Super Jet 701 Burndown signs...?

[JGringo]

Hey All,

I literally just bought a 90' SN Superjet with a stock 701 engine in it. It has a single carb and was running great all of Labor Day weekend...

Well... I went out with a buddy today and rode for maybe 20 minutes. Then it started getting really doggy and wouldn't open up the top end unless I jumped out of the water and held the throttle wide open. I blipped my way back to shore and put the ski on the trailer.

******

The plugs are now a whiter burned color from the previous tan color I had them running during the previous weekend.

There is no spotty water-like foam appearing, so I know I didn't drown my engine with water. HOWEVER, I did switch the fuel to 32:1 from what was previously run (45:1). The fuel filter is original I believe and the idiot who previously owned the ski bypassed the fuel selector and ran the boat straight off of the "reserve" outlet.

I feel like the fuel filter may be clogged, or the carb may be clogged...


I plan on pulling the head to look for excessive ring-wear, re-doing the carbs, re-routing the fuel lines correctly, and replacing the fuel filter.

The real question is, Is there anything I should be extremely cautious of??

 

[JGringo]

picture.

 

[D-Roc]

by going to 32:1 ratio you have in fact leaned out your fuel to air mixture. probably not enough to blow your motor but everything is possible. What kind of riding do you do? WOT? if you do extended periods of WOT and have a lean mixture the exhaust gasses are hot enough to remove the insulating coat on the pistons and melt down the top of piston on the exhaust side until yo0u hit the rings and loose nearly all compression. What is your compression at now?

 

[JGringo]

160 before this event. I haven't checked it since it bogged out because I was afraid of doing more damage than good. I had planned on pulling the head anyways...

For the most part, I do a lot of low-end riding like screwing around in a smaller area jumping waves and doing hood tricks.

 

[JGringo]

By the way, you don't happen to go to MTU in the U.P. of Michigan, do you?

 

[Matt_E]

Check compression.

 

[D-Roc]

is that code for some sort of school? lol, no i just have that kinda face that everyone thinks they know me. i would do a comp check before you pop the head because you should find leaks and problems before you crack a motor so you can recheck once its back together. this will ensure that you have fixed the problem. you will for sure need a new head gasket if you pop it open.

 

[JGringo]

150/148. Good Compression and I can smell fuel. I am gonna rebuild the carb and replace all the fuel lines and filters.

 

[D-Roc]

thats where it should be with a stock head so if it was my motor i would assume for now the motor is still good and check out the carbs. Are you running the same oil as the P.O. did? how is your piston wash?

 

[kevbo]

Look for water and debris in the tank, filter, and carb. Also make sure to check the carbs internal filter basket. It is difficult to hurt a stock compression/pipe 701 unless very poor gas was used.

 

[D-Roc]

hehe did you forget to put the gas cap on?

 

[Matt_E]

Amazing how much that makes it run like poop.
A couple of weeks ago I had a very very small hole in the bottom of my tank. The ski ran awful.

 

[JGringo]

lol I did remember to close the gas tank top. I know the previous owner ran 45:1, so I am an idiot and put 32:1 because that is what my buddy runs (which apparently is ALSO incorrect for an SXI Pro with a Factory Pipe).

Piston wash... you mean like the tops of the pistons? They seemed normal, slight carbon build-up (which is usually a sign of proper cooling). Good to know that it is difficult to wreck one of these things.

I did put fresh 93 octane with 32:1 Synthetic oil (same type of oil as previous owner) though. I have a feeling that it is a clogged fuel line, fuel filter, and/or carb. Definitely going to take the extra time and money to completely rebuild and re-run the lines.

 

[D-Roc]

someone was just telling me about that with an external fuel fill and the ski did not run at all after enough water got mixed in, haha. that there could be his problem, bad external seal or cap letting water in? i also though of a bad pulse line but not sure it would even idle if it was bad.

 

[JGringo]

I will check it all. The only thing that makes me think twice is the fact that it ran great for a solid 2-3 hours of riding, and then all of a sudden would run lean up top.

It screams (to me at least) clogged fuel filter.

 

[icecoled007]

When you switched from 45:1 to 32:1 you leaned out the fuel air ratio as said before. This should be your only problem. If you were tan/white before this will push you over to white. Put and run 40:1 from now on, 32:1 is too rich for your ski. 16 oz to 5 Gal of gas. Richen you screws out a bit and ride.

I wouldn't tear apart the motor, it should be fine. This winter invest in two Mikuni rebuild kits. I recommend genuine Mikuni not 3rd party and rebuild the carbs.

Once that is complete report back on how she runs.

 

[icecoled007]

Its really hard to read plugs on these skis. All your reading is the last minute of it running

If it gargles and loads up its too rich. If it hesitates and cuts out its too lean. Remember you need to watch both your low and high needles. If its just an OEM motor turn the screws to oem specs and it should run great

 

[icecoled007]

Also note that if you adjust your idle (turning your idle screw up (idle speed down)) will lean your ski out too.

 

[JGringo]

Thanks 007! I am gonna just rebuild the carb right away and do as you said (turn to stock specs).

Thanks for all the help!