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1999 XP Carb cleaning

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dimesismoneytoo

dimesismoneytoo

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Hey guys, got worked over by a shop. Drop the ski off before memorial day, and I kept in contact with this shop calling weekly for updates. I finally had enough and went up there to find out why it was taking so long. The jackass hadn't even touched the thing in nearly 2 months. I told him I was taking it and he tried to charge me a "storage fee" because it had been sitting in his shop for so long. Wanted $250. Y'all can guess what I said to that, use your imagination.

Okay on to the point, I took it to the shop to diagnose why it wasn't starting on the water. The only thing the guy did was figure that out. Says it's not getting fuel to the rear cylinder. I have the carbs out and was wondering where to start as far as cleaning goes. I going to replace the float in the fuel baffle while I have the fuel system open.

Thanks in advance.
 
Shop manual has procedure for cleaning filter. May need a rebuild or two. All the gray fuel lines changed?
 
In the world of 2-strokes, the general rule of thumb is a cylinder that's not getting fuel might be damaged as a result, so a compression test is in order.

As far as the carb goes, the rear (PTO) cylinder is the one that fills first with trash(which motor is this, 951?) I'd remove the fuel inlet cover of the bad carb and see if there's trash in the tiny filter. ( Item #9 in this drawing of a SBN46i for a 951), it might be full of junk and plugged up.

But, may as well pull the other cover off and disassemble the metering system, remove the high and low speed adjusters and hose out all the passages with a can of carburetor cleaner and compressed air (need an air compressor) to blow the junk out while the carb is on the bench.

Always use a good quality hardened screwdriver, not a worn out piece of junk. And, no need to overtighten screws and break them off, only need to be tight enough they don't vibrate lose. I like to oil my screws to avoid galling the dry threads.

Mikuni has a shop manual for BN carbs see google search and there must be a billion how-to videos on Utube for the mikuni super BN carbs.
 

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Sportster-2001-951C-Stock said:
In the world of 2-strokes, the general rule of thumb is a cylinder that's not getting fuel might be damaged as a result, so a compression test is in order.

As far as the carb goes, the rear (PTO) cylinder is the one that fills first with trash(which motor is this, 951?) I'd remove the fuel inlet cover of the bad carb and see if there's trash in the tiny filter. ( Item #9 in this drawing of a SBN46i for a 951), it might be full of junk and plugged up.

But, may as well pull the other cover off and disassemble the metering system, remove the high and low speed adjusters and hose out all the passages with a can of carburetor cleaner and compressed air (need an air compressor) to blow the junk out while the carb is on the bench.

Always use a good quality hardened screwdriver, not a worn out piece of junk. And, no need to overtighten screws and break them off, only need to be tight enough they don't vibrate lose. I like to oil my screws to avoid galling the dry threads.

Mikuni has a shop manual for BN carbs see google search and there must be a billion how-to videos on Utube for the mikuni super BN carbs.
Click to expand...

Compression is spot on in both cylinders. Front hole is 125, back hole is 130. Been told those are good numbers for the 951.
 
Yep, those are decent compression results. There's a pretty decent sticky Mikuni BN carburetor rebuild thread you can follow for the carb overhaul and probably billions of utube videos on the subject.
 
Where you at in Virginia Sportster 2001? I am at the" Beach " till Friday. Got any Ski's that need exercised?
 
Me Too. Got Parts on the way From Minnetonka4me to get My Ski's ready for Sunday. My Auto Mechanic son is home too. He is going to get a good taste of Ski wrenching.
 
Cleaned the carbs and might have figured out why it wasn't starting. Needle on the PTO carb was leaking. Was seating correctly while doing the pop off test. Adjusted pop off, and now it'll start up, now only thing to do it tune it. Anyone have some tips on tuning? Anything helps, thanks.
 
If its stock, set it to specs and it should run just fine.


Sent from my iPhone using Tapatalk
 
Factory suggested settings should perform quite well. A very good place to start, sometimes these settings can be improved on slightly but if they're not very close then there's likely something still ailing.

You're looking for an quick/easy hot restart after a 10 minute heat soak and no hesitation or flat spots in the throttle response all the way up through WOT. Some occasional 4-stroking (rich missing) is acceptable and a sign the mixture isn't too lean.

Plug insulators should settle out to a cardboard brown eventually, not grey or black, after about 1/2 hour of operation you should see a definite cardboard brown film, initially they take on a yellowish color. Grey is an indication of being too lean and black is soot from excess fuel.
 
Lake test day, and it's a flop. Finally got it to start on the water by choking until it gurgled a bit then hit the throttle and it would come to life, but would not idle. Let off the throttle and it would die. It's still acting like its not getting gas to the PTO cylinder. Open it up and only hits 5k on the tach. Pulled the plugs and the PTO plug has very little liquid on it and the mag plug is black. Brand new plugs.

Here are the plugs:
356.JPG
357.JPG

I'm almost to the point of selling this thing and buying a new one. Been working on getting this fixed for almost a year now, ad no one can seem to help me on it.
 
After correcting the leaking needle did you do a leak down test with the carb completely assembled?


Sent from my iPhone using Tapatalk
 
No, I didn't leak down test them. I figured I was forgetting something. I don't mind rebuilding them, it just bothers me that I paid someone last summer to rebuild them and 3 months later it just dies on the water and I had to be towed back to the ramp. And that no one can seem to figure out what wrong with it. I has spark to the PTO plug, I've checked numerous times. Compression is almost exactly where it should be. Battery is charging correctly, and has plenty of power. Brand new fuel lines and fuel selector. The only thing I can think of is that the carbs weren't done right and I got screwed out of $200. I guess I need to buy a rebuild kit and just rebuild them, again. Would that needle leaking by cause the ski to just die all of a sudden at WOT? Cruising along just fine no problems all day, then on my way back to the ramp at WOT just dies. DEAD. I'm just about to the end of my rope with it. Almost a whole summer wasted with broken in the garage.
 
Let's proceed.

If there's no fuel in the PTO carb fuel chamber, your accelerator pump won't squirt fuel while actuating the throttle. This is one way you can confirm the carb is dry.
 
dimesismoneytoo said:
1) The only thing I can think of is that the carbs weren't done right and I got screwed out of $200.

2) I guess I need to buy a rebuild kit and just rebuild them, again.

3) Would that needle leaking by cause the ski to just die all of a sudden at WOT? Cruising along just fine no problems all day, then on my way back to the ramp at WOT just dies. DEAD.

4) Almost a whole summer wasted with broken in the garage.
Click to expand...

1) Stuff happens, might be trsh in fuel tank (sand or soda pop the kids dumped in there?). This ski is of the age it doesn't make sense (to me) paying someone to repair it, time to take bull by the horns (IMO).

2) I'd at least replace the needle/seat sets if they're damaged which id likely. Gaskets from a kit would be optional but who wants to remove those carbs once more if they leak fuel into the bilge. No need to replace parts that don't need replacing (aside from needle/seat, 2.0 size), the round rubber metering diaphragms must not have holes in them and should be soft as rose petals, nearly.

If it ran good last year then it should this year too, once the one single issue is corrected.

3) Stopped getting fuel (for whatever reason), thus stopped running. squirt, squeeze, bang, fart. Must have all four.

4) Get busy, stop goofing off! :)
 
Do a pressure test on the fuel system? If it leaks gas, it sucks air. It will not tolerate any air leaks. Little internal filter clean? Have an inline fuel filter before carbs? Water separator / filter clean? Try cracking open gas cap when it died? Open gas cap now, does it vent pressure out? Take heart, when you find the problem it will be like, DUH, how did I miss this?
 
Mikuni Needle and Seat Valves - 2.0 786-35015-2.0 Amazon. $16.26 and free shipping.

The picture they show is not correct but the part you will get is.

If you are going to replace 1 I would do both. They are the same age and if one fails the other is probably not far behind.
 
BTW, while you've got those off, make sure your accelerator pump sucks and blows. No need to disassemble it if it seems to be working fine. No need to open an unnecessary can of worms.
 
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