut drive to the blade and it runs fine. So it may be a carb issue as it doesn’t seem to respond quickly to cutting the throttle and coughs back through the intake when it does slow down.
I’m.in the dark with these old 2 strokes, it could be running just right and I’m expecting too much of it. Then again I may be way off the mark on setting it up.
I will try to get hold of an appropriate plug and may replace the HT lead as it’s a bit frayed at the plug end, still give a hell of a kick if I brush past it.
I will carry on tinkering before I drag it to some grass lol. I live on a hill and dragging it back up without reliable engine power is quite hard.
Mick

[andyfrost]

Any reputable garden machinery dealer should have a proper tester , try to go for one that’s been in buisness for quite a while , most modern upstarts know next to nothing about coils and condensers.
Spitting and banging is quite often incorrect timing thoroughly check it.

Andy.

[wristpin]

Points and timing are all correct.

Did you set the timing from basics ie x degrees or fractions of an inch btdc or by using any arrows or marks that you may have found on the flywheel ?

[mickwhitt]

I set my timing by measuring the piston 5/32 of an inch BTDC. I take it that’s right? I simply measured it using a caliper gauge, what is the best way to be accurate? Make a L shaped probe with the bottom part machined to 5/32?
There were arrows and Mark’s on the alloy fan casing and flywheel but as I wasnt sure about them i didnt use them.
George from villiers parts says its probably an ignition issue.
I will check and reset the timing to rule that out before I start replacing things.

[mickwhitt]

This is a you tube video of her running.

[vhgmcbuddy]

In response to your question Wristpin, I had the head off and loosened the flywheel, got to TDC, rotated crankshaft back until the piston was 3/16″ down in vertical travel before TDC and then rotated the flywheel so that the mark on the flywheel matched the mark on the casing, then tightened the flywheel. Never done one before, is this correct?

It now won’t start at all.

I think the oil ring on the piston also needs replacing, has good compression but each stroke brings up quite a bit of oil and the head is fouling pretty quickly.

[wristpin]

It is possible that you may have mixed up two methods of setting the timing. Your original method of putting the piston to the specified amount before tdc and turning the fly wheel unit the points just open is correct.
On some engines, In an move to make things easier Villiers muddied the waters a bit by doing all the initial set up and then stamping an arrow on to the flywheel corresponding to a nib on the casting with the piston positioned at tdc. Muddle the two systems together and the timing will be somewhat amiss.
I would go back to your basic method. Set the correct points gap , turn the engine back to the specified figure and fit and lock the flywheel in the position where the points are just opening .

In case it is of use I’ve just scanned this for you. Interestingly in this edition there is no mention of the “short cut”.

https://www.dropbox.com/s/dhg5cytoyqgb8yr/Villiers%20Mk25%20C25%20ignition%20setting0001.pdf?dl=0

[mickwhitt]

I have cracked it I think. I know it doesn’t sound as good as eureka but it’s the same feeling.
I took the whole fan casing, fan and flywheel off this morning. Cleaned the points and set them to 14 thou.
I used a depth gauge I made to measure from the plug hole to the piston crown, added 5/32 and that came to 20.63mm
I then used that gauge to hold the piston while I set the points to just opening.
When I rebuilt the cowling and fitted the fan the two arrows lined up absolutely bang on TDC.
Two pulls is all it takes to start her now and she will start from hot or cold.

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