Rb what port timings for torque

[carlos fandango]

I posted this on another thread but no replies

What makes up a torqey engine as opposed to a revey one... in laymans terms????????

A wide low exhaust port ........smaller carb ....... longer stroke........box / low revving pipe........ gearing.???????

What else????? compression...transfer timings/area????

What effect would welding the casings up and opening the trans. up ?? torque or rev???

Im im looking at a torqey engine as my next project for spain ive got a welded up 200 casing, rb250 barrel (F@@ked), 60mm alpha crank, jl3 and jl4 .
Thinking of a 70mm steel liner (with the 60mm should be 230cc ) welded up ex port single bridge.


At the moment ive got Exhaust 185 deg and trans at 132deg
If i lowered the barrel by 1mm then id have Ex 180 and trans. 128
so is this the way to go
and if i get it sleeved i could alter them a bit more

All advice welcome
thanks
Russell

[Stampede]

would go for 185 exhaust and 125 transfer timing - my ts1 got with this setup (60mm crank, 35mm mikuni, lth manifold, vforce3 reeds, mb3 exhaust) 25,8 lbs ft torque!

opened the transfers on the barrel foot and exhaust port widened to 63% and boost port enlarged.

[Adspeed]

I say bout the same, I have a similar TS setup and its spot on. If I were using it to go to spain I don't think I'd be going down the steel liner route though....maybe an ally one? But popping a big liner to reduce cc's is gonna cause a lot of work and cost.

Is the Dev tour a revvy'er pipe than most? If so maybe a lower revving pipe. I have the Fat Mamba and it would suit although some have had build issues and its a long way to Spain for your pipe to break.

If your wanting to stick with the RB250 weld the exhaust up so its a nice single one, that would be one problem area sorted IMO.

TBH If I was riding all those miles I'd want something tried and tested and I think I'd be tempted to put a TS1 kit on there......

What exactly is the damage to the barrel?

[RinB]

I think definatetly weld up aux exhaust ports and if your doing that you
might as well get barrel fixed then re-nikacil or ceramic.Its amazing what can be welded up

Im at present doing 3 Rb's (2 RB22 & a RB25) for various people all of which are going for a single exhaust and ceramic lined with various port timing

Timing wise tend to agree with the timings above there or there abouts

[carlos fandango]

Thanks for the replies

So what the disadvantages of a steel liner over nicasil / ceramic?
One of the reasons i was going the liner route was so i could make the Ex. bridges slightly wider and more stable as id heard this was a problem area.
Wouldnt the ex. port with the two aux. ports be better for torque ie wider overall than a single port. and lowering the timings at the same time as the trans.

The barrel is an early rb250 with the rb225 port layout.

I still may go the 250 route
Whats the choices of piston for 72mm? do MB do 72mm racetour one?

Thanks
Russell

[carlos fandango]

What exactly is the damage to the barrel?

Barrel is unused a piece has been broken off the spigot, it could be run though.
but i wanted to get any known faults (ie bridges) sorted first.

[sean brady scooters]

here is just another idea/option for you,and something that you may like to consider...but maybe depending upon the thickness of your sleeve if you go that way..?
you could just go for a central bridge (of a decent width ) and carve out the sub port bridges...