Cookstown 100 - How to make cheap SV700

[squirrel_hunter]

There is no such thing as cheap power.

I've done the Hayabusa piston swap, so I'll start with that. It will not take you to 700cc. What it will give you is a lighter piston and a very, very small bore increase. Basically you need a set of pistons, pins, rings, head gaskets and you will need to have the barrels honed to take into account for the small increase in the clearance required for the new pistons. I also took the middle gasket out of the head gaskets on rebuild to increase compression. I'm not the first person to do this so there should be a better guide somewhere. If you're buying new I'd budget for around £700 for parts and the bore if buying from Suzuki assuming you'll do the build yourself. Mine didn't cost me that and I did it as I already had sourced the parts at a bargain price and was rebuilding the engine anyway. I didn't do a before and after power test but did feel a little increase in performance.

To get to 700cc I believe, as I've not done this myself but have looked into it, you need a bigger piston (84mm vs 81mm) and a rebore to suit. Uprated rods are optional from what I remember. Price wise I think its going to be roughly the same as fitting Hayabusa pistons if you don't change rods, but I would expect the power increase to be more noticeable than a piston swap. There are kits for the piston and bore or just the piston alone available, its a known modification. I've not heard of any piston that will increase the cc of the engine without need to rebore for the SV.

To go to 750cc it is my understanding that you will need rods and a crank, and above that the cases need to be enlarged for the new barrels (I do remember seeing a 800cc SV many years ago, but don't have any more information on it than that), however thats all outside of your requirements.

Coming back to your original questions, I dont know of anything other than jetting the carbs to suit though you could replace them with 39mm or 41mm FCR's though having not done this yet I dont know what potential increase it would give. If your engine is already putting out good power in Mini Twin spec I'd assume you've done all the usual things so there isnt really much else to do I dont think.

I would go for the 700cc big bore option myself, and then anything else thats an option such as suspension upgrades and such if they are allowed. But it aint going to be cheap.

[hardhat_harry]

Thanks for the help and its probably one for next year as Cookstown is in April. As for the fueling I am considering dumping the carbs and going injection (one for winter), that way I can bore out the throttle bodies to 42mm instead of trying to source expensive FCR's. My assumption was all Gen 2 throttlebodies, injectors, CDI, stripped out loom, aftermarket fuel pump and possibly flywheel to go that route. I do have spare gen 1 engines to try this stuff out. I want to stick with the Gen 1 bottom end as the crank arrangement can take a bit more abuse. The bike already has Racetec emulators and Nitrons top spec shock, I dont know if the rules allow a front end swap.

[squirrel_hunter]

Converting from carb to FI has been done, not sure what entirely is involved in there as I've not done it but I think you're on the right lines. My only thoughts to add there is the CDI and loom etc would need to be pre twin spark to make it easier I'd think. And I think they softened the firing with FI having ridden them back to back once so not sure about the flywheel as I remember reading something that it was changed for that reason, but you'd have to do some more research on that one.

However one question for you... you're sticking with the Gen1 as "the crank arrangement can take a bit more abuse", can you expand on that? My understanding is that the Gen1 suffered at the crank hence why in later models they fitted an oil cooler and then heat exchanger. Additionally the early Gen2 models (K3/K4) had a week point on the crank at the fly wheel, but that was anecdotal. I've seen lots of broken Gen1 cranks (some of which were not by me) but very few of the later Gen2s...

[hardhat_harry]

Removal of the thrust washer and the oil gallery arrangement. Seen quite a few K3/K4 crank end breaks, only ever seen earlier ones fail due to oil starvation.

[squirrel_hunter]

It been a while since I've had a set of cases apart and then I never did compare the layout of the oil galleries, never thought to but imagine there is some difference due to the oil cooler. But I'm not sure what what make one oil gallery better than the other?

As for the thrust washer why would having one or not be better or worse?

[Bibio]

i'm not into bike racing so i had to go look at the road track. its pretty much straight then 90deg corner stuff so no need for fancy suspension but very good brakes are in order. power will be a requirement so as much as poss but that then all depends on the rider but i would guess even the crapest rider should make pace due to the shape of the track.

tbh as long as you can hit max speed down the straights and brake very late then all will be good.