24mm carb is pathetic even for a bucket!

[F5 Dave]

So whaddayareckon? The F4 125 aircooled 2-stroke rule to limit carb size to 24mm is quite a limitation. Probably why there aren’t any fast aircooled 125s.

I mean compared with a water cooled hot 100 that may be running a 34 (RS 125s run 39 & bigger) the 24 has an area of 452mmsq compared to a 34 of 907mmsq. That’s half the size for a piddly extra 25cc & aircooled to boot!!

So who wants to front up to the next MNZ doodacky & give those poor 125 guys a boost, say 28mm might be better? (615mm).:sunny:

Actually there are some guys I believe who are running 28s & none of them seem to be cleaning up.

[Ivan]

So whaddayareckon? The F4 125 aircooled 2-stroke rule to limit carb size to 24mm is quite a limitation. Probably why there aren’t any fast aircooled 125s.

I mean compared with a water cooled hot 100 that may be running a 34 (RS 125s run 39 & bigger) the 24 has an area of 452mmsq compared to a 34 of 907mmsq. That’s half the size for a piddly extra 25cc & aircooled to boot!!

So who wants to front up to the next MNZ doodacky & give those poor 125 guys a boost, say 28mm might be better? (615mm).:sunny:

Actually there are some guys I believe who are running 28s & none of them seem to be cleaning up.

Yeah mate that size is gutless as considering you can change carbs on 150s and clean up a 125 aircooled puppy aint winning

[k14]

if you got it sorted perfectly on a 125 twin then a single 24mm carb can be made to be identical as 2 24mm carbs. would just need to get the timing and porting sorted. then you'd have a weapon me thinks.

i reckon they should increase the size limit to say 180cc too. let people bore out their FXR150's, seeing as they aren't very competitive...

[steve k]

So whaddayareckon? The F4 125 aircooled 2-stroke rule to limit carb size to 24mm is quite a limitation. Probably why there aren’t any fast aircooled 125s.

I mean compared with a water cooled hot 100 that may be running a 34 (RS 125s run 39 & bigger) the 24 has an area of 452mmsq compared to a 34 of 907mmsq. That’s half the size for a piddly extra 25cc & aircooled to boot!!

So who wants to front up to the next MNZ doodacky & give those poor 125 guys a boost, say 28mm might be better? (615mm).:sunny:

Actually there are some guys I believe who are running 28s & none of them seem to be cleaning up.

Sounds like a job for ya dave to go and lobby the rule makers if you want to run a bigger carb.....

On a different note you dont have a spare cdi that I could test my mb100 motor with. The one I have got is dead!!!!

cheers

[Jantar]

if you got it sorted perfectly on a 125 twin then a single 24mm carb can be made to be identical as 2 24mm carbs. would just need to get the timing and porting sorted. then you'd have a weapon me thinks.

i reckon they should increase the size limit to say 180cc too. let people bore out their FXR150's, seeing as they aren't very competitive...

Absolutely correct. Everyone seems to think that you must have one carb per cyclinder. Although that means that each cyclinder can be at optimum tune, you can get the same results from a single smaller carb feeding two cyclinders. Just look at what Burt Munroe did with a single carb on his V-Twin Indian.

K14, Didn't we discuss this very thing at work a ferw days back?

[WINJA]

Tr50 Has 12mm And 14 Mm Carbs , So Shadup

[stanko]

Im not sure I agree with this 100%, while that may be true for diesels, 2 stroke are quite a different beast and we are talking about 125 cc aircooled 2 strokes arent we? In a 4t the inlet opens and atmospehric pressure pushes fuel air into the cylinder valve closes it stops , simple eh? In a 2 stroke its a bit different as the suction caused by the pipe can suck the reed valve open again so the carb can fuel the cylinder twice in the same engine revolution, if there are 2 cylniders sharing this carb it would be crap as the pulses would be uneven. Thats my take on it.
Im all for 28mm carbs on 125 aircooled , mainly cos they are easy to get

[Jantar]

Yes, reed valves do add a complication to tryting to tune the inlet tract. What K14 and I were talking about was the simple piston ported engine such as a T125 stinger. A single 24 mm carb with a properly tuned and shaped inlet manifold would allow up to 80% more fuel/air flow than the two standard 17mm carbs.

[jonbuoy]

Didn't the V Boost system on the Vmax have one cylinder sucking from two carbs?

[TygerTung]

If the 125 2 stroke has a massive carby on it won't this make it a bit unfair the the fulla's on there 4 strokes? I mean it's hard enough as it is without them having to contend with a 125 2 stroke with a huge carby?

[Ivan]

If the 125 2 stroke has a massive carby on it won't this make it a bit unfair the the fulla's on there 4 strokes? I mean it's hard enough as it is without them having to contend with a 125 2 stroke with a huge carby?

Nah maybe on ya standered CG125 but someone like RG100!! who has a hotted up FXR 150 with Different carb and exhaust system on it ends up producing more power and speed than the 125 2 stroke with 24mm carb.
I have been at the last few meets and no 125 aircooled is near the front

[Motu]

Just consider yourself lucky you aren't feeding a V8 through 50mm like the NASCAR guys.

[Sketchy_Racer]

Nah maybe on ya standered CG125 but someone like RG100!! who has a hotted up FXR 150 with Different carb and exhaust system on it ends up producing more power and speed than the 125 2 stroke with 24mm carb.
I have been at the last few meets and no 125 aircooled is near the front


Hotted up aye? :killingme

oh you mean the XR250 carb.... that was jetted in my bck yard....

oh and that exhaust system... I thought you said it was shit? you know with the sharp 45 cut and weld .... then the home built muffler :lol:

I admit that it does go very well.....

What is hotted up is the CBR 150 with the full race sytem ... very nice that bike!

[TonyB]

So who wants to front up to the next MNZ doodacky & give those poor 125 guys a boost, say 28mm might be better? (615mm).:sunny: All in favour of Dave say "I":innocent:


Actually there are some guys I believe who are running 28s & none of them seem to be cleaning up. Yeah theres one of them down here. He can't ride too well though so maybe he's not a good example...

[Skunk]

All in favour of Dave say "I"
That's 'Aye'.

I'll let you know though when I get my 125 going. ;)

[speedpro]

First - 24mm carbs aren't hard to find 'cause that's what most if not all the eligible 125cc air-cooled 2-strokes come with. Second - the carb size only seems to be a real handicap on bigger/faster tracks. The smaller carb/bigger motor makes for a torquey setup which has advantages on something like Mt Wellington.

A 125cc 2-stroke will make more power with a bigger carb which would be useful on a bigger/faster track but then it would fade out with heat and be passed by all the water-cooled 100cc 2-strokes and the fast(yeah right) 150cc 4-strokes.

Having said that I can see where it could even things up where there currently "may" be an imbalance between the different F4 categories. However I see tracks, riders, conditions, and tuning contributing more to any current imbalance. Also things like the fact that there aren't, with the exception of the KE/KV Kawasakis, any 125cc air-cooled eligible engines with decent transmissions. Those Kawasaki engines being disc-valve are probably good for about 20hp even with the 24mm carb.

Also Joe from Coleman's had his Suzuki TS125 flying a few years ago so that just shows that it can be done with a 24mm carb. A lot of that was down to the rider though AND it was on Mt Wellington.

[speedpro]

I forgot - Stop stirring Dave!

[Hillbilly]

Both the the 2006 Cagiva Mito 125 and Aprilia RS 125 run Dell'Orto 28mm carbs as stock street bikes. So what's with the 24mm ruling?

[Ivan]

Hotted up aye? :killingme

oh you mean the XR250 carb.... that was jetted in my bck yard....

oh and that exhaust system... I thought you said it was shit? you know with the sharp 45 cut and weld .... then the home built muffler :lol:

I admit that it does go very well.....

What is hotted up is the CBR 150 with the full race sytem ... very nice that bike!

Im using A KB'r as example

[Jantar]

Also Joe from Coleman's had his Suzuki TS125 flying a few years ago so that just shows that it can be done with a 24mm carb. A lot of that was down to the rider though AND it was on Mt Wellington.
I also ran a hotted up TS125 before the TMs came out, but the Suzuki hot up kit included a 28mm carb.

[F5 Dave]

Hillbilly, those are both watercooled examples so aren't eligible under NZ rules.

Yes I agree that a Water cooled 100 will ultimately be a better bike esp for longer tracks.
Aircooled bikes have to run richer & lower compression if they are to hope to keep producing power for a whole race. The more power you extract, the more you are likely to lose it as it gets too hot.

The 125s are self regulating in that matter, perhaps the bad gearboxes is another disadvantage. I know someone who was toying with a 125 twin as described, but didn’t proceed as the gearboxes are 5 speed & bad ratios. But the ruling could be 28mm on single cylinder air-cooled to quell that argument.

The idea that slamming a 28mm carb on a 125 would produce a monster is unlikely as really a hot 125 is quite restricted with a 28, as I said RS125s came with 39s in the early days. More telling is aircooled MX bikes ran 34s.

I think it would be easier to make a competitive 125 than the current situation, the two routes are build a hot water-cooled 100 which has the most potential, but by far the most work, or just go for a 150.

As for Joe he just made do with animal riding & a blind disobedience to obey the laws of physics.:shutup: