Evolution 20gx slowing down

[cymaz]

Having completely repiped and re tanked the above engine after a couple of dead sticks....my fault I rushed the installation, there is a problem that got me thinking. I can't come up with a solution, so can you help.

On bench test the needle settings for WOT and transition from idle are perfect. However leaving it to run at idle, after about 30 seconds it slows and dies.

Is the LSN too lean, rich , what does anyone else think please. Non pumped carb, tank 1/2 inch lower, pressure fed, petrol on 32:1

Edited By cymaz on 09/06/2015 06:58:34

[..]

Well running & then dying like that would suggest that the engine is filling with fuel but as to if its because it's rich then I would say no if it's ok on the bench. Can you get the tank any lower?

I had this issue on an FW190 with a 4 stroke glow engine. The motor was sweet but the tank just kept filling the engine on low revs. WOT and it was fine as it could cope with the excess fuel.

[..]

Having re read your post I now realise that the engine is still on the test bench "Dohh"

Yes it definitely sounds to rich to me.

[flight1]

Cymaz try running with out the pressure pipe on, on that size engine you should have enought suck from the carb to do without. you will have to proberly richen the top needle slightly to compensate, if that dosent cure the problem look someware else.

A choke might be needed for first prim and start.

I am shur thiss will cure your issue

[Engine Doctor]

Hi Cymaz . You shouldn't have a pressure feed from the exhaust on a petrol engine ! That's asking for a blaze . But why does it not have a pumped carb .Has it been turned back to a glowengine or was it supplied like that ? It should have a pumped carb as per this Pic . Yes it sounds rich but sort the carb before it goes up on its own

[Bob Cotsford]

the older generation Evo petrol engines up to 20cc don't have a pump, just a pressure regulator built into the carb so they really do need the pressure line. It's only in the last year that the 15 and 20 were changed to a pumped carb.

 

Is it running the standard silencer or an aftermarket one?

Edited By Bob Cotsford on 09/06/2015 12:15:10

[cymaz]

Posted by Bob Cotsford on 09/06/2015 12:14:01:

the older generation Evo petrol engines up to 20cc don't have a pump, just a pressure regulator built into the carb so they really do need the pressure line. It's only in the last year that the 15 and 20 were changed to a pumped carb.

 

Is it running the standard silencer or an aftermarket one?

Edited By Bob Cotsford on 09/06/2015 12:15:10

Bisson Pitts muffler. Correct one for the 20gx, from Just Engines.

I could lean it out a touch. I assumed that as it was slowing down it was lacking in fuel?

Edited By cymaz on 09/06/2015 17:22:57

[Bob Cotsford]

I know that some of the RCG contributors tried the Bisson Pitts on the 10cc and found it best to block one outlet as the extra back pressure generated seemed to help. If you can't find a sweet spot by tweaking the idle it might be worth a try with a reduced outlet area to maintain the tank pressure.

[cymaz]

Posted by Bob Cotsford on 09/06/2015 21:41:04:

I know that some of the RCG contributors tried the Bisson Pitts on the 10cc and found it best to block one outlet as the extra back pressure generated seemed to help. If you can't find a sweet spot by tweaking the idle it might be worth a try with a reduced outlet area to maintain the tank pressure.

Cheers Bob, that might explain it. The low pressure not feeding enough fuel to the carb. The engine slows, reducing the pressure....a vicious cycle. I will close one outlet off, or at least, reduce the outlet on both, and report back..