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Perry carbs.

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Foxfan15/07/2019 18:21:40
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686 forum posts
6 photos

Hi all, I have just refurbed my Perry carb. equipped HB 25 with a new bearing and we eventually got it to run down the club on a test block by fiddling with the odd disc thing, but what, on Perry carbs, does one need to watch for? Should there be a spring under the head of the needle valve, as it turns on its own. What SHOULD be done with that thin brass disc? Is it something to do with those three marks on top of the carb body? Once we moved it to align with the central mark and it sprung into life and really went like the blazes, but still stops when throttled back. Any experience with Perry carbs. will be much appreciated as I'm chuffed to have got this rare and nice engine going again. Yesterday the crank felt like a ratchet. Today, thanks to BRT bearings in Wisbech, it's as smooth as silk. Any ideal prop recommendations too, would help. It has an 8x6 APC currently.

Martin

Trevor Crook15/07/2019 18:32:04
825 forum posts
63 photos

I had a Veco .19 with a Perry carb many years ago, so my memory is a bit hazy. I seem to remember there was a spring under the main needle. The brass disc adjusts the idle mixture - there should be a radial slot at the top that you put a screwdriver in to rotate it between the extremes marked on the carb body.

My strongest memory is that it was very sensitive to dirt in the fuel blocking the idle jet. When clean and set up correctly the engine ran beautifully.

I'm sure plenty of people with more expertise than me will chip in, or you could email Brian Winch.

Foxfan15/07/2019 18:36:16
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686 forum posts
6 photos

Thanks, Trevor. We moved the disc to the upright position and it ran for the first time and stayed running after removal of the glow stick, but although it slowed a fair bit, it soon stopped, suggesting we still need to experiment. Is there a starting pint on the needle (close it then open it so many turns, a la SU on your Sprite?) It seemed to run very rich, but Oh, how I've missed that smell for so long!

Martin

Colin Leighfield15/07/2019 20:00:46
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5889 forum posts
2459 photos

They were a fiddle. My HB61 had a Perry carb originally and it got more troublesome as time went by. Problem solved by chucking it and replacing with the carb off an Irvine 61, it ran without trouble for years until I wore the engine out. Still got it somewhere.

Edited By Colin Leighfield on 15/07/2019 20:01:54

Foxfan15/07/2019 20:03:11
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686 forum posts
6 photos

I have an Enya 35 and a Magnum and Leo 40s. Could their carbs be used on a .25?

Martin

Colin Leighfield15/07/2019 20:10:45
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5889 forum posts
2459 photos

If they will fit and the choke diameter is the same you’ve probably got a chance! Easy to find out. Interesting to see Trevor’s comment about the Veco 19 with a Perry carb. The HB61 that I had was identical to the Veco 61, built under licence or something like that. Perry carbs work very well until they go wrong. I seem to remember there was a disc with a slot in it you had to keep clean, or something like that.

Denis Watkins15/07/2019 20:12:29
3746 forum posts
179 photos

Martin

On removing the Perry carb, measure across that opening , the throat

Say 6mm, or 7mm, or whatever

Now another carb that size should run

Probably an OS25 carb

Colin beat me to it

Edited By Denis Watkins on 15/07/2019 20:18:28

Gordon Whitehead 115/07/2019 20:23:29
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308 forum posts
120 photos

Here you go  original Perry instructions.

If I recall, there's a fine slit in the spraybar which you ensure is clear by passing a piece of notepaper through it to remove any debris.

Gordon

 

PS. I flew HB .20s and .25s with Perry carbs for years with no probs.

Edited By Gordon Whitehead 1 on 15/07/2019 20:25:57

Edited By Gordon Whitehead 1 on 15/07/2019 20:27:20

Tom Sharp 215/07/2019 20:36:04
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3430 forum posts
17 photos

There is an O ring behind the big disk which rots in time. This then leaks air. Also dirt is a problem. There should be a spring on the needle. There is also another O ring where the carb fits into the engine, this could also be rotted.

I had several many years ago they mostly ran very well, but any sign of trouble I disassembled them and cleaned them. There were two slightly different versions.

Foxfan15/07/2019 23:06:04
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686 forum posts
6 photos

Thanks, chaps. I'll give it another clean up, more thoroughly this time, now I have the instructions I can see what's what

Many thanks,

Martin

Jonathan W16/07/2019 01:30:48
92 forum posts
11 photos

Perry carbs work great when properly looked after, but they are not tolerant of bodge merchants unfortunately. That's where they get a bad rep I think, from people who don't have the patience to keep these carbs sweet.

As previoulsy stated, cleanliness of the fuel supply is essential, so always run a filter. Decades ago, I ran a Veco 19 in a RC car, a very dirty environment. No problem from the carb due to running a filter.

The internal O ring condition is critical.

To inspect, unscrew the needle valve. There should be a spring on the needle. If missing, a ball point pen will probably yield a usable spring which can be cut to length.

Once the needle is out, you should see a small E clip which needs carefully prising off - don't lose it!. You can then extract the throttle barrel and the "reservoir" from either side of the carb body. The "reservoir" is the piece with the brass disc and inside it has the mixture adjusting slot, sealed with 2 O rings. The O rings are a standard BS size: 007 (1.78 x 3.68mm). Most standard O rings are Nitrile material, which won't last long in glow fuel. Try either Viton or EPDM material.

Here is a supplier: Link

Also, try to avoid over-tightening the carb retaining grub screws, otherwise the carb spigot can get crushed or even crack.

If you get frustrated with this carb, I'l have it smiley

Recommended prop for the HB25 is 9x4 or 9x5

Edited By Jonathan W on 16/07/2019 01:48:52

Trevor Crook16/07/2019 08:05:47
825 forum posts
63 photos

Not sure what the tie-up between Veco and HB was. Someone else in my club had an HB25, which looked very similar to my Veco19, except it had mounting flanges on the backplate.

Jonathan, you stirred my memory of removing fiddly circlips and unblocking the idle slot! I started the practice of using a filter in the filler line as well as the tank filter with that engine - good practice anyway.

Colin Leighfield16/07/2019 09:19:01
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5889 forum posts
2459 photos

I think Jonathan’s conclusion is fair enough. The Perry carb works very well but is intolerant of any muck or gumming up. I always used a filter with mine, never flown an I/c plane without one (excluding Mills .75 and Cox motors), but the Perry did need a bit of work after a while. The Irvine carb never needed any attention at all, so that was it really. I tend not to throw things away, the Perry is probably still in the bottom of the junk box somewhere, I haven’t rummaged in there for thirty years so perhaps I should have a look.

Stuphedd16/07/2019 12:03:35
643 forum posts
348 photos

I found and still do that Perry carbs and pumps are brilliant , and once you keep them clean like Colin says they are excellent !!

I also found that lots of people did not like them , so I offered to look after the carbs for them !! if you get my drift !

cheers

gangster16/07/2019 12:06:06
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929 forum posts
16 photos

If I remember correctly that big disc is a very sensitive adjustment to get the slow running mixture right Very sensitive As stated several times they are not tolerant of any dirt. I flew a Veco 19 and a 61 and at the time and ran on g max fuel. This seemed to have bits of castor bean in and it involves stripping the carb regularly. Had one on an HB40 Pdp pumper and it was good.

Peter Christy16/07/2019 12:18:48
1487 forum posts
Posted by Trevor Crook on 16/07/2019 08:05:47:

Not sure what the tie-up between Veco and HB was. Someone else in my club had an HB25, which looked very similar to my Veco19, except it had mounting flanges on the backplate.

The Veco 19 and HB20 were internally identical. All the bits seemed seemed to be interchangeable. The Veco was an excellent little engine, the Rolls-Royce of small engines in its day. I had one for years, and it powered my first "Lark" helicopter! However, the HB25 was an enlarged version designed originally for the Graupner Bell 47 helicopter. Aside from being bored out (I don't know if they changed the stroke or not) the .25 heli engine was also ringed, and that was a truly superb motor. I still have one in a "Lark" today!

The Webra Blackhead .61, HB61 and Veco .61 also seemed to share a lot of parts in common, as did their .40 siblings, so there must have been a tie-up, at least for a while. Webra then went down the Schnuerle port route with the Austro-Webras (which appeared to be identical to the HPs), whilst HB went the Perry port route.

However, to get back on track, the Perry carb was notoriously susceptible to the tiniest speck of dirt in the fuel, and could also be fiddly to set up. Once you hit the "sweet spot", the would run beautifully, but this required patience and tiny adjustments to achieve.

Most of us gave up and fitted Kavan carbs! These were just as good as Perrys - arguably better - and certainly easier to set up! They were also a little less fussy about fuel cleanliness! No "O" rings to perish, and being all metal, they didn't suffer from the plastic degradation that affected many Perry carbs.

I think Kavan carbs are still available, though not easy to find. All my HBs are now fitted with them!

--

Pete

Foxfan16/07/2019 12:20:30
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686 forum posts
6 photos

Well, a good cross-section of views there, gents, for which many thanks. I shall remove it and see what needs doing toi make it more reliable. maybe get those O rings and a better (fatter) one for the attachment spigot. I used one I had in a box of O rings, but it could be a bit thin in section. using Jonathon W's link I'll get some "prupper jubbs".

Cheers,

Martin

Tom Sharp 216/07/2019 19:49:39
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3430 forum posts
17 photos

I still have a Graupner Bell 47 helicopter fitted with HB 25 and the Perry carb is grey in color, whereas they are usually black. Could be a special. I also have a couple of K&B 35 engines fitted with Perry carbs. I also once fitted one on a Merco 35 with good results.

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