Stroking an RB20 ?

[carlos fandango]

Im about to order an rb20. I need a new crank aswell (116mm).
The question is can i put a 60mm crank in it? should make it 205cc

[J1MS]

I cant see why you havnt had a reply off anyone yet, even if it was just to say..... "I dont know".... but it probably is that no one really knows. I would give Ray or Ben at AF's a ring and put the question to them. the kit really is too new with little or no feed back yet. Hope it works well whatever you decide.

[RinB]

I cant see why you havnt had a reply off anyone yet, even if it was just to say..... "I dont know".... but it probably is that no one really knows. I would give Ray or Ben at AF's a ring and put the question to them. the kit really is too new with little or no feed back yet. Hope it works well whatever you decide.

Yep I think the same
If you do stroke it watch bottom ring on finger port supports as ring might catch
They have been known to on RB22

[RICSPEED]

I cant see why you havnt had a reply off anyone yet, even if it was just to say..... "I dont know".... but it probably is that no one really knows. I would give Ray or Ben at AF's a ring and put the question to them. the kit really is too new with little or no feed back yet. Hope it works well whatever you decide.

fair play mate he only posted it at dinner time and ive only just got home at 8.30pm

[sean brady scooters]

maybe J1MS............YOU should have replied straightaway.......yourself.........just to say that you dont know the answer............................

[CT.]

I have an Indian crank with an offset pin (60mm stroke) and RD400 rod and was asking myself a similar hypothetical question.

My thought was that running it without a base gasket would help to keep the port timings down and the 1mm shorter rod would compensate nicely for the longer stroke at TDC.... maybe I would have to play with head gaskets to squish it correctly...

[carlos fandango]

Thanks for the replies.
Ive decided to to go with a 58mm, as you say, it is new so no one knows
So its all on order, and will build as suggested by af.
Havnt decided on carb or head yet, may get a Readspeed one
Will keep you all informed how i get on

[RinB]

Thanks for the replies.
Ive decided to to go with a 58mm, as you say, it is new so no one knows
So its all on order, and will build as suggested by af.
Havnt decided on carb or head yet, may get a Readspeed one
Will keep you all informed how i get on

AS for head AF do a 9.5 one for a squish of 1.5mm which is what I set all my TS's & RB's

Smiffy

[Special X]

If you use an indian case the squish at least will be ok with a 60mm crank as the 1mm higher deck height compensates for the extra 1mm at the top of the stroke. Thats why some struggle to get 1.5mm squish with 58mm cranks if not using an Italian case.

Things to watch are the possibility you'll have to relieve the crankcase even with a 60mm crank (I did), the piston skirt clearing ok, and the aforementioned ring clearance.

[J1MS]

I managed to call into AF rayspeeds (My job ment me going over to scarborough Wednesday) and get to talk to Ben. I asked him about the RB20 and the option of a  60 mm stroke, he told  me  that when they started development with the RB20 the 60mm Crank was tried, the reason behind this I was told was Its a 150 engine and the standard crank is going to be junked, cus it wouldnt be strong enough, and the 60mm would make it a 205cc but he said they got better results from the kit when they tried the 58mm stroke crank. when I asked what he ment, He said It was smoother and seemed more responsive, where as the 60mm didnt give any noticable advantage The piston used at the moment is the yamaha blaster with an oval window cut in the Inlet skirt. When I asked him whats it like to ride compared to the 225, Its just a smoother power delivery which makes it a very smooth ride you didnt have to work to get the best out of it, its not as quick as the 225 but you wouldnt be far behind on the road. but if you want alot more power then the 250 is the one to choose, when I asked which he prefered he said one of each. Ive spoken to ray many times but this is the first time Ive spoken to Ben in person. He gave up half an hour of his time and showed me the 3 different kits and started up his 250. I would have stayed longer but as I said I was at work I did manage toget a look at the AF race clutch bits he advertises but dosnt seem to have any pictures of, one version can take upto 9 plates with a 10mm packer for the side case. and the other is a nitride hardened spider that ,fits the standard size clutch sprocket and I think he told me 6 plates but I might be wrong as I was too busy looking at the first one    9 plates