Athenaking Posted March 27, 2016 Report Share Posted March 27, 2016 So I put an Athena 392 big bore kit on my banshee last year. My other mods were 35.5mm flat mikuni slide carbs, k&t intake manifold, vforce 4 reeds, cpi in frame pipes, case port, +5 timing on stator, and also some transmission mods that aren't relevant to my issue. With the domes Athena sent me, I was only making 110psi in both cylinders but this was due to my elevation (4,500 feet). Knowing what I do know about motors I bought 18cc big bore domes to raise my compression. Before starting the motor I checked the compression with the new domes and it raised it to 140 on the nut in both cylinders which is exactly where I want it. The issue I'm having is, it ran great before, and now it has a bog on the top end of the throttle. Knowing that it needed more fuel because I raised the compression. I changed the mains from what they were, 290's to 300's. It still ha dyne same bog. Then I raised my needles 2 steps and the bog got worse and now when you are in first gear and pin it from about half throttle one of the cylinders seems to cut out. I am absolutely baffled by the problem, any ideas? Any help would be greatly appreciated!! Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted March 27, 2016 Report Share Posted March 27, 2016 How is the spark? Fat blue or lazy yellow? What fuel you using? Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted March 27, 2016 Report Share Posted March 27, 2016 I do a leak down test whenever I open the motor, PERIOD. I also do a squish test to make sure the squish band is copacetic. You say you raised the needles two steps. Did you lower the needle clips two grooves which raised the needles two steps? Rich Or did you raise the clips two grooves and inadvertently lower the needles two steps? Lean Either way, I'd put the needles back to the middle. What size pilots? You said you're at 4,500ft. Fresh fuel? What octane? What 2 stroke oil? What mixing ratio? What plugs? What gap? Floats set to proper height? Quote Link to comment Share on other sites More sharing options...
Athenaking Posted March 27, 2016 Author Report Share Posted March 27, 2016 I do a leak down test whenever I open the motor, PERIOD. I also do a squish test to make sure the squish band is copacetic. You say you raised the needles two steps. Did you lower the needle clips two grooves which raised the needles two steps? Rich Or did you raise the clips two grooves and inadvertently lower the needles two steps? Lean Either way, I'd put the needles back to the middle. What size pilots? You said you're at 4,500ft. Fresh fuel? What octane? What 2 stroke oil? What mixing ratio? What plugs? What gap? Floats set to proper height? Quote Link to comment Share on other sites More sharing options...
Athenaking Posted March 27, 2016 Author Report Share Posted March 27, 2016 I run avgas in it which should be around 100 octane. And as far as fresh? Not really. It had been sitting all winter and I'm running the same fuel, but where avgas doesn't have ethanol it doesn't go bad as fast as normal gas but that's still no excuse to not put fresh fuel in lol. I run ams-oil dominator at 36:1. The plugs are NGK b8es but I'm not familiar with gap? And also not familiar with setting the floats correctly but the overflows don't leak. Also I moved the clips one down from middle therefore making it richer. And to add to the complication I used my Milwaukee scope and looked down the spark plug hole and there is an 1/8" ring of piston wash all the way around the piston but yet the silencers are literally dripping oil and the cylinders were very wet. I'm just confused because I'm getting mixed signs of it being rich and lean. Also the pilots are 50 as well. Quote Link to comment Share on other sites More sharing options...
n2otoofast4u Posted March 27, 2016 Report Share Posted March 27, 2016 Cylds are full of fuel. Quote Link to comment Share on other sites More sharing options...
hoppedupandcutdown Posted March 27, 2016 Report Share Posted March 27, 2016 I guess I missed what are your signs of being lean? Quote Link to comment Share on other sites More sharing options...
registered user Posted March 27, 2016 Report Share Posted March 27, 2016 I haven't seen the athenas first hand but people say the exh is rather tall. this may be partly why you only saw 110 on your gauge. decreasing the dome cc may have put your comp ratio way up there even though its only 140psi. Quote Link to comment Share on other sites More sharing options...
Athenaking Posted March 27, 2016 Author Report Share Posted March 27, 2016 How do I get it out and will it stay out? And will t fix my problem? Quote Link to comment Share on other sites More sharing options...
Athenaking Posted March 27, 2016 Author Report Share Posted March 27, 2016 I guess I missed what are your signs of being lean? I'm not expierienced enough to know but the bog on the top end could actually be a lean pop? Cause if you hold it open it'll bog for a second then finally clear out like it's finally getting enough fuel. And also the piston wash should only be about thumb nail sized by the openings of the ports and there is a solid ring of piston wash all the way around the cylinder. Quote Link to comment Share on other sites More sharing options...
Athenaking Posted March 27, 2016 Author Report Share Posted March 27, 2016 I guess I missed what are your signs of being lean? I'm not expierienced enough to know but the bog on the top end could actually be a lean pop? Cause if you hold it open it'll bog for a second then finally clear out like it's finally getting enough fuel. And also the piston wash should only be about thumb nail sized by the openings of the ports and there is a solid ring of piston wash all the way around the cylinder. Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted March 27, 2016 Report Share Posted March 27, 2016 What model 35mm mikunis do you have? Did you say you're running 50 pilots? Quote Link to comment Share on other sites More sharing options...
Athenaking Posted March 27, 2016 Author Report Share Posted March 27, 2016 What model 35mm mikunis do you have? Did you say you're running 50 pilots? They are 34mm rectangle slide carbs that are bored to 35.5mm. And yes my pilots are 50's Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted March 27, 2016 Report Share Posted March 27, 2016 http://bansheehq.com/forums/index.php?/topic/131029-34mm-mikuni-flat-side-carbs/ 1 Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted March 27, 2016 Report Share Posted March 27, 2016 What did you mean in your first post, "it ran great before". Before what? All of those changes you listed, or just going to the 18cc domes? Personally I think you're rich as hell!! Quote Link to comment Share on other sites More sharing options...
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