What do you reckon.
They say torque down low with a small carby, but better top end with larger.
Will the 45 take much bottom low end torque off?

It depends... on whether you treat the throttle like a light switch!
I have twin HS4s on Barney and a 45DHLA (similar to 45DCOE) on Ha-Ha... both have similar cams & 1.5 rockers- it's no contest, 45DHLA walks away. As long as I don't tromp it hard below 2500...

Single HS4 is hardly enough for a 1275 (needs HS6 or HIF44), but is just OK on a 1098 or 998 I guess.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Yer i'll get to learn the weber i suppose.
So the idea is not to hard throttle too quickly off the line?
Thats what i HAVE to do with the SU

Yeah, different technique. Don't make the Weber's choke sizes too big for a 1098... 32mm would be good.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Will the high compression + 40thou oversize make a different to the choke size?

Not really. If you make the chokes too big and motor is otherwise nearly stock, it will be a pig to drive. Not enough air velocity thru the carb...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Interesting...
regarding air filters...
would stevo's (sg) K&N be a good one to run with?

I said this yesterday to Poeee... Go the Weber, baby!!!

Nothing like the sound of a barkin' 45 behind the firewall. However, you can forget the music. You won't be able to hear it.

And yes, if you jump on a weber too early, you'll flood the poor thing as the accelorator pumps open, and it'll cough and fart along until it catches up.

I think i have 38mm chokes in mine

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Cheap, Fast, Reliable. Choose two.

a webber on your motor is way overkill.
you aren't maxing out the potential for the hs4 yet..
has it got a stock needle?
you could try a more aggressive needle.

agressive needle?
I thought the needle either made it in tune or out of tune.
And also corrected the fuel/air ratio.

what does your motor rev out to?
and more importantly, how does it feel at 5000+rpm

given that you have a cam, LCB's and exhaust, i'd say you would need to change the carb needle from standard

It's not a stockie needle! hehe.
Steve's tuned it up.
5 grand is alright... nothing past 6.
And its got lec ign.
Valves just dont wanna work much harder than six thousand revs.

double valve springs then, i haven't put my set on yet.

a single 1+3/4" carb is more than enough for even the hottest 1100's

if i had a worked 1275, then i would put a webber on.

Yeah.
my rings are ****.
well and truly.... not chronic but theyre on the way.
so i'll keep thrashing the ring off this motor.
then do the 1275.
if i split the head, then i'll NEED to do rings, cos i'll end up having all this more power and it won't be able to take it (as i'd want to do a bit more porting of the head i have on it now)... says steve.

So i'll be getting this 45 for th 1275, so might as well see what it's like on my smallbore before i end up doin the 'big bore'

and... i still think you're crazy with your drums

i find it funny how everyone around me cooks their discs on cruises when i barely use the brakes. Something about never having working brakes and all that.

in your case, i would put the money towards your big block and run the 1275 with an SU until the money for the webber comes along.