Carburated 951 high idle issue - 01 Sporter LE

[st0k3d]

Having some issues with my old 2001 Sporster LE. This boat has a two cylinder carburated 951 engine. It ran pretty good all last season although by the end it was taking a little while to start...

Fast forward to this season we go drop it in the water and are finding we are having high idle issues and the carbs are sticking. Get the boat back on shore, pull carbs, and find the throttle butterfly on the PTO carb a little bent, carb not opening smoothly, carbs are all corroded, adjusters not working.

We ended up buying brand new carbs and just installed with fresh gaskets. Installed fresh BR8ES plugs and gapped to .022. Replaced all the old grey fuel line with fresh line from west marine, new clamps on everything.

Set low speed adjuster on carbs to 1.5 turns out as per manual.

Boat starts immediately now on first crank, but the idle is high. 4000rpm plus out of the water, and it will rev to the limiter sometimes. This is with the idle adjuster all the way out, and the throttle plates are closed totally with the cable loosened

I am thinking bad fuel? Not enough fuel? (although the fuel filter was full) Or an air leak somewhere?

I checked for leaks, couldn't find any, the gaskets are fully seated and carbs are tight. Compression is 140psi + and even on both cylinders.

I am afraid I am going to damage it trying to troubleshoot it. I am also scared I didn't get the oil pump synched good.

Anyone in Long Island NY that can work on it for me? Willing to pay what it costs to fix.

 

[st0k3d]

Can anyone confirm the things that I colored in green are the oil pump alignment marks? I know the two on the right are but the one left...

 

[El Toro 33809]

When it revs like that, it sounds like an air leak to me. Double check that.

I believe the marks you asked about are the oil pump alignment marks.

 

[Sportster-2001-951C-Stock]

#10 oil pump in photo is the 951DI pump, it has three outlet ports above the lever and one inlet port at the bottom.

Yes, confirm alignment marks on the lever and pump body once again, after the final idle adjustment. The oil pump cable pulls the pump valve open, which delivers more oil, so it's important to set it correctly as the throttle opens more oil is delivered. I think my pump lever has the numeral #9 on it, not #10 as in the photo, mine is a carb 951 motor, 2001 I aligned those marks as per the service manual using a mirror and flash light to obtain visual access. The tighter the cable adjustment, the sooner the oil pump output volume is increased.

Make sure those carb mounting gaskets aren't misaligned, open throttle plates fully and look down through the throttle bore and see if gasket material is hanging into the bore. Also inspect the outside mounting flange for a protruding gasket.

The suggested factory low speed screw setting for my 2001 sportster LE 951 is 1.25 open, not 1.5, not sure where you got your spec from. 1.5 would just make the idle richer though, sounds like your idle is too lean, like an air leak.

Corrosion, eh? Is this a salt-water boat by chance? Ah, yeah, Long Island would be. Ordinarily, fogging prior to storage should keep that from happening.

Those new carbs, are they correctly calibrated? Those are are sold with all kinds of jets and whatnot depending on the intended application, the factory spec needle/seat for my 2001 is 2.0, spring is 95gram silver, pilot jet is 75, main jet is 162.5

That oil pump alignment is muy importante, make sure there's enough oil and the mosquitoes aren't getting short changed. Too much, and you're wasting expensive oil on them.

 

[st0k3d]

#10 oil pump in photo is the 951DI pump, it has three outlet ports above the lever and one inlet port at the bottom.

Yes, confirm alignment marks on the lever and pump body once again, after the final idle adjustment. The oil pump cable pulls the pump valve open, which delivers more oil, so it's important to set it correctly as the throttle opens more oil is delivered. I think my pump lever has the numeral #9 on it, not #10 as in the photo, mine is a carb 951 motor, 2001 I aligned those marks as per the service manual using a mirror and flash light to obtain visual access. The tighter the cable adjustment, the sooner the oil pump output volume is increased.

Make sure those carb mounting gaskets aren't misaligned, open throttle plates fully and look down through the throttle bore and see if gasket material is hanging into the bore. Also inspect the outside mounting flange for a protruding gasket.

The suggested factory low speed screw setting for my 2001 sportster LE 951 is 1.25 open, not 1.5, not sure where you got your spec from. 1.5 would just make the idle richer though, sounds like your idle is too lean, like an air leak.

Corrosion, eh? Is this a salt-water boat by chance? Ah, yeah, Long Island would be. Ordinarily, fogging prior to storage should keep that from happening.

Those new carbs, are they correctly calibrated? Those are are sold with all kinds of jets and whatnot depending on the intended application, the factory spec needle/seat for my 2001 is 2.0, spring is 95gram silver, pilot jet is 75, main jet is 162.5

That oil pump alignment is muy importante, make sure there's enough oil and the mosquitoes aren't getting short changed. Too much, and you're wasting expensive oil on them.

Where did you get your factory manual from? I have been referring to a 2000 manual as it seems a 2001 doesn't exist?

OK on oil pump.

Gasket is good on throttle body I checked that. My fear is it is the crank seal sucking air now, I can't find a leak anywhere else.

Where did you see something that says 1.25 turns? The 2000 manual I have says 1.5. Ill check that, however I doubt my problem will be solved with that, still good to know.

Salt water boat? Unfortunately yes. No fresh water around here, plenty of salt water though... I did fog it pretty good, but (fresh) water got into the boat over the winter which I don't think helped.

As per the jetting thing...

Here is where I got them from, as long as this data is correct than my low jet is a little bigger than it should be? 77.5 vs 75 (stock) which would just make it run slightly richer?

http://www.atlanticjetsport.com/index.php?l=product_detail&p=1089

 

[Sportster-2001-951C-Stock]

Hi,
The 2001 manual I've been using is for the jet ski, not the boat. Same engine though, and seems to match my sportster LE engine in every way except for the obvious ones.

2000 1.5 idle mixture spec is a bit richer than 2001 spec of 1.25, could be pop-off (metering needle/seat orifice 2.0 + spring 95gram) is not the same as 2001? Not a lot of difference between 1.25 and 1.5, mine were 1.25 from the factory and had never been adjusted as far as I could tell because as soon as I began turning them the factory paint popped off around them.

Mine originally had #75 pilot jets and it was too lean in the mid range, so I installed #80 jets to overcome the bogging problem. #77.5 might have been enough to address the issue, I'd rather have #77.5 than #75 for this engine, based on my experience. The one example in life where it's acceptable to be fat but not obese.

I'm wondering if before installing your carbs, you set the throttle plates correctly? Back off on the idle screw and confirm both butterfly's close simultaneously? If one butterfly is slightly opened that might cause high idle.

Trailer idle speed over about 3200 RPM seems to be the runaway kneepoint, idle on mine drops about 50% in the water.

Have you confirmed your fuel pump pulse connection to crankcase is leak tight? A leak thee could allow a lean condition in the PTO(rear) cylinder.

Make sure your choke linkage is working properly so if it runs away you can pull the choke to stop it. Over-revving could damage the bearings by excessive inertia forces to the bearing cages, especially if they're plastic(some motors used plastic cages, speed and heat can easly damage these, ours may even be cageless type but I don't know for sure b/c I haven't actually seen them).

You could always temporarily adjust your oil pump slightly to the rich side (a bit tighter on the cable) while working on the engine, just to make sure there's plenty of oil.

I rechecked the oil pump on mine yesterday, the lever is stamped "09" and has just one line on the lever. Also, the line area on the lever has no paint in a semicircle that matches perfectly with the circular marked land on the pump body.

Aside: My throttle cable position switch doesn't work, so the 12* dynamic advance doesn't come in at 80% throttle as it should, I'm going to replace my cable and see if my top RPM will reach 7000+ RPM instead of the current 6000 RPM. I'll report the results in my carburetor thread, hopefully next week.

Funny coincidence, I bought my boat from a guy on Long Island, it has blue interior. Not sure who he bought it from but he bough it used.

Any Q's, please post!

 

[st0k3d]

I'm wondering if before installing your carbs, you set the throttle plates correctly? Back off on the idle screw and confirm both butterfly's close simultaneously? If one butterfly is slightly opened that might cause high idle.

I assumed that Mikuni set them right as everything came assembled together with linkage. With the idle screw still backed out it still idles high. I am 99% sure they are closed all the way with a high idle still.

Have you confirmed your fuel pump pulse connection to crankcase is leak tight? A leak thee could allow a lean condition in the PTO(rear) cylinder.

I did all new lines on the carbs with new clamps. I def got them good and tight.

Make sure your choke linkage is working properly so if it runs away you can pull the choke to stop it. Over-revving could damage the bearings by excessive inertia forces to the bearing cages, especially if they're plastic(some motors used plastic cages, speed and heat can easly damage these, ours may even be cageless type but I don't know for sure b/c I haven't actually seen them).

Yea I think the reed block is plastic IIRC. Choke works good. As of now the motor turns off with the kill switch so not a true run-a-way.

You could always temporarily adjust your oil pump slightly to the rich side (a bit tighter on the cable) while working on the engine, just to make sure there's plenty of oil.

I have to get in there and do this again, I had the cable adjusted all the way tight and something still didn't seem right. I wonder if I need a new one... which brings me to your next thing.

Aside: My throttle cable position switch doesn't work, so the 12* dynamic advance doesn't come in at 80% throttle as it should, I'm going to replace my cable and see if my top RPM will reach 7000+ RPM instead of the current 6000 RPM. I'll report the results in my carburetor thread, hopefully next week.

I might be in the same situation here, I don't think I can get this thing to 7200rpm, I think it gets around 6000 max. What is the fix for this? a new throttle/oil pump cable assembly with that little box on it?


----------------------------

Thank you so much for the help. I am planning for the worst here (leaky crank seal). Than the choice is to just buy a new short block vs trying to fix this one.

 

[Sportster-2001-951C-Stock]

"I don't think I can get this thing to 7200rpm, I think it gets around 6000 max. What is the fix for this? a new throttle/oil pump cable assembly with that little box on it?"

I believe that's the problem in my case, I verified yesterday the MPEM isn't receiving any signal from the hall effect sensor in the little box mounted on the throttle cable which just happens to be in the bottom of the bilge. This signal from the box is supposed to switch on at around 80% throttle and stay on to 100% throttle, the MPEM advances the ignition timing "up to 12*BTDC" when this signal from the throttle cable appears on pin 17 of connector #2 of the MPEM. I checked for this signal and it wasn't there, so I'm assuming a good portion of my missing 1000RPM is a result of a lack of ignition advance.

Engine bearings and over-revving:

Earlier I was referring to the possibility of plastic bearing cages being used on the internal engine bearings. Bearing cage materials need to be lightweight and some of the Rotax engines did use plastic cages. The problem with plastic cages is they are somewhat fragile and can be damaged (Suzuki also used this design many years ago, and over 11,000RPM they would shatter), heat can damage them, and some have even asked if 2-stroke oil chemistry may have some negative impact (in the case an incompatible oil additive package was used).

I don't know if the 2001 951 uses caged or non-caged type bearing(non-caged type is most robust), since I haven't torn one apart yet but if plastic type bearing cages were used, damage could result from over-revving. Thus, avoid over-revving in the absence of knowing if this engine uses plastic type bearing cages. An engine with broken bearing cages will not last long before grenading. 7200 RPM is well within the design limits but the governor isn't capable of regulating engine speed in the case of runaway could rev to ?????.?? and you might not know how high is high b/c the tachometer cannot read past the governor limit speed?

ie: Arrest runaway immediately, IMO.

 

[Sportster-2001-951C-Stock]

Hi,
I've been thinking about this still and realized that on my engine I haven't but plan to replace the two Tygon oil lines which run from the oil pump to the nipples on the bottom of the intake manifold. If one of these lines rots and breaks off, not only will the oil to that cylinder be interrupted and quickly lead to engine damage, but you will also experience an air leak.

Not sure if you've already contemplated this but it's worth considering, I think.

12 years is a long time and they're getting pretty old so I will probably be replacing mine soon, perhaps this weekend. I may have the tubing already from another project so I'll be looking at this.

 

[st0k3d]

Hi,
I've been thinking about this still and realized that on my engine I haven't but plan to replace the two Tygon oil lines which run from the oil pump to the nipples on the bottom of the intake manifold. If one of these lines rots and breaks off, not only will the oil to that cylinder be interrupted and quickly lead to engine damage, but you will also experience an air leak.

Not sure if you've already contemplated this but it's worth considering, I think.

12 years is a long time and they're getting pretty old so I will probably be replacing mine soon, perhaps this weekend. I may have the tubing already from another project so I'll be looking at this.

That is really thinking out of the box, I like it. While the carb's were off I did take a note at them and they seemed old, but still OK. However it is definitely worth a second look, and a semi-easy job (with carbs off). I thought about doing them, but opted out because I was afraid they wouldn't prime again?

 

[Sportster-2001-951C-Stock]

"I was afraid they wouldn't prime again?"

I'm thinking worse case, the two lines would just take a brief time to refill and it's probably easy to watch for air being displaced by the oil through the translucent tubing. Should work fine as long as the oil pump still has oil inside and not cavitating air. Regardless, it's perhaps a valid concern that I intend on addressing by fogging the motor before the restart. In fact, I shoot oil in my carbs all the time, just before blowing water out of the exhaust after removing from the water I squirt a couple shots of oil in both carbs so it's kind of a second nature phenomenon I guess. I've got a squeeze bottle for this purpose, sitting in my bilge.

 

[Sportster-2001-951C-Stock]

"The suggested factory low speed screw setting for my 2001 sportster LE 951 is 1.25 open, not 1.5"

Well, I was looking through my manual and guess what, the spec is 1.5, not 1.25! Sorry about that, my bad. I don't usually make mistakes like that, not sure what happened on that one.