Correct spring for 657x carbs

[Cheflen]

So I’m rebuilding the carbs on my 657x right now with a genuine Mikuni kit that a bought last year for something else, the previous owner removed the OEM springs when they tried rebuilding it with a knock off kit. The pop off I tested was way up in the 40s, and I know the 657x is supposed to be between 16-21psi. Does anyone know which spring is the correct one? Also I lost the springs somehow on the kit I bought so is there any way I can just get the springs somewhere? Thanks in advance.

 

[Cheflen]

Well I found the answer to my own question, luckily I was able to use the springs from my “parts carbs” and they worked out great, got the pop off to 20psi for both carbs with just dropping them in. And the parts carbs were the other ones that just came from my boat, I pulled them out and opened them up to find this
this is why I always go through the carbs on everything before even thinking about putting it in the water. Who the heck would even try and run it like this?!? You might not be able to see but there isn’t even any jets in there.

 

[mikidymac]

Well I found the answer to my own question, luckily I was able to use the springs from my “parts carbs” and they worked out great, got the pop off to 20psi for both carbs with just dropping them in. And the parts carbs were the other ones that just came from my boat, I pulled them out and opened them up to find thisView attachment 46480
this is why I always go through the carbs on everything before even thinking about putting it in the water. Who the heck would even try and run it like this?!? You might not be able to see but there isn’t even any jets in there.

I'm sure it's fine, more fuel = more power, LOL.

 

[etemplet]

Hmmmmm.....What year is your ski? I just looked on the SeeaDoo PWC Carb reference site and I'm seeing 22-37 pop off on a 1995 SPX (dual carb set up) I am presently rebuilding the 657X so I'll be going through the whole ski. I'll download the Manual and verify the pop-off for sure. Measure twice, cut once.

 

[Cheflen]

Hmmmmm.....What year is your ski? I just looked on the SeeaDoo PWC Carb reference site and I'm seeing 22-37 pop off on a 1995 SPX (dual carb set up) I am presently rebuilding the 657X so I'll be going through the whole ski. I'll download the Manual and verify the pop-off for sure. Measure twice, cut once.

It’s actually off a 1994 speedster, I use seadoosource to get all of my carb specs and they don’t have the speedster on there, so the closest thing I went to was the 94 Xp with the 657x and that one said to go with 16-21psi, I also ordered the 1.5 needle and seat, hopefully that is right too. I see the spec is different for the 95 spx so 22-37 is correct for that, I’m hopi g 16-21 is correct for me, maybe they just decided to up the pop off the next year. I would have posted this in the sport boat forum but I never get any replies when I post there so that’s why I just specifically said 657x

 

[etemplet]

I was just curious. I think you're on the right track with it. Good luck man !!

 

[AKnarrowback]

Just two cents.

When I went through my 94 xp with the 657x I fought low end performance. After getting the rv cover milled to spec and swapping the impeller for a lower pitch I ended up raising the pop off closer to 30 psi and noticed a significant low end performance gain.

To do this I ended up using some springs from a non Mikuni kit. Normally I would never do that, but I was trying to dial it in and that was the only way to get the pressure that gave me the best performance.

I did study the seadoo source page, mikuni book and charts and came to the same conclucion you did. On the 94 xp they had a low pop off pressure and bumped it up the next year. They just ran to rich on the low end and were a slug compared to what they are capable of with a simple carb tweak.

 

[Cheflen]

Just two cents.

When I went through my 94 xp with the 657x I fought low end performance. After getting the rv cover milled to spec and swapping the impeller for a lower pitch I ended up raising the pop off closer to 30 psi and noticed a significant low end performance gain.

To do this I ended up using some springs from a non Mikuni kit. Normally I would never do that, but I was trying to dial it in and that was the only way to get the pressure that gave me the best performance.

I did study the seadoo source page, mikuni book and charts and came to the same conclucion you did. On the 94 xp they had a low pop off pressure and bumped it up the next year. They just ran to rich on the low end and were a slug compared to what they are capable of with a simple carb tweak.

That makes a ton of sense, and I’m pissed I just read this after spending a couple hours assembling all 4 carbs, installing all of them, and putting together the rest of the exhaust and oil lines lol. Luckily my pop off was all the way at the top with 21psi, hopefully that will give me a pretty good performance, I have probably another month before I’ll be able to get this into the water but I’m pretty excited for it, after doing work on a ton of these things I’ve got it all figured out to make sure it’s all dialed in.

 

[Madpaddler]

AK is correct. I also have the 94XP and the manual is wrong/misprinted/something.. Use the black 80 gram springs with 1.5 needles and seats. Your popoff will be closer to 28-34psi and it'll run great.