2000 SXR stumbling at ~5500 rpm

S

Sibbles

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Joined
Jan 9, 2017
Messages
9
Location
Port Hope, Ontario
HI All

We have a 2000 SXR 600 here that is giving us some hassles. We don't have much history on the sled and we bought it as is. Wasn't running very well. After doing some extensive clutch work and general maintenance it was running fine for about 10 to 15 minutes. Then she started acting up, bogging down and limiting the RPM's in and around 5500rpm. If we give it more throttle she climb up to 6000 and backfire. However if it is cold outside the sled runs awesome until it warms up. With todays warm temperatures around 3C she acts up right away.

Pull the plugs and they are dark brown and maybe slightly wet looking (Bat that could be from running it on a stand outside due to lack of snow right now)

THORS bypassed
Carburetors cleaned and set to stock settings as per specs (Did find some debris in main jet of #3)
No fuel line pinches
Boots and Reeds Look good
Compression is over 125 on all cylinders and with in 3psi of each other
New plugs
Wires and coils checked and are around 10K ohms and dead short across coil input wires
Stator tests as per manual
Shut off switch is good
Key switch is good

What are we missing here?

Fuel problem?

Electrical?

CDI?

Any help would be greatly appreciated. Another other tests to narrow down the problem would be great.

Thanks All
 
did you check the regulator and regulator rectifier? make sure you're wire harnes doesnt have any spots where it rubbed through.
 
Hold up, were is the voltage regulator on this sled? Isn't it just going through the CDI. I know most sleds have them down on the lower right but this guy doesn't have that.
 
a friend of mine has the same sled with a similar problem, running like crap, backfiring, but his lights were also very dim, went through everything, he then replaced the reg and the reg rectifier and it ran great after that. they are located on the right side behind the blue cover, bolted to the footwell.
 
well would you look at that, staring at me through the holes. Lights aren't dimming at all and see good. I don't see a test for the regulator in the manual. Have you come across a test to see if its bad or not?
 
well would you look at that, staring at me through the holes. Lights aren't dimming at all and see good. I don't see a test for the regulator in the manual. Have you come across a test to see if its bad or not?
 
Lights appear to not change when it is acting up

Here is what we have this morning,

Started up fine, 2 min warm up and then did a few pulls from idle to almost the bar with slight brake on, pulled up to 7500 no issues. did this several times no issues.

Shut it down, waited five minutes, did the same thing again no issues until I was about 2 to 3 minutes of run time. Then she acts up again, from idle to almost the bar with slight brake on she will only get to 6200 rpm and stumbles........

Any ideas?
 
What clutch work was done? Is the float height good? Are the screens under the needle and seat clean? Are the choke plungers closing all the way? Try to blip the choke when it is acting up and see if it gets better or worse. Trying to throw ideas out there.
 
drew24 said:
What clutch work was done? Is the float height good? Are the screens under the needle and seat clean? Are the choke plungers closing all the way? Try to blip the choke when it is acting up and see if it gets better or worse. Trying to throw ideas out there.
Click to expand...

Ideas are all appreciated, two minds are better then one.

When it was purchased the primary had been welded near the outer shiv and then someone JB welded one of the slider ears back on, sketchy to say the least. A new clutch was put on using all stock parts for the 600. Secondary helix was broken, one bolt tab was right off. Replaced the helix with another original stock one.

Float height was set to 13mm as per the manual, the carburetors where completely stripped and cleaned. Main Jets were stock....133.5 and 134 if I remember correctly. Air pilot set 2 turns out as per manual. I think that all checks out unless you have read differently somewhere. Choke plungers did close and open all the way.

I have not blipped the choke while it was acting up, good call, I'll give that a try later on or tomorrow morning.
 
Sounds like you went through it pretty good. Are you confident all the bushings are good and not worn out in the clutches since I am guessing they are used? Another simple thing to check would be the cdi box to make sure it is the correct box for that sled. And if you check the cdi you could also check the harness where it goes around to make sure there are no wires rubbing. Although that would not explain why it only happens when it get warm.
 
drew24 said:
Sounds like you went through it pretty good. Are you confident all the bushings are good and not worn out in the clutches since I am guessing they are used? Another simple thing to check would be the cdi box to make sure it is the correct box for that sled. And if you check the cdi you could also check the harness where it goes around to make sure there are no wires rubbing. Although that would not explain why it only happens when it get warm.
Click to expand...

Yes, the clutches are all good and moving freely. I'd same I'm a little OCD with clutches...LOL.

The CDI is the correct one according to the part number and I've had almost the whole harness out of the thing looking for rubbing and splices other people may have made. Found two bad splices which i fixed but that didn't fix it.

I'm gonna run it up again tomorrow morning and see what happens when I blip the choke. I'm assuming if it clears up when choke is partially on then then the mix is running lean around that RPM and the needles are likely worn or a float is hung up perhaps.

Biggest issue with this sled is we have no history of it. I never ran right from day one. It has been beaten pretty good and has probably been in a few fender benders. Who knows what the previous people have done with it.
 
I think we figured it out

We noticed that the plugs were looking a little wet. So we dried them out and ran it again. Good at the start, pulled plugs they looked good, ran again, pulled plugs they looks a hint of wet, ran again and noticed over time they got wetter and wetter. At their wettest is when the engine would begin to act up. If we messed around with the throttle and loved it a bit it would spit out smoke and then run good for a bit then act up again.

So, it appears the engine is loading up with fuel over time (5 to 6 min)

Our Pilot screws were at 2 turns out. When the problem was occurring we were at half throttle ish. Maybe less at time. That means we are controlling fuel by the pilot main jet and needle. The needle and jets were all correct for the machine so this leaves us with pilot air screw adjustment.

Digging around the internet we found that different people were having better luck with other adjustments like 1 1/2 or 1 3/4. The manual said 2 turns out but then we came across a supplemental which said for certain models they wanted 1 1/2 turns. Depended on manufacture date from what I could tell.

Anyways we went with 1 1/2 turns and ran it a whole bunch of times. Less smokey, even on a warm day like today, darker colour plug with a hint of wet. (It's 4C out today) We could not reproduce the problem at all. All weekend we could reproduce the issue almost every-time.

Thanks for your help and we'll report in after we have a chance to ride it on a cold day and check fuel mixtures at a better temperature and load.
 
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