252wheelieking Posted September 7, 2011 Report Share Posted September 7, 2011 Thanks for your reply! I already pull of the cub and right now I am not sure about squish it had because the base gasket is in the trash! about thickness. It is better use 0.022" or 0.012" base gasket? From what I have been hearing the .012 base gasket will cause it to detonate because of small squish. I talked to a member on here today, that is out right now testing the .020 base gasket on his 421 serval now. I will let you know the outcome when I talk to him again. Quote Link to comment Share on other sites More sharing options...
Sands Posted September 7, 2011 Author Report Share Posted September 7, 2011 From what I have been hearing the .012 base gasket will cause it to detonate because of small squish. I talked to a member on here today, that is out right now testing the .020 base gasket on his 421 serval now. I will let you know the outcome when I talk to him again. Ok! But a 0.012 base gast will increase more squish than a 0.020. I just saw the crank without open the engine and it seems to be fine and I have the same opinion about rod bearings. There are no small pieces from domes or pistons inside the engine and even inside de pipes. I sent a PM to M&M and I am waiting his reply. Quote Link to comment Share on other sites More sharing options...
252wheelieking Posted September 7, 2011 Report Share Posted September 7, 2011 (edited) Ok! But a 0.012 base gast will increase more squish than a 0.020. I just saw the crank without open the engine and it seems to be fine and I have the same opinion about rod bearings. There are no small pieces from domes or pistons inside the engine and even inside de pipes. I sent a PM to M&M and I am waiting his reply. a .020 gasket is thicker than .012 gasket, therefore the piston would be futher away from the domes creating more area. The squish should be more than your previous squish test. Edited September 7, 2011 by 252wheelieking Quote Link to comment Share on other sites More sharing options...
pabansheematt Posted September 7, 2011 Report Share Posted September 7, 2011 Maybe... If you were me, what would you do? New pistons or just tore it a little on the top? About the domes, I will certainly buy a new set. I guarantee it's lack of fuel at full throttle. I know from first hand experience. LOL. When the shit hit the fan, were you wide open? Check your float height. Do you have a duel feed petcock? Quote Link to comment Share on other sites More sharing options...
Sands Posted September 7, 2011 Author Report Share Posted September 7, 2011 I guarantee it's lack of fuel at full throttle. I know from first hand experience. LOL. When the shit hit the fan, were you wide open? Check your float height. Do you have a duel feed petcock? Yes I have! Dual pingel fuel valve -> http://www.pingelonline.com/powerflo_banshee_race.htm And high capacity bowls for Keihin PWK39mm. Tell me one thing... My Banshee didn't run since last September where I put some lube oil inside cylinder to let them lubrified. In August I works for first time this year. Could it block the gigleurs at high rev and detonate? Quote Link to comment Share on other sites More sharing options...
pabansheematt Posted September 7, 2011 Report Share Posted September 7, 2011 Yes I have! Dual pingel fuel valve -> http://www.pingelonl...anshee_race.htm And high capacity bowls for Keihin PWK39mm. Tell me one thing... My Banshee didn't run since last September where I put some lube oil inside cylinder to let them lubrified. In August I works for first time this year. Could it block the gigleurs at high rev and detonate? I would check the carbs. What main jets do you have in it? Quote Link to comment Share on other sites More sharing options...
Sands Posted September 7, 2011 Author Report Share Posted September 7, 2011 I would check the carbs. What main jets do you have in it? 178 or 180. I didn't open it yeat. They came pre-jetted from the builder! Quote Link to comment Share on other sites More sharing options...
Matt21 Posted September 7, 2011 Report Share Posted September 7, 2011 178 or 180. I didn't open it yeat. They came pre-jetted from the builder! Deto... let M&M hook you up with what you need. Quote Link to comment Share on other sites More sharing options...
Sands Posted September 7, 2011 Author Report Share Posted September 7, 2011 He just need to answer PM. Quote Link to comment Share on other sites More sharing options...
pabansheematt Posted September 7, 2011 Report Share Posted September 7, 2011 He just need to answer PM. Let me ask you this. Do your spark plugs come loose? I still think you have severe deto caused by lack of fuel. I just built a 421 cub for a guy. We ended up with 185 mains ( 39mm PWK's) Quote Link to comment Share on other sites More sharing options...
RadarRacing Posted September 7, 2011 Report Share Posted September 7, 2011 I wrote that wrong last night . .044" is 1.1 mms. .042 or just over 1 mm is often about as close as many will want to run squish clearance. If you were supposed to use a .018 or .022 thousandths base gasket and you used a .012 it could have given you detonation problems with only .32 squish. Especially with any type of pumpgas. Lack of fuel is very common as well. I thought both sides had the problem. Quote Link to comment Share on other sites More sharing options...
No Limit Powersports Posted September 8, 2011 Report Share Posted September 8, 2011 Let me explain a few things. First off you have detonation. No if ands or buts about it you are seeing detonating. Its not sand, or dirt or anything else what you are seeing is detonation. Second off the base gasket does not soley contribute to total squish. The thinner base gasket with the same step in the dome will have a tighter squish. We can run any base gasket we want if we set the step in the dome where it needs to be for the desired overall squish. Now with that said a 68x58 cub or serval calls for a .012 base gasket to get the port timings were calvin blueprints them at. That does NOT mean that is where we have to leave them but that is our starting point or reference point. Detonation can be caused by a lot of variables. Lean is one, whether this means jetted to lean, or running out of fuel, lean is lean. Dome design can cause detonation, a poor dome design can and will cause detonation no matter whether your jetted correctly or not. To tight of squish causes the squish velocity to be to high and cause detonation. There are a hundred things that can cause detonation, and the head design IMO is one of if not the single most important part of a 2 stroke engine. I have spent countless hours testing different dome designs and even more time calculating everything under the sun trying to get what i consider the best. Now like i said in my earlier post i feel your dome design is less than favorable and a different dome is your answer. The detonation is very hard on the motor including the crank. If i were building the motor i would pull the crank and check it out thoroughly and check to see if the welds held, if its still in true, and if the bearing are ok. Then i wouild replace the pistons and put new domes in it. Make sure its sealed and run it. If you have any more questions or need anything feel free to pm me or call me Thanks Andy Quote Link to comment Share on other sites More sharing options...
camatv Posted September 8, 2011 Report Share Posted September 8, 2011 all true here!! i've never seen damage like that from deto if deto alone did that to the dome and the piston holy hell!! thats a new one to me!! BUT my PERSONAL bikes i ahve been able to hear them if they deto adn correct it befoe it got really bad.. most time i have seen what looks like a sand blasted edge OR a blown off ring land area. but most time the head lifted and the coolant came in and caused the deto to become much worse and the reaction and extreme lean condition from the coolant introduced caused the piston to blow and the lands to explode off the pistons.. did it eat a plug? just looking at the crank through the cases is not going to tell you shit.. as stated split it. i have found cracked lower rod bearing cages on no slop perfectly tight lower rod bearings, found cranks that were welded with filler rod added that had twisted and th e filler came out taking out the crank totally BUT it seemed fine in the case. i have seen main bearings blow ball retainers and that end up eating cylinders. and blowing completely out the pipes and out the exhaust.. ye ha carnage at its best HA HA split the case and figure it out. get some better domes preferably known CC and for the proper fuel you want to use, and triple check your squish clearance when you reasemble it being that your in portugal i;d order a few base gasket thickness's and save some on shipping. Quote Link to comment Share on other sites More sharing options...
Pasi S. Posted September 8, 2011 Report Share Posted September 8, 2011 (edited) In Portugal we have 95 and 98 octanes. Yes I know. We have also 95 E10, 98 E5, 99+ V-Power ans RE85 here in Finland. But those numbers are RON, not MON or even R+M/2 AKI´s. Ask from your OIL comppany. -Pasi S. Edited September 8, 2011 by Pasi S. Quote Link to comment Share on other sites More sharing options...
Pasi S. Posted September 8, 2011 Report Share Posted September 8, 2011 It shouldn't be... I think that they couldn't sell 98 octans if the fuel doesn't have it. Yes they can. The 98 is RON and it is like 93-94 USA gas. The 95 here in FInland, and I think most of the Europe is 91 USA gas. That is the same thing like having 4x45W in your car stereo HAHAAA!! One other thing is that we have to richen up a little here in Finland, because we have more oxygen in our gas comparing to USA. (can´t say that this is true in all Europe countrys). This is out of those Dragracers who have used the same motor in Finland and USA. Do I smell a leaking boost-bottle necks here? J/K I´m sure that Andy will help you out of this issue! -Pasi S. Quote Link to comment Share on other sites More sharing options...
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