Twin 48's - no primer or choke???

[showmepro1200]

The machine we just picked up has twin 48 Riva ProSeries carbs on a Riva intake. Whoever built this thing had the gas lines direct-feeding the carbs, with one line for each of the main and the reserve tubes to a single carb(I found that they extended the reserve pick up to match the regular). I am planning on putting back the fuel switch, which (I think) is no major deal, but here I find there is no choke OR primer on the boat??? Someone clue me in on how they started it in the past please?

Also, back to the fuel switch - can I run both carbs with a Y from the main hose from the switch, will that be enough fuel?

 

[750SX]

They just kept cranking and cranking till it started. It probably had multiple starters replaced.

 

[waxhead]

If its a race boat then its fine
They will start just fine
ON a surf boat i like primers incase it gets wet
I run alot of engines with out primers and they work fine as long as the engine is in good shape

 

[Big Kahuna]

primers are for skis where the carbs are not tuned correctly, but like Wax said, they help if you have gotten any water in motor.


you can drill and install a press in primer fitting on those carbs.

 

[D-Roc]

i just pull my FA off for the first start of the day. put my hand over one carb and crank it a second. then the other carb. this chokes the carbs and pulls the fuel into the lines so it doesn't have a bit of a lean startup like the primer does. after that it starts right up. actually some days i fires up without the cold start procedure.

 

[Mouthfulloflake]

How does the primer give it more of a 'lean' start than your method?

i just pull my FA off for the first start of the day. put my hand over one carb and crank it a second. then the other carb. this chokes the carbs and pulls the fuel into the lines so it doesn't have a bit of a lean startup like the primer does. after that it starts right up. actually some days i fires up without the cold start procedure.

 

[D-Roc]

because it can burn off the fuel before the fuel lines get primed. if you give it a couple more shots while it is starting to catch the fuel in the lines you should be fine. i just prefer to fire the motor up with the carbs primed so it doesn't do a lean rev up.

 

[SuperJETT]

Properly tuned and maintained carbs will start with no primer/choke. If you need carb rebuilds, the fuel may leak back to the tank and it will take longer, but not that much longer. As mentioned also, you can just wrap a rag around one flame arrestor or pull it and block the top of the carb with your hand to act as a choke.

 

[Soul Man]

When Wamilton built my motors he always said if you are jetted right you don't need a choke. No choke on my boats for 4-5 years now. I give it a few cranks for a couple seconds, but once fuel gets into the carbs it usually fires right up. Takes a few cranks first start of the day, but after that it fires right up even if cold: I'll start in my shop, then it may be an hour before I'm at the riding spot and in the water, but even then it fires immediately.

Just replaced my starter due to rust after about 3 or 4 years, never burned out a starter (829cc Lamey stroker with 185psi comp), so I'd disagree with 750SX's comments about "just had multiple starters replaced"

May be a little safer having one line to each carb, but I think one line with a "Y" should feed enough fuel without going lean. I've always felt that with dual lines you run a risk of one getting plugged/clogged and that will lean out your one cylinder, as opposed to both which will shut the engine down. Pro's and Con's to both ways.

Without a switch you can't run reserve, but you'll also always be pulling fuel from the bottom of the tank. If you suck in a few drops of water the carbs will suck it up before it accumulates enough to cause a problem (I haven't had a problem with water in my tank since I went to the dual pick-up system). otherwise, running normal with reserve, you could potentially build up an inch or two of water in the tank over time. The couple drops at a time won't cause any problems (of course it would be ideal to never run ANY water through your motor/carbs but the reality of freestyle is you WILL get water in your tank and intakes) Wammer told me that you should learn how long you can run, and just keep your tank filled up. If you rely on reserve, that means you run out of gas (to indicate you need to go to reserve) which leans out the motor. Not a problem on stock motors, but on a high perf. motor that may be enough to cause problems, especially if you happen to be WOT when you suck up that air. Of course running out of gas with no reserve will do the same thing if you aren't being careful about your fuel level. Again, pro's and con's to both. Also, Wammer felt the valve was one more thing that could go wrong or block/limit flow. not sure that is a real world concern, but something to think about.

I have one line to each carb, reserves "T" into single line back to tank, no choke or primer, no valve and happy with it. Your results may vary

 

[Mouthfulloflake]

but its turning over without any fuel/oil for the all the time it takes to hold you hand over and start up?

I agree with the neither really needed.

but I do like the primer, it is a NICE thing to have when you run out of fuel in the ON position in the middle of boat traffic and want to restart FAST when you change to reserve. a couple of pumps and you are up and running.

because it can burn off the fuel before the fuel lines get primed. if you give it a couple more shots while it is starting to catch the fuel in the lines you should be fine. i just prefer to fire the motor up with the carbs primed so it doesn't do a lean rev up.

 

[D-Roc]

soul man, bang on! that is how i feel and have my ski setup, mouthfulloflake, when you shoot a bit of gas down the carb and fire the ski up it burns that fuel up first. sometimes the carbs kick in right away with the fuel from the tank, other times the primer shot burns up and the ski stalls or...it can go lean and run away. i have seen this happen several times on pro built brand new motors on a cold start. its not a big deal most people have primers or drip a bit of gas down the carb from a bottle. I have easy to remove FA's so i just choke it to cold start it, if it even needs it.

 

[showmepro1200]

Soulman, I like your thinking on the single vs. dual-feed on the gas lines, prefer to have it just quit than burn a cylinder. As long as I can get away with the single feed, that's the way I'll go.

I'd like to have the reserve and the valve for safety sake. I don't usually run to reserve very often, and I do have the water separator on the boat too, to help keep out water.

What you describe on your machine sounds like exactly what Im looking at now - one line each carb, returns "y" back to one line to the tank, no valve, no choke, no primer.

Another question - for freestyle riding I see these round F/A's as just asking for a water injestion problem - what is a good solution for getting something like the oem Yamaha dual carb hood on these (like my RN with the dual 38's)? Or am I analizing too much here? I'm certainly going to tell my son to run the bilge ALL the time when he's riding for sure.

 

[Big Kahuna]

there is really no feasible way to run an OEM flame arrestor on the Riva's. No way to mount them. Thrust Innovations have a way to install an set of single 44 oem flame arrestors on carbs like yours but it is expensive.

I run K&N filters with no outwears or anything like that. If you have a good hood system that keeps water out and a bilge/scupper setup that gets rid of water quickly you should be alright.

 

[D-Roc]

one thing i thought about with straight lines to the carb vs using the switch is you can't shut off the fuel supply to the carbs while not riding. If it sits in the sun, I worried about gas tank pressure pushing on the carbs seats. not sure if it does anything bad or had any problems yet, (my ski is in the cool garage) but if the seats leak it can just run fuel into the cases. with the switch you can shut it off all together. something to ponder. doesn't wammer make something to run stock SN flame arrestors?

 

[Big Kahuna]

http://www.thrustinnovations.com/index.php?main_page=product_info&cPath=1&products_id=10

 

[D-Roc]

https://www.wamiltons.com/index.php?main_page=product_info&cPath=3&products_id=350
here is the same thing from wammer. both cool as hell and easy to remove i would imagine.

 

[Soul Man]

I had the same reservations about the flame arrestors, but I now run just the round ones (from Blowsion) with no outerwears. Good hood, watch how long you stay underwater, good bilges and a scupper. make sure if you do a sub that you don't do another until you bilge stops pumping water, otherwise you can build up water.

I tend to roll to the right with all my stabs and attempts at Barrel rolls so I land on the right side a lot. That means if I fall etc. the ski will be on it's side with the carbs down. Even with that, I don't have problems with water ingestion. I try to right it ASAP when I fall. Sometimes it will sputter/run rough for a few seconds (likely from swallowing some water) but it clears right up. Once you sink a ski, pull the plugs etc. to dry it out, and see how easy it is to get running you don't worry about swallowing a few ounces now and again. Obviously you don't want to do it, or try to do it but these motors don't mind it too much now and again.

I had a hard time getting rid of the stock flame arrestors, had a hard time getting rid of my reserve etc, all for the exact same reasons you are citing, but overall it really does work well and doesn't cause any problems.

 

[Soul Man]

I do like the idea of those adapters, sounds like a good idea. If I didn't have some nice new yellow Bling-A-Lischious F/A's from Blowsion I might get those....

 

[750SX]

one thing i thought about with straight lines to the carb vs using the switch is you can't shut off the fuel supply to the carbs while not riding. If it sits in the sun, I worried about gas tank pressure pushing on the carbs seats. not sure if it does anything bad or had any problems yet, (my ski is in the cool garage) but if the seats leak it can just run fuel into the cases. with the switch you can shut it off all together. something to ponder. doesn't wammer make something to run stock SN flame arrestors?

Just crack the cap when storing.

 

[crammit442]

]primers are for skis where the carbs are not tuned correctly[/b], but like Wax said, they help if you have gotten any water in motor.


you can drill and install a press in primer fitting on those carbs.

I believe that's a common misconception. With small carbs that may be mostly true, but not so much on skis with bigger carbs. Think about it this way. Even on brand new computer controlled cars fuel system enrichment is used during startup because the engine is cold and requires more fuel. It can be done through more fuel(primer) or less air(choke). Of course the engine management sytem takes care of all this, so you're not even aware it's taking place. A jetski motor is no different. Worse if anything since the fuel has a longer journey to reach the combustion chamber. Fuel doesn't evaporate as well when the motor is cold so you need more of it to maintain the air/fuel ratio needed to burn. If your modified boat always starts cold with no choke or primer you are likelier rich than perfectly tuned. And good luck w/o a primer if you ingest a little water and stall in the surf.:nono: