rb250 build 5 gear

[cee]

hello

I'm thinking of building an rb250 in the future, I dont want something to pull wheelies, I want something that goes as fast as possible

will it have effect if I use a 62mm 116 conrod with spacers in place of a 60mm 107 crankshaft?

about gearing, a 5 gear will have a smaller ratio between 4th and 5th, will this improve a lot on it? or does this rb250 needs more rotations and is it better with a 4gear?

anyone on here with an rb250 with 4 or 5 gear? what can you expect from topspeed?

[jonashford]

I have an RB260 with a cyclone gearbox in it, 62mm Crank welding to the top of barrel steel liner, super tourer exhaust, its done 6500 miles this season. Im a lot over weight I ride it to rallies with full riding gear and a tent on the back it does over 80mph (real speed)no problem, pulls well in to the wind and uphill, I rarely go much over 70mph as thats fast enough for me.

[MAB]

Hi Jon,

Jon so is your RB steel lined and no issues at all running temp I know you do a lot of miles .

Cheers

Mark

[jonashford]

No issues, its steel lined. I had to replace the rings and reeds at 4000 miles, the barrel has just been up to afs for them to inspect it, there was hardly any carbon on the piston crown or in the ron moss head! The piston was a little worn so I got a new piston slightly bigger, Ben gave the barrel a hone and its good to go. Temps are anywhere from 130c at 60 - 65 mph & up to 160 at 60 - 65 mph. I find that the wind and hills etc have a big impact on temps I quite often see 170 - 180c at 70 - 80 mph. When I went to woolacombe this year I went down the m42 m5 for around 145 miles, did it in 2 1/2 hours incl 2 petrol stops no problems at all. The engine ran faultlessly all year 6500 miles done since april, c2c, euro, wooly, exmouth etc etc...

I have to say that the Ron Moss head has been a god send, keeps the barrel really cool, like me!

[MAB]

Nice one it sounds like a good engine Jon and the miles you have covered prove that mate.


Cheers

Mark