[sleepybrew]

Can you please explain this a little more to me? How would the pump fail if one cylinder runs? I’m confused

fuel pump uses pulse from crankcase to work a diaphragm in the pump. if that fails it sucks gas through the pulse line at a high rate. twins use one cylinder for this , and if it's the one in question i would look for gas in the pulse line

 

[XCR1250]

appreciate the info,I see guys have swapped for the mikuni carbs. What all does that entail to make the swap

It's been more than 10-12 years since I've done any so a bit obscure now.

 

[Elliot99xc700]

fuel pump uses pulse from crankcase to work a diaphragm in the pump. if that fails it sucks gas through the pulse line at a high rate. twins use one cylinder for this , and if it's the one in question i would look for gas in the pulse line

well I pulled the plug on that cylinder below the exhaust and nothing came out so I think I’m safe there, and I don’t have any other gas leaks that I can see. I believe the carb is the issue

 

[Elliot99xc700]

It's been more than 10-12 years since I've done any so a bit obscure now.

copy that, anyways I appreciate all the help man. I think I’m going to try and swap the carbs and see if that’s the trick. I ordered a set last night, won’t be here until the weekend. I’ll update results once I swap!

 

[XCR1250]

copy that, anyways I appreciate all the help man. I think I’m going to try and swap the carbs and see if that’s the trick. I ordered a set last night, won’t be here until the weekend. I’ll update results once I swap!

Hopefully not the same kind.

 

[too slow]

so above I listed a carb kit, is that what I would need to replace the jets and rebuild the carbs? Otherwise I found a set of carbs for 150 I was going to buy and swap them. Thoughts?

Our guys never owned those sleds more than 2 seasons, but as long as they had them they ran well. Just had to remember to drain the carbs at the end of the season or you'd be pulling them apart months later. I can't ever recall our guys bad mouthing the stock carbs once they were tuned with the use of vforce reeds.

 

[XCR1250]

Our guys never owned those sleds more than 2 seasons, but as long as they had them they ran well. Just had to remember to drain the carbs at the end of the season or you'd be pulling them apart months later. I can't ever recall our guys bad mouthing the stock carbs once they were tuned with the use of vforce reeds.

That's true if you didn't keep them too long, wife had bought a used 99 XC 700, was fine for a few years then carbs began to cause problems, we sold it to a salesman at Hayward Power Sports some years ago, they converted it to Mikuni's.

 

[orville-x]

appreciate the info,I see guys have swapped for the mikuni carbs. What all does that entail to make the swap

I agree with the comments about the Keihin carbs having a few issues that pop up over time. Swapping for Mikuni flatslides isn't that complicated. There used to be (or maybe still is) a "sticky" topic in one of the Polaris forums for doing that retrofit. I did that swap with my '98 back when I was running a significantly modded engine - had to jet from scratch anyway, so a good opportunity to swap carbs. The swap will require a couple parts in addition to the carbs. Different throttle and choke cables, tee the fuel lines together, a bit of clearancing at the front of the airbox to fit around the carbs.

 

[Elliot99xc700]

I agree with the comments about the Keihin carbs having a few issues that pop up over time. Swapping for Mikuni flatslides isn't that complicated. There used to be (or maybe still is) a "sticky" topic in one of the Polaris forums for doing that retrofit. I did that swap with my '98 back when I was running a significantly modded engine - had to jet from scratch anyway, so a good opportunity to swap carbs. The swap will require a couple parts in addition to the carbs. Different throttle and choke cables, tee the fuel lines together, a bit of clearancing at the front of the airbox to fit around the carbs.

specific year/model to look for the mikuni? And where would I look to find the cable for throttle and choke cables? And off chance you know what jetting id need? Living in Minnesota. I just have never worked with carbs let alone small engines, so this is all super new to me, but I figure if I can do a top end, carbs can’t be that much harder

 

[D-rail]

Look at the Polaris parts lists (Babbitt's, partspitstop, or (Browse) for 2002-2005 700 engines/carbs. Use those cables, etc. I looked for the "sticky" which had tons of info on this Mikuni switchover, didn't see it, so do a search on here to get familiar with this should you choose to adapt to the Mikunis.

Swap meets, salvage yards like Mohakwks in Hibbing or Ske's in Esko, or ebay should have a carb ""rack" for these, running about $100. Get the 40mm ones, the 600's ran 38mm. SkiDoo had run racks, but their spacing was different, so don't get those! Jetting for a stock machine, I'd start with 440 or 450 mains, whittle down to maybe 410's depending on the piston "wash". The wash is the area on top of the piston (the "crown") that stays clean, right at each transfer port, looking down the cylinder with a good light... you want the size of the wash to be about the width/length of a fingernail. The rest of the piston should have some carbon deposits on it after some time, which is normal. If the top of the piston is clean, with a larger wash area, you can usually jet down, one step at a time, but it takes some time to develop enough carbon, and corresponding wash, usually a couple hundred miles. Be safe and start big, some stock machines, and even SLP recommended even bigger jets when they told customers to jet their new pipe to be safe, approaching 480 and even 500, but that is unusual.

RMK carbs have different slides, they tend to run lean. They also have leaner jet needles. Try to find regular XC or XCSP carbs to avoid having to switch components. The main jets in these will prolly be just fine for what your sled will require. Use the pilot jets and air jets that came with the model years I listed, they will be close, too. Making the connection to the airbox is important, don't leave the bells open and exposed to underhood temperature, and pressure changes. Some guys went with Fernco connectors, they might need to be slightly modified to fit your current airbox. .Make sure you properly vent the carbs to inside the airbox, leaving them out and not connected makes the carbs run a little rich. There might be a black electrical box on the side of the Mikuni carb that is not needed for your year sled. You can just leave it in place. It helped set the throttle position sensor (TPS). It's been a number of years since I did this, so I'm hoping I gave you some tips that are gonna help.

 

[Elliot99xc700]

Look at the Polaris parts lists (Babbitt's, partspitstop, or (Browse) for 2002-2005 700 engines/carbs. Use those cables, etc. I looked for the "sticky" which had tons of info on this Mikuni switchover, didn't see it, so do a search on here to get familiar with this should you choose to adapt to the Mikunis.

Swap meets, salvage yards like Mohakwks in Hibbing or Ske's in Esko, or ebay should have a carb ""rack" for these, running about $100. Get the 40mm ones, the 600's ran 38mm. SkiDoo had run racks, but their spacing was different, so don't get those! Jetting for a stock machine, I'd start with 440 or 450 mains, whittle down to maybe 410's depending on the piston "wash". The wash is the area on top of the piston (the "crown") that stays clean, right at each transfer port, looking down the cylinder with a good light... you want the size of the wash to be about the width/length of a fingernail. The rest of the piston should have some carbon deposits on it after some time, which is normal. If the top of the piston is clean, with a larger wash area, you can usually jet down, one step at a time, but it takes some time to develop enough carbon, and corresponding wash, usually a couple hundred miles. Be safe and start big, some stock machines, and even SLP recommended even bigger jets when they told customers to jet their new pipe to be safe, approaching 480 and even 500, but that is unusual.

RMK carbs have different slides, they tend to run lean. They also have leaner jet needles. Try to find regular XC or XCSP carbs to avoid having to switch components. The main jets in these will prolly be just fine for what your sled will require. Use the pilot jets and air jets that came with the model years I listed, they will be close, too. Making the connection to the airbox is important, don't leave the bells open and exposed to underhood temperature, and pressure changes. Some guys went with Fernco connectors, they might need to be slightly modified to fit your current airbox. .Make sure you properly vent the carbs to inside the airbox, leaving them out and not connected makes the carbs run a little rich. There might be a black electrical box on the side of the Mikuni carb that is not needed for your year sled. You can just leave it in place. It helped set the throttle position sensor (TPS). It's been a number of years since I did this, so I'm hoping I gave you some tips that are gonna help.

Dude. Thank you! This was a huge help!

 

[orville-x]

specific year/model to look for the mikuni? And where would I look to find the cable for throttle and choke cables? And off chance you know what jetting id need? Living in Minnesota. I just have never worked with carbs let alone small engines, so this is all super new to me, but I figure if I can do a top end, carbs can’t be that much harder

Look for something '03 and newer. Those have a longer inlet "bell" that closely matches the dimensions of the Keihin carbs. They also have air screws instead of air jets for low-speed tuning. You need the carbs to be from a 700 or 800. Whether you find XC/Pro-X or RMK carbs doesn't matter a great deal. RMK carbs will have smaller main jets and leaner needles, but will often have "richer" slides. That is often a benefit if you are tuning from scratch. It is easier to pull fuel out than it is to get more fuel into the range of throttle opening where slides are important. For cables, use the throttle and choke cables from an XC, Pro-X or RMK from the range of years the carbs came from. For jetting, start with something close to what the XC came with stock. Typically a 45 pilot jet, 2.0 slide, main jet around 430. The needle depends on exactly what you have for slides. As an FYI, the "sticky" topic I mentioned is in the XC forum. It is titled 40mm rack on '98 XC 700.

 

[Elliot99xc700]

Look for something '03 and newer. Those have a longer inlet "bell" that closely matches the dimensions of the Keihin carbs. They also have air screws instead of air jets for low-speed tuning. You need the carbs to be from a 700 or 800. Whether you find XC/Pro-X or RMK carbs doesn't matter a great deal. RMK carbs will have smaller main jets and leaner needles, but will often have "richer" slides. That is often a benefit if you are tuning from scratch. It is easier to pull fuel out than it is to get more fuel into the range of throttle opening where slides are important. For cables, use the throttle and choke cables from an XC, Pro-X or RMK from the range of years the carbs came from. For jetting, start with something close to what the XC came with stock. Typically a 45 pilot jet, 2.0 slide, main jet around 430. The needle depends on exactly what you have for slides. As an FYI, the "sticky" topic I mentioned is in the XC forum. It is titled 40mm rack on '98 XC 700.

awesome. Again thank you guys for the information. I will start the hunt for a set of mikunis

 

[Elliot99xc700]

Update: got this thing running top notch again. It was the carbs. I ended up going with a set of carbs out of a 2000 xc700 which were updated a little bit. Got the carbs synced and fired it up and with some tuning I got it where she needs to be. I just wanted to say thanks to everyone for all the help, and at some point I’m going to look into swapping over to the mikunis.