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Old 02-21-2012, 10:21 PM   #1 (permalink)
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yet another rxl that bogs

Here's the scoop;
Have a 1991 RXL 650 SKS, got it in the fall, First ride of the year I got 15km from my truck, thing runs hard to 45 mph and falls on its face (bogs bad enough it will almost toss you over the bars), tried to baby it back to the truck and it progressively got worse until it would not move itself. I let it cool down for a bit, fired it back up and it ran fine until about half way back to the truck. Stopped and let it cool down, fired it up, got it back to the truck problem free. later found that belt deflection was too tight and offset was wrong. Both have been adjusted to spec since. Went ice fishing a week ago, same problem again. Checked compression (115 on all 3), but decided to check piston skirts anyway, no damage, plugs look a little dark but should run decent enough. tried to go for a boot tonight but left my parking lot at work and same problem AGAIN! Brought it in the shop, checked some of mrholmquist's old posts and dug up his procedure for resetting the tps, followed it to a t. With stop screw all the way out, cable released from throttle lever set tps to .480 volts, turn stop screw in to get reading of .659 volts, reconnect cable, check freeplay, fire up and verify idle at 1900 -2000rpm. Got out the door and to the end of the parking lot and it did it again. By the way, did I mention there are no codes flashing? After my long-winded tale anybody have any input? Been at this for weeks and still scratching my head. thanks in advance
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Old 02-21-2012, 11:08 PM   #2 (permalink)
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Just finished tuning this exact year. Thought I would offer a couple things to ck from what you have described. First thing I would get after is the cooling system, sounds like when you let it cool it runs decent for a while. Make sure it is full, then jack up just the front of the sled, remove radiator cap and start the engine let it warm up a bit while checking for bubbles coming out of fill neck. If you do not see any and level does'nt drop noticeably, cap it off while running and let it build pressure, then loosen air bleed screw and ck for air there. Also ck the water pump belt condition and adjustment. Deflection is 1/4". Next I would run a fuel pressure test, you should have 35-37 psi at the rail. I use a tee at the inlet hose on the pto side of the rail, as there are no easy provisions such as a schrader valve. If pressure is good then I would suggest you down load the diagnostic soft ware, and make the connector you need, and get into the system to have a further look see. I will try to include the links for this. If it does not work you can ck this forum about that info, also mrholmquist has done this as well. He has made the connector for a couple people some time back. I made mine myself and it works great. You can read real time data and ck all the sensors and specs. I would also re ck for bad spot in your tps switch, they can be very intermittent. An analogue meter works better for finding dead spots, NEEDLE DROP IS EASIER TO SEE, digital meters get a little jumpy. Even my fluke which I use for measuring dva voltages on marine 2 stroke ignitions (refreshes every 16,000ths of a second). Here is a manual which covers some trouble shooting to get you started. You have to scroll down a ways to get to diagnostic of E.F.I. H-C Engine - 85 Engine Electrical - Inc Wiring Diagram - Electric Start
Here is FREE software down load page, it is in swedish but can be translated to english. Connector cost is about $25 to make, and is straight forward. Rensun kotisivut - Polaris RXL - Select Monitor for PC

Last edited by POL3INAROW; 02-21-2012 at 11:22 PM.
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Old 02-22-2012, 03:03 PM   #3 (permalink)
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I also have an analog meter, and yes, i agree the digital one is too jumpy to check for dead spots. Did use the analog one to check, and did not see any dead spots on the tps. As for fuel pressure, I will check it next time I have a chance to look at it, but out of curiosity, if it were a fuel problem would the plugs not show it? I will check it but that depends on the next time my ball and chain works night shift.
As for the connector, I remember seeing plans for it on an old post but I can not seem to find it again. Could you point me in the right direction? If not, is Mrholmquist still making 'em? Thanks again.
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Old 02-22-2012, 03:36 PM   #4 (permalink)
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i know this is simple but try changing the fuel- drain all the fuel and put new in, i just went through this- 2 sleds ran great last year started and they bogg this year, they had about a gal and 1/2 ran it a little added fuel still bogg, drained all fuel put 1.5 gal in runs perfect. i know they are not efi but it is worth a try- cheap
do a google search on fuel shelf life- it is scary
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Old 02-22-2012, 03:48 PM   #5 (permalink)
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i know this is simple but try changing the fuel- drain all the fuel and put new in, i just went through this- 2 sleds ran great last year started and they bogg this year, they had about a gal and 1/2 ran it a little added fuel still bogg, drained all fuel put 1.5 gal in runs perfect. i know they are not efi but it is worth a try- cheap
do a google search on fuel shelf life- it is scary
I guess I should have mentioned that the first thing I did was siphoned every drop out of the tank. I have run this one long enough, trying to figure out problems, to put two full tanks through it. But this is absolutely a good suggestion had I not thought of that. Oh, while I had the throttle bodies off yesterday I pressurized the fuel system to make sure the injectors were not dripping. Best mention that has been checked too.
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Old 02-22-2012, 03:54 PM   #6 (permalink)
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good luck
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Old 02-22-2012, 05:53 PM   #7 (permalink)
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Sounds like a fuel system restriction to me. If either one of the two fuel filters is partially clogged you may have the correct fuel pressure feed to the engine at idle. However when the fuel demand is increased if the filters are clogged the volume of fuel will not be able to keep up with the demand. This will cause the pressure at the rail to drop off and therefore the engine to lose power. replace both filters , check the fuel line inside the tank is in good condition as well as the screen on the end of it and ensure there are no kinks in any of the fuel lines. See if this helps.

You will need an inexpensive plastic low pressure in line fuel filter, it is actually the same one the carburettor equipped sleds use.

You will also need an expensive high pressure metal fuel filter. Fortunately
fram makes an inexpensive equivalent , the Fram part number is G4777
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Old 02-22-2012, 06:16 PM   #8 (permalink)
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Originally Posted by mrholmquist View Post
Sounds like a fuel system restriction to me. If either one of the two fuel filters is partially clogged you may have the correct fuel pressure feed to the engine at idle. However when the fuel demand is increased if the filters are clogged the volume of fuel will not be able to keep up with the demand. This will cause the pressure at the rail to drop off and therefore the engine to lose power. replace both filters , check the fuel line inside the tank is in good condition as well as the screen on the end of it and ensure there are no kinks in any of the fuel lines. See if this helps.

You will need an inexpensive plastic low pressure in line fuel filter, it is actually the same one the carburettor equipped sleds use.

You will also need an expensive high pressure metal fuel filter. Fortunately
fram makes an inexpensive equivalent , the Fram part number is G4777
x2 on all that i just replaced metal fram filter on my rxl only 13-14 dollars from walmart dealer wanted 50
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Old 02-23-2012, 02:21 AM   #9 (permalink)
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Originally Posted by mrholmquist View Post
Sounds like a fuel system restriction to me. If either one of the two fuel filters is partially clogged you may have the correct fuel pressure feed to the engine at idle. However when the fuel demand is increased if the filters are clogged the volume of fuel will not be able to keep up with the demand. This will cause the pressure at the rail to drop off and therefore the engine to lose power. replace both filters , check the fuel line inside the tank is in good condition as well as the screen on the end of it and ensure there are no kinks in any of the fuel lines. See if this helps.

You will need an inexpensive plastic low pressure in line fuel filter, it is actually the same one the carburettor equipped sleds use.

You will also need an expensive high pressure metal fuel filter. Fortunately
fram makes an inexpensive equivalent , the Fram part number is G4777
Yes of course I forgot to include what mrholmquist has mentioned due to fatigue. ck all the obvious first.
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Old 02-24-2012, 04:42 AM   #10 (permalink)
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I also have an analog meter, and yes, i agree the digital one is too jumpy to check for dead spots. Did use the analog one to check, and did not see any dead spots on the tps. As for fuel pressure, I will check it next time I have a chance to look at it, but out of curiosity, if it were a fuel problem would the plugs not show it? I will check it but that depends on the next time my ball and chain works night shift.
As for the connector, I remember seeing plans for it on an old post but I can not seem to find it again. Could you point me in the right direction? If not, is Mrholmquist still making 'em? Thanks again.
It is just a usb to rs232 ttl adapter, the wiring diagram is on the link for the download I think. If not I will look around for it. Rensun kotisivut - Polaris RXL - Select Monitor for PC

That is the link to show you what you need, and what to do.
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Old 02-24-2012, 07:44 PM   #11 (permalink)
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Ok, I got it hooked up about 5 minutes ago. KOEO I got around 33 psi at the rail on PTO side, with the engine running i got about 34 psi whether i revved it or let it idle. So I guess fuel filters are the next step from what I gather from the gurus here. Will try to track some down and go from there, will let you know how it turns out.
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Old 02-24-2012, 11:23 PM   #12 (permalink)
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Ok, I got it hooked up about 5 minutes ago. KOEO I got around 33 psi at the rail on PTO side, with the engine running i got about 34 psi whether i revved it or let it idle. So I guess fuel filters are the next step from what I gather from the gurus here. Will try to track some down and go from there, will let you know how it turns out.
Forgot to mention to pinch off vacuum source to regulator to see if pressure increased as well. It is not fool proof but it lets you know that it is operating. You should see some fluctuation when you rev the sled, cause vacuum drops momentarily and should increase pressure momentarily, but then again if your blocked up it could hinder pressure increase. You should only see approx 5 psi. fluctuation on hard acceleration and not as much on deceleration.
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Old 02-25-2012, 09:24 AM   #13 (permalink)
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Well, I will see about finding some fuel filters (small town) change 'em out, recheck the lines, gotta check that pickup line and screen in the tank, and I will recheck fuel pressure to see if it makes difference. Of course I will have to try pinching off that regulator vacuum line. As for the fluctuation in pressure under acceleration, I just had it running in the shop, wasn't riding it so I could only rev it to just about engagement. Thanks for throwing that extra little tid bit in there, I will have to try it.
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Old 02-25-2012, 10:42 AM   #14 (permalink)
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Your welcome. I have had one stick in one position before, created a similar problem. If you can, put it on a stand, and when its warmed up run it up until it just engages. Then open it up briefly a few times form there. That will be the heaviest load you can put on it at that point. Also on your high side filter, a wide variety of diesel motors will have a high pressure filter ahead of the injector pump. So if you have an equipment supply place near you check with them as well. Good luck on the search.
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Old 02-25-2012, 01:08 PM   #15 (permalink)
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I managed to find that high pressure filter, got it changed, no difference in the fuel pressure, but I can't seem to see the low pressure plastic filter. Is it below the fuel pump on the bulkhead? When I pinch off the vacuum hose the pressure does rise slightly, and of course if I briefly pinch off the return hose it will climb very rapidly. As for the pickup in the tank, how do I check that one, as far as i recall most of those weighted strainers were brass and inherently non-magnetic. I am currently at the shop doin a top end in an 800 IQ so I eagerly await your reply. Got about 6 fresh inches in the last day and a half, would like to maybe go for a boot tonight if we / you guys can figure this thing out. Thanks again!
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Old 02-25-2012, 04:38 PM   #16 (permalink)
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The entire fuel pump and pickup assembly are removed from the top of the tank.
You have to take the seat off to do this.
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Old 02-25-2012, 05:21 PM   #17 (permalink)
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no RJ that is the way a cat is , on this sled the low pressure filter is inline between the fuel tank and the fuel pump.

For future reference:
That high pressure filter is the same one used on a Nissan car
Fram part number G4777 can buy it for about 10 bucks
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Old 02-25-2012, 05:39 PM   #18 (permalink)
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Thanks mrholmquist, I took the number you gave me previously and got on frams website to get cross reference numbers and an application list to make the parts people's job easier and make tryin to find a filter a whole lot simpler. I managed to "fish" the strainer out of the top of the tank, it was clean and the line appeared to be in good shape. But like I say, there was no change after changing the high pressure filter and with the airbox removed I could not see a plastic filter in the line to the fuel pump. I guess scratching your head beats scratching your @$$ though.
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Old 02-25-2012, 05:51 PM   #19 (permalink)
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google "polaris parts lookup"

go to the polaris website "browse"

http://parts.polarisind.com/Assemblies.asp

lookup parts diagrams for your sled and go to the page "engine mounting"

the filter is key #33
part number 2530008
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Old 02-25-2012, 06:21 PM   #20 (permalink)
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Thanks mrholmquist, I took the number you gave me previously and got on frams website to get cross reference numbers and an application list to make the parts people's job easier and make tryin to find a filter a whole lot simpler. I managed to "fish" the strainer out of the top of the tank, it was clean and the line appeared to be in good shape. But like I say, there was no change after changing the high pressure filter and with the airbox removed I could not see a plastic filter in the line to the fuel pump. I guess scratching your head beats scratching your @$$ though.
Sorry I was in the shop with a tricky one today. 99' xc runnin rich. I tried every thing I could think of then some more. Turns out after a few hours of scratching MY head, the primer went bad internally and the carbs were pulling fuel from the primer feed line. First one for me! I did not catch it because it has a choke as well, and I used that like the customer said he does, oh well chalk one up for learning.

The plastic filter should be installed in between the tank nipple and fuel pump. If there is nothing in that line then someone has removed it which is not good. The next place for debris to get lodged is the very small screen in the pump inlet. The pump is in a nasty spot. you might be able to remove the feed line and see in the pump, it is angled in that type of direction. I have a feeling something else is going on at this point myself though. Hopefully not. Next thing I would do after trying to ck the pump out for debris, is to run a pump pressure test, you have to be careful with this one. Need to dead end the gauge in line with the pump, should see up around 80 psi. you may also want to run it with the gauge on it and the regulator pinched off as well. Then I would be going the Polaris select monitor route.
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