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Inlet maifold / carb extension for Laser

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Martin Whybrow15/11/2014 19:50:34
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884 forum posts
33 photos

Has anyone ever come acros an inlet manifold / carb extension for a Laser engine? I have a Laser 90 inverted and the carb is 2" lower than the centre of the tank and it causes fuel to syphon; I've tried a regulator and pump, but do not seem to be able to get the engine to run right. I'm now contemplating moving the carb higher but need an extension pipe to do so. Failing that, I'll have to take out the Laser and fit an OS FS70 (which I'd rather not do).

Percy Verance15/11/2014 20:14:01
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8108 forum posts
155 photos

Is there room for a smaller header tank below the present one Martin? If so it only needs to be a very small tank (2oz) to do the job. A good number of heli pilots use header tanks with complete success. Maybe it'll work for you?

Martin Whybrow15/11/2014 20:31:40
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884 forum posts
33 photos

Surely a header tank will still have the head of fuel from the main tank?

Chuck Plains15/11/2014 20:59:43
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1096 forum posts
244 photos

I've never used ic models, so I can't advise you. But I could drill and turn a piece of ally for you if needs be. If you need it, measure the relevant bits with a vernier and let me know. My recently acquired lathe is looking bored (pun intended) on the shelf. thumbs up

Martin Whybrow15/11/2014 21:03:07
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884 forum posts
33 photos

Chuck, that's a kind offer; unfortunately it requires a pipe with a 90 degree bend to raise the carb.

Stevo15/11/2014 21:31:45
2699 forum posts
419 photos

Oh Martin... I'm sure I will face this one day... I've shoehorned a laser 75 into a Blackhorse Homerun, but inverted I ran into the problem you are having. I ended up rotating it 90 degrees so it stuck out the side...

Although I cannot offer a solution, (apologies) I'm sticking around here to see what the outcome is.

Chuck Plains15/11/2014 21:58:37
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1096 forum posts
244 photos
Posted by Martin Whybrow on 15/11/2014 21:03:07:

Chuck, that's a kind offer; unfortunately it requires a pipe with a 90 degree bend to raise the carb.

Ah, yes, 90degrees does present a teensy problem for a lathe. laugh Ah well. No sweat then.

jeff2wings15/11/2014 22:21:58
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800 forum posts
1926 photos

S/S flexi pipe or micro bore central heating pipe with machined adapters silver soldered on for carb/cylinder head connection , winkpeace of cake .

Martin Whybrow15/11/2014 22:48:16
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884 forum posts
33 photos

I've hatched an alternative plan, details here

Engine Doctor16/11/2014 09:45:00
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2341 forum posts
28 photos

Hi Martin . You have answered your own question. You are correct in thinking that the head of fuel will still be too high an will syphon to the bottom tank and then into your engine. The carb extention would work best but,...........the one I posted was for a OS type engine and is a simple job to make . Lasers are a different animal and while its possible to make an extension it would be more challenging. Could you not mount your laser on its side with the carb uppermost ? This would surely sort most or your problem. The only other engine that would be fine without any mods would be a YS as they are designed to work with a tank pressure of 10 to 13 psi ,but they are expensive. Without seeing your installation it appears you are between a rock and a hard place and have limited choices if you wish to keep the laser installed inverted. The OS 70 is a well sorted engine ,why not use it?

John Payne16/11/2014 14:52:11
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162 forum posts
63 photos

Hi Martin, I cured one of mine with a similar issue by using a longer length of fuel tube and routing it up over the level of the tank, on the engine side of the firewall, so the fuel had to go "uphill" to get to the engine, It did the job and it didn't seem to effect the way the engine ran. I'm sure I saw that tip on this forum some time ago. It's a simple fix and is worth a try. Cheers, John.

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