2001 sportster 5900rpm max

[Sportster-2001-951C-Stock]

See this thread, post 454:

http://www.seadooforum.com/showthread.php?66994-2001-Seadoo-Sportster-LE-Just-got-it!/page19

This throttle cable in this photo is incorrectly attached to the MAG carb bell crank so the throttle cable cannot fully open the throttle:

 

[shuka]

Tested tps switch with power on key in enigine not running. Total volts 5 the whole time during trottle movement is this correct? Or does engine need to be running?

 

[Sportster-2001-951C-Stock]

Tested tps switch with power on key in enigine not running. Total volts 5 the whole time during trottle movement is this correct? Or does engine need to be running?

Key on engine off is how I made my TPS measurements, 12v source and ground to the IC is all you need to test it's output function (5v MPEM voltage pulled low by TPS is TPS on signal). So of course you only have a short time to accomplish the measurement before the MPEM shuts off 12v again.

Maybe your hall effect switch is actually good but you have a cable adjustment issue, it's possible I suppose if someone's been changing/modifying things from the factory configuration.

Anyway, looks like I was about 1000 RPM shy of where I thought I should be, see post #6 in this thread:

http://www.seadooforum.com/showthread.php?63048-Carb-Teardown-Found-Water-in-FP-Diaphgram

Repairing the TPS switch got me another 500 RPM and if I recall quite a bit more speed and acceleration both. The RAVES were hanging up by this time as well so once they were cleaned again I was finally making 50 MPH on the dream-o-meter(r) as others had reported. The water has to be rather smooth though and wind must be slight, to reach 50 MPH.

 

[shuka]

Will 1000 rpm give any more horsepower or is that all speed. Because if i dont get any horsepower from 5900 to 6900 than i dont care. My top speed is 42 now and thats fine im lookin for the horsepower that 1000 rpm would give me.

 

[Bonmotwang]

Will 1000 rpm give any more horsepower or is that all speed. Because if i dont get any horsepower from 5900 to 6900 than i dont care. My top speed is 42 now and thats fine im lookin for the horsepower that 1000 rpm would give me.

I am already happy with 30 with my family on the boat!

 

[Sportster-2001-951C-Stock]

Will 1000 rpm give any more horsepower or is that all speed. Because if i dont get any horsepower from 5900 to 6900 than i dont care. My top speed is 42 now and thats fine im lookin for the horsepower that 1000 rpm would give me.

I can understand. My pure guess is you are leaving around 20~25hp on the table if the TPS advance isn't working. Remember, the TPS doesn't have any effect under 80% throttle and I rarely run above 80% throttle, mainly just during acceleration I use WOT for short periods but cruise is comfortable around 5000RPM, which is about 50% throttle I would estimate and there is no TPS ignition advance in this throttle range. So this function will be used maybe less than 2% of running time in my case.

I wanted to ski slalom behind my boat though, so I needed this burst of power.

TPS switch simulation idea: If you want to try the ignition advance feature you can temporarily wire a switch to ground this 5v from the MPEM terminal pin but it will be dangerous to ground this under 80% throttle position, it will probably cause detonation to occur in that case and might roast the pistons due to too much ignition advance at part throttle under 80%. If you try this then first go to WOT and THEN ground the pin and you can see the difference then decide if you want to repair the TPS switch. DON'T go under 80% throttle unless you FIRST unground the pin though, detonation from too much ignition advance will quickly damage the engine.

You should notice a big difference, but it will not cause any damage if you decide not to use the TPS ignition advance feature, in fact I guess your engine will see less stress in that case.

 

[shuka]

So you are saying i should change the trottle cable so the switch is change because its attached to it?

 

[Sportster-2001-951C-Stock]

So you are saying i should change the trottle cable so the switch is change because its attached to it?

I experienced this problem with mine, the TPS switch was not working to pull low the 5v and provide the ignition advance signal to the MPEM. My solution was not cable adjustment b/c the switch was broken, so I replaced the rear section of the cable to resolve the problem and now it works correctly.

I cannot say in your case why the TPS signal is not reaching your MPEM, I guess either the TPS switch is broken or the cable is misadjusted.

If in your case the switch is broken, it is possible to disassemble the switch and replace the SS41 hall effect IC but this is the more tedious less expensive solution. For this hall effect device, Pin 1 is 12v supply, pin 2 is ground, and pin 3 is signal output to MPEM

Here is the IC from an ebay seller and I attached the data sheet as well. This same sensor is also used in the speedometer pickup along with a 5.6v 1/2 watt zener diode, I can supply a drawing of that circuit if you need to repair your speedo sensor.

http://www.ebay.com/itm/5pcs-Bipola...226?pt=LH_DefaultDomain_0&hash=item43aaa3998a

 

[shuka]

I had boat out for weekend and messed with the trottle cable. Had wife drive at full throttle and i leaned in and tried see if the carb would advance any more and it would not. So is there a adjustment on carb to advance throttle more.

 

[Sportster-2001-951C-Stock]

With engine off, if you place the throttle in WOT position and look down into the carb throat you should see the throttle butterfly is parallel with the carb throat. If yes, this is the normal position of WOT, the butterflies are allowing maximum air+fuel.

Do not mistake the choke butterflies for the throttle butterflies, the choke butterflies are at the mouth of the carb where air first enters and the throttle butterflies are at the opposite end of the carb, downstream of the large fuel venturi that looks similar to a rifle sight.

BTW, I would advise against operating your engine with the airbox removed if possible, the fuel mixture may be too lean in that case.

 

[shuka]

Thanks i will check to see if thats the case. I did not know that about the air box thanks i will do that again

 

[shuka]

Changed throtte cable and still no higher rpm 5900 max. There has to something stupid im not seeing. I thought i read something about under 6000 rpm it this or over 6000 its that. I cannot find that post again but it was saying that 6200,6300 rpm max was something different than 5800, 5900 max rpm. Any ideas?

 

[Sportster-2001-951C-Stock]

I thought you weren't getting the 5v pulled low signal by your throttle cable? Is that working now?

The other two possibilities are the RAVES aren't moving up or the waterbox valve isn't cutting back cone pipe water injection.

There's a pneumatic check valve connection at the PTO crankcase near where the carb pulse line is connected, if the tubing there is cracked or broken there will be no pressure to operate the RAVE valves. Sometimes that check valve can get plugged with gum too, so you could try forcing air into and out of it to test and make sure it's working.

The waterbox valve may have some debris like sand caught in the spindle that moves up and down with the bellows restricting the bellows from moving upward when waterbox exhaust back-pressure increases.

I honestly don't remember for sure when my RAVES open but seems to me the kick from that was around 5200 RPM. Without the RAVE event you certainly won't reach full power either. This happens when the MPEM energizes the solenoid to allow check valved crankcase pressure to reach the RAVE bellows.

 

[shuka]

How do i force air into the water box valve? And thanks for dealing with this, my wife says im crazy the boat runs great so leave it alone but i cant i knowing 5900 is not the top rpms so it just bothers me.

 

[Sportster-2001-951C-Stock]

How do i force air into the water box valve? And thanks for dealing with this, my wife says im crazy the boat runs great so leave it alone but i cant i knowing 5900 is not the top rpms so it just bothers me.

Yeah I know, it bugs me when my stuff isn't working quite right too, I noticed my RAVES seem to be sticking and I'm ready to run out there and clean them, LOL....

What I meant was your RAVES rely on pressure from the PTO crankcase and to test the check valve function you can disconnect the air line that goes into the RAVE solenoid and the other end that comes from the PTO crankcase, inspect the tubing for cracks and test that air only moves in one direction through the check valve, towards the RAVE solenoid.

As far as the waterbox valve goes, if you disconnect the two water lines and unscrew it from the waterbox (it shouldn't be super tight on water box, just hand tight enuff it stops when threading in) and make sure the pintle valve stem inside moves up and down, and remove the cap to make sure the bellows inside isn't roen or something, if the bellows is tor it will leak and drip water down the side of the waterbox. But if there's some sand of trash inside the valve stem and the bellows can't move the stem upward then you could have too much water injected into your expansion cone pipe, too much water injection would screw up the exhaust tuning and slow you down.

Speaking of exhaust, some guys have found the short rubber hose that connects the cone pipe to the water box can delaminate inside and partially plug the exhaust system, that kind of failure isn't easy to find when it happens.

 

[shuka]

test that air only moves in one direction through the check valve, towards the RAVE solenoid. How do i check the direction the air moves? My waterbox valve threads were stripped and was leaking so i used sealer to stop the leak and it worked no more leak can this still be a problem. Here is a pic of the valve

 

[Bonmotwang]

How do i force air into the water box valve? And thanks for dealing with this, my wife says im crazy the boat runs great so leave it alone but i cant i knowing 5900 is not the top rpms so it just bothers me.

LOL. I will be in the same boat when my wife realized that I am replacing the whole engine and the bill is $1500++.
Plus my boat is running 6500RPM like a happy bird.

Sent from my iPad using Tapatalk

 

[Sportster-2001-951C-Stock]

test that air only moves in one direction through the check valve, towards the RAVE solenoid. How do i check the direction the air moves? My waterbox valve threads were stripped and was leaking so i used sealer to stop the leak and it worked no more leak can this still be a problem. Here is a pic of the valve

If some sealer entered the waterbox valve while you were installing it then it could interfere with it's operation. Maybe if the plastic threaded portion is in bad condition you can replace the valve with a used one from ebay.

For testing the check valve in the RAVE air supply, there's no need if you already verified for sure the RAVES actually move open when the solenoid provides pressure. Many times though, the tubing can crack or come off so follow the line from the RAVE solenoid back to under the PTO carb.

The RAVE air pressure check valve is located about 2~3 inches from the PTO crankcase nipple near where the carb pulse line connects. If you can blow in the crankcase end and push air through it towards the RAVE solenoid but cannot push air the other direction then it's working. Also, make sure there's no leaks in the tubing otherwise the RAVES may not receive the air pressure required to lift them upward.

The check valve is item #26 in this drawing, confirm all of the RAVE tubing is connected and in good condition:

http://partsfinder.onlinemicrofiche...e=seadoojb&a=146&b=6&c=0&d=-AIR-INTAKE-SYSTEM

 

[shuka]

What is the life span of the 951 engine or how long will my engine last? Can it last a long time if i take care of it?

 

[Sportster-2001-951C-Stock]

It's generally known to run about 250 hours in a ski but I think many people push the 951 skis b/c of the power.

I don't know how many hours are on my 951 but one way to know the condition is to measure compression. From the factory, the 2001 951 blew 130psi, based on my understanding. Mine blows 122psi now so I suppose it's got some wear. My opinion is anything under 120psi should at least get a new top end b/c once the compression drops off then it won't be long until bits of aluminum start coming off the pistons.

Also, if your compression is low you should take a look at your piston skirts to see if they're scored and worn looking. A great opportunity to do this is while cleaning the RAVE valves. If you see scoring and the compression is low then rather than wait till after it grenades and destroys the case you could install a top end or send it off for reman.

Fortunately these motors are rather inexpensive when it comes to marine engines but since they're out of production there'll be fewer parts available for them in coming years so get your spares while and when you can.

 

[shuka]

Where do you look for scoring with raves off? Or how?

 

[Sportster-2001-951C-Stock]

When you remove the raves you can look down into the rave slot to inspect the piston skirt while rotating the crankshaft. This gives you the opportunity to see a portion of the piston skirt in various places and scoring indicates pending problems.

Also a compression test should be done on a regular basis to monitor the cylinder condition b/c increased combustion gas blow-by past the rings will damage the piston and a kind of snowball effect begins to take place where wear increases at a much faster rate.

It's not uncommon in 2-strokes, it's expected the engine will need to be rebuilt due to piston wear in these high performance engines. The key to catch it before mechanical failure occurs and avoid case damage.

 

[shuka]

How do i turn crankshaft or where do i do it from?

 

[shuka]

Also whats the best way to check compression

 

[Sportster-2001-951C-Stock]

There's a large round disk at the aft end of the engine, normally under a plastic cover held on my two plastic wingnuts. This is the output shaft of the engine and you can roll the motor over by hand (after removing spark plugs) by turning this disk (it's called the PTO (Power Take Off)).

Compression test:

Obtain a compression tester (Harbor freight is usually acceptable) and it comes with instructions but basically:
Remove all spark plugs
Turn off fuel source (for safety)
Position throttle to wide open full throttle
Place spark plug wires onto the grounding posts (these are on the rear plastic e-box of 951)
Connect the gauge hose using the same length attachment as spark plug threads.
Connect gauge head to gauge hose.
Crank the motor using the electric starter. A few seconds is usually long enough but watch to see when gauge is no longer moving upward. This is your compression pressure.

A healthy 951 carbed engine such as yours will blow around 130psi