380cc/390cc Big Bore/Stroker Kit

[dns1764]

http://www.fourstroketech.net/


has anyone put the 390 kit on their bike?? if so whats the power like and how much does it effect the reliability?

[sd1]

Any stroker motor is a potential bomb motor....but I have seen some last a long time, but when they let go ..it all goes...the power on the low to mid range will be very good...but you will lose top end a bit...depends on kit and how well the crank is balanced....but the kit has to be well made.....so many issues..valve and piston clearances etc..

[shiley55]

i wouldnt recomend going that big unless you have like 2 grand or more to do it right and your ready to buy 10 dollor a gallon vp fuel i mean you might as well look into getting the head ported and polished new carb and honestly new exhaust cause 300ex exhaust isnt designed for that much . you would just be chokeing up the motor and deff wouldnt get a rev box casue higer rpms then the motor was made for and a huge *** bore dont go well together and when the motor goes be ready to spend even more plus if your going all out with your motor you might as wellget all new bearings and everythign cause what is the use to put all that money into it and blow it all to hell over a dumb bearing persionally the largest i would go would be a 350 stroker powroll.com they have nice kits pluse you can build what you want from what they have and other stuff

[dns1764]

thats what i figured. i just ran into the website and had never seen anything that big

[laeger400]

Originally posted by dns1764
http://www.fourstroketech.net/


has anyone put the 390 kit on their bike?? if so whats the power like and how much does it effect the reliability?

yes i ran the 380 kit with the head fully built by f/s tech (ported big valves) i bored the casesa and built the motor. the cylinder was nycasilled and i ran sidewinder sprockets and chains(they where the only ones that held up) sizes where 15/33 with 18 and 19s and 14/33 with 20 and 21s . i used a 400ex carb. i had curtis sparks mod the cdi box. the bike was one of the nicest 300ex stock frame bikes around. that doesnt even cover the frame modds i done. i also ran a earls oil cooler and changed oil filter every day io road. and changed oil after every weekend or trip or race. the motor had about 32-35 horse not exactly sure but it was badass for a 300 i was smokin z400s and 400ex stock or 440s i loved it. ive had 450s, a full laeger 265 national quad and numorus other bikes and the 380ex was by far the funnest of them all i think mostly cause it was the underdog. i weighed 180 at the time and i pulled hard and when i let a 120 lb kid ride it was stupid fast lol.

[laeger400]

Originally posted by shiley55
i wouldnt recomend going that big unless you have like 2 grand or more to do it right and your ready to buy 10 dollor a gallon vp fuel i mean you might as well look into getting the head ported and polished new carb and honestly new exhaust cause 300ex exhaust isnt designed for that much . you would just be chokeing up the motor and deff wouldnt get a rev box casue higer rpms then the motor was made for and a huge *** bore dont go well together and when the motor goes be ready to spend even more plus if your going all out with your motor you might as wellget all new bearings and everythign cause what is the use to put all that money into it and blow it all to hell over a dumb bearing persionally the largest i would go would be a 350 stroker powroll.com they have nice kits pluse you can build what you want from what they have and other stuff

i also ran on pump gas. the bike was reliable as hell but you are right i spent some chedda on and i did most of it myself except( sleeve,head, and nycasill) but i think i had about 1300 in it give or take a 100.

[laeger400]

Originally posted by sd1
Any stroker motor is a potential bomb motor....but I have seen some last a long time, but when they let go ..it all goes...the power on the low to mid range will be very good...but you will lose top end a bit...depends on kit and how well the crank is balanced....but the kit has to be well made.....so many issues..valve and piston clearances etc..

that is why i went with the 380 kit because it is just a big bore you still have top end and the big cc change gives you plenty of bottom end. when i built this i had seen a full laeger 416 stoker big bore from f/s tech it was a 20g quad full laeger chassis with 250 geometry and a badass motor but when i called micky he said that the 380 would be close on bottom end but faster on top end and it was. hell all this talk and bring up old memories is wanting me to build another just to have lol.

[dork]

ha ha, thats great to hear from someone with one. thats the best part, being the underdog. i built one the same way for my buddy and he had no problem running with, and sometimes beating all the new 400cc + bikes. also, that engine has been one of the most reliable modded engines i've built. with the stock stroke and bigger rod/wristpin they are strong. plus those old 250x/350x/300ex engines have lots of meat in the cases/cylinder for big sleeves. and the FST kit uses pump gas, comes out around 11:1. just keep fresh oil in it and run a cooler. where'd you have it nicasilled?

[laeger400]

millinium in wisconsin, or just ask mickey to do it. yes all this talk im half convinced to build another one lol.

[QuadCobbler]

Originally posted by laeger400
yes i ran the 380 kit with the head fully built by f/s tech (ported big valves) i bored the casesa and built the motor. the cylinder was nycasilled and i ran sidewinder sprockets and chains(they where the only ones that held up) sizes where 15/33 with 18 and 19s and 14/33 with 20 and 21s . i used a 400ex carb. i had curtis sparks mod the cdi box. the bike was one of the nicest 300ex stock frame bikes around. that doesnt even cover the frame modds i done. i also ran a earls oil cooler and changed oil filter every day io road. and changed oil after every weekend or trip or race. the motor had about 32-35 horse not exactly sure but it was badass for a 300 i was smokin z400s and 400ex stock or 440s i loved it. ive had 450s, a full laeger 265 national quad and numorus other bikes and the 380ex was by far the funnest of them all i think mostly cause it was the underdog. i weighed 180 at the time and i pulled hard and when i let a 120 lb kid ride it was stupid fast lol.


Do you have any video of this bike or any pics? There aren't to many peolpe doing big bore 300s any more. Just though it would be cool to see one to get an Idea of the power it would make