Scooterotica

drunkmunkey6969 wrote:

J1MS wrote:I Spoke to Mr Kemp about the cranks used on the RB, asking him what he would recommend, a full circle crank was not his first choice.

I remember Mr Kemp saying somthing along the lines of... if it's not in the crank case to start with, then how can it be drawn into the cylinder, best to fill the case with air and fuel rather than metal and let the pipe do it's best to fill the cylinder.
This was some time back.

LPC?

sorry to hijack thread, what became of the crank you done dan is it in a motor anywhere..

this one ?

http://scooterotica.org/forum/viewtopic.php?f=7&t=40

sean brady scooters wrote:this one ?

http://scooterotica.org/forum/viewtopic.php?f=7&t=40

yep that and wasnt there another. are they still under testing

well ,actually I have done a few now for various folk .
but that particular "uber crank" went into an RB20 motor that Dan built for Andy longbottom .
Andy was completely unaware of this special crankshaft in his motor for quite a while ,in fact we didnt let on till about after six months of him running it around..
maybe it was a bit cheeky of us to use him as a guinnie pig ,but we thought this was a good way of testing it out thoroughly and getting completley un biased feed back from him.
When he first collected and tested his scoot he actually remarked at how smooth and responsive the motor was ,and that it went really well and sounded "Wick" ...I cant remember the actual dyno figures myself ,but do remember that it was very healthy .
and as I say ,hes been running it around for ages now with no probs and has had great fun on it.
hopefully Andy himself ,and Dan could tell you more.
One of the others I did went into one of the "Foxhat" 260,s...and again the feedback was that the motor was very smooth and vibration free..

Did it make more power or less compared to a full circle?

sean brady scooters wrote:well ,actually I have done a few now for various folk .
but that particular "uber crank" went into an RB20 motor that Dan built for Andy longbottom .
Andy was completely unaware of this special crankshaft in his motor for quite a while ,in fact we didnt let on till about after six months of him running it around..
maybe it was a bit cheeky of us to use him as a guinnie pig ,but we thought this was a good way of testing it out thoroughly and getting completley un biased feed back from him.
When he first collected and tested his scoot he actually remarked at how smooth and responsive the motor was ,and that it went really well and sounded "Wick" ...I cant remember the actual dyno figures myself ,but do remember that it was very healthy .
and as I say ,hes been running it around for ages now with no probs and has had great fun on it.
hopefully Andy himself ,and Dan could tell you more.
One of the others I did went into one of the "Foxhat" 260,s...and again the feedback was that the motor was very smooth and vibration free..

cheers nice one

we,ve never had the chance or opportunity or time /financial inclination to do any sort of "back to back "testing on the dyno ourselves to either prove or disprove that these modified cranks provide more power in the simple case of a crank swap from full circle to modified.
and why would we bother ..as to do so would be not only confusing but futile and pointless as i,m sure your aware ..
LPC ratio motors require special pipes etc etc to make them work to that advantage.
and also ,there are many other ways to lower primary comp ratios and other factors which come into account.
its just not a simple matter of full circle cranks verses cut /modified cranks is it.because the size and duration of inlet ports /transfer ports etc all affects the volume and crankcase comp ratios.
for eg ,you could have a full circle crank in ported cases or un ported cases,or even a bigger diameter full circle crank in that would give you more volume between the webs and so more volume and lower primary comp.
and so,perhaps ...this whole debate /topic would make an interesting article in scootering mag given your contacts,means and resourses ..and investagative attributes to unravvle the complexatives surrounding this and give us all some deffinitive answers .as i for one would appreciate that.
all i can re itterate ,is that the lower primary comp ratio thing seems to work in certain cases ,and with certain specs...and that i,m just being intuative here and going by experience ,feedback and gut feelings that have been confirmed so far.

un hijacked lol

GP CRANKSHAFT-58mm STROKE-TUNGSTEN BALANCED
If you are looking for the best standard stroke GP crankshaft you can install without having to modify your engine case, this is it. Manufactured for Tino Sacchi in Italy, this crank features full circle webs for optimum crankcase pressure. It also has tungsten steel inserts for balance and extra rotating mass, which smooths out idling and low rpm performance, especially when used with a lightened flywheel. It is fitted with a race spec connecting rod assembly and it will fit any Series 1, 2, or 3 engine with a Series 2/3 type magneto flange and GP flywheel (except TV175 Series 1). Hot Stuff!

this is the crank ive got will it be ok in my rb 22 (ive welded the pin)
cheers jon

FREAK wrote:un hijacked lol

GP CRANKSHAFT-58mm STROKE-TUNGSTEN BALANCED
If you are looking for the best standard stroke GP crankshaft you can install without having to modify your engine case, this is it. Manufactured for Tino Sacchi in Italy, this crank features full circle webs for optimum crankcase pressure. It also has tungsten steel inserts for balance and extra rotating mass, which smooths out idling and low rpm performance, especially when used with a lightened flywheel. It is fitted with a race spec connecting rod assembly and it will fit any Series 1, 2, or 3 engine with a Series 2/3 type magneto flange and GP flywheel (except TV175 Series 1). Hot Stuff!

this is the crank ive got will it be ok in my rb 22 (ive welded the pin)
cheers jon

If you have it then if it was me i would try it, have an AF crank in mine since the RB came out still going strong other swear these (AF) are no good.