forumsearcher Posted January 12, 2008 Author Report Share Posted January 12, 2008 Possible 4mil cylinders? That would give you another 2mm at TDC and BDC. I just measured my stock cylinder from the base to head, it is about 4.04" my best measurement show the cub from base to head at 4.11. This is an additonal .07" overall... VERY STRANGE!!! I am not sure what to do now. I definitely need to verify the cylinders to be correct. Hmmm..... That would be great to have 421 setup. It doesn't look like next weekend will be an option for riding.... Quote Link to comment Share on other sites More sharing options...
forumsearcher Posted January 12, 2008 Author Report Share Posted January 12, 2008 Well let me reply to myself on this one. If my best measurement shows the cylinder as being .07" larger but infact it is .08" higher, then this would be the extra 2mm needed to be a cub for a 4mil stroke crank. It is diffilcult to guess use my previous squish measurement compared to what is would be if I had the 4mil crank, because the pistons are different. Is there any other thoughts on how to verify the cylinder? Quote Link to comment Share on other sites More sharing options...
Dave I. Posted January 13, 2008 Report Share Posted January 13, 2008 If I remember correctly those little casting ears on the intakes have numbers cast in them..... For a stock stroke cub they should be 4.038 and piston .018 in the hole with a .022 gasket For 4 mil cylinder they should be 4.079 and piston .010 in the hole with a .022 gasket Quote Link to comment Share on other sites More sharing options...
Dave I. Posted January 13, 2008 Report Share Posted January 13, 2008 Also, a 4 mil and 392 both use the same piston as long as its on the 110mm stock rod. So you could do the math with your previous squish measurement Quote Link to comment Share on other sites More sharing options...
wesw Posted January 13, 2008 Report Share Posted January 13, 2008 after reading this thread, all i got to say here is proof to let a builder put it together or buy most everything from them. that why there is not confusion of what parts are what. best of luck. Quote Link to comment Share on other sites More sharing options...
06BaNsHeE Posted January 13, 2008 Report Share Posted January 13, 2008 after reading this thread, all i got to say here is proof to let a builder put it together or buy most everything from them. that why there is not confusion of what parts are what. best of luck. Quote Link to comment Share on other sites More sharing options...
forumsearcher Posted January 13, 2008 Author Report Share Posted January 13, 2008 after reading this thread, all i got to say here is proof to let a builder put it together or buy most everything from them. that why there is not confusion of what parts are what. best of luck. Yea, I probably should have bought all the parts from one location. Luckily this is a hobby and is a fun learning experience. I know what not to do next time... Thanks for the thoughts on the 110 rod and piston. I will check the casting tomorrow, I think the puzzle is getting closer to being solved. Quote Link to comment Share on other sites More sharing options...
wesw Posted January 13, 2008 Report Share Posted January 13, 2008 yeah but your inablility to know certain things might end up costing you more money. again best of luck sounds like a major headache. Quote Link to comment Share on other sites More sharing options...
forumsearcher Posted January 13, 2008 Author Report Share Posted January 13, 2008 If I remember correctly those little casting ears on the intakes have numbers cast in them..... For a stock stroke cub they should be 4.038 and piston .018 in the hole with a .022 gasket For 4 mil cylinder they should be 4.079 and piston .010 in the hole with a .022 gasket Dave, you are the man... Thanks for sticking it out. The casting in the intake shows 58. Wow, wish I would have known that before... HAHAHA. I am kinda excited now to build the 421 setup since I have basically built the 392 at least twice by now. I think I will go ahead and go with a the 4mm crank and long 115 rods so I can use the normal 573 weisco piston. The additional cost of the pistons wont break the bank. I should be able to sell the "used" pistons and my crank to help offset the new stroker crank cost. Another learning experience of this was that the cub NEEDS to have a "clean up" port job to fix casting flaws. I just used my dremel again to cut out the casting imperfections. It is very easy to do so for other DIYers go ahead and do a clean up port yourself. The transfers were really bad on my cylinder. One of the transfer ports was probably blocked by about 50% with left over casting flaws. Also the smaller left and right intake ports needed to be cleaned up. I did a minimal clean up on the edges here but the excess casting is obvious. Sorry I did not get any pictures before the clean up, but google has a lot of information with pictures on clean up port jobs... Hopefully this thread helps someone else in the future. I imagine there are not many people out there that try to build a 392cc engine with a 421 cub, but my mama always said I was special. :biggrin: Quote Link to comment Share on other sites More sharing options...
Dave I. Posted January 13, 2008 Report Share Posted January 13, 2008 glad ya got it figured out. Quote Link to comment Share on other sites More sharing options...
dutch350 Posted January 13, 2008 Report Share Posted January 13, 2008 I dont think you will be disapointed next time you ride it! Quote Link to comment Share on other sites More sharing options...
No Limit Powersports Posted January 13, 2008 Report Share Posted January 13, 2008 The cub should have some clean up done at the factory but it def can benefit from some more. You will be very happy with a the 421 setup if setup properly. If u want give me a call on monday and ill help u get everything right so u won't have any more costly mess ups. Andy M&M ATV Quote Link to comment Share on other sites More sharing options...
forumsearcher Posted January 13, 2008 Author Report Share Posted January 13, 2008 The cub should have some clean up done at the factory but it def can benefit from some more. You will be very happy with a the 421 setup if setup properly. If u want give me a call on monday and ill help u get everything right so u won't have any more costly mess ups. Andy M&M ATV Thanks, I already sent you a millon emails. I'll definately call Monday... Quote Link to comment Share on other sites More sharing options...
forumsearcher Posted January 26, 2008 Author Report Share Posted January 26, 2008 Well I got a crank and new pistons slapped everything together, check the squish to be .042", and took her out. She runs like a beast. I have overheated a couple times with the 170 / 50 setup. Now I am running 185 mains and 50 pilots. I still think it is a little lean though. But the power is incredible... Thanks for everyones help. Now time to hit the dunes for some fine tuning on the jets... I am sure +4 swingarm and new cpi pipes will be in my future... Quote Link to comment Share on other sites More sharing options...
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