92 Sea Doo GTX: Replacing OEM BN38-34 8075,8076 Dual Carbs with 2 New Mikuni SB38-34-8113's

[Rlauro5202]

1992 Sea Doo GTX 5860. Prior owners butchered carbs. Purchased two new Mikuni BN38-34-8113's, description stated for single, dual and triple installs.
Installed exterior hardware on the carbs to accomodate Mag and PTO sides, units fit perfect onto manifold intake.

Question: Do these 8113's need to be modified internally? The Pilot is 65, Main: 107.5, Needle/Seats 2.0. Checking the original BN38-34's it appears they use the same jet sizes. I recall reading somewhere that the carbs have 62.5 pilot and 67.5 pilots, not sure if this is accurate, and if it is, which carb gets which pilot? Obviously I don't want one cylinder running hot, seizing or blowing the engine.

Also, the return fuel lines in these original carbs have restrictors: Mag 3.0mm, PTO 0.5mm from the PWC's Sea Doo Shop Manual. I don't believe the new 8113's have restrictors, so if I need restrictors, can they be installed on the actual fuel lines at each carb? Best way to do this? I've heard using a 3.0 mm jet and 0.5mm jet zipped-tied to each fuel return line?

Much appreciate experienced advice here. I don't have the experience obvioulsy and I am "on my own" with this ski -noone wants to deal with it due to its age, which I understand. My son bought it and trying to help him and be a dad.

Thank you, much gratitude.
Rob

 

[mikidymac]

Run the same jetting..
2.0 needle and seat.
107.5 Main
62.5 Pilot
95 gram spring
Low 1-1/4
High 0

You are just going to have to try them and check the plugs.

No restrictors.

 

[Rlauro5202]

Thank you for responding.

These new carbs do not have any restrictors in them which I understand is typical of aftermarket carbs, albeit they are Mikuni carbs.

Being that there are no restrictors, why should I not be concerned about these running lean, nothing in the return fuel path to create back pressure. Thoughts?

 

[Rlauro5202]

Run the same jetting..
2.0 needle and seat.
107.5 Main
62.5 Pilot
95 gram spring
Low 1-1/4
High 0

You are just going to have to try them and check the plugs.

No restrictors.

Thank you for responding.

I do t believe these new carbs have restrictors in them which I read somewhere online that it is typical of aftermarket carbs, albeit they are Mikuni carbs.

Is that something you have experience with RE aftermarket’s and no restrictors?

If there aren’t restrictors i should or shouldn’t be concerned about these carbs running lean? I have nothing in the return fuel path to create back pressure. Thoughts?

Thank you - trying to get this unit back in water safely.

 

[Ernest Jones]

I'm in the same boat (hahaha) Neighbor bought an old '95 XP. Engine is a 717 with 130 PSI front and rear.
The existing carbs are shot and obtaining decent cores for rebuilding seems to cost more than going new.
I'm just trying to help him get it running properly before the summer is up.
I'm guessing both BN38-34-8113's came with the fuel pump section? Did you just use the old plate for the PTO side?
Did the linkage all transfer properly?
Did the BN38-34-8113's have choke plates?
Has anyone done this successfully or am I worrying too much? We're up in Canada so we have to order them out of the US and do a big song and dance so it's best to get the orders in right the first time because you're stuck with them.

 

[Rlauro5202]

I'm in the same boat (hahaha) Neighbor bought an old '95 XP. Engine is a 717 with 130 PSI front and rear.
The existing carbs are shot and obtaining decent cores for rebuilding seems to cost more than going new.
I'm just trying to help him get it running properly before the summer is up.
I'm guessing both BN38-34-8113's came with the fuel pump section? Did you just use the old plate for the PTO side?
Did the linkage all transfer properly?
Did the BN38-34-8113's have choke plates?
Has anyone done this successfully or am I worrying too much? We're up in Canada so we have to order them out of the US and do a big song and dance so it's best to get the orders in right the first time because you're stuck with them.

Prime units, no choke. Linkage fit to a tee. Used old plate to remove pump on new pto side.

Problem is I don’t open carbs and reset so I don’t know if there are restrictors in the fuel return ports.

Ski starts but bogs when I give it a little throttle at 3/8 open. Had water running on trailer for idle and 3/8 open but then shut off and now won’t crank. Battery fully charged. Ugh.

Plugs out and engine turns by spinning pto by hand so not seized but wasn’t running long and only up to 3/8 throttle.

I’m stuck on next steps.

 

[Ernest Jones]

Hi Rob, thanks for the reply! I have no idea what they are talking about when they say they are prime units. Are they trying to say they have accelerator pumps on them? Either way, you answered the important stuff so I deem them safe for my neighbor to order

Did you transfer the existing jets to the new carbs as mentioned by mikidymac? This would be essential to return to OE jetting for your boat. If your jetting is back to stock for your boat, I would think you could use the factory low and high settings on the carb and be very close.

I know nothing about restrictors but it does not sound concerning to me. I would not restrict anything in the fuel system and just run the stock jets with the stock screw settings (High and Low) and see from there. But...I would check the pop-off as well to be sure it's in spec. Oh, did you also sync the two carbs so they are both equal when open and at idle? Did you check the throttle cable adjustment to ensure you're getting WOT and whatever play they suggest in the lever? Should all be pretty simple if you follow the factory's path, I think.

BUT, I am no expert on 2 stroke or SeaDoo so....this is my first go round... helping my neighbor in this case.

If your issue now is that the engine won't crank, check for voltage across the solenoid / starter relay when pressing the start button. The solenoid is in the plastic box with all the wires. This is assuming the kill switch is not activated (lanyard thing). My neighbor cranked his for so long that he fried it. Mind you, given it's a 1995, who knows how much cranking that thing has had over the years! I suspect smart money on something like a boat would of this vintage would be new starter solenoid and brushes regardless just to be sure you don't get stuck in the middle of nowhere.

Oh, and like everyone says, check the compression before starting one of these adventures. Otherwise you could end up with everything perfect and sweet, and lots of dollars, only to find out the engine needs serious work.

Hope this helps.

 

[Rlauro5202]

Hi Rob, thanks for the reply! I have no idea what they are talking about when they say they are prime units. Are they trying to say they have accelerator pumps on them? Either way, you answered the important stuff so I deem them safe for my neighbor to order

Did you transfer the existing jets to the new carbs as mentioned by mikidymac? This would be essential to return to OE jetting for your boat. If your jetting is back to stock for your boat, I would think you could use the factory low and high settings on the carb and be very close.

I know nothing about restrictors but it does not sound concerning to me. I would not restrict anything in the fuel system and just run the stock jets with the stock screw settings (High and Low) and see from there. But...I would check the pop-off as well to be sure it's in spec. Oh, did you also sync the two carbs so they are both equal when open and at idle? Did you check the throttle cable adjustment to ensure you're getting WOT and whatever play they suggest in the lever? Should all be pretty simple if you follow the factory's path, I think.

BUT, I am no expert on 2 stroke or SeaDoo so....this is my first go round... helping my neighbor in this case.

If your issue now is that the engine won't crank, check for voltage across the solenoid / starter relay when pressing the start button. The solenoid is in the plastic box with all the wires. This is assuming the kill switch is not activated (lanyard thing). My neighbor cranked his for so long that he fried it. Mind you, given it's a 1995, who knows how much cranking that thing has had over the years! I suspect smart money on something like a boat would of this vintage would be new starter solenoid and brushes regardless just to be sure you don't get stuck in the middle of nowhere.

Oh, and like everyone says, check the compression before starting one of these adventures. Otherwise you could end up with everything perfect and sweet, and lots of dollars, only to find out the engine needs serious work.

Hope this helps.

Ernest -
Prime means not carbs with choke. You can replace the choke pull near console with a dual primer unit by mikuni. Instructions included. East install just a little elbow grease due to tight area.

I am ordering two new pilot jets from OSD at 52.5. These carbs come with 65 pilots. Main jet at 107.5 matches original moline dual carb spec for my unit ‘92 gtx sea doo. Check OSD site, Nick has carb reference charts with settings and rebuild kits. Guy is super knowledgeable but apparently super busy.

Solenoid is bad on this unit. I checked it by jumping terms and started kicked in. Assuming solenoid is time for replacement.

 

[Ernest Jones]

Thanks!

Neighbor ordered the two new Mikuni's. I get it with respect to priming. Much like the rubber bubble on a chainsaw that you press in. More stuff for him to buy and I suspect it's only just beginnng.

 

[Rlauro5202]

Please check the reference chart for Mikuni Carbs that I referenced above (OSDParts.com). You may need to order Pilots and/or Main Jets. Open new carbs and check both needles/pop-offs and Pilot/Main jets to confirm they are the same if yo don't have to replace. Something I didn't do but am doing now. Order the Mikuni dual primer, don't buy off amazon.
Also, recommend replacing fuel supply/return lines from tank. Check gas tank reserve/supply lines as well.

Good luck. patience...

 

[Ernest Jones]

I couldn't find the Mikuni brand dual primer. Anywhere. I'm find myself wondering if they even make one? In the end, for expediency I ordered one up from Amazon (gasp) even though I didn't want to. Theory being as long as we have the carb parts we can always change the actual pump later if it's bad. I did manage to find some good fuel line though. This was not a easy as it seemed. In the end I went with Thermoid SAE 30R7 hose in a 1/4" (hope that's correct size). Its rated for fuel and oil and should be a one & done. I'll be moving the OE jets to the new carbs when/if it all arrives as planned.

 

[mikidymac]

A word of caution..
All of the primers suck and do not last anymore. Do not run then on any of the fuel feed lines as when they fail you will get air into the system and run lean and possibly ruin your engine.
IF you have to run a primer then make a low hanging point on your carb return line to the tank to the bottom of the hull. Install the primer tee in this low point so it can use the volume of fuel in this low point for priming.

 

[Ernest Jones]

Excellent advice - thank you mikidymac!!

I figured all the primers were junk from the reviews but had not considered their impact on the rest of the system. I will isolate it. Or possibly see if I can transfer the choke plates (haven't seen the carbs yet so don't know).