Advantages of a twin over a single? [Archive]

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

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

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

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 :doh:

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

As F5 Dave said, we have discussed this before :doh:

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

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.

ajturbo

24th July 2009, 17:36

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

in MY case....

the rider

fi5hy

24th July 2009, 19:19

Mine highly tuned hahahahahahahahahahhahahahahhahahahahahahahahah not :bye::soon:it will be

DELLORTO

24th July 2009, 19:28

As F5 Dave said, we have discussed this before :doh:

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....

but crf250,450's are known for having the least amount of top end out of all the other jap mx'ers

koba

24th July 2009, 19:44

Soo, from what has been said:

Twin = Best in theory
Single = Best in practice?

For four-strokes power potential is generaly limited by valve area.

The outside of the valves flow the most (open longer) so having two smaller valves is better than one big one, they are also lighter so are more rev friendly.

Basically a twin can have more valve area than a single.

It also has better balance and lots of other shit.

BUT

Real world shit gets in the way and it is generally easier to run a single, innt?!?

I think the easiest solution is to learn to ride like fish and then you don't have to worry what the motor is aslong as it goes and there is beer in the fridge!

fi5hy

25th July 2009, 00:15

beer in the fridge!

BEER SOMEONE SAY BEER:drinknsin

Buckets4Me

25th July 2009, 10:16

Soo, from what has been said:

Twin = Best in theory
Single = Best in practice?

got to say that a cbtwin is better in every way than a cbsingle
other than the cb125t you get an fxr or lonchin
what els is competitive and popular ????

as for 2 strokes a single is easier because of carb (but you can work around that) how about a 4 cylinder 100cc 2stroke ???

DELLORTO

25th July 2009, 12:27

cbr125,150's are compeditive, but yes cb125 singles from what ive herd arnt too compeditive....

speedpro

25th July 2009, 13:01

cbr125,150's are compeditive, but yes cb125 singles from what ive herd arnt too compeditive....

As with most things in bucket racing a lot of perceptions are based on what others are observed to have tried or achieved. An XL125S engine with a XL200 cam is very competitive and reliable but who can remember one doing well? A CB single is a good cheap choice for a beginner. Typically they aren't developed or ridden well and this colours others perceptions of their potential. Pete Sales did well on his and that Shirriffs bloke won an Ohakea GP on one. Since then the FXRs have arrived and JC has leant on the CB125Ts to good effect but those two singles at least would give any of them a good run.

DELLORTO

25th July 2009, 13:14

yes there are some good singles that arnt fxr's,cbr's ect But most people now are wanting fxr150's because they look good and go good, ive noticed that the whole "bucket" thing is starting go.... which is good because the bikes are looking better and we might be recognized properly

speedpro

25th July 2009, 14:38

There's nothing like turning up to Wanganui or Nelson on a bucket and not being "recognized", . . . . . . until the flag drops :yes:

How many of us really care if buckets and bucket racing are "recognized"?

FXRs are definitely a good choice, for lots of reasons.

DELLORTO

25th July 2009, 14:54

crazyhorse

25th July 2009, 15:13

Twins sound horny - gotta get one - hmmmmmmmm!:done:

Yow Ling

25th July 2009, 15:32

Twins sound horny - gotta get one - hmmmmmmmm!:done:

I think quite alot of people have fantasies about twins

onearmedbandit

25th July 2009, 15:41

Some of us even have the videos Yow...

one fast tl1ooo

25th July 2009, 16:05

gota :love: the twins, he he he

koba

25th July 2009, 21:32

As with most things in bucket racing a lot of perceptions are based on what others are observed to have tried or achieved. An XL125S engine with a XL200 cam is very competitive and reliable but who can remember one doing well? A CB single is a good cheap choice for a beginner. Typically they aren't developed or ridden well and this colours others perceptions of their potential. Pete Sales did well on his and that Shirriffs bloke won an Ohakea GP on one. Since then the FXRs have arrived and JC has leant on the CB125Ts to good effect but those two singles at least would give any of them a good run.

There is a well set up single CB125 down here, it is a farken well sorted and quick bike.

fi5hy

26th July 2009, 10:27

There is a well set up single CB125 down here, it is a farken well sorted and quick bike.

Yea this one

quallman1234

26th July 2009, 10:38

Yea this one

It certainly isn't slow. When i rode it at easter, i managed to beat ALL the fxr's bar one (at kaitoke in the last race).

koba

26th July 2009, 10:59

It certainly isn't slow. When i rode it at easter, i managed to beat ALL the fxr's bar one (at kaitoke in the last race).

With conti gos on it...

Must be an awesome bike aye :o

speedpro

26th July 2009, 13:42

#15 used to belong to Murray Cross . . . . ages ago

Henk

26th July 2009, 15:13

I'm realy hapy that CB singles are perceived as slow. Gives me a possible excuse for being hopeless other than the fact that I suck. Of course this means that I have to be careful not to let anyone who can actually ride anywhere near it.

Pumba

26th July 2009, 21:31

Yea this one

Thats right that one is a CB, I have ridden it as well and it is a very strong competitive engine, shame bout the frame and seating position:confused:

speedpro

26th July 2009, 21:38

More correctly the engine is an XL125S, good head and nice gearbox.

speedpro

26th July 2009, 21:39

More correctly the engine is an XL125S, good head and nice gearbox. A CB125N engine looks similar but only has a 5-speed though they do come with a useable disc front end

Bend-it

29th July 2009, 12:56

I think quite alot of people have fantasies about twins

Twins sound horny - gotta get one - hmmmmmmmm!:done:

More correctly the engine is an XL125S, good head and nice gearbox.

Sorry, I've gotten a little lost here... but is the XL125 a single or twin?

'coz twins and good head in the same sentence might just be too much for some of us young 'uns here!!