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View Full Version : what would be the real world difference between a 45 crank and a 47



forgiven
01-20-2007, 10:52 PM
I am still a little fuzzy on what the stroker crank will do for a mini but I have heard "stroker cranks are almost a must on a mini" and seemingly the one of choice would be the 47. I can get a 45 here http://reimerminiatvracing.com/engineparts.html for 100 bucks but a 48 is two hundred and 47's are seemingly in the same ballpark. My question is what EXACTLY does the stroker crank give me and would I see a tangible difference between the 45 and 47. It is also my understanding the bigger the stroker crank the less reliable the motor. How would that weigh into this decision? I want something fairly reliable but if I had to tear it down each year...so be it.

Any info on this would be greatly appreciated.

markvette
01-21-2007, 09:48 PM
great, my kind of post. i have built more 47 and 48mm stroker crank motors than i can count. my son raced a 47 stroke by 54 bore for 2 years and now runs a 48 stroke crank with a 54 cylinder. the stroker motors are very reliable. you really need to run them with the 54mm cylinder. most 50 and 52mm cylinders are short cylinders and you would have to use a spacer plate to make it work then your port timing will be off bad. also a 47 will fit the cases with no modifications but to use a 48 you have to cut the cases or the rod hits. i do this with a dremel tool. alos to answer your question the 47 and 48 stroker motors are a lot stronger than a 45 stroke. the 45 came from the old dinlis, for a couple of years they came stock with a 45mm crank and were over 90cc which actually made them illegal to be sold to kids under 16 to ride. i have my sons 05 eton with a 110cc stroker in it for sale. the 110cc is the 48 stroke crank with a 54mm cylinder.

Mark

forgiven
01-22-2007, 02:06 AM
Sorry...forgot to mention I have a 54mm cylinder and a high compression head just sitting in my attic.

So does the stroker crank give it more low end or what and where is the advantage?

Additionally are there any pictures of what I would have to do to the case to accomodate the 48?

Lastly how bad would it be to keep the stock carb on this?

I am looking for as much torque as possible.

markvette
01-22-2007, 07:53 AM
another thing i forgot to mention. the skirt of the piston has to be shaved about 3/8" on both cranks or it will hit on the crank. tons more bottom plus you can feel an advantage everywhere. there are no pics but i could walk you through it. you dont have to take that much out of the cases for the 48 but it does have to be cut. also the squish would have to be set up right. i dont like to run less than .030 or the compression is too high and you will have crank bearing failure. you can use the stock carb but you wont get near the rusults. we built a 108 which is the 47x54 with stock carb and exhaust for a predator that was used as a trail quad. very good setup for a trail quad as it is quiet with the stock exhaust and tons more bottom end for trails.

Mark

forgiven
01-22-2007, 02:42 PM
That is exactly what I am looking for since we harescramble and trail ride. The predator is OK but lacks a lot of bottom end.