SXR SXR running weird after long WOT run

[subhard]

Over the winter I installed a wet pipe and rebuilt my carbs using all of FP specs. It ran great for last three weeks, until yesterday I ran WOT for about a minute straight, when it all of the sudden it died. It started right back up, but had a low end bog/hesitation.

Compression is at 155 each cylinder
Fuel is full, fresh, 90 octane, premixed at 40:1
Plugs looked a little dark, but not terrible. Put fresh ones in with no change

The top end is still good, it only hesitates towards the bottom. It also runs perfect out of the water with no hesitation at all. Any ideas?

 

[Delusnl]

Did you check for water? Sounds like you might have inhaled some, has the tank been flushed? It shouldnt be the tank if it ran great for three weeks but never you never know you coulda just got some bad pump gas. Had this happen to me once where it randomly died and i ended up taking in some water...stuff doesnt burn very well.

 

[balsam lake glass cutter]

do you guys all run your sxr's at 40:1 my 2011 calls for 60:1 ?

 

[Big Kahuna]

did you replace the pump fitting that comes with the pipe to let more water come in? Sounds like you did not and it overheated.

 

[subhard]

did you replace the pump fitting that comes with the pipe to let more water come in? Sounds like you did not and it overheated.

I did put the bigger fitting in the pump. I rode straight to a dock immediately after the incident and the pipe and motor werent crazy hot. This is also with 45* Alaska water.

 

[Big Kahuna]

sounds like you may have had a slight seizure.

 

[subhard]

sounds like you may have had a slight seizure.

Is there any way to fix this low end bog/hesitation then?

 

[Big Kahuna]

play with your adjustment screws. How much warmer is it now vs 3 weeks ago

 

[subhard]

play with your adjustment screws. How much warmer is it now vs 3 weeks ago

It's a little warmer. 5-10 degrees max. I opened up my low speed screws a quarter turn and my highs about 1/8. So I'm at hi 5/8 open, low 1.25 open and its much better now. I guess FP specs were too lean. Which is funny because I had read the opposite.

 

[subhard]

But I'm still confused as to why it was fine until the event yesterday. What did that WOT run do I wonder.

 

[subhard]

Well I finally got around to pulling my head today. Found some scuff marks in the mag cylinder.

Im guessing that was the culprit. I'm glad and surprised my compression stayed at 165. I didn't find any metal shavings or anything. Other than a bunch of oil residue everywhere, everything else looks fine. And that scuff mark doesn't have any deep gouges or anything either. I'm gonna keep riding it as is, just with richer carb settings and no long WOT runs. Unless anyone has a better idea.

On a separate note, why do my cylinders look so different?

(before cleaning)

(after cleaning)

 

[Octane_114]

do you guys all run your sxr's at 40:1 my 2011 calls for 60:1 ?

yeah my sticker on my 09 says 60:1, i still mix 50:1 though

it's your elevation, why it would be lean. cylinder ran a little lean + little hotter so it dis colored.

 

[subhard]

I tore my meniscus and I'm off my ski for a couple weeks, so I'm gonna go ahead and get my motor bored for new pistons. I don't really trust anyone here in ak to do the work, so who/what is the best place to send my top end to? Money isnt an issue so im open to the idea of a full port job. I've never looked into any real motor mods before, just bolt ons, so this is all new to me.

 

[subhard]

Got my cylinders honed and put in new pro x pistons. I'm testing tomorrow...

Hope all goes well

 

[Cannibal]

That mag is lean. Check your carbs well for debris in jets and inlet filter, and check popoff. If all that checks out, it will be a good idea to air test. Any oil in the front cover?

If you can't find anything, go ride, but don't hammer on it and check piston wash again. Might need to go up a size on the mag carb or turn out the screws a bit more. It's not unheard of to have to set the carbs differently.

 

[subhard]

Everything checked out and break in went great. It ran awesome. After 5 gallons I pulled the plugs and the mag looked nice and chocolately, the pto looked pretty rich. So just to be on the safe side, I richened up the mag so it would be a little on the rich side during break in. Worse case scenario I turn it back. After another couple gallons here is what the plugs look like.

And I'm still getting 180+ in both cylinders.

Yay

 

[subhard]

And here are the carb settings I'm gonna run for a while.

 

[djkorn1]

I would avoid Long WOT runs (more than 5 seconds) with that compression and a pipe. Also, cut a 1/4 inch off of your plug wires. They could be getting burned up causing the original problem.

 

[Crab]

You running up at Big Lake?? I lived up in Anc. for 8 years....

 

[IceRocket1286]

Thats perfect compression even on a stock motor. Nice cold seizure though, glad you got it back up and running