Big bore kits

[NTECUK]

Had a search on hear can't find anything .
Has any one tried to get there bike to 750cc?
And did anything (clutch etc) give up when they did.

[andrewsmith]

PM
SV650 Racer (Sarah Jordan)
They regularly do 700 and 750 motors.

I think the biggest risk is crank failure and reduced motor life.

Yes we run 700cc bored out bikes and a 750cc bike which runs a 84mm bore with a stroker billet crank.

All of them have to run Carrillo rods, lightened and balanced crank, race generator and slipper clutch before we build them to keep them reliable.

We have not experienced any crank failures on the ones we run with the stock crank as we run the crank correctly balanced/lightened and with the race generators. IMHO its not the crank thats the issue its the weight of the flywheel weight as they are too heavy and it torque sheers the crank. The rods as stock are weak so we change those and the slipper clutch keeps stress off the motor under heavy downshifting and makes it nicer to ride anyway.

Most common issue we had was head bolts - you need stronger ones, rods and rod bolts. Other than that for a motor that is stressed beyond belief over stock they are strong if built correctly.

[andrewsmith]

There's you answer.

Sarah you's done anything with 800 kits or is that seriously pushing the motors limits?

Originally Posted by andrewsmith

There's you answer.

Sarah you's done anything with 800 kits or is that seriously pushing the motors limits?

Nothing with 800's mainly due to the classes we run in have a limit of 750cc for the water cooled V-Twins.

The 750cc bike though is proper fast, running a kit gearbox it will pull over 160mph!! and sticks with the Ducati 748 and 749s.

Not cheap to build properly though and if you dont do it properly or do it on the cheap then you will have reliability issues. We wont build them unless they are done correctly.

[andrewsmith]

fair enuf
Supertwins, where ER6's have been dyno'd at 100 bhp+ at the crank.

Just out of curiosity what would the build cost be for a rolling chassis at supertwin spec?

Originally Posted by andrewsmith

fair enuf
Supertwins, where ER6's have been dyno'd at 100 bhp+ at the crank.

Just out of curiosity what would the build cost be for a rolling chassis at supertwin spec?

Dyno's vary big time and a crank measurement is pretty useless unless you have an engine dyno otherwise your relying on maths to give you a figure.

The 750cc makes approx 90bhp on our dynapro dyno, a crank figure would be 100. Divide the BHP by .9.

BUT that bike has its power very capped as it runs in a power to weight class and is at its limit on the rules. It could make 100bhp on our dyno if we wanted.

Rolling chassis cost is as open as your wallett, depends massively what front end you fit, what fork kit is fitted, wheels, etc etc. Usually we ask for a maximum go no further budget limit and work to that.

[andrewsmith]

Fair enuf, so £12k inc bike would get you somewhere

[NTECUK]

Might be sensible then to see if I can get on with a sv1000 for a road bike. Going to cost less to swop the bodywork

[andrewsmith]

There is someone on here running 750 on the road (i think).
Bing here is one possible
http://forums.sv650.org/showthread.php?t=165581

Fastdruid has got a big bore on one of his bikes