Advantages of a twin over a single?

**nudemetalz** · 24th July 2009, 15:06

Dunno if this has been discussed, but what do you people think about the advantage of running a twin over a single...?

ie Sully's CB150twin to a well tuned Loncin like Fishies.
I've ridden Craig's twin and Fishies' Loncin, they're both quick and have good power spread.

What about 2-strokes?
Like say a tuned RD125 Twin (reed-valve) to a RX125.
or GT125 to a GP125

Back in the old days, I raced a CB125 Twin which was very mildly tuned (carbs and ignition). Revved to the moon and was still quite competitive.
Also remember see Pete Sales' T90 back 1989 which used to go well too.

Opinions?

**slofox** · 24th July 2009, 15:14

If it's a V-Twin, I'll have it...

**MSTRS:Me** · 24th July 2009, 15:19

Depends on the track. And whether F5Dave is the pilot...

**Buckets4Me** · 24th July 2009, 15:24

2 stroke twins have a max carb size and I think it was hard to get it to breath threw 2x 12mm carbs or the equivalent of a 24mm single carb

and twin 4 strokes would be heavy but there are some fast cb125's (fast for a short track not so fast on a long track???)

my 1.5 cents worth

**nudemetalz** · 24th July 2009, 15:36

Originally Posted by Buckets4Me

2 stroke twins have a max carb size and I think it was hard to get it to breath threw 2x 12mm carbs or the equivalent of a 24mm single carb

I thought the equation was not actually 125 max carb size divided by 2.
An RD125 has 2 x 20mm carbs. Does this make it not legal for buckets?

**F5 Dave** · 24th July 2009, 15:50

We've covered the carb size before. total area equivalent of 24mm carb so think it turned out to be 2x 17.8mm carbs or some such. Std carbs are too big by the letter. 2pi x R squared for area.

CBs can be made to go well by Mr Connor.

all 2 stroke twins have 5 speed gearboxes (& not well spaced ones at that) so even with serious work to replace the generally unsatisfactory iron bored cylinders the gearboxes are a hindrance on a highly tuned bike. Though a mild bike it may be ok.

It has to be said an MB or H100 is a lot easier (if you can find an MB5 gearbox).
Speedpro's TS100 & TS125 were mover's too.

RX125 have crap spaced gearboxes.

**ajturbo** · 24th July 2009, 16:06

the GT is a weapon... even in my hands....
that is why i want to get it back on the track.....

as for the carb size... as it is STOCK i personal think it should be allowed.... but hell, if i win ( tui) and i get DQ'ed i am NOT going to cry as the ONLY reason i race is for the enjoyment... weather it is last or first... i do not care...

or if i bin it or not

**R6_kid:Me** · 24th July 2009, 16:10

My thought would be that a twin has lighter rotating mass (per cylinder) than a single and should be more balanced and therefore able to rev better.

**DELLORTO** · 24th July 2009, 16:26

ive ridden a JCR cb125t and compared to my fxr150 it has much more low end power and torgue for getting out of corners, but since the fxr is DOHC the top end on it far more than the cb125t's...

**nudemetalz** · 24th July 2009, 16:30

As F5 Dave said, we have discussed this before

With the DOHC vs SOHC discussion,..the Honda CR250F/450F motocross bikes have a SOHC (unicam) engine, and they don't seem to lack top-end....

**ajturbo** · 24th July 2009, 16:50

Originally Posted by nudemetalz

As F5 Dave said, we have discussed this before

With the DOHC vs SOHC discussion,..the Honda CR250F/450F motocross bikes have a SOHC (unicam) engine, and they don't seem to lack top-end....

yeah... but that was Soooooooooooooooooooooooooooooo
long ago.... hahahahha

**F5 Dave** · 24th July 2009, 17:24

Originally Posted by R6_kid

My thought would be that a twin has lighter rotating mass (per cylinder) than a single and should be more balanced and therefore able to rev better.

Yes, no doubt a twin has many advantages. Given equal technology, gearbox, weight & size it would be a twin every time.

But the twins largely seem to be archaic or compromised in some form.