Different Carburetors On Diffrent Years Of Superjets And Stock Superjet 650 Carburetor Pop Off/Jet Sizes

[SR-71]

I need some help, Im not so sure i can trust what my mechanic said?

I have a stock 1991 SJ650 that has just had a new set of reeds installed after one broke and went through the motor (I did all the work myself replacing the entire set of reeds/inspecting the motor and not the shop). Everything is still in excellent shape as we opened the crank case and saw no damage, and both cylinders tested with 155psi of compression, and saw no scratches when we borescoped the motor. Sadly we tore into the carburetor (which was our first guess to do as we couldn't get the ski to run or suck fuel through the lines) before we found it was a broken reed on the front cylinder, we had rebuilt the carburetor exactly as the manual shows, but we still had a enormous amount of trouble getting it to run right (particularly the pop off pressure). I then decided to take the carburetor to my mechanic as I have spent half my summer on this silly carburetor. He was telling me that the pop off pressure should be 55 psi stock, as and that I have the wrong carburetor for my year model. He said that the aluminium block that holds the clear plastic circles that act as check valves on the pump side was for another year of carburetor (a 1995) and I need one for a 1991. I'm pretty good with engines and when I Put the carb kit in myself everything (all the gaskets and diaphragms and pump parts in the new kit) fit and looked right so??? Plus The ski ran awesome before we jacked with the carburetor. It has a 120 for the pilot jet and a 115 for the high speed jet.

Are these the stock jets and pop off pressure for a 1991 superjet 650 and is there any difference besides the jets and dual carbs between different years of superjets?????

Thank you in advance to any one who can help me make sure I'm not getting told the wrong thing by a shop. ; )

 

[CHRISRACERX]

If you used a mikuni kit go back and check to see if you have the correct rubber gasket/diaphragm thingy over top the section where the little carb filter goes. They give you 2. The correct one will cover the oring that goes around. The other will show a mall amount of the oring near the filter. This will cause a pressure leak. Make sure your fuel screws have the oring, washer then spring. If the original spring wasn’t crusty I would reuse that one. The kits don’t give all the springs. So the nice bright shiny silver one might be the wrong one that may cause the pop off pressure to be off. If it ran good before it will again.

 

[SR-71]

Thanks, I went through the carburetor multiple time and eventually got it to run. It would just run extremely rich and not have very good performance. I tried all the springs and eventually just put the original spring back in, but I still had no luck getting it to run the way it did before. That is why I took the carburetor to be done by a local jet ski shop, but I'm not sure what he is saying is true about there being different carburetors for different years of superjets.

Dose anyone know if there any difference besides the jets and dual carbs between different years of superjets?????

 

[Cody Sampson]

Hi @CHRISRACERX are you refering to number 5 in the picture below (BLUE NUMBER 2)... are you saying if you put this in with the number 6 gasket you will get a pressure leak? I just rebuilt my carb and wasnt sure if I should have both 5 and 6 in or just 6... only 6 came out. I am having troubles tunning see my other thread here -- http://www.x-h2o.com/index.php?thre...ni-rebuild-kit-any-input.190173/#post-1985239

 

[mikidymac]

He is talking about 5 and 5a, depending on the carb the cutout in 5 and 5a is different.

 

[CHRISRACERX]

Yes I’m talking about 5 and 5a. That paper style gasket #6 you are referring too is for the 44mm carbs. SR-71 has a 38mm with his 91 SJ. The 38’s use the oring then the rubbery style gasket before the fuel pump body. To tell the difference of the 2 carbs easily-38’s have 3 bolt holes on top and 44’s have 4. But make sure you have the correct rubber style gasket for your carb

 

[SR-71]

I finally got to talk to mechanic today, he showed me the difference in the carbs. We found that a stock superjet 650 dose have a 44mm carburetor (it has 4 bolts on top, and in my manual it's a 44mm), but it had a fuel pump body from either a later year 44mm carb or a 38mm carb (it had a grove on the fuel pump for a oring but there isn't a grove on the carb itself for the other orings). It turns out the actual body of the later 44mm carburetors (1995 and up we think) the fuel pump body uses a series of orings to seal it, similar to how the 38mm carburetor does. Verses the older ones that don't have any orings. We figured this out because we finally found two different exploded views for both styles of the 44mm with orings and without(they look exactly the same from the outside the only difference is the seals/grooves for the orings in the pump). Also my mechanic had many 44mm carburetors (both look exactly identical from the outside) from different years and there are some years with orings and some without. So it turns out there is a difference in the carburetors. I'll try to get pictures of the diagrams to show it.

 

[CHRISRACERX]

There you go, I didn’t know that. I thought all the 650’s used 38mms. Guess all the singles on the wr3 n vxr’s had the 38’s. I thought the skis with the 760 n 1200 were the first with the 44’s. At least you found the issue. Got some knowledge myself too.

 

[SR-71]

Thanks for all the help. There isn't as much to work with as far as documentation specific specs for these early superjets. I hope this can help clear it up for others to, cause I know I was confused.

 

[High Speed Industries]

There you go, I didn’t know that. I thought all the 650’s used 38mms. Guess all the singles on the wr3 n vxr’s had the 38’s. I thought the skis with the 760 n 1200 were the first with the 44’s. At least you found the issue. Got some knowledge myself too.

All Yamaha 650/701 single carb engines come with a 44.