old 46 mm buckshot carbs vs new blowsion 46 mm carbs?

[kabaraka]

hi all , my 2000 sj has been using 46 mm buckshot carbs for many years and were recently rebuilt. i just scroll through blowsion website today and found dual 46 mm mikuni carbs kit on sale for around 660 usd so i am thinking to change to the new ones but would like to ask you guys if the performance will drop or it will run better with the new one from blowsion? i dont know much about jetski technical so anyone please help me decide. many thanks in advance for your answers.

 

[kevbo]

Standard 46 mikunis have venturis so they will flow slightly less but be much easier to tune. Typically aftermarket companies will bore out the venturi and install their own discharge nozzle. Its the easiest way to make money in the whole PWC industry. You have to be more careful with carb sizing because they can start acting too big very fast. I prefer standard carbs on smaller engines for this reason.

 

[TheBuzzard]

46s are 46s. If your carbs are tuned and it runs right, you will gain nothing by wasting 660$ on new carbs. Supposedly this chart might work. I'd like to know what exact jets, seats and springs are working in your setup.

 

[Pro-pulsion]

Here's an old post from Supertune Chuck, post number 16. He found this info from greenhulk about the cfm data between the various sbn and sbn modified carbs, the original info is the same as below it just doesn't look like this chart. I re-arranged it to be comparing each brand to itself in it's own different sizes. Hopefully it's a little more understandable and easier to make comparisons. It's a great read and what I used to decide on going with the sbn 46 carbs as they were intended to be from Mikuni.

"The following data was gathered on a Super Flow 600 flow-bench set at 20 inches of water for all tests.
Along with this data, we have also denoted the full throttle CFM numbers, as measured at 20 inches of water. They are listed in alphabetical order by carburetor brand name.

CFM @ 20" (100%open) - Pilot Circuit / Main Circuit / Carburetor Max CFM

AMC 46 - 21.5 / 31.7 / 293

BMR Full Spectrum 46 - 23.0 / 58.0 / 299

Buckshot Magnum 44 - 23.3 / 31.0 / 268

Buckshot Magnum 46 - 26.0 / 37.2 / 286

Buckshot BRM 47 41 - 20.5 / 47.5** / 293

Keihin CDK II 42*** - 22.5 / 28.8 / 195

Mikuni "I" Body 44*** - 22.5 / 32.2 / 239

Mikuni "I" Body 46*** - 23.2 / 33.0 / 246

Mikuni Super BN 44*** - 30.0 / 49.0 / 230

Mikuni Super BN 46*** - 34.8 / 46.0 / 253

Novi Max Flow 44 - 25.7 / 66.0 / 269

Novi Max Flow 46 - 28.0 / 65.0 / 304

Red Top 44 - 20.3 / 37.9 / 269

Red Top 46 - 21.0 / 34.8 / 296

** The signal reading randomly fluctuated on a 2-4 second cycle within this range, with no stabilized 20" reading lasting over 5 seconds. Signal reading would not stabilize until pressure was reduced to 8".
*** Tests were run with bolt-on arrestor adapter."

Red Top Carbs (seeking info)

Today I stumbled across a set of 46's from a friend of mine at a killer deal which sparked some interest to obtain more information about these carbs. I was wondering when and by whom these carbs were made. Also what is particularly good or bad about them and how do they work compared to other...

www.x-h2o.com

 

[kabaraka]

46s are 46s. If your carbs are tuned and it runs right, you will gain nothing by wasting 660$ on new carbs. Supposedly this chart might work. I'd like to know what exact jets, seats and springs are working in your setup.

my carb has 115 main 110 low with 2.5 n/s and 95 gram spring. the engine is 62t 64x cylinder 85 mm pistons with factory type 4 dry pipe. the only problem now is that when i first get into the water or after the ski sits for a while when i rest between riding, l had to blip the throttle a few times before the ski has snap power then it will be fine. feels like it needed to clear out the fuel or starving for it i dont know. is it about tuning or something is wring inside the carb like n/s leaking?

 

[TheBuzzard]

Yea sounds like gas flowing into the motor thru leaky needle. I've had it bad before and instead of fixing it right away, I'd loosen the gas cap, keep the nose of the ski down when not riding. Pressure in the tank will flood the motor. Do you have to hold the throttle wide open to get it to start after it sits?

 

[Pro-pulsion]

@Pro-pulsion

The Novis are impressive. No wonder they were the best Jetski Carbs for decades.

Any CFM numbers on Full Spectrum Carbs?

Not that I'm aware of, this info I believe was posted back in 2008, maybe Full Spectrum wasn't a thing back then?

 

[kabaraka]

Karbarator,

Do a Pop-Off test to see if the Needle Valves are leaking.

Did you install new Needle Valves during the Carb Rebuild? At the very least, the Valve O-Ring should be replaced. But if the Needle Valve Cone Tip has a groove then it will leak.

i replaced only the needle valves and used the old seat and o-rings. should replace with new ones?

 

[kabaraka]

Yea sounds like gas flowing into the motor thru leaky needle. I've had it bad before and instead of fixing it right away, I'd loosen the gas cap, keep the nose of the ski down when not riding. Pressure in the tank will flood the motor. Do you have to hold the throttle wide open to get it to start after it sits?

it starts just fine. easy start actually. i just push the start button and it will fire right up. anyway i guess i will have to change new set of needle and seat to make sure it will have no leak.

 

[kabaraka]

i aslo need the carbs so bad

yes me too at least it is new and fresh hahaha