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Discussion Starter · #1 ·
Doesn't seem to matter what I do to my sled it never runs to full potential. It has a bad low end bog, midrange is decent then won't pull the rpms up top. Got rid of the Keihin carbs, still have problems even with flatslide mikuni's. Didn't have much time to tune the flatslides because of weather but went from 460/450 down to 440/430 on the mains and no difference. Played with the fuel screws and no difference. Changed the needle setting and it helped a bit.

Stock pipe or twin pipes it runs virtually the same with the twins having slightly better midrange. The clutches are all in excellent shape. Tried different reeds and cdi from another 700 and it runs the same. Timing was verified correct with a dial indicator.

What other then clutching or carbueration could cause a sled to run like crap all the time and not respond well to adjustments? Could it be electrical? Maybe the fuel pump? I'm out of ideas...

Edit: Forgot to mention compression is good and equal on both cylinders.
 

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Discussion Starter · #3 ·
What is the compression? How many miles on the engine, and clutches? Have you ran it on the stand at 8000 rpm and checked where the timing is?[/b]
Compression was 120 both sides with my cheap guage, throttle wide open, 3 pulls, hot engine.

The engine has 1500-2000 miles, the sled was not a runner when I bought it. It has a new case, crank, pistons, one cylinder was replated and a hot seat high compression head.

The chassis has over 7000 miles. I don't do any of my own clutch work, the dealer has serviced both last year when changing weights, springs and helix. I was told everything looks good.

The timing was also verified by the dealer last march and is at factory specs.
 

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Discussion Starter · #5 ·
what did the tm come off , RMK,switchback or xc/prox? are they tm-40? they run differnt cutaways and may use differnt jetting.[/b]
They were off a 2002 XC 800. The only thing different between them and the 40's on the 700 is the needles, everything else is the same and I have jetted to 01 XC 700 specs.
 

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the 02 xc 800 40's have 1.5 slides.. I am just about to throw a set from my 02 xc 800 on my buddies 99 700.. and also go with the 01 700 specs I can say that his 99 always seemd to have a crappy low end til it is warmed up good.. always stutterd in the lowend.. kind of a bad bog.. I notice it when I ride it.. and hate it.. it did get better with a set of vf 3's it always had a Boost Bottle.. and I was thinking about have him remove it.. goin forward..
 

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Did you check for broken or loose motor mounts and torque stops? The front ones can be a real pain. Another place to check is the plug ends on the plug wires at both ends. My sons 98 RMK 700 blew the ignition module. Looking it over later, it had a wire burned off inside and I'm sure that caused the coil to go. Another is the exhaust donut on the header, that will kill performance, check exhaust spring tension too.Good Luck.
 

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Not all dealers check the 8000 rpm timing. Running the engine on a stand at 8000rpm, with the track spinning at 100mph, and your head under the hood is a bit unnerving the first few times.
 

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Not all dealers check the 8000 rpm timing. Running the engine on a stand at 8000rpm, with the track spinning at 100mph, and your head under the hood is a bit unnerving the first few times.[/b]
You know any tricks for doing this?
Last time I did it, I put in real light wts, and was still nervous as hell!
 

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I have a 1999 xc700 and when it was new it had a slight low end bog. With a boost bottle and a little carb tuning (smaller mains, and air screw playing I got rid of it.) Sled has always been a rocket though. Do you know what clutch parts you have installed? The dealer I was going to didn't know what they were doing. And was known for swapping parts off new sleds when they needed something and didn't have it in stock for a sled they were working on.
 

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Discussion Starter · #11 ·
I have a 1999 xc700 and when it was new it had a slight low end bog. With a boost bottle and a little carb tuning (smaller mains, and air screw playing I got rid of it.) Sled has always been a rocket though. Do you know what clutch parts you have installed? The dealer I was going to didn't know what they were doing. And was known for swapping parts off new sleds when they needed something and didn't have it in stock for a sled they were working on.[/b]
For clutching it has 62 gram weights, almond/gold primary spring, r12 helix in #2 with a silver/blue secondary spring.
 

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You know any tricks for doing this?
Last time I did it, I put in real light wts, and was still nervous as hell![/b]
PSI recomended procedure for timing my Genesis 925 at 8000 is remove belt run the motor up to 8000 just long enough to see timing marks. Pull up needles 2 clips to compensate for high rpm light throttle. Doing this with stock clip setting will lean out the motor and possible seizeure. Its still not too fun but better than a track letting go at 100 mph.
 

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What are you revving now?Is the tach calibrated?Stock gears?I would put a polaris almond round in the primary,all else the same.
 

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Discussion Starter · #14 ·
Tach is calibrated with 23/40 gearing. Last year uncalibrated it ran 8500-8600 rpm give or take, which was around 8300-8400 rpm actual since it read about 200 rpm high uncalibrated. Changed the carbs it still has the bog down low but now won't pull the revs up top (bogs at 7000 rpm). I have talked to others with Mikunis on older XCs and they run 440 jetting with the stock pipe. Seems to be too rich for my sled even with twins.

I was reading the troubleshooting in the manual, one section says a faulty fuel pump could cause low rpms and rich conditions. It also says backfiring can cause fuel pump damage, what is the likelyhood the fuel pump is bad?
 

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I would never run it without the belt on. With the weights in the clutch, it will engage very hard, could damage the clutch. Choke staying on? Could be the fuel pump, you never know. Have you checked the crank indexing?
 

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Discussion Starter · #16 ·
The crank indexing has not been checked. It is almost new...but I suppose it could be defective.

The chokes are definately not on, I have the cable adjusted up properly on the rack. These walbro pumps are not rebuildable.
 

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Anything over 8,000 rpm is too much for that motor. Keep it at or below 8000 rpm.
I had a '99 700 XC SP and even with clutching and going down one main jet size it was still a dog. I dont know what changes Polaris made from the '98 to the '99, but the '99 cant hold a candle to the '98.
You could try a dual-angle helix. That would help it get off the line better, Id also suggest heavier weights in the drive clutch to get the max rpm down.
 

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Octain is right on the rpms. SLP single pipe peak power is 7800rpms. Power drops off hard after that. Twin pipe peak rpm is 8000-8200 rpms. Also drops off hard if the rpms are too high. And the 220 cylinders might like less rpms. As for the 99 xc700. I must have got a good one!!
 
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