twinzr900 Posted April 8, 2008 Report Share Posted April 8, 2008 (edited) right now i have a 4mm stroker w/ 5mm long rod bored .20 over...i believe my CC'S are around 39?...but where do u guys get your 421 strokers from? just curious. thanks. Edited April 8, 2008 by twinzr900 Quote Link to comment Share on other sites More sharing options...
BellicoseBanshee Posted April 8, 2008 Report Share Posted April 8, 2008 68mm bore and a +4mm crank increases the engine size from stock to 421cc (for example, 421 cub). Quote Link to comment Share on other sites More sharing options...
twinzr900 Posted April 8, 2008 Author Report Share Posted April 8, 2008 so how many over is equal to 68mm bore? (.20,.40 etc..) and is mine more CCs then what i think or no? kinda go into more detail. thanks ..just trying to learn some more Quote Link to comment Share on other sites More sharing options...
BellicoseBanshee Posted April 9, 2008 Report Share Posted April 9, 2008 so how many over is equal to 68mm bore? (.20,.40 etc..) and is mine more CCs then what i think or no? kinda go into more detail. thanks ..just trying to learn some more 0.100 is the maximum the stock cylinder sleeve can be bored. I would not go beyond 0.080, but some people do it and have good results. Your engine, 64.5 bore with the +4mm crank, is 379cc. There are many different possibilities as far as displacement goes. Cubs have 65mm and 68mm bore for stock stroke, 68mm bore for the +4mm crank and many other strokes. The stock jugs can be resleeved with big bore sleeves which makes the engine size around 400cc. There are more options for cylinders as well. If you are really interested in the various combinations, look at websites like Casacde, Trinity, and others, for they have many options listed. CP Industries Inc., the company that does the cheetah and cub cylinders, has some pretty cool stuff on its site. Hope that helps... Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted April 9, 2008 Report Share Posted April 9, 2008 If you want a 421 buy a complete cylinder kit like a cub, don't bore your cylinders out unless you have to. The extra cc's aren't worth that much power and at 68mm bore your stock cylinders are done if you burn it down. Also, IMO the big bore sleeves for stock cylinders aren't a very good option either, you sacrifice too much valuable transfer area for more displacement...limits your power potential. Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted April 9, 2008 Report Share Posted April 9, 2008 If you want a 421 buy a complete cylinder kit like a cub, don't bore your cylinders out unless you have to. The extra cc's aren't worth that much power and at 68mm bore your stock cylinders are done if you burn it down. Also, IMO the big bore sleeves for stock cylinders aren't a very good option either, you sacrifice too much valuable transfer area for more displacement...limits your power potential. 66mm is the final bore on stock cylinders unless they have been resleeved with big bore sleeves. A 4 mill stroker with a 66mm bore is 400cc's. That is what I am at. I am running a set of cylinders that have been RESLEEVED and Drag Ported by Dan Wade from Patriot Racing. First bore is 66mm last bore is 68mm (421cc's with a 4mill crank) Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted April 9, 2008 Report Share Posted April 9, 2008 so how many over is equal to 68mm bore? (.20,.40 etc..) and is mine more CCs then what i think or no? kinda go into more detail. thanks ..just trying to learn some more 66mm is a 2mm over bore or .100 over so 68mm would be 4mm over or .200 over. If you run a stock stroke long rod crank or a 4 mill long rod crank you usually run wisco 795 series pistons for 64.00mm bore through 66.00mm bore. Once you start running over 66mm you usually run Yamaha Blaster pistons. Blaster pistons start out at 66mm and go through 68mm. You do have to run special domes made for blaster pistons if your running them in stock cylinders. Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted April 9, 2008 Report Share Posted April 9, 2008 66mm is the final bore on stock cylinders unless they have been resleeved with big bore sleeves.A 4 mill stroker with a 66mm bore is 400cc's. That is what I am at. I am running a set of cylinders that have been RESLEEVED and Drag Ported by Dan Wade from Patriot Racing. First bore is 66mm last bore is 68mm (421cc's with a 4mill crank) OOPS, typo Quote Link to comment Share on other sites More sharing options...
Animalman294 Posted April 9, 2008 Report Share Posted April 9, 2008 It really does help to do your research and do it right the first time around. You are on the right track asking the questions, but you also need to stop and ask yourself what you are wanting to do with the bike when you get it pumped up more. That will ultimately determine what you should do with your cylender's......... :biggrin: Quote Link to comment Share on other sites More sharing options...
Wildcardracing Posted April 9, 2008 Report Share Posted April 9, 2008 It really does help to do your research and do it right the first time around. You are on the right track asking the questions, but you also need to stop and ask yourself what you are wanting to do with the bike when you get it pumped up more. That will ultimately determine what you should do with your cylender's......... :biggrin: Agreed! Very...Very good advice! :thumbsup: Quote Link to comment Share on other sites More sharing options...
slowblueshee2 Posted April 9, 2008 Report Share Posted April 9, 2008 66mm bore is .80 over bore leavin you .90 and .100. 4mm crank and 66mm bore makes a 396 to be technical. You can reach your displacement number by multiplying the strokexhalftheborexhalftheforex3.14xnumber of cylinders. For example 5.8(4mill)x 3.3(66mmbore)x3.3x 3.14x2(cyl.)=396.6 Quote Link to comment Share on other sites More sharing options...
twinzr900 Posted April 9, 2008 Author Report Share Posted April 9, 2008 i got ya now! thank you for the good info! so the 5mm long rod does not add any CCs then just the 4mm crank. Quote Link to comment Share on other sites More sharing options...
dajogejr Posted April 9, 2008 Report Share Posted April 9, 2008 Correct. The 4 mil stroker is 2mm offset from stock on the web. So, 2mm more on the bottom and 2mm more on the top of the stroke....4mm total. The long rod is used to lessen the angle of the rod to piston. The rod wants to shove the piston through the front of the cylinder, by using a longer rod AND offset piston with an altered pin height, there is less stress on the overall rotating assembly. I wouldn't get big bore sleeves for a stock cylinder. Once you get bigger sleeves, your transfer ports become much smaller, and most of your power comes from your transfers.... I think a properly ported set of stockers is damn near if not just as good as a big bore on stock cylinders. Quote Link to comment Share on other sites More sharing options...
BellicoseBanshee Posted April 9, 2008 Report Share Posted April 9, 2008 I wouldn't get big bore sleeves for a stock cylinder. Once you get bigger sleeves, your transfer ports become much smaller, and most of your power comes from your transfers.... I think a properly ported set of stockers is damn near if not just as good as a big bore on stock cylinders. That is exactly what I was about to add. :thumbsup: Quote Link to comment Share on other sites More sharing options...
GleasmJA Posted April 10, 2008 Report Share Posted April 10, 2008 I'm reading through this and now have a question. So can you get a 4mil long rod in stock cylinders?? Quote Link to comment Share on other sites More sharing options...
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