Villiers MK20 HS

Got ourselves a new jigsaw puzzle over the weekend    
Villiers MK20 HS with 5:1 reduction box.
Seems to be all there apart from, as usual, the tank. Certainly needs a new exhaust.

Exhaust studs sheared



Without welding gear to tack on a nut, what's the best method to try and get them out?

Hi Paul,

Cannot see how much stud is still left, but if there is still enough to die a thread you could then put 2 nuts on and tighten together loads of heat and hopefully they will come out, or square them off with a grinder or dremmel and use vise grips with heat, if not enough stud left your going to have to drill them out i'm afraid, it is possible to get reverse drill bits to do the job called easy outs.

Oops copied wrong image.
No thread left so filed flat, drilled out,  loads of Plus Gas and heat and then tried with stud extractor.
Disaster!!  Gave it a bit too much welly and snapped a bit off the casting.  



Guess we'll break it down and sell the bits on ebay. You live and learn.

Hi Paul,

I have a spare head for mk 20 with exhaust studs intact, good valve seats, which you can have for cost of postage, depending on what size piston you have/ bore as the one I have is standard.

Regards

R

Sorry just checked bore is +20 but I have piston which could be better but will do, but will need new rings

Hi Rich,
Thank you for a very kind offer.
I think ours is standard but need to check. Presumable oversize is stamped on the top of the piston - don't have stick micrometer. According to the the 'Operating Instructions' only .015"  and .030 oversizes were available.
Sadly, £37.50 for a set of rings, plus another thirty odd quid for the other replacements we've identified so far, means it's becoming a rather expensive project. Could probably buy a runner off ebay for less.
Will give it some thought and get back to you. Cheers

Huge thanks to Rich for the cylinder and piston. Project on the go again.

Can anyone help with our next problem?
We have been cleaning up the reduction gear and, having removed all the studs, we still cannot get the end cover off. Is it just being help by the end cover bearing? Don't want to do any damage, but we can't see how to get the nuts on the two mounting studs on the inside of the casing?

Got it!
A bit more confidence and the whole thing came off the rear casing.

Hi Woodsman,

Good to hear that the project is back on track again.
Which tool did you use to manage the dismantling of the reduction cover?
We are awaiting for some additional pictures

Do you know if some parts of a other Villiers engines are interchangable with a Mk15?
Sometimes this is mentioned on E-bay.

Best regards,

Steef Pronk

Hi Steef ,

Two screwdrivers followed by two spanners..
Our understanding is that MK20 and MK 25 engines shared the same basic components. Only the bore was different  - Bore = 63.0 mm versus 70mm giving swept  volume of 205.2cc  versus 256.5 cc.
Our understanding is that  MK15 was an overhead valve engine - so different layout to side valve engine.
Not had any experience of side valve so hesitate  so comment

Hi Steef,
Some pictures as requested:






Bit of a puzzle now. We are missing the nuts from the four studs holding the reduction gear to the crankcase. We thought they were 5/16" BSW in the crankcase and 5/16" BSF in the gear casing. However, we can't get a 5/16 BSF nut on. The diameter is 0.305"  - bit small for 5/16" but maybe just wear and tear. However the threads are 26 TPI. That would make it 9/32" BSF but then the diameter should be 0.218".
Very confused!

Hi Paul,

I've recently downloaded a reparation manual of several Villiers engines.
This manual decribes the reduction gear as well.
I will send it to you by PM.
Hope this will help.

Best regards,

Steef

Finally gave in and took the oldball studs to FastPack in York. They also checked thread pitch but could not identify correct nut. Can anyone suggest what it might be - 0.305" diameter and 26 TPI ??

Started to clean up the innards and noticed a nasty big end knock. Split the big end and it appears that it's overheated and melted the bearings. Oh dear    Looks like this engine is turning into a pick and mix job.

Woodsman wrote:Finally gave in and took the oldball studs to FastPack in York. They also checked thread pitch but could not identify correct nut. Can anyone suggest what it might be -  0.305"  diameter and 26 TPI ??

One solution to this would be to re-make the studs in a more normal thread size.

I don't have a thread table here to check, but off the top of my head, aren't Brass threads 26 TPI.  And for some strange reason sizes (at least all the common sizes), are the same pitch; 26 TPI.
Seems very odd that a brass thread should have been used on steel studs in an alloy casting!  Unless someone had a heap of them and replaced the existing ones?
BTW, most male threads when measured are often noticeably under the nominal size, sometimes even when new.

Cheers
Darryl

Yes, making new studs seems like the way forward - maybe get some 5/16" BSW bolts and chop the heads off.
Will have to see how we get on with the worn crank.

How about this:



I'm fairly convinced that the 26 TPI thread is 5/16 BSC (that's British Standard Cycle just in case you were wondering).
In the example above the external diameter is 0.309 inch, so close to your original measurement.

Nice one Blue Cat!
Will try our usual suppliers and see what they come up with.
Many thanks.

Well if your usual suppliers come up wi' nowt, I have a few here.

Thanks Blue Cat. Will follow up on return from holiday - off to Hong Kong

Reading through page one I thought to myself "That's BSCY thread". The exact same thing happened to me on a JAP engine, & my local fixings place failed to recognise it. Seems strange that Villiers used it though, I would've thought they'd use either UNF or BSF.

I printed off a load of thread charts from the internet (look for PDF files, they seem to print off better) & laminated them. Punched a hole in the top centre & they all hang from panel pins in my workshop. Couple them with a set of thread gauges & digital vernier & you'll never be stuck again
I've found my laminating machine very useful for the workshop, as well as my engine info sheets & period adverts I display at the rallies.

Hi Matt,
Now you've made us feel foolish! We also have a full set of laminated thread charts, plus thread gauge and digital vernier, but never thought to look at BSCY. Dur!
However, given the worn crank, we've decided to use this engine as a donor and move on the the MK20 which also has a reduction gear. Will start a new thread.

It's one of those threads you don't expect to find on a stationary engine. But it's also one of those "live & learn" moments that'll never get repeated. It took me ages to identify it on my JAP, I didn't have any thread charts or gauges, I had to count the threads against a steel rule & google what I found. Took me ages! That's when I decided on keeping thread charts in the workshop (although it was more of a shed at the time, it's come on massively since then).