Super Jet Troubleshooting Superjet - 1995 701

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papabrad1

Location
Michigan
Recently picked up a 1995 Superjet (701) with a bogging issue. When riding it seems to only have 50% of its power and wont rev up fast.

I rebuilt the carb but it didn't seem to change anything. I'm new to these but I did notice a line from the fuel tank going nowhere. Would this cause a lack of gas getting to the carb? I'm assuming its a pressurized system.

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hink320

hink320

Location
sask, canada
papabrad1 said:
Recently picked up a 1995 Superjet (701) with a bogging issue. When riding it seems to only have 50% of its power and wont rev up fast.

I rebuilt the carb but it didn't seem to change anything. I'm new to these but I did notice a line from the fuel tank going nowhere. Would this cause a lack of gas getting to the carb? I'm assuming its a pressurized system.
Click to expand...

That line is supposed to have a vent valve in there. It's a one way valve that allows air in, you wouldn't have any pressure in your fuel tank without that vent valve.
 
Barbieri972

Barbieri972

CB/T2 Speed Shop
Location
Ukiah, California
I have a 650 that runs the same way and I think it's cause of the vent as well, try putting the valve on there, if that doesn't help I might have more advice but try that
 
Tyler Zane

Tyler Zane

Open Your Eyes
Location
Panama City Beach, FL
That valve isn't the issue although it should be fixed. The valves purpose isn't exactly explained in the manual, but I believe it to be for emissions. Its not to pressurize the tank although that is a result of having it. The fuel pump doesn't rely on a pressurized tank, otherwise it wouldn't run right until pressurized. Plus the fuel pump is strong enough to suck the tank in if the valve is stuck.

The only time i have had a fuel tank check valve be an issue is when it wouldn't let air in tank because it wouldn't flow either way. In that case the ski will fun fine for a few minutes and then just flat out die from fuel starvation. In that case I ripped the valve out and ran the ski all week without one.

I'd start with the basics, check compression and check spark over a 7/16" gap.
 
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papabrad1

Location
Michigan
I'll add a valve today and check compression. I never rode a Superjet before so I don't really know how fast it should feel but it doesn't seem much faster than my js550.

Is top speed around 45? I guess I can use my GPS and test to see if it achieves that to guess if its hitting peak RPM.
 
rowsto

rowsto

Location
Australia! North qld
tzane said:
That valve isn't the issue although it should be fixed. The valves purpose isn't exactly explained in the manual, but I believe it to be for emissions. Its not to pressurize the tank although that is a result of having it. The fuel pump doesn't rely on a pressurized tank, otherwise it wouldn't run right until pressurized. Plus the fuel pump is strong enough to suck the tank in if the valve is stuck.

The only time i have had a fuel tank check valve be an issue is when it wouldn't let air in tank because it wouldn't flow either way. In that case the ski will fun fine for a few minutes and then just flat out die from fuel starvation. In that case I ripped the valve out and ran the ski all week without one.

I'd start with the basics, check compression and check spark over a 7/16" gap.
Click to expand...


^^ correct, it's just a valve to let air in as fuel is taken out but not to let fuel leak out if the ski is upside down or if you have a full tank and doing some spirited riding. Running your ski without one will not effect performance
 
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papabrad1

Location
Michigan
Did a once over on the the carb again and added a valve. Compression is around ~130 on my gauge. I wanna try a different one though cause I'm skeptical how good this cheap-o is.

From idle to WOT in the water should I expect the ski to shoot outta the water? I'm not to familiar with how much power a single carb 701 should have. Seems to be running good now.
 
Roseand

Roseand

The Weaponizer
Site Supporter
Location
Wisconsin
papabrad1 said:
Did a once over on the the carb again and added a valve. Compression is around ~130 on my gauge. I wanna try a different one though cause I'm skeptical how good this cheap-o is.

From idle to WOT in the water should I expect the ski to shoot outta the water? I'm not to familiar with how much power a single carb 701 should have. Seems to be running good now.
Click to expand...
With stock exhaust and compression, no. It's not gonna shoot right out of the water.

Sent from my SM-G920V using Tapatalk
 
rowsto

rowsto

Location
Australia! North qld
Roseand said:
With stock exhaust and compression, no. It's not gonna shoot right out of the water.

Sent from my SM-G920V using Tapatalk
Click to expand...

Yes it will. Theres a number of things that could be causing the lack of power. From memory stock compression should be around 150, reeds could be worn, prop could be worn, filters could be blocked etc
 
Roseand

Roseand

The Weaponizer
Site Supporter
Location
Wisconsin
rowsto said:
Yes it will. Theres a number of things that could be causing the lack of power. From memory stock compression should be around 150, reeds could be worn, prop could be worn, filters could be blocked etc
Click to expand...

A heavy waterlogged stock motor 61x square nose isn't going to get airborne grabbing the throttle from idle to WOT(especially with no pipe or good prop and some decent compression) .

Sent from my SM-G920V using Tapatalk
 
P

papabrad1

Location
Michigan
I noticed my plugs getting pretty black and wet even with the carb adjusters pretty far in. I replaced the spark plug boots and cut back the wire a 1/4 of an inch.

Much faster : )

I pulled the plugs again after a good 15 mins of riding at (75% - WOT) and they were dry and white/clean. Should I increase the adjuster a tad more? I'm looking for dry brown right?
 
Roseand

Roseand

The Weaponizer
Site Supporter
Location
Wisconsin
White and clean means you may need to do more than touch your top screws. Yes, you can use a tach to tune. However, i know many, including engine builders who don't use a tach unless for absolute fine tuning. For a lot of WOT it's a very good idea to do me check everything with a tach though.

Basically it's just called power tuning your main jet.. You want a main jet that's big enough that when the screw is turned out so and so turns, it's too rich for it to rev all the way clean. This is what they call "4 cycling" due to how it sounds. It's best to do this either strapped to a trailer or with nose against something real firm. If it's real secure you can easily hook up a tach to get it perfectly dialed in. You want to find peak RPM, and then I believe you want to be 50 RPM rich of peak so you wont blow it up.




Sent from my SM-G920V using Tapatalk
 
rowsto

rowsto

Location
Australia! North qld
papabrad1 said:
I noticed my plugs getting pretty black and wet even with the carb adjusters pretty far in. I replaced the spark plug boots and cut back the wire a 1/4 of an inch.

Much faster : )

I pulled the plugs again after a good 15 mins of riding at (75% - WOT) and they were dry and white/clean. Should I increase the adjuster a tad more? I'm looking for dry brown right?
Click to expand...


Yes brown is ideal. No need to complicate the tuning process, if youre happy with your off idle acceleration open your top. If you keep opening your top and find its still getting better its time for a bigger jet. Theres a good guide on the factory pipe website on how to do it properly, if youre serious about tuning it properly read that and listen to the professionals. Do as Tzane said, tune under normal operating conditions
 
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