Flat side carbs vs Diaphragm

[Crazy88]

Hi Guys

Heres my second post/question.

I have a '99 1200 Bandit, its turned into a bit of  project and want to squeeze as much torque/bhp out of her before going down the big bore route.

ATM I have the standard carbs and going to tune it with a stage 3 kit and assorted bits that go with it.

I have heard that I should consider Flat slides over the standard but not sure as the pros and cons between the two.

Can someone elaborate and if the flatslides are the way to go which one would you recommend, I was looking at 38mm flats, but how do I know what brand and where to go for them.

 

Thanks in advance

[Captain Chaos]

Since you're going to turbo it anyway in the near future*, keep the CV's.

 

* yes you will.

[colinworth79]

Stock bandit 12 just over 100 hp as standard . Everything done to the engine n/a looking 160 - 170 ish .  Turbo up to about 300 ish keeping it rideable .

Not sure really what your after from the above post but not going silly you want to change the whole exhaust system , find some gsxr cams and raise the compression  as there fairly low as standard .

Carbs various different ones to go for . I've just fitted some 40mm TMR mikunis to my gsxr 1100 that work really well. but it's not stock internally and has a fully yoshi system ect .

[Crazy88]

Im swapping out ny exhaust for a full bore system as part of the upgrade, Im going for stage 3 with K & N oval filters, this is all as a start, I was just curious about the carbs as I was thinking of swapping the originals out before I get it tuned to skip doing it later.

What cams for the '12 will be the most suitable? Is it better to change both or just one?

Cheers

[wraith]

Your now going down the rabbit hole 

This has been asked meany time and will be asked meany more 

So, cam to my limited knowledge any of the oil cooled gsxr cams (tappet type not the latter models) will be a improvement over the b12 cams best, if you can find some gsxr750jk I believe. Or just get a set of street/race cams from Kent etc.

As to your question on carbs, 

If you want power flat slides a the time some will say 36mm are a good all round size for open road and city some will say 38mm. Down side need to be set up on a Dyno for best results and if you're not 100% on the way they work much harder to tune yourself.

Also cost more.

Also different way of riding with them, as unlike CV carbs you need to feed the power on by the throttle not just bang it wide open like with CV and let the CV do the work for you.

Or a mid way house, and cheeper, find a set of gsxr750 38mm oil cooled carbs and rubbers they make a good improvement, not as much a slides but hay.

Ps. If you are keeping the CV carbs use the K&N dual pods not the individual filters the duals are much better 

Enjoy and good luck 

[BikeJake]

I spoke to Roger Upperton about my plans and he said the standard carbs were easily good for 150bhp plus. 

[fatblokeonbandit]

1 hour ago, BikeJake said:

I spoke to Roger Upperton about my plans and he said the standard carbs were easily good for 150bhp plus. 

Exactly, I’ve got 2 150 rwhp motors on Standard 36mm mikky roonies

spend the money on cams head work and 1216 kit before flatside

[coombehouse]

Don't forget that if you have knackered wrists like me, the heavy  return springs on the flat slides are a problem. 

[Reinhoud]

I had Mikuni RS34's on my bike, I  didn't notice any gains in power, it just had an incredible throttle response...

Probably more torque in the lower revs... Did I already mention it gave an increadible throttle response?

Edited August 28, 2022 by Reinhoud

[BikeJake]

19 hours ago, fatblokeonbandit said:

Exactly, I’ve got 2 150 rwhp motors on Standard 36mm mikky roonies

spend the money on cams head work and 1216 kit before flatside

Yeah that's what Roger said. 

[coombehouse]

20 hours ago, fatblokeonbandit said:

Exactly, I’ve got 2 150 rwhp motors on Standard 36mm mikky roonies

spend the money on cams head work and 1216 kit before flatside

If the bike doesn't need a rebore, I would skip the 1216 kit too, a 5% capacity increase isn't going to make a massive difference. 

[Gixer1460]

3 hours ago, coombehouse said:

If the bike doesn't need a rebore, I would skip the 1216 kit too, a 5% capacity increase isn't going to make a massive difference. 

I'd disagree there - my 1127 with a 1186 kit made a tad under 20 rwhp more with no other changes other jetting - just sayin like.

[coombehouse]

25 minutes ago, Gixer1460 said:

I'd disagree there - my 1127 with a 1186 kit made a tad under 20 rwhp more with no other changes other jetting - just sayin like.

That's probably due to the big bore kit pistons being designed to also give more compression as much as anything. If 50cc capacity increase gave that much power on it's own, think of how fast mopeds would be!

[fatblokeonbandit]

My 3rd engine is a standard bore with High Comp pistons from Dale Winton, same head work and cams and exhaust and it feels totally different 

not been o. Dyno yet but definitely revs more freely but dosent have  the torque out of bends,

yes it was a saving but not much they cost the. Same as 1216 pistons

[Dezza]

Diverging from the point but keeping with the cost-effectiveness theme, it may make more sense to first upgrade a Blandit's suspension and brakes, and to remove some excess mass before spending a whole load on engine upgrades.

[Jonny]

On 8/29/2022 at 11:18 AM, Dezza said:

Diverging from the point but keeping with the cost-effectiveness theme, it may make more sense to first upgrade a Blandit's suspension and brakes, and to remove some excess mass before spending a whole load on engine upgrades.

...by putting the engine in a GSXR750 frame!

[Crass]

On 8/29/2022 at 11:18 AM, Dezza said:

Diverging from the point but keeping with the cost-effectiveness theme, it may make more sense to first upgrade a Blandit's suspension and brakes, and to remove some excess mass before spending a whole load on engine upgrades.

Indeed. People always think you need more power to go faster when in fact you usually need the thing to go round corners, not tie itself in knots on the bumpy bits, and stop faster. Unless you're building a drag bike.

[Gixer1460]

17 minutes ago, Crass said:

Indeed. People always think you need more power to go faster when in fact you usually need the thing to go round corners, not tie itself in knots on the bumpy bits, and stop faster. Unless you're building a drag bike.

Still applies - just not the going round corners bit 

[bluedog59]

On 8/29/2022 at 11:18 AM, Dezza said:

Diverging from the point but keeping with the cost-effectiveness theme, it may make more sense to first upgrade a Blandit's suspension and brakes, and to remove some excess mass before spending a whole load on engine upgrades.

+1. Stock engine, decent full system, upgrade the wheels/brakes/suspension and add lightness. Now you can go out and annoy lots of Power Ranger sportsbikes on what passes for roads in this country.

Even better if it looks reasonably stock with a nice little rack on the back. I did try running a top box as well but it upset the handling.

[BikeJake]

The only thing that puts me off the CVs is the fact that on other projects CVs gave problems with POD filters.. Combined with the fact I dunno how much a modded standard airbox is good for? 

[george 1100]

Take a look at the amount of posts on here and all other oil cooled related platforms and every second post is CV carb related running issues. There's your answer

[Gixer1460]

9 hours ago, george 1100 said:

Take a look at the amount of posts on here and all other oil cooled related platforms and every second post is CV carb related running issues. There's your answer

Probably because most cv's are full of plastic that is 30-40yrs old and been flogged to death in all that time! If you could obtain new cv's it would solve a lot of the problems!

[george 1100]

Exactly, motors are flogged also, may be modded, air-box gone, pipe change, even fuel has changed, some have lightened their bikes, combine with flogged carbs, it's no wonder so many people are having tuning issues. 

Edited September 1, 2022 by george 1100