building a stroker 6.25 with 84mm pistons

[roadrunnerdk]

hi there

my plan is to build my 09 busa engine with a 6.25 stroker from a gen1 (4,25 stroke in the gen2) and 84mm pistons
my budget doesnt allow me to go all the way and get a ported head with other cams
so my question is how much power can i expect from this 1535cc engine with stock head and cams?

which cams would you guys recommend if i in the future should buy a ported head and cams

and if there is any free advice and things that are nice to know
when building an engine like this I would love to hear it
ANY ADVICE IS WELCOME

thanks for reading
lars

[WC SWB]

personally, i wouldn't bother with the crank if you can't do the cylinder head, you'll be choking that thing to death. i would go with the 84mm piston and a good head/cam package, and skip the crank for the time being.

i'm not an engine builder, but i think most would be inclined to agree.

[money maker]

I was thinking the same thing

2

[TurboR]

With a stock head it's gonna be like breathing through a straw under water. I have the pistons and block combo for sale you need for the 6.25. JE stroker pistons with a Gen I 3 mil block.

[sportbikeryder]

It would make alot of bottom end, but probably out of breath about 1500-2000 rpm too low.

[Moody]

as already stated you could do alot more other things with that money spent on a crank, but not saying you cant do it if you already got the crank. you would see the torque increase down low for sure but not gona benefit awhole lot on horsepower off the 1441cc kit

[roadrunnerdk]

the thing is that i got the crank for free from a friend who has gone the turboway and the rest of the parts needed to build the 1535 i plan to buy over a the winter and then put it together
i thought maybe this way i could build the 1535 and have some fun with it while sawing/looking for a good head and cams in the future

thanks for the input so far everybody

[Ridehard]

I had a 1535 gen1 Busa with carpenter head and cams. Made 246hp on bob's dyno. Using Q16 fuel.

It made 223 with just the 1397 head and cams. I wouldn't recommend the setup without having head and cams but it will be faster than what you have. May also blow up a lot faster too.

The stroker crank is the biggest wild card. I know you got it free but a 1441 would be much safer and make more power once you add the head and cam.

Sell the 6.25 crank and build a 1441.

[Moody]

if you want to sell the stroker crank let me know! i almost have enough parts to build another motor. i might even trade out for a perfect stock gen 2 crank.

[Moody]

I had a 1535 gen1 Busa with carpenter head and cams. Made 246hp on bob's dyno. Using Q16 fuel.

It made 223 with just the 1397 head and cams. I wouldn't recommend the setup without having head and cams but it will be faster than what you have. May also blow up a lot faster too.

The stroker crank is the biggest wild card. I know you got it free but a 1441 would be much safer and make more power once you add the head and cam.

Sell the 6.25 crank and build a 1441.

i bet there was day and night difference in the torque and where the pull was on the stroker versus the 1441

[Ridehard]

i bet there was day and night difference in the torque and where the pull was on the stroker versus the 1441

It was just a 1397 at first I never had a 1441. But yes the 1535 pulled like a freight train compared to the 1397. But I had the entire package which works well together. Not sure what it would have done minus the head and cams.

Here are the phases my bike went through. (2003 Busa)

Stock 165hp pump gas

Head cams 194hp mrx01

Head cams pistons 224hp mrx01

Add 6.25 crank 246hp q16

[StuckinIRAQ]

In knew a guy who had a GS1150. The motor was a MTC big block 1500cc. He put a stock head on it, with stock cams. With 1.4 sixties, it ran 10.40s = Pretty bad. It was a beautiful bike with all high-dollar items on it, until he had a falling out with his builder, so he took everything back and finished the bike himself.

Bottom line / lesson to be learned: get those parts, but wait until you have the money for the head & cams. The guy with the 1150 simply couldn't wait any longer, and all he had to show for it was a 1500cc motor with brand new crank with straight-cut gears, etc ...... that ran about the same as a much, much smaller motor ...... that had the head and cams done to it.

Hope this helps.

[Moody]

but i do agree that everything has to work together, therefore big stroke with little head is obviously not going to benefit like a big stroke with a big head. although, a big stroke with little head is better than little stroke with little head. either way if i already had it i would probably go ahead and do it but thats me and my broke ass way of thinking (that was how i was raised)

[Ridehard]

but i do agree that everything has to work together, therefore big stroke with little head is obviously not going to benefit like a big stroke with a big head. although, a big stroke with little head is better than little stroke with little head. either way if i already had it i would probably go ahead and do it but thats me and my broke ass way of thinking (that was how i was raised)

Lol! Main reason I caution against it is because of the reliability. My 6.25 lasted less than 30 passes and I never sprayed it. Ran good oil and safe fuel with a safe tune but still spun a bearing.

A lot of people have had better luck than me but going with a stroker will definitely be less reliable than a stock bottom end. I wouldn't risk blowing a motor again unless I was ready to go all out and get the best performance possible. Not worth blowing a motor for a little more torque.

[TurboR]

My 6.25 lasted less than 30 passes and I never sprayed it. Ran good oil and safe fuel with a safe tune but still spun a bearing.

How often did you change the oil? What did you have for oil mods? Oil pump gear? Oil pressure valve? You may think this is a little OCD, but the key to a stroker motor living is frequent oil changes. Frequent as in every trip to the track. Just my honest opinion. It works for me on my small bike. I highly suggest a non stroked motor though if you are not going to do frequent oil pan inspections and want to still be streetable.