xbr/rs

[Propellor]

Thinking of grafting an xbr engine into an rs frame.

Should I see a psychiatrist?

[timbo]

Nope, but anyone buying a new R1 or big beemer for £15 grand plus, probably should! There is loads of members on here seem to have achieved same successfully 

[Propellor]

Nope, but anyone buying a new R1 or big beemer for £15 grand plus, probably should........ 

 

[SteveC#222]

500cc into RS250 has been done several times and is supposed to make a great bike - I believe Steve H had one. I haven't seen one with an XBR engine, it's usually done with an FT or XL engine rather than an XBR. I'm not sure where/how you would site the oil tank - the XBR has a dry sump - but it's probably do-able.

I've seen an XBR in a Brit single rolling chassis - Matchless or AJS? - and that looked pretty cool.

[xbally]

I think if it could be done it would make a great bike.I've thought about it a lot but don't have the mechanical nous to do it myself unfortunately.Another problem could be getting it insured as we know only too well insurers don't like modified bikes.When i am out on my RS i often think :if only this had an XBR engine and when i am on my XBR i often think : if only this had the (lack of ) weight of the RS!

[guest564]

I don't think that the XBR engine will bolt in like the XL/FT engine.

[Propellor]

I don't think that the XBR engine will bolt in like the XL/FT engine.

Well, yes and no!

Got the rs injun out and popped an empty xbr injun in. The frame needed tickling literally only 1mm off the area where cylinder head touches on a seam weld on the frame.

The "yes" bit: the rear engine bolts line up perfectly. In she goes, easy as you like. Sprocket alignment good. Not worrying about the front mounts as I expect to remake these anyway. Besides I have ideas regarding stiffening the frame. This is looking good, but then......

The "no" bit: stepping back to get the bigger picture the cylinder looks too upright. Not the same angle as in the xbr. First thoughts are that you could go with it like that but it doesn't look "right" and I think I'd like to get the engine laying at the same orientation as it does in the xbr for practical reasons too. Don't want to risk any lubrication issues. So, that means some reworking of one or both of the rear mounting plates. Ok, so be it. In for a penny......

[Moto63]

We have the thecno oligy. (I think) 

[Propellor]

I think if it could be done it would make a great bike.....

..........if only this had an XBR engine and when i am on my XBR i often think : if only this had the (lack of ) weight of the RS!

Here's the rub. The RS frame is clearly very light. Skimpy! But looking at the robustness of the bottom end of the RS engine it seems fair to conclude that they made this a semi stressed member, contributing to the frame stiffness. So, would one risk simply dropping an xbr engine in there without putting some metal around it? Personally I wouldn't risk it. The frame rigidity might be compromised and you might risk cracking the engine case?

So, for me, the solution is to add framework between the front and rear of the engine. This adds weight. Maybe I can remove weight elsewhere to compensate a little? We'll see.

But then you look at the forks and think mmm, bit flimsy for the higher speeds and I'm looking for an ace handling bike anyway. Then the brakes.... Etc. next thing you know, you end up with a bike the same weight as the xbr!

Don't get me wrong, I'm going ahead with this regardless. But you see my point? Tbh, I'm really looking forward to getting stuck in.

Still not decided fully, but this bike may be for track use only.

My train of thought is to go more modern with the running gear. Better strength to weight ratio and lower unsprung mass. But we'll have to see how things pan out. I have other projects running at the same time!

[SteveC#222]

At the risk of repeating myself, before you get too far into it, where are you gonna' stick the oil? You need a resepticle for around 2 ltr (1600ml refill). I don't know the RS frame, but could you convert the top tube into an oil tank?

[Propellor]

At the risk of repeating myself, before you get too far into it, where are you gonna' stick the oil? You need a resepticle for around 2 ltr (1600ml refill). I don't know the RS frame, but could you convert the top tube into an oil tank?

I'd casually brushed aside the worry of what to do with the oil.

There is enough space under the seat for an ally or stainless tank. The oil in frame idea is good, but probably a step too far for me at this stage. You'd be getting into out and out frame building. Something I'd love to try, but not yet. So it'll be a tank under the seat. I'm lucky that I can now get to look at an ikuzawa on a regular basis, so hopefully I can glean information from that.

[SteveC#222]

I'm lucky that I can now get to look at an ikuzawa on a regular basis, so hopefully I can glean information from that.

Not GC's Ikky per chance? ( may well be there's only 3 in the country!!).

The Ikuzawa used the engine as a stressed member with no lower frame rails and that Mr 'arris knows a thing or three about frame making!

As for uprating the frame/forks, the Rs500 seems to work well with the standard rolling gear with the FT/XL engine and I wouldn't have thought the XBR lump would be much different weight wise.

[Propellor]

I'm lucky that I can now get to look at an ikuzawa on a regular basis, so hopefully I can glean information from that.

Not GC's Ikky per chance? ( may well be there's only 3 in the country!!).

The Ikuzawa used the engine as a stressed member with no lower frame rails and that Mr 'arris knows a thing or three about frame making!

As for uprating the frame/forks, the Rs500 seems to work well with the standard rolling gear with the FT/XL engine and I wouldn't have thought the XBR lump would be much different weight wise.

Yes. GC's ikky. My brother bought it last year.

Yes, I was looking briefly at the fact that Harris didn't use the lower front hole. But as to the extent to which the Harris frame relies on the engine to assist in rigidity, that's another thing. I have a pretty firm idea of the way I'm going to add to the frame. I'll post up photos once I get going.

Running gear. Well you have ask why the xbr ended up the weight and size it did. True, to an extent it is to build a bike the physical size people expect, I suppose, but also because a faster and heavier bike needs forks and wheels of a, certain size to properly fulfil the role.

The main attraction to what I want to do is just to stretch my abilities a bit and have some fun both building and riding the thing.

[SteveC#222]

Running gear. Well you have ask why the xbr ended up the weight and size it did. True, to an extent it is to build a bike the physical size people expect, I suppose, but also because a faster and heavier bike needs forks and wheels of a, certain size to properly fulfil the role.

The main attraction to what I want to do is just to stretch my abilities a bit and have some fun both building and riding the thing.

There's about 20kgs diference between them - 136kg for the RS against 157kg for the XBR. Some of that will be the 2nd silencer on the XBR and oil tank & plumbing so not that much really.  I suppose part of it was that the RS was around when we still had the 250cc learner laws so may be it was made on the slim side so that once you passed your test and got the 500 it felt like a 'big bike'.

[guest564]

The Ikuzawa used the engine as a stressed member with no lower frame rails

So did Tigcraft, Hagon, Spondon and many others