High rpm

Hey guys a little question for the people who have a sportbike. Do you keep your engine in high rpm often (over 12 000rpm) and if so have you had any problem with your crankbearing? Beacause me and my friend are building up an engine and he already has a balanced crank forge rod and we would like the make it rev a little higher (somewhere around 14 500rpm). We know the rest of the engine can tolerate that kind of speed but we talked with someone a diablo racing and he said that on their racing bike (about 15 000rpm) the crankbearing lasts about 2 or 3 races. I know they put more stress on their bike but so do we (95% of the time at full throttle). You guys have any thoughts on this? What would you recomend as max revs? Because opening the crankcase is a pain. Thanks

Well it depends on your bike, the size on the engine, valve springs etc... I rev my Gixxer 750 to 14 000 all the time and when I ride in the twisties, I'm always above 10 000rpm and still on original bearings at 15 000km. Bearings are not a hard thing to change so even if you have to change them every once in a while, it's not a big deal.

Thanks. I'm asking because me and my friend would like to ride more than always fix the engine (3 cylinder 3pistons 1 head 1crank and alot of transmission part have failed last summer) But at the same time we want more performance. Everything else than the bearing I'm sure the rest will hold on (the ignition is good 20 000rpm, balnced forged crank, forged rod bigger carburator, and hey its a 2 stroke so now head problem here) Anyway going to diablo soon so we'll see what they propose. And thanks for your advice whitezomby. Anyone else has an advice on this?

Well if your building a 2 stroke engine, you will always have to change pistons and rings no matter what you do, even more if your going to run high compression.

Yeah I sadly know by experience about blown piston and rings...but that's an half an hour job and doesnt cost that much. And with a good tuning of the carburetor and keeping the heat down we've manage to keep it for 10k km so thats ok. But a crank especialy a forged balanced one is expensive and a lot longer to change. And crank bearing to are a pain in the ass to change on this thing. If they could last 15 000kms that would be good I guess. Or maybe I'm dreaming to the state of tune we are now (racing high comp overbore piston, higher rpm, bigger carb, racing this racing that....) Oh well we'll see thanks for the advice whitezombie! Guess I'll be pushing home this summer...

No problem. What are you putting that engine in?

Its gonna be either a ysr or a scooter. I know its sounds ridiculous but its just a fun machine and it costs nothing. Insurance wont let us have nothing else neither as I need a car. So we have fun with those things and learn how to tune well has those things costs nothing. So far we more than doubled the top speed and we can mach a Protégé 5 in acceleration to 100km/h. Best top speed yet is somewhere over 140 km/h. We might try nos this summer too. We'll see. Problem we kinda got attach to this scooter. With the 70cc and racing piston it has enough power to have fun in small roads. No one believe us it can be fun until they pop wheelie exiting a turn . Thanks for your advice and by the way nice bike! (you have a real one!)

Man I need to try your scooter out when it's ready, I would love to see what it can do.

Thanks for the compliments on my bike. Right now, it's getting furred. It's more of a stunt bike now anyways.

That would be cool, I'll try to organise something when it gets warmer outside and when it gets rolling again...the ring melted in the piston.....where do you live?

South shore of Montreal. My mom lives in St-Sauveur, she just bought a house there.

I'll send you a pm when its rolling...

cool