Just looking for more suggestions...

[indy_500]

My dad has a 99 XC SP 700 with 7500 miles on it. All season last year he told me it was boggy but he just kept riding it. I've been tinkering with it for the past week. From a dead stop if you punch the throttle it bogs and then backfires. I don't have the best gas in it but it shouldn't be bad enough to cause any problems. (and it shouldnt matter as it did it all season last year). I've adjusted and synced the carb slides in multiple settings trying to get rid of the problem. Cleaning the carbs to heck and back. no broken reed petals, no cracked piston skirts, good compression (120/120), next thought was the fuel pump. Well, I finally ordered up all the clutch tools (jam nut and spider tool and clutch holder) since his spider needs to be rebuilt, and i figured I'd throw in the fuel pump rebuild kit for $8 so i did and it will be here this afternoon. I'm hoping that will fix it but does anyone have any other suggestions? Next should I be going onto the stator? When running 40+ mph it's never boggy, still hits 100+ on the dream-o-meter and revs up to 8100 rpms like it should. Also I've sprayed starting fluid on the case, crank seals, and carb boots and no leaks...

 

[xcr440]

I think you are on the right path with the clutch. Perhaps the weights and/or rollers are sticking causing the issue. If that's not it, at least you know they are good. 7500 miles is a LOT if they've never been worked over.

 

[trailshredder]

I think you are on the right path with the clutch. Perhaps the weights and/or rollers are sticking causing the issue. If that's not it, at least you know they are good. 7500 miles is a LOT if they've never been worked over.

x2......week spring in secondary clutch causing belt to sink prematurely.

 

[Rupp Collector]

I don't think clutching will cause backfiring. Have a friend that bought his new and did the same thing. Put a boost bottle and the little air deverters in the carbs and it really cleaned it up on the bottom end.

 

[indy_500]

The secondary has new spring and buttons, primary has new weight bushings and spring (EPI Gray/EPI Purple Setup) and the spider rebuild kit came today (Thank god it came with new weight pins as the old ones are shot). But... That's not causing the backfiring. Seems like more of a fuel delivery issue.

 

[snoluver1]

The secondary has new spring and buttons, primary has new weight bushings and spring (EPI Gray/EPI Purple Setup) and the spider rebuild kit came today (Thank god it came with new weight pins as the old ones are shot). But... That's not causing the backfiring. Seems like more of a fuel delivery issue.

Backfire is usually a sign of a rich condition. If it only does it out of the hole and then clears up, I would be looking closely at the pilot circuit for the problem. Also, pretty common problem on those carbs is for the choke plungers to stick in the carb body. Since it is not really a choke, but an enrichment valve, it could very well cause the symptoms you describe if one is sticking or not seating all the way in the bore.

 

[Wyelde]

With 7500 miles on the sled, you might want to check your compression also. It could be that it's time for a top end refresh

 

[snoluver1]

Also, with that many miles, a fresh needle and seat wouldn't hurt and cheap enough to try.

 

[nytro_rtx]

Backfire is usually a sign of a rich condition. If it only does it out of the hole and then clears up, I would be looking closely at the pilot circuit for the problem. Also, pretty common problem on those carbs is for the choke plungers to stick in the carb body. Since it is not really a choke, but an enrichment valve, it could very well cause the symptoms you describe if one is sticking or not seating all the way in the bore.

Also, with that many miles, a fresh needle and seat wouldn't hurt and cheap enough to try.

Agree with snolover, these would be the things I would look @

 

[skeeter2010]

I would recommend checking a couple things did you put the twist in the spring for the secondary? and also set the belt height on secondary.
I had problem with my carbs, the tip o the fuel screw broke off in the seat the only way to tell is to remove both screws and compare the lengths, it ran really rich until I was at higher speeds. The sled also got really bad fuel milage until I replace the carbs The screw is located on the side of the carb infront of the slide.

 

[(TK) Mustard Bucket]

Clean the power valves, new plugs, new gas, check fuel pump AND LINES including impulse line, get all the stupid little stuff ruled out then start rebuilding your big expensive stuff. A bog followed by backfire usually indicates an intermittent fire on one or both sides making excessive fuel to air ratio and unburned fuel flashing off in the exhaust. Does it bog when you pin it on the stand or only when under load?

 

[indy_500]

Clean the power valves, new plugs, new gas, check fuel pump AND LINES including impulse line, get all the stupid little stuff ruled out then start rebuilding your big expensive stuff. A bog followed by backfire usually indicates an intermittent fire on one or both sides making excessive fuel to air ratio and unburned fuel flashing off in the exhaust. Does it bog when you pin it on the stand or only when under load?

It does it on the stand also. I'm only rebuilding the primary because the one roller is cracked and it fell off thankfully the weight isn't torn up somehow.

 

[polarisrider1]

How about the TPS sensor or switch. Those liittle buggers can do strange things to a running motor.

 

[ezra]

tps could be it. I built a tester last yr for poo tps not hard to do look on u tube.think i spent 5 bucks at radio shack did my poo tested a buds and his also needed adjustment.
then gave it to a bud who owns a shop I do my best to not work on poo.

 

[snowfreak56]

I say carb issue possibly pilot jets sometimes just cleaning is not the fix..Keep us posted.

 

[obob]

I 2nd, The Temp Sensor! I have 2002 and it is a known fact, and I experienced it first hand One day out riding, Low end bog. I thought what the heck, Carbs must have gotten crap in them. On the drive home i remembered reading about symptoms of a bad temp sensor. They actually make a plug in bypass, for testing this. You can make your own, and test it tomorrow.
Just unplug the temp sensor and make a jumper to complete the circuit for the wiring harness. and run your sled.

 

[fastmod62]

I have a pair of carbs off of a 99 XC700SP that only had 990 miles on it when it got totalled out if your interested. $100.00

 

[indy_500]

Well the bog has gotten put on hold as I can't get the spider off. Tried heat over and over and over again, had a 5 ft. piece of pipe on the end of my 25" breaker bar and finally busted the EPI spider tool.

 

[indy_500]

Thanks for all the suggestions guys. Will try as many of them as I can until I solve this problem. Keep em comin if ya got any more! Can't really tinker around starting it up over and over without the clutch on it...

 

[indy_500]

Got the clutch fully rebuilt, rebuilt the fuel pump, and put a new fuel filter on. Started it up, it ran great on the stand for 5 minutes and the .05 miles i rode around the yard until the sled just quit. Doesn't seem to be getting any gas. Going to clean the pilots again probably put in new needle and seats and then im not sure where to go from there this is a disaster LOL