Magnum GP10

[Bill R]

Hello all,

I found a Magnum GP10 in the loft. As I recall, It last ran about 18 years ago.

I cannot locate the manual and would appreciate any setting info for the carb.

not only does it have a needle valve but 2 spring tensioned screws as well.

Any info would be very well received.

Thanks in advance.

 

Bill R.

 

[Former Member]

[This posting has been removed]

[Martin Harris - Moderator]

To add a bit to Phil's advice, the air bleed needle will point at a tiny hole in the front of the carb body - take a squint down it and you should see the tip of the needle. Check that it is approximately half way across the hole as a starting position.

 

When Phil refers to the throttle stop being fully open, he means that the hole in the throttle barrel can be fully closed - if you screw this adjuster in slowly you'll see how it will open the throttle slightly...then go back until it's properly closed.

 

Start with the main needle 2 1/2 turns open which will almost undoubtedly be too rich but you'll tune this out once it's running.

[Former Member]

[This posting has been removed]

[Bill R]

Thanks Pol and Phil,

This is what the hobby is all about. I changed the glo plug and will check the other items. Thng won't start anyway as yet. The needle was set at 2-1/4 turns out from closed which was probably still a bit rich as it never had any great running time originally. I never touched the other two screws but can now experiment a little. It looks like the barrel closes right off, way past the hole before it hits the end stop. I have set the throttle maximum with the barrel hole in the centre of the carb inlet. I think I just need to clean out the idle and get it somewhere near to get it started and then it should be easy!!.

Just a newbie after 50 years away from the hobby so these things are a bit different from the old diesel engines.

Thanks again.

 

Bill R.

 

[Former Member]

[This posting has been removed]

[Steve Hargreaves - Moderator]

Might be worth pointing out that these "air bleeds" work in the opposite sense to a more modern carb with an idle needle......with an idle needle screwing it in slightly makes the mixture leaner....with an airbleed its the opposite...screwing it in makes the mixture richer.

 

This is simply because the airbleed acts on (yep you guessed) the air supply to the motor whilst the idle needle acts on the (liquid) fuel...

 

Hope this helps...

[Bill R]

Hello Phil,

My apologies to Martin for getting his name wrong. Thanks to Steve for his input. I was wondering why  the idle screw was flat at the end instead of tapered.

I set the throttle stop with the barrel fully closed. The air bleed [idle] screw was 3 1/4 turns out from fully closed. I think thissetting may be too lean to start. I tried for a half hour or so after flushing through with a bit fuel and everything seems to be working ok. Compression is there and no leaks from the backplate or the carb base. A little oil weep from the spinner end but overall a leak free engine. Pressure tested the tank [new] and flows are ok. I just moved the needles in 1/8 turns in and out but no joy as yet. Raining this am so will try again. I dont know the correct start settings so its playtime untill I get the thing fired up.

Thanks to all once again.

Bill R.

 

[Martin Harris - Moderator]

What sort of glowclip are you using?  Is it making good contact?  I'm assuming you've checked the plug is glowing from your battery?

 

While the plug's out, you could squirt a few drops of fuel in before putting it back - this often helps an engine to fire and if it does but won't continue, you've got a blockage somewhere in the carb. If so, my favourite trick is a bicycle pump (with a retract adapter - or similar) linked to some fuel tube on the inlet nipple to blow through the carb while wide open with the main needle in and out.

[Bill R]

Hello Martin,

Thanks for that info. I changed the plug as it was just sputtering without a glow. I fitted a Model Technics F5 medium grade, first checking it had a healthy orange glow to it. Same length as the plug that was fitted. I will try the pump and a few drops of fuel down the hole but it will be next weekend now as I travel around a bit at work.

Regards,

Bill R..

[Bill R]

Hello Guys,

Finally got the engine started and running. With a 6" x 4" Graupner prop it certainly is a screamer. Blew the fuel line out with a pump as suggested wiggled all the scews and started with 1 turn out on the air bleed and one turn out on the main jet. Started first time. The settings are very very critical. 3 clicks out on the main just takes it off the boil. 1/4 turn further out on the air bleed and its a winnet. - winnet start. Left it one turn out on the airbleed and one turn plus 3 clicks on the main needle. Starts first time, picks up great and sounds like 10K plus rpm.

Thanks for all the the helpand input.

One very satisfied customer.

 

regards,

Bill R.

 

[Steve Hargreaves - Moderator]

Well over 10K on that prop I would think Bill......a 6 x 4 is a 1/2A (or 0.049) prop......a 7x6 or a 8 x 4 would suit it better I think....

[Bill R]

Hello Steve,

Not much draft out the rear end. It was originally fitted to a 3 channel Cessna wih a 7 x 6 prop fitted I seem to recall. Duff info from the local modelshop though they are more into trains!

I will try a 7 X 6 and see how it runs.

Thanks.

 

Bill R.