CB250RS café racer project

[xwhatsit]

It sounds tempting. However I'm a bit worried... like Tychver says, the CB250RSs eat chains like they're going out of fashion. They were notorious for it... that's why Honda revised the hub design when they produced the electric start.

If there were a few people, what sort of cost would you expect?

[NordieBoy]

Hmmm. Was the 520 an o-ring chain?
Spin a wheel with an o-ring vs non o-ring and you'd understand some drop in speed.

[dogsnbikes]

Update...the seat design is comming together as is the over all shape of the bike..even if I am still waiting for the rear shocks and the headlight to arrive.. and hope to have the other CB650 front guard next week which will be the new rear guard mounted to the swing arm with Stays

I will be picking motor up in August..will run a 2n1 exhust system plan is to postion the muffer under the engine..

any ideas of how the shorten exhust system will affect the bikes performance..Is there a miniumin length they should be?

Am looking for either a CBR or GN left hand switch block that will also operate the choke,

Yesterday I shortened the rear end and will be using the old hoop bracket as the tail light mount etc

[tychver]

Hmmm. Was the 520 an o-ring chain?
Spin a wheel with an o-ring vs non o-ring and you'd understand some drop in speed.

I thought O ring chains only had greater friction when cold and once you were actually riding they were almost the same as non O ring?

[NordieBoy]

I thought O ring chains only had greater friction when cold and once you were actually riding they were almost the same as non O ring?

Nope.

Spin the rear to lube the chain on my bike after a race with an o-ring chain and then do my brothers with a standard chain and his spins far more freely.

[tychver]

Update...the seat design is comming together as is the over all shape of the bike..even if I am still waiting for the rear shocks and the headlight to arrive.. and hope to have the other CB650 front guard next week which will be the new rear guard mounted to the swing arm with Stays

I will be picking motor up in August..will run a 2n1 exhust system plan is to postion the muffer under the engine..

any ideas of how the shorten exhust system will affect the bikes performance..Is there a miniumin length they should be?

Am looking for either a CBR or GN left hand switch block that will also operate the choke,

Yesterday I shortened the rear end and will be using the old hoop bracket as the tail light mount etc

Wow dunno how I missed this post!

Rear shocks sound good. How much work does it take to get the GS550 shocks to fit? Are they a direct swap? I'm guessing they'll be a pretty good upgrade over the standard shocks! What are you doing about spring rate? They'll be sprung too heavy for an RS won't they?

[dogsnbikes]

didn't take too much work had to modify the top bushes
and make up a spacer but the lengths are the same
the load rate is ok as they are adjustable and they accomadate my size and riding style better

[jester_parks]

There`s no daubt that the conversion will work....for the better!
You must understand that the RS is 20 years of age - and so is its chain technology!
The chains produced nowadays are of much better quality and therefore stronger. To run a heavy 520-chain on the 250RS like in 750s is a waste of power and having too little anyway definitely a lthing to avoid.

[jester_parks]

Got down to the job to take the photographs in the workshop:
in order to accommodate the big liner you must - as we all know - enlarge the bore in the upper crankcase. This is straight forward as the cases will split horizontally. However I found it interfering with the oil-channel, which gets the oil up to the head through the cylinder-stud. This is not really a sound solution and I will look for a way to do that via an external oilhose. For the moment I will proceed as shown in the photographs. Relocated the oilchannel with the help of a dremel - and do so in the cylinder - and added some material with liquid-metal. Its going to work, but the better solution will be to close it alltogether and use a oilline running outside....

[xwhatsit]

Gah! I didn't think about that. You're using a TT350/XT350 liner aren't you, Christof? Same with me -- I think they're a little thicker than they need to be.

I might use the liquid-metal (JB-Weld is good enough I hope ) too, not keen on the idea of running external oil lines -- then again there's a reputation for poor top-end lubing with these motors, perhaps it's a good idea.

[jester_parks]

I think the external oilline is a good idea, but no so easy to manage: from the crankcase you can reroute the oil fairly easy - the problem is where to feed it into the head. I am working on that matter, but don`t expect quick results. I fell off my off-road-bike and broke my hand, so was sidelined for 5 weeks

[vifferman]

I will be picking motor up in August..will run a 2n1 exhust system plan is to postion the muffer under the engine..

any ideas of how the shorten exhust system will affect the bikes performance..Is there a miniumin length they should be?

It may end up with more power at high revs, but less at lower revs.

I might use the liquid-metal (JB-Weld is good enough I hope)

Well, I used it to fix a crack in my clutch cover many moons ago, and also to repair glove box hinges on a Fiat. Both are still doing well.

[tychver]

I've finished all my prep and filling on my cibbie. New paint next weekend

[maybegunnadoo]

Ok, Frame all striped ready for painting. have sourced a Xl500 engine locally and am going to weigh and measure it to see what is major difference between the 250 and the 500. Weight wise the Xl was only 2-3kg heavier thathan the CB and the engine popped out 32 hp to the cb's 23 I think. The local library up here has manuals for both bikes and the similaritys are astonishing. Anyone got any ideas on triangulation of the frame?

[jester_parks]

The XL500-engine will fit without any daubt: it has been done before!
As the engine is "longer" though, you have to adapt the cylinderhead to frame pillars.