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Old Jul 20, 2014, 03:56 AM
Who let the dogs out?
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Thanks Steve
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Old Jul 21, 2014, 06:13 AM
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hey Mum I shrunk the kids ,,,,,

Well not the kids - but the contra on the non-runner. After realizing from your previous posts that the spare muff with the large hole on top was a Penny Slot muff, and the thread inside the non-runner's contra matched it, I made a Penny Slot adjuster, however this showed up the contra as too loose. Maybe the reason for the short runs, so as I have many times I heated up the contra to grow it ... but ... it shrunk by a thou and a half. So from being a sloppy fit to now a fall through fit.

So tomorrow's job is to make a new contra and hopefully turn it into a runner ... that internal thread is not going to be easy ...

On reflection it appears the contra is steel not cast iron .. but .. the slack fit might be the reason it won't run, as things heat up the leakage grows and the fire goes out ?
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Old Jul 21, 2014, 04:32 PM
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FWIW Penny Slot and Comp. Special heads are different........Penny Slot has more fins than Comp. Spec.......But they do screw onto each other.
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Old Jul 21, 2014, 08:12 PM
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1972 ARM (American Racing Machine) 2.5 cc Team Race - built and designed by Roger Theobald and John Barr at the K & B factory. Only about 90 made
http://www.ebay.com/itm/1972-America...item20e950c652
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Old Jul 21, 2014, 10:36 PM
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Since the last photos - made a new contra and now using the Penny Slot muff with a fabricated Penny Slot compression adjuster. Does this look correct now ?

Thought it would run nicely, but again maybe a few seconds more running before simply stopping - just like before. Again using the venturi I know works off the other engine.

However now I know that it looses almost all compression after just those few seconds of running - so it looks like it needs a new piston. After it cools it has terrific compression but I think now that the oil trapped by the exhaust wings helps to seal it at handcranking but when it starts it looses that seal and dies.

Photo of my handiwork with the Penny Slot adjuster and the correct muff now on the other running engine.
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Old Yesterday, 12:33 AM
Sticks, Tissue & old Diesels
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Ed, as Gossie mentioned above. The heads are different (5 fins on the Comp Special and 7 on the Penny Slot).
I didn't want to bore the guys with photos that I've posted before, but maybe you need some kind of reference, so here are both your engines, exactly the way they should be:
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Last edited by brokenenglish; Yesterday at 01:17 AM.
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Old Yesterday, 03:08 AM
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Ah yes. It's all very tricky for young players.

If you look at my Comp. Spec. It has an aluminum tank off a MK2.......Your lucky to have a nice red plastic one for yours Ed, as they tend to warp and go all "funny"with age.

Sounds much like it might be worn out piston trouble on the difficult one......Maybe?????
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Old Yesterday, 03:29 AM
Sticks, Tissue & old Diesels
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Quote:
Originally Posted by gossie View Post
If you look at my Comp. Spec. It has an aluminum tank off a MK2.
Gossie, that's not necessarily the case. Many Comp Specials were sold with the alloy tank, after Mk II production stopped.
I always use the alloy tank for running, for exactly the reason you mention, although many plastic tanks are still remarkably good after 60-odd years...
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Old Yesterday, 04:37 PM
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Quote:
Originally Posted by brokenenglish View Post
Gossie, that's not necessarily the case. Many Comp Specials were sold with the alloy tank, after Mk II production stopped.
I always use the alloy tank for running, for exactly the reason you mention, although many plastic tanks are still remarkably good after 60-odd years...
Ah ripper......Value has just doubled. LOL.
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Old Yesterday, 08:19 PM
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Thanks a million for the help so far guys.

Never came across an engine like this before. Have restored terrific compression by growing the cast iron piston - it grew exactly 1/2 thou and now holds comp hot or cold. But it hasn't fixed the non-running problem. Just ran the other engine same fuel - same venturi/needle valve and its terrific - 5,000 steady on a 9 x 5 wood. But this one will fire and run a few seconds then stop ad-infinitum almost.

Now for the boffins - there was another cylinder amongst the things that came with these 2 engines along with a carefully cut up crankcase, maybe by using a slitting saw so they have definitely been played around with. Question is:- could the "spare" cylinder with big ports be the match to this piston ... or is the timing between the different Mk's significant that if the wrong cylinder is on the engine would this cause it to behave the way it does? The non-runner has a serial number of R132/9 if that means anything, but maybe the piston is not the original one anyway. Have tried blowing compressed air in the crankcase with the piston at tdc and there isn't any leaks.

Have probably spent 12 hours on this little guy, sure would like to sort him out.

Video here of how it behaves ...

MVI 9666 (0 min 7 sec)
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Old Yesterday, 09:12 PM
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It's almost like it's not getting any fuel??????? Can you up the comp. more by screwing down the head?

Will it run if you keep your finger over the intake as in when choking it.

The number I feel means the case is a MK2 as there is no "C" after it.
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Old Yesterday, 11:05 PM
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...and you're sure the other engine ran fine with this intake assembly?

It really looks like a leaking shut off lever, but this would be so easy to check, I assume you have done so already.

Really has me stumped.

Can you check for compressed air flow at BDC?
Air should just rush up the transfer and out the exhaust.

Mind you, just thinking about it, it's a lot easier to put air into the case at TDC than BDC, so maybe not such a bright suggestion.
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Old Yesterday, 11:14 PM
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Another mystery engine

I have just acquired this rather rare engine.

I know what it is, but does anyone else?

3.5 cc Schneurle ported with rear drum induction (and an OS clone carbie)
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