cline Posted March 6, 2012 Report Share Posted March 6, 2012 I am really excited to head down the road to my first rebuild/upgrade but I need all of your help because I hear terms used but even after reading my ass off in here I still find myself not being able to answer my questions. When it comes to cranks I hear 4mil 7mil and 10mil. Then I also hear some members say they have strokers and them some don't mention it. I have seen that there are different rod lengths such as 110mm and 115mm. This is what I hear but now I'd like to be able to understand what I'm reading. What is the difference between stock, 4mil, 7mil, and 10mil? Is a 4mil motor and a 4mil stroker motor different and if so what is the difference? Is the rod length what makes the difference in between the two? Thanks for your help and please check back because I have more questions but I'd rather understand this first before I reply with my others. Thanks again! Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted March 6, 2012 Report Share Posted March 6, 2012 Stock stroke 54MM , 4mil (4MM stroker) stroke is 58MM , +7 = 61MM stroke, +10 = 64MM stroke. Stock rod is 110mm C to Center. Long rod 115mm is used to improve angle of rod in relation to stroke as piston is moving up and down. Quote Link to comment Share on other sites More sharing options...
Coupelx Posted March 6, 2012 Report Share Posted March 6, 2012 people put the word stroker in because they think it sounds cooler. kinda like saying your chevy has been punched (bored) .030 over. in reality it makes you sound like a dork. Quote Link to comment Share on other sites More sharing options...
cline Posted March 6, 2012 Author Report Share Posted March 6, 2012 outstanding guys, thanks thus far. So the stroke lengths make a lot more sense now just being added from the stock stroke. Can you explain to me another term that I have heard. I have heard some say, "I have a true 7mil motor without spacer plates." What would be the difference between a regular 7mil motor and a 7mil motor with spacer plates? Larry you stated that the 115mm rod length "is used to improve angle," so does this suggest that everyone uses a 115mm rod? If not why wouldn't a rider want an improvement and choose to go with the 110mm length? Lastly if a comparison was done all mods being the same what would be the difference in horsepower from a 4mil to a 7mil? Thanks for being patient guys while I try and learn. Quote Link to comment Share on other sites More sharing options...
Coupelx Posted March 6, 2012 Report Share Posted March 6, 2012 outstanding guys, thanks thus far. So the stroke lengths make a lot more sense now just being added from the stock stroke. Can you explain to me another term that I have heard. I have heard some say, "I have a true 7mil motor without spacer plates." What would be the difference between a regular 7mil motor and a 7mil motor with spacer plates? Larry you stated that the 115mm rod length "is used to improve angle," so does this suggest that everyone uses a 115mm rod? If not why wouldn't a rider want an improvement and choose to go with the 110mm length? Lastly if a comparison was done all mods being the same what would be the difference in horsepower from a 4mil to a 7mil? Thanks for being patient guys while I try and learn. lets use a 4mil for ease of reference. the pin is offset 2mm so now the piston will go down the bore 2mm more and up 2mm more. this causes the piston to come out of the top of the jug. the old way of fixing that was to put a spacer plate under the jug. the newer and more common way is to have the head cut deeper to clear the piston as it comes out of the top of the jug 2mm. The 115mm rod makes it so the rod is at less of an angle which is said to have less wear on the piston. there are some downsides in some applications but you arent likely to run into these unless doing 1 off stuff. You will use a different piston that has the wrist pin hole 5mm higher to compensate for the longer rod. the difference between a 4 and 7 is a few hp and tq. someone probably knows for sure and can post. a 7mil crank is the biggest stroke that will readily fit in a stock cylinder (which was the idea behind it). if you are going with an aftermarket cylinder you might as well jump to a 10 instead of the 7. Now on a stock stroke most including myself like the 110 rod since it tends to be a rev happy engine. Quote Link to comment Share on other sites More sharing options...
Larry's Shee Posted March 7, 2012 Report Share Posted March 7, 2012 Man, you sure are asking lots of tech questions Generally speaking 4mil stroker cranks run the 115 "long rod" but the can be had with "short" rod (said to rev out quicker?). Conversly stock stroke can be had with long rods. As to "true" 7mil I would presume it would have to be an aftermarket cyl, only way to have cyl long enough without spacer. Wouldn't have a clue as to HP difference between 4mil and 7mil, even given identical port timings. 4mil stroker is very popular because you don't have to modify (trench) the cases. I totally understand your questions as there are so many possible engine combinations that it makes my brain hurt sometimes Quote Link to comment Share on other sites More sharing options...
sidewayz Posted March 7, 2012 Report Share Posted March 7, 2012 Thanks for this post and all the great answers. It clears up a lot of the same questions i had. Is there a section on here for "noob"most often asked questions and answers? Maybe a sticky for it so any of us newbies could just read up in it so we dont polute the site with clutter? I know most of you know these things in and out. It sure would help me and any other new banshee owner. Quote Link to comment Share on other sites More sharing options...
Coupelx Posted March 7, 2012 Report Share Posted March 7, 2012 Man, you sure are asking lots of tech questions Generally speaking 4mil stroker cranks run the 115 "long rod" but the can be had with "short" rod (said to rev out quicker?). Conversly stock stroke can be had with long rods. It is said they rev out faster/better because of less dwell (time spent at TDC or BDC). Quote Link to comment Share on other sites More sharing options...
cline Posted March 7, 2012 Author Report Share Posted March 7, 2012 Couplex and Larry, Both of you are awsome and I really appreciate the time you two took in writing up the info you gave up for me as well as some of the other newer guys. This took me from lost in the sauce as I was prior to today to at least having some sort of a clue when it comes to a bundle of tech questions that I had. This puts me a lot closer in narrowing my options when I choose my direction to do my upgrade. Thanks again Quote Link to comment Share on other sites More sharing options...
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