Penny's Banshee Posted August 9, 2011 Report Share Posted August 9, 2011 I bought a used bike and the person i bought it from said it has a 4mil crank in it. what is the best way to figure this out without splitting the cases? the rods have an R on one side and a 29 on the other. if that helps at all. Quote Link to comment Share on other sites More sharing options...
#1JUANstunna Posted August 9, 2011 Report Share Posted August 9, 2011 Measure the length of the stroke in the cylinder from BTC to TDC. Quote Link to comment Share on other sites More sharing options...
Koolguyson Posted August 9, 2011 Report Share Posted August 9, 2011 Only real way to tell is to measure the stroke. If you need help with it, I am in Arroyo. Quote Link to comment Share on other sites More sharing options...
dirtydownunder Posted August 9, 2011 Report Share Posted August 9, 2011 does it have a spacer plate or cut domes ? spacer plate you can see under the cylinders. with the domes, you have to remove the head. does it run a cooll head ? this is a 4mm longrod crank from M&M http://a3.sphotos.ak.fbcdn.net/hphotos-ak-snc6/167782_10150095692637002_573727001_6162540_1745238_n.jpg Quote Link to comment Share on other sites More sharing options...
SuprSlow50 Posted August 9, 2011 Report Share Posted August 9, 2011 There are two ways that I have done before. The first is to pull the gas tank off and meaure the stroke of the crank from TDC to BDC with the butt end of a caliper, or with the tank off you should be able to pull the sparkplug and read the part number on the top of the piston to see if it is for a 4mil crank. It may be hard by eye, as I have never tried it that way, but I have an earscope that I have been using to read the fuel rings on nitrous motors and they work great for reading the part numbers too, has a light and a magnifying glass. Hope this helps. Quote Link to comment Share on other sites More sharing options...
coryv4 Posted August 9, 2011 Report Share Posted August 9, 2011 There are two ways that I have done before. The first is to pull the gas tank off and meaure the stroke of the crank from TDC to BDC with the butt end of a caliper, or with the tank off you should be able to pull the sparkplug and read the part number on the top of the piston to see if it is for a 4mil crank. It may be hard by eye, as I have never tried it that way, but I have an earscope that I have been using to read the fuel rings on nitrous motors and they work great for reading the part numbers too, has a light and a magnifying glass. Hope this helps. on my 4mil it has +4 stamped on the inside of the crank right next to the rod pin Quote Link to comment Share on other sites More sharing options...
Koolguyson Posted August 9, 2011 Report Share Posted August 9, 2011 There are two ways that I have done before. The first is to pull the gas tank off and meaure the stroke of the crank from TDC to BDC with the butt end of a caliper, or with the tank off you should be able to pull the sparkplug and read the part number on the top of the piston to see if it is for a 4mil crank. It may be hard by eye, as I have never tried it that way, but I have an earscope that I have been using to read the fuel rings on nitrous motors and they work great for reading the part numbers too, has a light and a magnifying glass. Hope this helps. True and not true. It could be a short rod stroker, in which case it will use a standard banshee piston. BUT it will/should have a spacer plate at that point. The only real way to know is to measure the stroke. You have no idea what somebody could have put in there. Quote Link to comment Share on other sites More sharing options...
Penny's Banshee Posted August 10, 2011 Author Report Share Posted August 10, 2011 It does have a cool head and i took the domes out about a year ago in my buddies shop and they were misplaced. I might take you up on that Koolguyson when i get some free time ill pm you and maybe we can get together so you can teach me a thing or two. Thanks for the input from everyone. 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.