Author Topic: 1914 HUMBERETTE "Cyclecar" Valve Timing  (Read 221 times)

Offline Lillianbrooks

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1914 HUMBERETTE "Cyclecar" Valve Timing
« on: September 15, 2020, 05:27:43 AM »
Hello all, I guess I'm an imposter because my "bike" is in fact a Cyclecar - a 1914 Humberette, 998cc, 84x90, 50 Degree, V-twin.  In an attempt to get more sting out of it, I'm appealing to the experts - YOU, for advice. i believe original timing was Inlet opens TDC, closes 50 past BDC and Exhaust opens 50 before BDC, closes TDC.  It's very like an early J.A.P. motor and from what I've read on your forum, the J.A.P. Inlet opens 16 before TDC, closes 65 after BDC and the Exhaust opens 65 before BDC, closes 25 after TDC - which is a hell of a difference.  Then I look at other British bikes of that era and get more confusing stats.  My dilemma is do I leave it alone or go for the J.A.P. or similar setting - so I'm asking any old blokes on the Forum, what do you think. (I've never found an original SMITHS carburettor and have previously run brass Zeniths.  I'm now about to fit an Amal model 289, my limited brain-power reasoning that if it feeds a BSA 500cc. it should feed my 998cc twin.). ANY SOUND ADVICE WELCOME.

Offline cardan

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Re: 1914 HUMBERETTE "Cyclecar" Valve Timing
« Reply #1 on: September 15, 2020, 06:20:04 AM »
It's very like an early J.A.P. motor and from what I've read on your forum, the J.A.P. Inlet opens 16 before TDC, closes 65 after BDC and the Exhaust opens 65 before BDC, closes 25 after TDC  - which is a hell of a difference.

Hi,

Yes indeed a hell of a difference, because those numbers go with a JAP racing engine of the late 1920s - something like a KTOR fitted to a bike lapping Brooklands at 100+ mph, not a 1914 light car. A pre WW1 engine with any overlap of the valves is a rare thing indeed, and only a handful of wizard tuners of the day would dare to suggest anything other than closing the exhaust valve before opening the inlet. Much was learned from aircraft engine development during the war.

Your dilemma is easily solved. Leave it alone, or sell it to someone who appreciates it for what it is. The Humberette is in many ways the prototypical "sports car" of the veteran era. Standard, and well sorted, they run along very nicely and climb most ordinary hills, and a hoot to drive. Find a Smiths carburettor and get all those little jets just as they were intended to be in 1914...

Not sure whether this is "sound advice" as I don't classify myself as "any old bloke", but at least I haven't resorted to fitting AMAL carburettors to my veteran bikes.

Cheers

Leon

Offline chaterlea25

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Re: 1914 HUMBERETTE "Cyclecar" Valve Timing
« Reply #2 on: September 15, 2020, 09:07:03 PM »
Hi,
The 16/25 timing also applies to the 500/600 "sports" sidevalve 
(only this afternoon I was timing up a J.A.P KT V twin (1929) and it has overlap , I have not measured up the amount yet as I put the crank pinion for a minute down and it seems to have gone AWOL  >:(

Some years ago I was asked to come up with cam timing for a 1904 Minerva single cylinder car when a new cam had to be made. I suggested the J.A.P 16/25 timing , It worked out well, The owner of another Minerva visited and test drove the car commented "I wish mine went that well"

I know that owners of Veteran Triumphs play with the cam timing to improve performance and hill climbing by advancing the inlet cam (?)
Does the Humberette have a single or separate cams? experimentation is more difficult with a single camshaft
The J.A.P KT has three key ways in the crank pinion so the timing can be fine tuned

John

Offline Lillianbrooks

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Re: 1914 HUMBERETTE "Cyclecar" Valve Timing
« Reply #3 on: September 15, 2020, 11:35:05 PM »
Thanks Leon, you certainly don't mince word.  Not used, here, to such "direct" advice. you are my first experience with a Forum. Here's a few facts from an old bloke. You're talking to an Australian who's had the Humberette for about 14 years  (and has had genuinely restored veteran and vintage cars. with correct parts, including carburettors, for 50 years), does appreciate his Humberette and certainly would fit a Smiths carburettor if I could find one.  We don't drive cyclecars around villages here but punish the poor little things on 100 km rallies at times, sometimes on inappropriate roads.  There are about 14 Humberette in Australia and none with a spare Smiths carburettor. (I have searched Ebay for 14 years for said carbie. Find me one and I'll fit it!)
Thank you for your advice.  I will leave the timing alone.  The rest of your advice and opinions was unnecessary.

Thanks John for your answer. It's appreciated. The Humberette has separate cams but Leon seems to have given me good advice, in his charming way, to leave it alone - so will do so.

Offline cardan

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Re: 1914 HUMBERETTE "Cyclecar" Valve Timing
« Reply #4 on: September 16, 2020, 02:54:41 AM »
Here's some JAP timing figures, from the 1920s.

The Collier brothers' Matchless that raced at Brooklands pre WW1 had 0 degrees overlap, with both exhaust closing and inlet opening at 20 degrees after TDC. http://earlymotor.com/leon/misc/html/timing.htm

Hope you've swapped out the original rods for a pair of Carillos! Enjoy "punishing" the Humberette, but don't expect everyone to be impressed.

I have a Smiths carb somewhere, or I did have, but I think it was a bit large for a Humberette.

Leon

Offline Lillianbrooks

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Re: 1914 HUMBERETTE "Cyclecar" Valve Timing
« Reply #5 on: September 16, 2020, 08:56:08 AM »
Thanks Leon, I have previously used at one stage a SMITHS from a Bullnose Morris but of course needed a manifold extension, whereas the Smiths for a Humberette uniquely fits between the cylinders. Am still operating the original piggy back rods and have just had them re-bushed ,etc. Please let me know when you've found a SMITHS that fits between cylinders.










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Offline R

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Re: 1914 HUMBERETTE "Cyclecar" Valve Timing
« Reply #6 on: September 16, 2020, 09:33:18 AM »
Just out of curiousity I went looking to see what this little jigger looks like.
https://images.prewarcar.com/pics/fb-1080x1080-caradverts/216403/1630_1486287173_resized_humberette1.jpg

Its a proper little car. !
And it notes there someplace that it had a sizeable production.

The Smiths carb sounds intriguing.
Can't say there is one under my bench....
Apparently if you paid an extra 15 quid you got a watercooled version of the engine.


Offline R

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Re: 1914 HUMBERETTE "Cyclecar" Valve Timing
« Reply #7 on: September 16, 2020, 09:38:45 AM »
There is even one sectioned in a museum
Not a very good pic...

https://collections.museumsvictoria.com.au/content/media/6/24356-small.jpg

Offline Lillianbrooks

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Re: 1914 HUMBERETTE "Cyclecar" Valve Timing
« Reply #8 on: September 18, 2020, 09:43:51 AM »
Now you know what I'm talking about when I say it sits between the cylinders - and why I have to add a manifold to fit any other carby - including a Smiths from Morris, etc.  Mine is a water-cooled model.  Unlike U.K. from what I've read, we often start with "wrecks".  Mine had the wheels rotted off before the owner would sell so it lives on 19" m/c rims.

Offline Lillianbrooks

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Re: 1914 HUMBERETTE "Cyclecar" Valve Timing
« Reply #9 on: September 18, 2020, 09:48:09 AM »
My radiator's not original but I have a modern core surrounded by a look-alike Humber radiator shell.

Offline Lillianbrooks

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Re: 1914 HUMBERETTE "Cyclecar" Valve Timing
« Reply #10 on: September 18, 2020, 09:50:53 AM »
Another shot of Yvette Humberette.

Offline Rex

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Re: 1914 HUMBERETTE "Cyclecar" Valve Timing
« Reply #11 on: September 18, 2020, 11:07:29 AM »
  Unlike U.K. from what I've read, we often start with "wrecks". 

Then that's strange logic by someone. You think a wet temperate climate would be better for the longevity of old cars and bikes than a warmer dryer one? :-\

Offline R

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Re: 1914 HUMBERETTE "Cyclecar" Valve Timing
« Reply #12 on: September 18, 2020, 09:44:49 PM »
Depends on whether its coastal or inland, and tropical north or chilly south.
And British barns would seem to be more waterproof long term ??

What a pretty little veteran !
I can well see the need to use a later amal if the Smiths is unobtanium ....

Offline john.k

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Re: 1914 HUMBERETTE "Cyclecar" Valve Timing
« Reply #13 on: September 18, 2020, 11:33:53 PM »
Ah ,yes,I see a Queensland rego ,and a HMCCQ 50 th anniversary badge ,a recent pic,even if the 50 th has turned out to be less than ideal............Anyway,I would suggest maybe a 276 Amal may be more suitable,as this was the size generally used on 500sv,and ohv ...the 289 being more of a sports bike carby......Since the motor is watercooled ,there is no risk there ,and as others have done the same without overstressing the works ,and the mod is reversible......No harm in changing the timing either ,but have regard for the maximum revs ...no point going beyond whats needed....The 15/60 timing used to be good for all sorts ,cars and bikes,and you also doubtless have valves made of more recent materials ,so the extreme caution of the veteran era is not necessary,as valves never break as they once often did.