ATP single 48 carb settings

[magic30]

Hi all,

I know... Go dual carbs. But this is what I have and I hope to ride the rest of the season on it, so I am hoping to get some carb baseline jetting/settings.

Background, Just bought a ski with:
- jetworks 771
- power factor pipe
- stock electronics, but msd enhancer
- setup for pump gas

I ride around 1500 ft elevation.

Ski was complete minus carbs that the seller was keeping. I have a single ATP 48mm carb on an ATP manifold that I am thinking to run for the time being, until I can save up for carbs. This carb came off a jetmaniac/blue 718 with a b pipe. I emailed jetworks and they said they have no experience with ATP carbs and could not give me any baseline to start with.

Would the jetting that was used on the 718 be close enough (and safe) as a starting point or does anyone have a starting point that can be provided?

Any help is appreciated, carbs/tuning is not an area of expertise.

Thanks in advance

 

[Flash-FX]

Coming directly from ATP's site, here's his sales pitch.
December : ATP Freestyle Carb.
Introducing the ATP Freestyle Carb specifically designed and manufactured with Freestylers in mind.

With a unique annular discharge system utilising a 44mm inner Ventura and a 48mm throttle valve with an unprecedented throttle shaft design. This enables the Carburettor to work at the high pop off pressures that Freestyle riders long for.
The Carb greatly compliments the ATP Single Carb Manifold.
They can also retro fit your own 44mm or 46mm Mikuni Carb with this modification.
www.queenfordjetski.co.uk

The link is dead but it sounds like a really good carb to use on a high volume 1 into 2 manifold. You are going to have to experiment from the beginning. Hopefully it's easy to remove the carb for jet & pop-off changes. (I've done this before and cut a big hole in the side of my ski to access the carbs). Start with the idle circuit and go up from there. The power factor pipe is going to be better than the b pipe. Be patient.

 

[magic30]

The carb ran well on the 718. I am mainly looking for a safe starting point since I know every engine is different. Should I try the carb on the 771 as is and tune from there, or should I haphazardly up the jets a few sizes to start with?

I can pull the carb out the bin and check what is in it this weekend if someone has an idea from running a similar setup previously.

I haven't found much info on these carbs.

Thanks again.

 

[fastgtfairlane]

What jetting is in the carb now? Could try going up one size on the pilot and 2 sizes on the main. Ex- 120p, 150m. Try- 125p-160m and see what happens. It's just about impossible to give jetting over the internet. You'll just have to start somewhere and go from there.

 

[magic30]

What jetting is in the carb now?

I will pull it apart this weekend and see. I am out of town this week.

 

[magic30]

What jetting is in the carb now? Could try going up one size on the pilot and 2 sizes on the main. Ex- 120p, 150m. Try- 125p-160m and see what happens. It's just about impossible to give jetting over the internet. You'll just have to start somewhere and go from there.

Just checked and it has a 125 pilot and 177.5 main. 2.0 n&s. Silver spring (I think it is dull).

 

[long beach local]

Just checked and it has a 125 pilot and 177.5 main. 2.0 n&s. Silver spring (I think it is dull).

I have an atp 48 carb on a Dasa single manifold. 175m 135p- 140p I think 115g 2.5ns The carb likes a lot of fuel your setup sounds in the ballpark I wouldn’t run smaller jets until you try it.

 

[magic30]

I have an atp 48 carb on a Dasa single manifold. 175m 135p- 140p I think 115g 2.5ns The carb likes a lot of fuel your setup sounds in the ballpark I wouldn’t run smaller jets until you try it.

Thank you for the info.

I am still not certain if I will run the carb or not at this point. I am leaning towards just biting the bullet and having art set up a pair of blackjacks for me.

 

[long beach local]

Thank you for the info.

I am still not certain if I will run the carb or not at this point. I am leaning towards just biting the bullet and having art set up a pair of blackjacks for me.

My setup runs great no issues with the carburetor ever . I have a single setup 48 powerbomb 62t on my Freak for the surf and it also is flawless. I am a single carb fan though ,been told there is a disadvantage in top end but I can’t tell lol mileage is same as dual 38s. bottom end may be better.

 

[magic30]

My setup runs great no issues with the carburetor ever . I have a single setup 48 powerbomb 62t on my Freak for the surf and it also is flawless. I am a single carb fan though ,been told there is a disadvantage in top end but I can’t tell lol mileage is same as dual 38s. bottom end may be better.

I like the idea of a single carb. It ran well on my old 718. My main hesitation with going dual 44/46s is the ride time (and cost).

I'm just not great at tuning and when the engine builder (jetworks) is advising against using it, it has me weary. I'm concerned I may be chasing my tail getting it to run right.

 

[Roseand]

What jetting is in the carb now? Could try going up one size on the pilot and 2 sizes on the main. Ex- 120p, 150m. Try- 125p-160m and see what happens. It's just about impossible to give jetting over the internet. You'll just have to start somewhere and go from there.

This is great advice. Best to start rich.
However. I highly recommend going with a carb setup that is recommended by your builder. There is nothing more satisfying than just having to tweak your screws a little bit to get perfectly dialed. I hate tuning carbs. 771 is a tried and true combo, he should most definitely be able to set you up with something extremely close.

 

[magic30]

This is great advice. Best to start rich.
However. I highly recommend going with a carb setup that is recommended by your builder. There is nothing more satisfying than just having to tweak your screws a little bit to get perfectly dialed. I hate tuning carbs. 771 is a tried and true combo, he should most definitely be able to set you up with something extremely close.

I have been doing a lot of reading on the topic the last couple weeks and have emailed jetworks a few times. This seems to be the consensus and I'm leaning towards it.