Project Fuel Injected Turbo FZR250, half

I think you'll be pleased with the R6 shock - unfortunately I don't think the OEM 250 spring will transplant (likely due to length), but don't quote me on that.

 

on this i see that you have put the trigger wheel on the stattor side . is the stattor behind the cover or did you fully remove it?

 

That was a trick used locally on twin shock motoX bikes in the 60's and into the 70's. Very hard at that time to get alternative springs.
To get really tricky you can taper turn the outside of the compressed spring. At least a semi progressive rate.

 

Fortunately in the 8.X - 9.X spring rates there's lots of bikes which have OEM springs installed in that range (suitable length and diameter dependent of course) - anyone swapping one out for a different spring rate seem to let them go for not many $$
Just off the top of my head - 1996 YZF600R spring rate is 8.4Kg/mm for example

I thinks somewhere there's a photo with an R6 shock beside an OEM FZR250 shock - the spring length is significantly different from memory with the FZR250 spring being much longer - I think @GreyImport may have taken that side by side shot of both shocks.

BUT I suspect that yours isn't an OEM FZR250 shock, so you might be in luck there.

I do like the idea of adjusting the spring rate on a lathe, that's damned clever, a truly ingenious solution invented by necessity!

 

Do you know if your forks springs are OEM?
I went through the racetech site extensively, nearly any bike of the approximate weight of the 250 when I put my rider weight into the spring rate calculator came up with the same spring rage of ~.85Kg/mm - the stock 250 springs are just over half of that.

FWIW - I've used a pair of of the larger Irwin clamps to slightly compress shock springs to remove the preload - I bought a pair of shock spring compressors from supercheapauto in an impetuous flurry, got back and realised that they don't fit within the coils due to their spacing and spring O.D. - blonde moment...

https://www.supercheapauto.com.au/p/toolpro-toolpro-coil-spring-compressor-pair/12548.html

Looking at what they are they could be replicated with 5/8 or 16mm full thread bolt, hex nut coupler(s) and some pipe cut and welded

https://www.bunnings.com.au/hobson-m16-galvanised-hex-nut-coupler-50-box_p1100055

One drilled nut so it spins against the bolt head, then with both nuts some reasonably thick walled, suitable diameter pipe cut and welded securely to the nuts - only reason I didn't do that at the time was I didn't have suitable pipe to hand.

I was surprised to find not much at all available much on ebay for not too many $$

 

That's the one that looked to be the business that I did find on ebay, I was impatient
If it saved you an hour or two and eliminated the risk of an injury or mishap or potential part damage - I think it qualifies as worth it TBH

 

oh dear, the old injector duty and min pulse width. highly misunderstood topic ive found...

it is a challenge once you break the 12K range, as the time you have to inject it all in by gets shorter and shorter... 200RPS, thats already 5mS/rev...

at 85% for the standard injector rating... not much time at all.

hit 18k and yeah... 3mS. 300RPS! and well, 85% of 3mS isnt that much more than the minimum 1mS open time already. (closer to 1.2mS min time, really... i vaguely recall 1.5mS being the standard default on most ECUs?)

at least its fourbanger so you can double that time...

so you get the big injector to deliver enough in the limited time available, and suddenly that minimum of 1mS is way too much.

its my personal theory as to why the move is to singles and twins in modern EFI bikes... besides the cost of making four cylinders, camshafts, valves...

its easier to make em run slow and stick with one injector that covers the range than it is to make a dual injector setup that can blend the two smoothly. need a small one for low RPM, small throttle settings, need a big one for the high RPM/WOT areas.

and thats really the only way around it... IF its important.

as this is a track bike... its sort of a moot point. whos idling or running at low throttle/rpm anyway? if its going to be on the street though, and be rideable... it IS important.

i sort of have the same issue with my lil DIY ECU., my method is simply going to be inject every second rotation until i reach an open time where i then split it in two and inject on every rotation. in my case its no real big deal, its just a few interrupts and a comparison on values. im also using the same approach for cold starts. press the button for "choke" just sets a timer to inject on every revolution for a few thousand cycles until registers decremented to zero then its back to "normal", by which time.. it should be warm enough last thing on that is the other button that simply kills the injection if it ever gets flooded...

i got a totally different approach to the ECU side of things though, so anything i say can safely be ignored




a really easy, and dodgy way to calculate times?

assume VE to be 90% or so at WOT. say 25-30% at idle.

throw in boost, 15 psi... you now have 180% VE. more? less? who cares? close enough is good enough until you get to fine tune it.

its been so long i forget the rest....um...

oh yeah. 1M3 of air is 1.2KG. for ideal stoich you need 14.7:1.

so for every 1.1-1.2M3 or so of air, you need 100g of fuel... for stoich.

how many intake cycles at 90% VE does it take to ingest 1.2M3 of air?

and at 180%?

and at 25%?

its good enough to make the choice between an 80g, 128g, and i forget what other rates are available at this size..


anyway, i think i figured out i can get down to about 10:1 at 12k with an atmosphere of boost on a 140 with a 128g... yet still get 1mS at idle, and well... at a certain point you can just keep the injector going for a full rotation, only close it on every second one... or dont close it at all?

been about four or five years since i was actually thinking of this... my memory is as fuzzy as the logic i plan on using...

 

regards springs... the things are deadly. the "one time tool" that never gets used again is worth it.

i go that on step further, clamp the compressors between some 2x4s with some blocks so there is absolutely zero chance that they can do the sneaky and try slipping around the spring to one side... theres a nice hole in the roof of the mechanics shop at my place as evidence of what they can do...


ouch. turning a spring in the lathe? thats something i have never contemplated before.

i recall having a... device... that needed new springs. went to a place in st marys.

he knew what the ... device... was straight away, no fooling him!

meh. was happy to spin a few up for me. money is money and a spring is a spring, regardless of what it came out of...

though progressive tapered wire may cost a fair bit more than the little things i needed... and then i believe that theres only a fairly limited range of wires they have, whereas manufacturers can spend that bit more on stocking a "custom" grade...

shame that getting a place to run some wire through a centerless grinder is going to cost a fortune, especially if its tapered, and only worth it if youre going to get a fair bit done at a time...

 

So you've managed to get a spring to the correct length and rate for what you calculated you need - colour me impressed