96 SLX780 Rough Idle, Hard Start, and Miss

[rickreeves1]

Still having some issues with my 96 SLX780. It has a rough idle and a slight miss at idle. It's also hard to start. Here is what I have done so far. I replaced the spark plugs and checked the gap. I cut back the wires about half of an inch at all the boots. This was suggested by randy at Watcon. (Great guy by the way, extremely helpful) I tested for spark with an inline tester. I cleaned/grinded the inside connectors of the boots. I cleaned the inside of the air/fuel seperator. I removed the fuel cut off switch and replced it with a new inline filter. I disassembled the fuel pump and it seems ok. I checked the low speed idle adjustment on all carbs. The only thing I can think of is it may need a timing adjustment or it is time to crack open the carbs and rebuild them. I have no problem rebuilding the carbs. It can't be any harded than a holly double pumper. I was hoping to wait until the winter so I would not loose any ride time. I thought about bad gass but several tanks have been through it already. Is there a suggested cleaner I can run through it that may help clean out the fuel system? Any ideas or further suggestions? I wanted to get some video when I was riding with the seat off but I was worried about dropping the camera in the water.

Thank you

[axgrider73]

My Virage was doing the same thing and it was the carb.

As many of people have found out: "You can rebuild the carbs now, or rebuild the carbs AND engine later."

[ph2ocraft]

"You can rebuild the carbs now, or rebuild the carbs AND engine later."

Perfect, I wish I would have said it.

[Tony]

Perfect, I wish I would have said it.

Said it?, I'm doing it!!!!

[ph2ocraft]

LOL Look at is as a learning experience and just how much better you are with your Polaris product.

[ph2ocraft]

Still having some issues with my 96 SLX780. It has a rough idle and a slight miss at idle. It's also hard to start. Here is what I have done so far. I replaced the spark plugs and checked the gap. I cut back the wires about half of an inch at all the boots. This was suggested by randy at Watcon. (Great guy by the way, extremely helpful) I tested for spark with an inline tester. I cleaned/grinded the inside connectors of the boots. I cleaned the inside of the air/fuel seperator. I removed the fuel cut off switch and replced it with a new inline filter. I disassembled the fuel pump and it seems ok. I checked the low speed idle adjustment on all carbs. The only thing I can think of is it may need a timing adjustment or it is time to crack open the carbs and rebuild them. I have no problem rebuilding the carbs. It can't be any harded than a holly double pumper. I was hoping to wait until the winter so I would not loose any ride time. I thought about bad gass but several tanks have been through it already. Is there a suggested cleaner I can run through it that may help clean out the fuel system? Any ideas or further suggestions? I wanted to get some video when I was riding with the seat off but I was worried about dropping the camera in the water.

Thank you

The one other thing I would do is check crank index andmake sure you aren't chasing a ghost.

[xlint89]

Have you checked compression? Checked for a vacuum leak? And definately index the crank.

[rickreeves1]

Have you checked compression? Checked for a vacuum leak? And definately index the crank.

How do I go about doing this? Details?

Thanks


hmm... sounds like I better order the carb rebuild kits. The 96 780SLX has the Super BN Mikuni carbs correct? Anyone have the part numbers for these? Are there different quility kits? With auto carbs it's usually best to stick to the manufacturers kit. Is it the same with ski's? I've seen some from Jetlyn, some from Mikuni, and some in a plastic bag with a printed label.

Do I also need to buy needle and seat valve or jets? The Mikuni kit I saw says it does not come with those.

Thanks

[axgrider73]

How do I go about doing this? Details?

Thanks

Have you checked in the Tec Section???

[xlint89]

Have you checked compression? Checked for a vacuum leak? And definately index the crank.

Compression: buy or rent a tester from auto parts store. Hold throttle open while cranking engine until needle stops climbing. Record number and continue with the other 2 cyls. Vac leak: Seal carbs and exh. pipe air tight. Then apply 9 lbs. of vaccuum or pressure through the pulse line fitting on the block. It should hold for a few minutes. If not, you have an air leak somewhere. Most likely gaskets around carb area or crank seals. Indexing crank: Proper way is with a dial indicator and a degree wheel. Use dial indicator to determine EXACT top dead center of each piston. They should be exactly 120* apart. Poor man's method (not as accurate, but will give some kind of idea) Find TDC on MID piston, then measure the distance of the other 2 cyls by dropping something like a new unsharpened pencil down the plug hole. Use a razor blade to make a mark on the pencil. Do the same for the other cyl and compare them. Try it a couple times to verify the heights. They should be the same, or REALLY REALLY close.