RB250 set up.

[10 inch Terror]

Hi all, I'm after a bit of advice on the best set up for my RB250 motor. I had it built 2 years ago by a dealer up north. It came with a Supertourer pipe, 35mm mikuni carb and Rimini 5 speed box. Anyway after 30 careful miles the Xmas tree spat a couple of teeth after having a new Xmas tree sent out I fitted it but lost all confidence in it so its sat in my shed ever since. Over that time I used the Supertourer and carb on other bikes and replaced them with an NK Race and 34mm Koso carb respectively. I have now lent it to my son in law to use and he's put about 100 miles on it today. He says it's fine up to 5th and then dies a death. I know the carb is only roughly jetted and was always going to sort that at a later date. My question is what's the best set up for a non tuned RB250? I know it's a mine field and every motor can and will differ but any suggestions would be helpful as I have to start somewhere. Thanks in advance Pete.

[wack 63]

On a tuned Ts1 with an NK I changed to a short 5th gear to keep it in the revs. Only lost a few mph top speed but much easier to ride.

[10 inch Terror]

On a tuned Ts1 with an NK I changed to a short 5th gear to keep it in the revs. Only lost a few mph top speed but much easier to ride.

Cheers whack. When you say short gear would that be the 34 or 36 tooth loose gear? I'm not too sure which 5th gear is in there if I'm honest? I did ask for a touring set up hence the Supertourer pipe. Any more info gratefully received. Thanks again Pete.

[jonashford]

36


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[wack 63]

35 is standard and as said 36 is the short 5 th. What sprockets are you running?

[Lambretta Sash]

Had this set up on barrell no9 35tmx fran race bolted on rb250 kit 60 x 107 crank tried 4.6 but found 4.8 final ratio best to use. should pull from 30 in top gear to flat out with ease.
Had similar issues with 5 speed box on my own lammy, but on another note a 38hp rb motor i built has had one in for 3yrs and no probs at all........

[22/2]

i put a 5 speed in mine, took a tooth of the cluster, if you carry on with the 5 speed expect to break it unless its the supreme version, when it was in i also run the short 5th, it was great, if you want reliability in the gearbox my advice (there are others) would be Indian GP 200 with 18 or 19 front 47 rear.

The trouble with the regular 5th is when you want it you need good power to pull it, your probably up in the 75+mph area when you change up and not in the power, with the wind resistance etc its hard to get it to go, put in the short 5th and all that will improve, Anyone who has genuinely ridden a lammy over 85 mph will tell you they are not that nice to ride at that speed for any length of time, gear it down a bit and have fun with the acceleration although that may increase the wear and tear rate.

Do you know how much power and torque it produces?, 6 plate clutch is a must, I'm not a fan of Mikuni as their not good for fine tuning but that said they do a job, no experience of the Koso. The NK is fine, thats what they were designed for, similar to a Franspeed on my set up.

Get the 5 speed out put in a GP200 or Li 150 and get on it before you miss the summer.

[10 inch Terror]

I was sent the supreme cluster as a replacement but the rest of the box is the standard version. As said I'm not that confident of it and would change it for a proven set up without hesitation. The problem is I have a 46 AF Race clutch and don't really want to buy a 47 basket just to suit a particular box. Ideally I'd like to use the 46 and change the front sprocket only. I have spare chains of various lengths and an assortment of sprockets to play with. The carb is not miles out according to the plug colour Anyway. I may swap the pipe for an NK Road as I know they work are a good fit and reasonably cheap. I've sort of donated the scoot to my son in law now and any money to be spent will be spent by him.

[vespanic]

Not sure if this will help but I have the symptoms you describe when I changed to 20 x 46 from 19 x 46 on the 5 speed Rimini box. Going to the Euro was mainly ok but kept having to change down to 4th on the motorway. Once up to speed with throttle kept wide open no problem. My first 5 speed had broken teeth problems, but been thrashing it now for almost two tears and fingers crossed it is still in one piece. This was 2 up with no luggage. Rides better one up.

[Lambretta Sash]

Im yet to try another cluster or 5 speed box, you can use a 4 speed box to good effect on a well set up motor.
Std out of box should get you too a genuine 80 mph,
Id go gp200 19 x 46 with fran race or nk race, or 4.8 final ratio
i found the early one piece pipes the best.