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VFJ 750cc std bore testing

49K views 134 replies 37 participants last post by  Patriot50 
#1 · (Edited)
Got the std bore setup installed last week and did some testing. I was happy it was the highest HP std bore kit I've done to date. Just a bolt in kit, pistons, custom grind cams, valve springs, PCV, Muzzy duals. stage 3 spidermod clutch, Stock heads no porting or decking, stock cylinders, no decking or surfacing, stock valves, stock throttlebody.

~65.6 average RWHP. and it holds the HP line above 60 rwhp all the way to 60 mph.

while this is great. I feel like I can get even more RWHP out of this setup. Before we add ported heads, 38mm throttlebody. I feel that would get us over 70 rwhp right now. but I don't want to have the added expense and time down for porting and bored t/b as I believe the power is there without it. well see....

also, the torque is up more than the other kits I've tested as I do not require insane RPM's to make the power. We are only shifting out at 7600 rpm making this power to the wheels.

There is NO dead spots in the lower rpm range, common with some other setups, there is ZERO lag hitting the gas. it takes off like a ROCKET and literally hits 50 mph in about 4 seconds.


So....it's going back to testing with some additional cam profiles and possibly a zero gap secondary ring package instead of the zero gap top ring package.

While this setup may have made the best RWHP to date of any bolt in std bore setup that I've tested, it didn't make close enough to the 70 rwhp with a bolt in setup like I wanted it to.

ALSO. we did not drill and tap ANY additional venting for the crank case and running the vent hose to the airbox like stock. NOT A DROP OF OIL IN THE AIRBOX!!

I'll post up the charts later I have to get them off the dyno computer and I have 4 clutches to finish to go out today.

just a heads up, the std bore kits are working, but not 100% finished to my liking yet.

John
 
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#2 ·
wow thats awesome. cant wait til you get it finished to your liking haha.
 
#4 ·
we'll see, I want to max it out as far as possible while keeping ultimate reliability, no race gas, no crazy compression.

with the cams I am using there is no low end crapping out (where it spits and blubbers until 10 mph) so common with large duration cams. these are .420 lift and near 270 duration setup too!!

this was all done on pump gas sunoco 93 octane.

I'm sure with race gas and me adding some timing it may pick up 1-2 possible HP. but that's not how I'm going to do it.

John
 
#10 ·
Great, i'm waiting for the final result and price ! :)
 
#11 ·
full kit price, cams, pistons, springs, (gaskets pending size) will be under 1000.00 they are a little more expensive vs off the shelf stuff, or other builder kits but they are more expensive pistons, cams, and ring packages.

Like everything I sell, I will try to get the best rock bottom price on all components and pass the savings on to my customers.

The testing phase is what takes the most time. we have the brute we are using for testing and when that's done, we have to install the whole kit again in another brute and it HAS to yeild the same exact results to be marketable the way I want it to be. no messing around.

with my setups you get the total package. You don't just buy the parts and hope you can figure it all out on your own once you get them installed. Ihave it covered from the first bolt you unscrew to the first run you take.

I can set you up with complete custom Clutching, Spot on FI tuning, Carb tuning, I can even install and dynotune the machine. Years of experience wth these motors, clutching, tuning makes this a fairly simple task for me.

John
 
#13 ·
The kit is installed ran, abused and then it was pulled apart this week to diagnose what the pistons looked like and see whats happening.

we are trying another piston ring setup to see if we can yeild some even better results and then test again.

when I'm totally satisfied with the results, things will get put into production.

when the standard bore stuff is done and functional, then we move on to the bigger kits that are 2012 specific. I still have different intake and exhaust valves to test.


luckily for the 2012 brute's they can be made 880cc direct bore in, they have larger cylinders than previous years. not many people know this about the t-4 and the '12 brute

all in time. nothing happens very fast around here when it's 90* out.
John
 
#17 ·
80hp would be a hell of a trail bike. I had a 1005 stroker on the dyno the other day making 88-89 rwhp range all motor. at that power level the fun is just beginning!!


There's still much testing to be done. Parts like pistons, gaskets, cams, valves. everything is a waiting game and takes forever to get anything completed for 1 off custom parts. then if it doesn't do what it was supposed to, it's back to the drawing board.

I literally have a motor cut in 1/2 at my home garage and have made up nearly a dozen cam profiles down to the intake opening/closing degrees as well as the exhausts. That's the next step, it'll be costly and time consuming to get done on it's own. then I have to rely on the cam company to ensure the specs I give them they can carry over to the profile correctly.

John
 
#19 · (Edited)
no the cylinders will not fit in a pre 2012. they are larger in diameter and would require some case boring like trying to put the brute cylinders in a 700cc motor. the 2012 can be bored to 880cc as where the 05-11 models can only go to 840cc.

here's how the cylinders go bore and plating for the aluminum cylinder models
633cc i model motors can be bored to 87mm tops
750cc motors can go to 90mm tops 05-11
2012 cylinders can go to 92mm



hopefully this weekend the 750cc standard bore setup will be complete and fully tested. it just has to be dyno tuned and clutched.

John
 
#20 ·
perfect

:rock:
 
#22 ·
You aught to get yourself a flow bench....unless...you already do! :)

Btw, I noticed you had KFX 700 cams in a prairie 700 once. Did you feel any differrence? I gotta pull the damn valve covers off to re-seal on my P700, and was thinking of the cam swap since I can get them cheap, and they shouldn't require spring changes.
 
#24 ·
and the weekend went well?

:D
 
#25 ·
Got it all done. Not that thrilled about the RWHP#'s (even though it's the best std bore I've tested yet) it came in at 64 rwhp on average. We did loose 1 rwhp peak, but picked up mid and top end. The bike runs fabulous, no oil spitting and no catch can, vented right to the airbox. This brute 750 can pull a muzzy full system piped and dyno tuned (71 rwhp) can am 1000 outlander by a hair.

The rwhp is far enough off the mark I want (need 5-6 more rwhp), so it's back to the drawing board until I get better results. Don't get me wrong. the kit is killer fast, ultra responsive and runs absolutely fabulous, smoother than stock, but not good enough for what I want to produce.

#1. pistons are a little too heavy, they need .010-.020 more deck height and don't need as expensive ring package.
#2 cams need to get more exact profiles made on the cams. they work great, but I believe can work better IF I can get the profile the way I want them

I know porting the heads and larger throttlebodies will add more power. but that's not what I'm trying to achieve. I want better base #'s from just dropping in the parts.

John
 
#26 ·
standard bore test run

feels really strong pulled ahead of buddy mikes daul muzzy 71RWHP OUTLANDER 1000 more than once never had a change to get in some good drag races on video .did get it up to 76mph but ran out of room to stay in it.i will work on some drag races next time out.jeff
 
#27 ·
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