rusty1100 Posted October 13, 2010 Report Share Posted October 13, 2010 Well I burned up my 4 mill crank a while back and had to replace it with a stock crank because of money purposes, and now it revs high and even the powerband kicks in but doesn't go as fast as it is reving. It's kinda like a 4 cylinder car when your trying to pass someone and your rpms go way up but your barely gaining speed. What the crap do I need to do to fix this. One other thing I did was adjust my carbs so that when it is WOT, the slide is all the way up, and the idle screws arent touching anything, could this have something to do with it. I just installed lighter springs which replaced the screw in part on top of the carbs and thats what I used to adjust the slides, just screwed it out until the slides were all the way open when WOT. Thanks, Rusty Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted October 13, 2010 Report Share Posted October 13, 2010 If your jugs were ported for the 4mil ,they are now wrong for stock stroke. Did you change domes or remove spacer plates ? How do plugs look? Quote Link to comment Share on other sites More sharing options...
stroking Posted October 13, 2010 Report Share Posted October 13, 2010 your clutch is slipping Quote Link to comment Share on other sites More sharing options...
rusty1100 Posted October 14, 2010 Author Report Share Posted October 14, 2010 If your jugs were ported for the 4mil ,they are now wrong for stock stroke. Did you change domes or remove spacer plates ? How do plugs look? The guy that I bought it from did say that it had a mild port job. No I didn't change domes and I didn't have a spacer plate because it was a vitos crank with standard rod length. Would changing the domes help? Im running 21 right now. your clutch is slipping What would cause that and how do I fix it if it is the problem? Quote Link to comment Share on other sites More sharing options...
Pasi S. Posted October 14, 2010 Report Share Posted October 14, 2010 I´m not an expert here but if your previous crank was 4mill 110rod and now you have stock stroke 110rod crank you have to change the domes for stock stroke. You stroke is now 54mm and it use to be 58mm. When your piston is at TDC it´s 2mm lower now. Your compression is lower and squish is huge IMO. Quote Link to comment Share on other sites More sharing options...
AKheathen Posted October 14, 2010 Report Share Posted October 14, 2010 I´m not an expert here but if your previous crank was 4mill 110rod and now you have stock stroke 110rod crank you have to change the domes for stock stroke. You stroke is now 54mm and it use to be 58mm. When your piston is at TDC it´s 2mm lower now. Your compression is lower and squish is huge IMO. yes, it doesn't matter if it was 110mm, or 115mm rods, that just changes the pistons. either there is a 1.5mm plate under the cyls that could be mistaken for a gasket, or between the head and cylinders, or the domes are cut deeper for the extra stroke. i used to have some domes to trade ya, but i traded those away. i would definitely check the squish. it will really kill some power. Quote Link to comment Share on other sites More sharing options...
rusty1100 Posted October 15, 2010 Author Report Share Posted October 15, 2010 Pasi S., on 14 October 2010 - 12:13 AM, said: I´m not an expert here but if your previous crank was 4mill 110rod and now you have stock stroke 110rod crank you have to change the domes for stock stroke. You stroke is now 54mm and it use to be 58mm. When your piston is at TDC it´s 2mm lower now. Your compression is lower and squish is huge IMO. yes, it doesn't matter if it was 110mm, or 115mm rods, that just changes the pistons. either there is a 1.5mm plate under the cyls that could be mistaken for a gasket, or between the head and cylinders, or the domes are cut deeper for the extra stroke. i used to have some domes to trade ya, but i traded those away. i would definitely check the squish. it will really kill some power. Ok thanks for the info. I do know that my domes are 22+1 (the 21 I typed was a typo) with a noss cool head. How exactly again do I measure the squish, and what should it be? The clutch thing sounded so my simpler...lol. Thanks for all the help. Quote Link to comment Share on other sites More sharing options...
Darthwall Posted October 15, 2010 Report Share Posted October 15, 2010 If you are running a stock crank and it was ported for a 4mill and not changing the domes you have almost no compression and with the porting you are most likely in the upper rpms? so not much bottom end and lots of high? change your domes then you will have alil more top Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted October 15, 2010 Report Share Posted October 15, 2010 When you have head off, crank it to top dead center. Is the edge of the piston near to flush with the top of cylinder? If you went from a 4mil long rod to stock stroke short rod you lost 2mil for stroke and 5mil for shorter rod. Quote Link to comment Share on other sites More sharing options...
J-Madd Posted October 15, 2010 Report Share Posted October 15, 2010 You check the squish by putting piece of solder in the spark plug hole and across the top of the piston parallel to the wrist pin. Kick it over then pull out the solder and measure the very end of it with calipers. I predict your not even gonna be able to smash the solder because your squish is gonna be 2 mm off due to going from 4 mil back to stock stroke without changing domes. You typically would want squish 0.045" or so on that motor. Some run them it tighter on highly tuned drag motors. If there is no spacer plate, and both cranks are short rod (110 m) you can use the same pistons and just by some off the shelf banshee domes, check the squish and run it. Not knowing if the ports were moved, I couldn't tell you if would run or not, though, Quote Link to comment Share on other sites More sharing options...
EvilBanshee Posted October 16, 2010 Report Share Posted October 16, 2010 I had a similar problem. Not sure if this is your case, but i had the exact same thing happen to me that your describing. What happened was that under load, i was actually droping a cyclinder due to bad Plug caps. so it was just running on 1 cyclinder. but sounded crisp and was revving high. just not pulling hard at all!!! Quote Link to comment Share on other sites More sharing options...
rusty1100 Posted October 17, 2010 Author Report Share Posted October 17, 2010 I had a similar problem. Not sure if this is your case, but i had the exact same thing happen to me that your describing. What happened was that under load, i was actually droping a cyclinder due to bad Plug caps. so it was just running on 1 cyclinder. but sounded crisp and was revving high. just not pulling hard at all!!! Thanks for all the info. I'm going to buy some new domes, I didn't even think about that when I changed the crank . Guess you learn as you go. EvilBanshee, that is exactly what it is doing, sounds crisper than it did even before all of this, so i'm gonna check that out too. I'm not going back to square one but do have to back up and punt, per say. Thanks again everyone. Thats why I love this place. Before you guys, I would have never even attepted to work on my own banshee. 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.