Help Needed With 96XP!!

[Hicktown]

Hey guys, well after a few good reliable seasons since rebuilding the engine on my 96XP about 3 years ago, she's been giving me all kinds of fits and problems this year. The problems came to a head last week when she left me stranded on the opposite side of my lake and had to get towed back. A little background: about a month ago I was having a different problem where it would die out at times under acceleration, BUT it would always restart, seemed to otherwise start and run fine, and never left me stranded. During that time I rebuilt the carbs thinking that would solve the issue. It did not. I ended up replacing the neg battery cable and that fixed that problem. I noticed when I put the rebuilt carbs back in, the motor would start easily when cold. But when hot it was sometimes a lot more hard to start. Sometimes I would have to hold the throttle wide open for 10+ seconds when restarting. She would start up but barely idle with the throttle wide open for sometimes 10-15 seconds, which I'd never experienced before this carb rebuild. Thought it was strange but the ski otherwise ran great, and sometimes it would start quick when warm. It seemed the longer I would let it sit after shut off, the harder it would get to re-start. This is all just background info to what happened last weekend, riding the ski hard and fast when it randomly just died out and would not restart. A couple times I managed to restart it and would do the same thing I described before: hold throttle wide open while the ski would BARELY stay alive and idle. Again this is holding the throttle wide open and it would barely idle. Eventually wouldn't re-start at all and had to get towed back.

Now the ski will start but won't run in the water for very long without dying. Seems to run on the lift while giving throttle, but won't idle for a long time at all. Compression is good. Changed plugs, verified good battery connection, cut plug wires, etc. One thing I noticed is that I have a see-through Fram fuel filter before the carbs, and there doesn't seem to be a large amount of fuel sitting in there. Of course that's just me and I can't say for sure if that's normal or not. I honestly have no idea where to look now. All the gray fuel lines have been replaced years prior. As I said compression is good. Fuel filter is brand new, and water filter was cleaned out. Fuel selector is bypassed. Any ideas???

 

[mikidymac]

I don't like the additional fram filters as they can plug with water and just plain restrict flow.

However I suspect a leaking needle and seat. Check the carbs for pop off and leak down.

 

[Hicktown]

I don't like the additional fram filters as they can plug with water and just plain restrict flow.

However I suspect a leaking needle and seat. Check the carbs for pop off and leak down.

Thanks, yeah I'm suspecting something with the carbs as well. The guy I took them to has rebuilt them for me in the past and says he uses mikuni rebuild kits, but maybe he messed up the needle and seat. Would that cause the ski to die out at a high speed however?

And yeah I am going to get rid of the fram filter. What's a good way to do that without putting in a whole new fuel line?

 

[Hicktown]

Anyone else?

 

[mikidymac]

There isn't one. Just buy a couple feet of standard 1/4" black automotive fuel hose from the local auto parts store.

 

[Mickirig1]

Do a pull and twist test on all the fuel line connections. Make sure no nipples are broken or cracked. Jumping wakes and waves can cause changes in the sealing ability of the connections. Consider bypassing the fuel selector and under hatch filter/ water separator from the system. They both can leak air into the system. It is so much easier to suck air then fuel. Pull the choke out when it will not start. This increases the fuel flow to carb. Read the sticky above the forum on carbs. Consider opening the gas cap when it acts up. The vents may not be working. You should replace them after so many years. The Ski has any years on it, the vents may be original equipment.

 

[Cliff787]

Ditch the fuel filter as it restricts fuel flow to the carbs under load( i.e. Starting the motor and running the ski in the water from zero to WOT) and isn't needed at all(I've been there, Done that.) A Shop added a tiny fuel filter to my fuel line while I was racing back in the day without my knowledge (I don't know WHY it was added) and I had WORST time trying to figure out what the heck was happening after I got it back from the Shop. It turned out to be that dang little filter restricting fuel flow under load. Removed it and BINGO! Ran like a dream! I believe the filter restricts flow to the engine because of a lower vacuum signal when the piston is on the downs stroke of the cycle and doesn't create a strong enough signal to pull enough fuel past/through those added fuel filters.

I believe the carbs have been rebuilt correctly. But be sure to ask if those N/S have have changed out.

Also have the carbs been water tuned (Hi/Lo screws been adjusted) on the ski after the rebuild of them?

 

[soccerdad]

Have you tested the compression lately?

 

[Hicktown]

Have you tested the compression lately?

Yeah compression is good, 145 and 150.

 

[Hicktown]

Ditch the fuel filter as it restricts fuel flow to the carbs under load( i.e. Starting the motor and running the ski in the water from zero to WOT) and isn't needed at all(I've been there, Done that.) A Shop added a tiny fuel filter to my fuel line while I was racing back in the day without my knowledge (I don't know WHY it was added) and I had WORST time trying to figure out what the heck was happening after I got it back from the Shop. It turned out to be that dang little filter restricting fuel flow under load. Removed it and BINGO! Ran like a dream! I believe the filter restricts flow to the engine because of a lower vacuum signal when the piston is on the downs stroke of the cycle and doesn't create a strong enough signal to pull enough fuel past/through those added fuel filters.

I believe the carbs have been rebuilt correctly. But be sure to ask if those N/S have have changed out.

Also have the carbs been water tuned (Hi/Lo screws been adjusted) on the ski after the rebuild of them?

Thanks, I am definitely going to eliminate the fuel filter this weekend and see what happens. I did not tune the carbs in the water, as the rebuilder said he set them at the right settings, and it did run great my first few times out other than restarts, so I assumed the tuning was right.

 

[Hicktown]

Do a pull and twist test on all the fuel line connections. Make sure no nipples are broken or cracked. Jumping wakes and waves can cause changes in the sealing ability of the connections. Consider bypassing the fuel selector and under hatch filter/ water separator from the system. They both can leak air into the system. It is so much easier to suck air then fuel. Pull the choke out when it will not start. This increases the fuel flow to carb. Read the sticky above the forum on carbs. Consider opening the gas cap when it acts up. The vents may not be working. You should replace them after so many years. The Ski has any years on it, the vents may be original equipment.

Thanks, all good tips. Gonna go through all this over the weekend and see if it fixes it.

 

[Cliff787]

To be sure your carbs are adjusted correctly and you're getting max rpm & throttle response. The tuning is pretty easy.

You'll need a few sets of brand new NGK BR8ES plugs for the testings.

1.) Back the trailer until the back half of the ski is in the water.
2.) Be sure the ski is securely attached to the trailer(front and back)
3.) Start the ski and GRADUALLY bring the motor revs all the way up to 5k-5.5k rpms and notice how the engine responds(either revs nicely or bogs or somewhere in the middle).

4.) Once You rev the motor up to 5k rpms. Pull the lanyard and then pull the brand new plugs and look at the porcelain color. It should be a nice chocolate brown color which indicates the correct amount of oil is getting into the motor. Anything lighter in color means the carb adjusters (Lows) need to be turned out 1/8th of a turn until that chocolate brown color has been achieved.

*Assuming this is a totally stock ski. No Hi adjusters need to be adjusted.

 

[Hicktown]

Well, I will say this. After I had the carbs rebuilt, the ski ran better than it ever has. From a dead stop to WOT there was not a bit of hesitation. And it could idle forever without loading up the carbs and dying out. So, I think they are adjusted well although I can't say that for sure.

 

[mikidymac]

On a stock ski if everything is correct they will run perfect on the stock settings. Not really any reason to mess with the settings.

And as Cliff said if you want to check by the plugs the correct way is with a WOT plug chop, not tied to a trailer and not at 5,000 rpm. But even this is not an exact science as you need to look way down into the porcelain for the brown ring to read it correctly as just looking at the insulator tip will only tell you if you are way too rich or way too lean.

It was fine back in the day when I was tuning all the time but now that I am older and wiser I run my stock skis with all stock settings and just enjoy them every chance I get with no muss and no fuss.
Quick look that the plugs are between black and brown and good piston wash and then just rinse and repeat year after year.

 

[JJinSC]

One other thing that can cause your needle and seats to flood the engine and cause hard restarts is a clogged fuel vent. Check your pressure release vent to make sure it is functioning properly. If not, the fuel tank pressure build up will cause the carbs to pop-off and flood the engine with gas.

 

[Hicktown]

Update: tried pretty much all the ideas in this thread over the weekend, and still it will not run! Got rid of the fuel filter and bypassed the water separator filter, checked all fuel connections, and tried running it with the gas cap off all to no avail. At the moment, it will idle while in the water but still on the lift for a little while. After 30 seconds or so it will slowly start to lose RPMs and eventually die out. I also noticed it's smoking a lot more than normal. I also noticed that I have a broken front motor mount. This is really just baffling to me! Only a few weeks left of riding this season and I would love to take advantage of them.

 

[Mickirig1]

Sometimes, no matter what you do the carb has to be replaced! I ran into this with one of my ski's. Rebuilt it like a Doctor, sterile procedure, clean as it can be, still not working! Replaced the carb with a used one. Did not touch it, other then to adjust the low speed screw. Runs perfect! End of this season I am going to rebuild it. The old "not replaced often gaskets" can / may be the problem

 

[Hicktown]

Sometimes, no matter what you do the carb has to be replaced! I ran into this with one of my ski's. Rebuilt it like a Doctor, sterile procedure, clean as it can be, still not working! Replaced the carb with a used one. Did not touch it, other then to adjust the low speed screw. Runs perfect! End of this season I am going to rebuild it. The old "not replaced often gaskets" can / may be the problem

Thanks, yeah I feel like I've been beating around the bush by not taking another look at the carbs. I just find it weird that ever since I had them rebuilt, it's abnormally hard to restart the ski on the water. That has to be the root of the problem, at least I hope it is. Went ahead and got a good used set of carbs off eBay, will get those installed this week and see what happens.

 

[mikidymac]

Make sure you rebuild those used carbs with genuine Mikuni kits and verify they have the correct jets in them. I wouldn't throw on a used set of carbs and hope it fixes everything.

 

[Hicktown]

Make sure you rebuild those used carbs with genuine Mikuni kits and verify they have the correct jets in them. I wouldn't throw on a used set of carbs and hope it fixes everything.

Well the seller claims they came off a running ski that had a wrecked hull, and he went through the carbs and they look good. I'm inclined to put them on and see what happens.

 

[mikidymac]

I wish you luck but that is a good way to fry your engine if they have any dirt in them. A lean 2-stroke is a dead 2-stroke.

 

[Hicktown]

I wish you luck but that is a good way to fry your engine if they have any dirt in them. A lean 2-stroke is a dead 2-stroke.

Well shoot, now you're scaring me into getting them rebuilt, LOL. Last thing I want is a fried engine, of course.

 

[Cliff787]

If You get impatient(and it sounds like you are) and do not verify the jetting inside and the adjustment screw settings of those used carbs. You're taking on ALL of the inherent risks of a potentially seized engine and even more lost time, lost money and lost sanity.

It doesn't take too much time to open them up and verify the jetting and settings to avoid a major setback...

 

[Hicktown]

How do I verify the jetting?

 

[Cliff787]

Is this an all stock ski or modded engine?

Just take off the plate w/the 4 screws on the "Control" (changeable jets/springs/valve size) side the carbs (plate has a small tab at one of the corners of the cover) and remove the black round diaphragm and take the 2 screws off the "kidney" shaped cover. Under there is the two jets you need to verify. Also pull the needle/seat to see what that size is also. Should be a 1.5 seat valve(with the o-ring).

Stock jetting for an SBN40I:

Main jet(larger of the two jets) is 142.5

Pilot jet(smaller of the two jets and sits deeper in it's hole) is 70.

Modded engines will use larger jets.