Strm Trpr Posted March 27, 2016 Report Share Posted March 27, 2016 Read thru this thread. Last post is good info. http://bansheehq.com/forums/index.php?/topic/58613-34mm-mikuni-flat-slides/ Another good read. http://bansheehq.com/forums/index.php?/topic/33644-4mil-stroker-dune-port-34mm-mikunis/ Quote Link to comment Share on other sites More sharing options...
Athenaking Posted March 27, 2016 Author 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!! It ran great before I put the 18cc domes in. It already had everything else. And that's the conclusion I'm starting to come to as well. I was running 290 mains before I put the 18cc domes in, then I put 300 mains in after the 18cc domes but I just put in 280's and am going to run it tomorrow and see how it does Quote Link to comment Share on other sites More sharing options...
camp0429 Posted March 27, 2016 Report Share Posted March 27, 2016 I've never had to re-jet just because of a dome change. Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted March 27, 2016 Report Share Posted March 27, 2016 Oh, and to the OP, Amsoil Dominator is formulated to be mixed at 50:1. Look in the applications paragraph. And Google, "amsoil dominator 2 stroke oil mix ratio". https://www.amsoil.com/shop/by-product/motor-oil/2-stroke/dominator-synthetic-2-stroke-racing-oil/?code=TDRQT-EA Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted March 27, 2016 Report Share Posted March 27, 2016 Leak down test? Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted March 27, 2016 Report Share Posted March 27, 2016 (edited) 18 CC on a 68mm bore and stock stroke is a lot of compression! Even though the exhaust is high and you are up in elevation, that motor still needs lots of Octane. Have you tried 110? AV fuel is about 100 or so, which might not be enough. Sounds typical of a motor needing octane but someone throws fuel at it to compensate. Also, a 50 pilot is huge. Other jets are a bit off. Switch oils if you wanna run an oil rich mixture. Those synthetics made to run lean will follow plugs when mixed like that. Post pics of the plugs. Edited March 27, 2016 by trickedcarbine Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted March 27, 2016 Report Share Posted March 27, 2016 The domes you put in were big bore domes but what about the angle. Are your Pistons 13* , is your dome 11*. All things that need to be dbl checked. Most off the shelf big bore domes are 11* 2 Quote Link to comment Share on other sites More sharing options...
RadarRacing Posted March 27, 2016 Report Share Posted March 27, 2016 Sounds like you have dome issues if you had it running great before. We see quite a few posts about athena cyls and problems. Some of that in my opinion is the person buying these cyls on ebay or wherever is wanting to save a buck and will also "save a buck" and throw some new or used carbs , domes, parts of unknown trusted origin in their bike. Before putting the motor together and starting it, you should know the squish clearance and check for leaks. I am guessing your compression tester needs thrown in the trash and if your squish is between .042 and .054 with your OLD DOMES then use them and quit taking advice from the morons that give engine building advice on facebook pages. 1 Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted March 27, 2016 Report Share Posted March 27, 2016 The domes you put in were big bore domes but what about the angle. Are your Pistons 13* , is your dome 11*. All things that need to be dbl checked. Most off the shelf big bore domes are 11* Sounds like you have dome issues if you had it running great before. We see quite a few posts about athena cyls and problems. Some of that in my opinion is the person buying these cyls on ebay or wherever is wanting to save a buck and will also "save a buck" and throw some new or used carbs , domes, parts of unknown trusted origin in their bike. Before putting the motor together and starting it, you should know the squish clearance and check for leaks. I am guessing your compression tester needs thrown in the trash and if your squish is between .042 and .054 with your OLD DOMES then use them and quit taking advice from the morons that give engine building advice on facebook pages. That's exactly why I said to do a squish band test. You say it ran good with the domes that came with it but you wanted more compression. Why didn't you call who you bought the kit from and talk to them first before buying OTS big bore domes? OP, do you know what model # pistons are in the motor? Like sleeper and radar said, you have a dome issue. Quote Link to comment Share on other sites More sharing options...
Athenaking Posted March 27, 2016 Author Report Share Posted March 27, 2016 I ordered the kit from Athena and I've called their customer service or whatever a few times and the people I've talked don't seem to know how to even wipe their asses. But that being said, what should my squish be? Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted March 27, 2016 Report Share Posted March 27, 2016 Radar mentioned .042" - .054". The angle of the squish band relative to the piston dome angle is also critical. Where did you get the 18cc big bore domes? My suggestion is contact Athena's customer service and ask for technical assistance and tell them you're running 100 octane AV gas at 4,500ft. One would hope they can get you the correct profile domes for use with 100 octane AV gas at 4,500ft. If they can't help you, call Driveline Performance, which you should've done in the first place for a no nonsense bolt-on 392 kit and see if they have any experience cutting domes for Athena 392 big bore pistons. Quote Link to comment Share on other sites More sharing options...
sleeper06 Posted March 27, 2016 Report Share Posted March 27, 2016 Wsm has domes for that set up in 13* 1 Quote Link to comment Share on other sites More sharing options...
Strm Trpr Posted March 27, 2016 Report Share Posted March 27, 2016 Wsm has domes for that set up in 13*I'd start there.Forget the cs agents at athena. Quote Link to comment Share on other sites More sharing options...
Athenaking Posted March 27, 2016 Author Report Share Posted March 27, 2016 I bought pro designs cool head big bore 18cc domes. And just barely I went and bought some 110 fuel, mixed my ratio at 40:1, bought new plugs and gapped them at 0.03 in, and dropped my mains to 280. I went and rode it and it ran the best it has so far. But it still isn't a perfect powerband. I pulled the plugs and put my scope in the cylinder and more of the piston is cleaned off then before. So maybe my problem was partly my plug wasn't gapped right and my compression was putting out the spark? And partly because I wasn't using high enough octane fuel? But the fact that I dropped them to 280's and more of the piston is cleaned off, makes me want to raid the main jets back to what it was at 300. Quote Link to comment Share on other sites More sharing options...
trickedcarbine Posted March 27, 2016 Report Share Posted March 27, 2016 Pics of plugs Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.