sheldonoga Posted October 7, 2011 Report Share Posted October 7, 2011 Can someone help me with this?I need to no what one would be beter for trail riding and sand drags on the weekends.the other thing is i no with the 4 mill you can use stock cylinders but can you still use stock cylinders with the 7 mill?my cylinders are 65.50 with la sleeves im using weisco pro light pistons.i build a lot of honda car motors so this is new to me.if anyone can lead me in the write way of how to do a build like whats all needed would really help thanks. sheldon oga Quote Link to comment Share on other sites More sharing options...
sheldonoga Posted October 7, 2011 Author Report Share Posted October 7, 2011 thanks,will i have to change the piston or could i use the same ones?I think im going with the 7 mill it sounds like a good project.i was looking at tdr for the crank is that a good place?im in hawaii and there is no place that sell parts. thans for the help anything larger then a 4mil crank you need to trench your cases Yes you can run a 7 mil crank in stock cylinders. However you will need to have the proper machining in the domes for the crank. I cant go too much in specific as I didnt do enough reaserch into a 7mil stock cyl set up. But I do know 100% its a fairly comon simple enough build. On a 7 mill a lot of people would suggest a solid clutch set up possibly with a lock up. Moded trans to make it smoother for shifting and some straight cut gears. Pancake bearing bigger carbs ext... all the other supporting mods. Porting specifically for the amount of stroke.... Quote Link to comment Share on other sites More sharing options...
Azryll Posted October 7, 2011 Report Share Posted October 7, 2011 What kinda trails are they? Like somewhat open or super tight? If they are really tight bigger than a 4mil might be to much. Also for the price of building a 7mil you can build a 10mil. Just depends on what you want, a really good trail bike, a good drag bike, or something in between that does decent at both but is not optimal for either. Without knowing what your "trails" are like or how often you do them I would lean toward the 4mil only because its a good all around motor (less expensive to build and you can still beat most 4 strokes). You can get 70-75 hp pretty easy but not have so much power you'll need a huge swingarm. You'll never be able to use the all the power of the other motors on the trails. If you plan on doing lots of dragging or have large open areas go bigger. Quote Link to comment Share on other sites More sharing options...
jbooker82 Posted October 8, 2011 Report Share Posted October 8, 2011 Most guys dont run 7 mills any more. Since you have to trench the cases they just go a head and do a 10mill. It costs about the same to build a 10 mill and a 7mill. Quote Link to comment Share on other sites More sharing options...
Jereme6655 Posted October 8, 2011 Report Share Posted October 8, 2011 There's another point that i just noticed that no one has hit on.......RACE GAS. Octane is your friend when your running big motors like 7 or 10 mil bikes....most of them wind up breathing the hard stuff....which can be expensive... Do you have access to race gas in Hawaii? You could also do a 4mil serval setup......which will give you the benifits of being a great low end grunt trail bike and still a real hard runner up top. and you can get 80+ hp on PUMP GAS. To answer your other question though......no you can't use stock cylinders for a 7mil because the stroke of the crank is that much farther it would make your piston and your head come together in a way that you'd never want to see again..... the 4 mil cranks have to run blaster pistons in order to offset the added stroke of the 4mil..... and i know that all our site sponsors on here have the parts to do a +4mil ready to go for another awsome build... Quote Link to comment Share on other sites More sharing options...
Coupelx Posted October 8, 2011 Report Share Posted October 8, 2011 There's another point that i just noticed that no one has hit on.......RACE GAS. Octane is your friend when your running big motors like 7 or 10 mil bikes....most of them wind up breathing the hard stuff....which can be expensive... Do you have access to race gas in Hawaii? You could also do a 4mil serval setup......which will give you the benifits of being a great low end grunt trail bike and still a real hard runner up top. and you can get 80+ hp on PUMP GAS. To answer your other question though......no you can't use stock cylinders for a 7mil because the stroke of the crank is that much farther it would make your piston and your head come together in a way that you'd never want to see again..... the 4 mil cranks have to run blaster pistons in order to offset the added stroke of the 4mil..... and i know that all our site sponsors on here have the parts to do a +4mil ready to go for another awsome build... Just because its a big engine doesnt mean it has to be a race gas burner and the 7mil crank can be used with stock cylinders unlike the 10mil crank which requires somewhat serious mods to do so AND theres no reason you couldnt have a 7mil stock cylinder bike that is trail friendly. You run blaster piston because of the 115mm (5mm longer than stock) rod not because of the stroke. You simply run a 'stroker' dome or a stock head that has the domes cut deeper since the piston now comes out of the top of the cylinder by 2mm for the 4mm crank and 3.5 for the 7mm crank. Quote Link to comment Share on other sites More sharing options...
sheldonoga Posted October 8, 2011 Author Report Share Posted October 8, 2011 thanks guys,i run race gas now but its 16.00 a gallon.I want to run pump now .sound like the 4 mill is the way to go for me.so i have wiesco 513 pistons that are 65.50 can i get domes cut and use them or will i have to use blaster pistons?one other question does boost ports in the intake make a big deal?i was thinking of putting them in cylinders. Just because its a big engine doesnt mean it has to be a race gas burner and the 7mil crank can be used with stock cylinders unlike the 10mil crank which requires somewhat serious mods to do so AND theres no reason you couldnt have a 7mil stock cylinder bike that is trail friendly. You run blaster piston because of the 115mm (5mm longer than stock) rod not because of the stroke. You simply run a 'stroker' dome or a stock head that has the domes cut deeper since the piston now comes out of the top of the cylinder by 2mm for the 4mm crank and 3.5 for the 7mm crank. Quote Link to comment Share on other sites More sharing options...
Coupelx Posted October 8, 2011 Report Share Posted October 8, 2011 if you manage to find a 4mil crank with stock length (110) rods you could use your current pistons but they are few and far between. the longer rod reduces sideload and wear on the piston. In order to see the full benefits of the 4mil you will need to have them ported. The boost ports can help if done right. forgot to add earlier you run wiseco 795 series pistons with a stroker crank. not necessarily blaster pistons as they start at 66mm so arent really suited for stock cylinders. Quote Link to comment Share on other sites More sharing options...
sheldonoga Posted October 8, 2011 Author Report Share Posted October 8, 2011 thanks, so any 795 series piston will work?is the 795 made for the strocker?when you say port it are you talking about the port hight for the intake and exhaust.thanks for all the help im doing all the work my self so all the help i get is good.im new to building 2 strokes.if anybod has pictures of what a good port job looks like could you send some so i can try and port my cylinders the same way.thanks again everybody if you manage to find a 4mil crank with stock length (110) rods you could use your current pistons but they are few and far between. the longer rod reduces sideload and wear on the piston. In order to see the full benefits of the 4mil you will need to have them ported. The boost ports can help if done right. forgot to add earlier you run wiseco 795 series pistons with a stroker crank. not necessarily blaster pistons as they start at 66mm so arent really suited for stock cylinders. Quote Link to comment Share on other sites More sharing options...
Coupelx Posted October 8, 2011 Report Share Posted October 8, 2011 at this point you would be better off having someone else port it, its not just grinding it out to match. the 795 series of pistons has the wrist pin moved higher up for the longer rod. 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.