What's the truth on the FULL CIRCLE STROKER CRANK?

I've heard that some say that it is the greatest mod on earth. And I've also heard that some say that it is a POS that makes top end revs drop and other have said that it didn't really add anything.

So which is it???

Thanks, James.

Stroker cranks by design increase low end torque and reduce max revs.

So if you want more bottom end pull at the sacrifice of top end, you may want to try one.

Thanks for the reply RoboCop.

Yep...what he said.

I know its about a balancing issue rather then a lightening issue. I still treat it like a lightened flywheel on a car. Better acceleration with a lighter flywheel! Lose top end cause you dont have the momentum from a heavier flywheel. So what Robocop posted all makes sense!

The full circle crank is good if you've done a big bore kit or a 4 port head. Then all you have to really do is put a 7 tooth front,then you'll be flying!

My favorite low cost mods would be a bbk and pipe. That's it. Maybe some cheap CF reeds. A rejet is necessary. To me, this is a great setup.

OR

If you really wanna go fast, give a call to Matt at PSWS or Brooks at ADA. Both have high quality reed and head kits available.

Yep...this will be my next mod.
Already have the psws reed valve w/race carb..and it is the schitz.

My FF Cag setup consists of the following: IP2 PIPE, BIG BORE KIT, DELL'ORTO SHA 14/14 ON A NO.80 JET, K&N FILTER, BOYESEN SUPERSTOCK FIBRE REEDS & A DENSO IRRIDIUM PLUG.

I like the look of the ADA 4-petal reed setup - that looks way cool to me. The fact that it costs as much as a new Cag puts me off a little. But the drop in rpm with the FCSC sounds like I am going back on myself. I can see where you are both coming from in terms of physics with the FCSC with a 7tooth pinion. But won't I be just droping some MPH in the begining changing cranks and then topping the MPH up again by chaning the gearing???

Your thoughts welcomed.

James.

if you get a fcc and bbk, you might loose some speed from the fcc, but you can get a 7 tooth gearing and it will take that extra low end and add it on top, so you will be able to choose what you want, extra low end, or really high, im trying to hit 40, with a bbk and fcc and ported motor, with 7/68....I think I should be able to hit 40...hope soo....nice replys
john

if you have an fcc and a bbk. your rpms will go down at least 1000 which means -3mph . these two can let you prolly pull one more tooth bigger pinion which at those rpms =4 ish mph. soo theres no point in doing those mods if you want top speed IMO

but dont you have to machine your cylinder for the headkit?

My bike LOVES the FCSC. I think you guys are loosing top end cause of the viberations. My bike has ABSOLUTLY no viberations at all and was hitting about 38 MPH with CF reed , FCSC, IP2 pipe and ported carb.
When i added the four port is when i lost 4 mph. I'm oin the proscess of getting a big bore to replace the four port and hopefully that will put me over the 40 mph mark.

Thats Exactly what I want to do...nice SUX2BU, I like that setup, pm sent to you...
John

bbk will slow you down too

HOW will 8cc slow you done? I dont get that?? if it takes 1-3 mph on top, it will still give you MASSIVE amount of low, mid, and you will be able to gear it higher AND STILL have good low end and you will be at 35+....Its weird...Im confused

i meant slow your rpms. and a bbk doesnt give you THAT much low end

bbk adds 8 cc...thats double the FCSC...now thats lot, it should be a biggggg difference...I will tell you in a week...cant wait, ill tell the truth...and speed results and rpms...
John

I agree with sikk, adding the bbk to SUX2BU's setup will not give him the top end gains he wants. In this case, the increase in discplacement will not give him a gain in RPMs. It will however give him power in the low to mid range. The bigger and heavier piston of the bbk will not allow gains in RPM up top, not to mention combined with the longer stroke of the FCS. Because of the heavier piston of the bbk, that with throw it off balance even more with the FCS. The vibrations will also hinder gains in RPMs. Adding additional mounts/supports to the chassis to help reduce vibrations will not help the engine itself with the vibrations that are still there internally. Those who have gained RPMs up top with the FCS is strictly because it is a stuffed crank (increased pressure in the case) and it's weight. The longer stroke will hinder higher revs. As I have mentioned in another thread, I don't have much increased vibrations at all with my FCS, Im using the stock 40mm piston that I lightened. However, gains in top end may be possible with the bbk's 44mm piston if the transfer ports on the bb barrel weren't so **** big.

SUX2BU probably lost top end with the 4-port because his 4-port might have the transfer ports ported too big and/or the boost port is too big. I had a head where I only ported 1mm throughout the transfers and also lost a bit of top end. On my current barrel with a boost port 4-port, I did not port the transfers at all, just match ported them to the case at the base of the barrel. The boost port is also smaller than my previous barrel. No loss in top end like my previous barrel.

I tried getting my hands on a fcsc about 1 month ago but unfortunately the aussie knob who put the order in did a runner and has not be heard from since. I can't believe you guys arn't trying these out, ffs. Let me just point a few things out.
1. When you increase stroke length your port timing is lowered, that means the engine is going to find it harder to rev, you have to sort out the port timing.
2. increasing the stroke of an engine will limit it's rpm if the piston speed has hit a safe limit, with a 35mm stroke that's well over 17krpm's, port timing and induction are the main areas that need work.
3. most cranks need to be balanced, if i had a fcsc i'd do it properly, starting at splitting it, weighing the gudgeon pin, big end, piston assembly ect ect. may need tungsten rods oposite the journal and aluminium plugs oposite, it's a compromise between good balance at one rpm and a few harmonics where the engine wont be used, phill irvings book "tuning for speed" has the method. It may bounce around at 4000rpm but spin like a turbine at 15000. Just use the top piston ring at those rpm's, the otherones just wearing the bore and being heavy.
4. the full circles are filling up the crankcase, good for primary compression ratio, bad for our inline-crankcase induction. you could fix this problem by making a reed cage that's at 90 degrees to the ones we have, make it so the end of the V is in line with the gap between the crank halves.
5. the area under the cylinder is the best place to have a bit of volume, this is the main area transfer gasses entering the cylinder come from.

I think a bottom of the cylinder spacer would take care of 1,2,5 in conjunction with a domed head. numbers 3 will be more fun, and number 4 is not so hard, it's just crying out for a big v-reed cage.

btw, you guys know what rpm the c1's are pulling? know what stroke they have? my old motorcross engined 250cc dirt kart is pulling over 11,000 with 64mm stroke.

BTW... I have also heard of people only using the top piston ring when a BK is used. What is the purpose of this? Pros and cons?