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Old 11-14-2014, 10:11 AM   #1
stealthtiger OP
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Question Advice please: 950SM issues, loss of power, bad plugs, and oil consumption

Hey guys,


Looking some input here, I have a few issues.


Issue 1: The bike died on me.



I was riding in second gear and it started to cut out and more throttle made it worse. I was able to restart it while coasting in neutral and then pulled over. Let it sit for a few minutes and it started up and I rode it home.



Based on my research I suspected a fueling issue, perhaps gunk in the carb vent bowls or the jets. I have subsequently talked to some people with more knowledge than myself, of which there are many, and I believe the real issue was a bad spark plug that was causing the bike to occasionally run on one cylinder. I replaced the plugs and it seems to start fine and run ok. You can see the old plugs here, they both look black, and I think that means that oil is getting into the cylinder but Iím not 100% on that.


Issue 2: The bikeís midrange power is gone.


When I took the carbs apart I found some build up in the jets but very little. I was able to clean them completely with carb cleaner and a little bit of fishing line gently run through them. There was no build up in the float bowls. AS per the manual and a how to I found on here I measured the number of full rotations it took to tighten down the idle air mixture screws. 3.5 turns till they were seated. When I replaced the jets I only backed them out 2 turns because everything I have read has said that they should be between 1.5 and 2 turns from fully seated.


Could that change be the cause of my loss of midrange? I took it to the track after I had put the carbs back together and it was a very consistent result of full power in the 1st part of the rev range, what felt like half power on the 2nd, and then a very strong pull onward to the limiter in the 3rd part. Now, unfortunately I canít say what exact revs this happens at because the SM doesnít have a tach and I donít have the means to test it otherwise.


Issue 3: The bike seems to be using an excessive amount of oil.


I believe the bike goes from the top level of the oil sight tube to the lower level in well below 1000 mi, I know these bikes have some tendency to burn oil but it feels excessive. I donít have an exact usage per mi unfortunately so I canít say whether this concern is valid. But the black spark plugs make me think that oil is getting into the engine.


I have the oil breather seal and engine case gasket sitting here as I have read that they have a tendency to go bad and that might explain the oil consumption, I just wanted to put this long list on here in hopes that some kind soul will take pity on me and explain how many things I have screwed up! ;) I would really like to enjoy my KTM next season hassle free as the times I have been able to let the hammer down on this bike are some of my best motorcycling experiences.


Thanks in advance and sorry for the long post.
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Old 11-14-2014, 07:20 PM   #2
renogeorge
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I'd be planning a compression check. How many miles?

Did you check the carb diaphrams for holes, tears, cracks? Check for problems with needles--clip out, bent, trash in needle jet???

Check that carbs are properly seated on manifolds. Very easy to be off and have a vacuum leak.

Other lines for vacuum leaks? Carb vent lines run just below bottom of airbox?

Coils seated on plugs? Frayed wires in wiring to coils?

Good luck
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Old 11-14-2014, 07:37 PM   #3
Chuckracer
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The cutting out then restarting sounds like fuel pump.
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Old 11-14-2014, 08:16 PM   #4
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Sorry to hear about your problems. If it was a sudden loss of power I'd say it's either a fuel blockage or an electrical fault.

You have gone some way towards hunting down the issue. I'd put the oil consumption to one side for now.

If you didn't find any damage in the carb diaphragms, the jets are clean and in place, the boots are tight and not split, the choke is not sticking, the vacuum pipes are in place, fuel flows freely from the tank, the fuel pump pumps happily, then I'd say it's not a fuelling problem that made it suddenly cut out.

I would put your fuel screw back to where it was assuming it was running ok before this event. That's not to say your pre-event jetting is perfect, but that's another thing to look at after you find why it quit.

Renewing the plugs was good. By the way they do look black and wet but it depends when you pulled them. I had a coil fail and it only showed after warming up. Running on one cylinder, down on power but through the whole rev range.

Also had a backfire on startup spit a loose carb clean off. Ran like a lawnmower at low revs but picked up after mid revs as it sucked the carb back onto the manifold.

Assuming your valves are reasonably adjusted, I'm wondering if you have an ECU problem.

When you pulled your carbs did you find a lot of oil in the air box and on your air filter?

Good luck
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Old 11-14-2014, 09:25 PM   #5
Sumi
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+1 on the fuel pump for the cutout/power loss.

As for the oil consumption, it might be the balancer shaft seal.
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Old 11-15-2014, 06:04 AM   #6
stealthtiger OP
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Quote:
Originally Posted by renogeorge View Post
I'd be planning a compression check. How many miles?

Did you check the carb diaphrams for holes, tears, cracks? Check for problems with needles--clip out, bent, trash in needle jet???

Check that carbs are properly seated on manifolds. Very easy to be off and have a vacuum leak.

Other lines for vacuum leaks? Carb vent lines run just below bottom of airbox?

Coils seated on plugs? Frayed wires in wiring to coils?

Good luck
18K miles. I had a compression check earlier this summer, everything checked out

Zero noticeable issues w the carbs, made very sure to put them back like I found them.

Definitely seated properly, they popped into place and were tightened down

Carb vent lines are clear

Just replaced plugs, no issue w coils seating. That front plug is a b&%^ to get out
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Old 11-15-2014, 06:06 AM   #7
stealthtiger OP
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Originally Posted by Chuckracer View Post
The cutting out then restarting sounds like fuel pump.
It didn't restart on its own though, I just hit the starter again while coasting in neutral. Would a fuel pump issue be intermittent or constant in your opinion?
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Old 11-15-2014, 06:10 AM   #8
stealthtiger OP
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Quote:
Originally Posted by ICERIDER View Post
Sorry to hear about your problems. If it was a sudden loss of power I'd say it's either a fuel blockage or an electrical fault.

You have gone some way towards hunting down the issue. I'd put the oil consumption to one side for now.

If you didn't find any damage in the carb diaphragms, the jets are clean and in place, the boots are tight and not split, the choke is not sticking, the vacuum pipes are in place, fuel flows freely from the tank, the fuel pump pumps happily, then I'd say it's not a fuelling problem that made it suddenly cut out.

I would put your fuel screw back to where it was assuming it was running ok before this event. That's not to say your pre-event jetting is perfect, but that's another thing to look at after you find why it quit.

Renewing the plugs was good. By the way they do look black and wet but it depends when you pulled them. I had a coil fail and it only showed after warming up. Running on one cylinder, down on power but through the whole rev range.

Also had a backfire on startup spit a loose carb clean off. Ran like a lawnmower at low revs but picked up after mid revs as it sucked the carb back onto the manifold.

Assuming your valves are reasonably adjusted, I'm wondering if you have an ECU problem.

When you pulled your carbs did you find a lot of oil in the air box and on your air filter?

Good luck
Not a sudden loss per say, it cut out lightly and then preceded to get worse over about two city blocks. Fully cut out after I gave it more and more gas to effect the issue.

I'm going to pull the carbs again and put the idle air mixture screw back where I found it. Was thinking about installing H2W jets while I was in there, good idea or bad idea to do that while diagnosing a problem? And what is "pre-event" jetting?

Carbs are seated

I pulled the plugs when the bike was cold. Probably sat for two weeks.

Zero oil in the airbox/filter
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Old 11-15-2014, 06:11 AM   #9
stealthtiger OP
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Originally Posted by Sumi View Post
+1 on the fuel pump for the cutout/power loss.

As for the oil consumption, it might be the balancer shaft seal.
That's what I'm hoping. I have the seal and the case gasket right here
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Old 11-15-2014, 07:18 AM   #10
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Quote:
Originally Posted by stealthtiger View Post
Not a sudden loss per say, it cut out lightly and then preceded to get worse over about two city blocks. Fully cut out after I gave it more and more gas to effect the issue.

I'm going to pull the carbs again and put the idle air mixture screw back where I found it. Was thinking about installing H2W jets while I was in there, good idea or bad idea to do that while diagnosing a problem? And what is "pre-event" jetting?

Carbs are seated

I pulled the plugs when the bike was cold. Probably sat for two weeks.

Zero oil in the airbox/filter
'Pre-event' meaning that your carbs/jetting/fuel screw were probably OK before you had the problem, so I'd leave those settings where they were until you sort out what made it stop on you.

I wouldn't get too excited about your plug reading just now.

Check all your electrical plugs are secure. Some folk have a cut-out caused by starter solenoid corrosion in that region, including the main fuse there and terminals.

The initial cut-out could well be the pump contacts reaching the end of life. The fuel pump cycles after switching on the power, but when the engine's running it's just looking for a drop in the carb float levels as the fuel gets used, and pumps very slowly to top them up. If your pump died, the float level would drop until the carbs are empty. During that process you would get symptoms as you describe where the fuel around the jets decreases but the air is still getting in, more as you open the throttle. This is an increasingly weak mixture until after farting and banging He stop! I'm a bit surprised that it restarted soon after with only the button, and not an off-on which would have fast-cycled the pump. I might be wrong here about the fast-cycle but I'm sure someone will correct me. Can you hear your pump when you turn on the ignition?

What's confusing is that you seem to have a good enough fuel flow to give you full revs up the the limiter, but a seeming problem at mid-revs. But I suppose the failure could be a worsening thing and intermittent at first.

Try getting a new set of points and checking the pump shaft for corrosion while you're in there.
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Old 11-16-2014, 07:48 AM   #11
stealthtiger OP
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Quote:
Originally Posted by ICERIDER View Post
'Pre-event' meaning that your carbs/jetting/fuel screw were probably OK before you had the problem, so I'd leave those settings where they were until you sort out what made it stop on you.

I wouldn't get too excited about your plug reading just now.

Check all your electrical plugs are secure. Some folk have a cut-out caused by starter solenoid corrosion in that region, including the main fuse there and terminals.

The initial cut-out could well be the pump contacts reaching the end of life. The fuel pump cycles after switching on the power, but when the engine's running it's just looking for a drop in the carb float levels as the fuel gets used, and pumps very slowly to top them up. If your pump died, the float level would drop until the carbs are empty. During that process you would get symptoms as you describe where the fuel around the jets decreases but the air is still getting in, more as you open the throttle. This is an increasingly weak mixture until after farting and banging He stop! I'm a bit surprised that it restarted soon after with only the button, and not an off-on which would have fast-cycled the pump. I might be wrong here about the fast-cycle but I'm sure someone will correct me. Can you hear your pump when you turn on the ignition?

What's confusing is that you seem to have a good enough fuel flow to give you full revs up the the limiter, but a seeming problem at mid-revs. But I suppose the failure could be a worsening thing and intermittent at first.

Try getting a new set of points and checking the pump shaft for corrosion while you're in there.
I see what you mean. I did start right back up but died soon after and I didn't get a full restart until it sat for about 3 min. Then turning it back on I would have activated the fuel pump. So your thought process concerning fueling could jive with my seat of the pants experience.

I'll definitely look into it, I found a new set of points online. Thank you for the input. Would I be able to just look for corrosion to know if it's bad or could it be bad without being able to see it?

I here a very solid "putt putt putt" from the pump every time I swtich the bike on after the key is in and before I thumb the starter. I've never heard it not activate before starting.
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Old 11-19-2014, 01:55 PM   #12
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Well, If your pump is doing the "put put" when you turn on the ignition I would say you don't have a problem with it. Although 18,000 miles does seem to be a problem time for some pumps. The other thing that says your pump is probably ok is that you can red line it. I know it's tricky with speed limits etc but can you maintain full power for a reasonable period to verify max fuel flow? The other way would be to connect a pipe to the pump outlet and switch it on to see the flow. The corrosion would be on the pump plunger shaft, but to be honest this is probably unlikely in your case as your pump is mounted high up unlike the Adventure which is under the engine and can get wet.

Did the engine cut out only in 1st or 2nd gear and not in higher gears? As you probably know there's a system on 1st & 2nd connected to the CDI to tame the power. You also mention mid-rev performance drop. If fuel and air is unchanged from before this problem then it is very likely an ignition problem. By the way my coil problem was an actual failure and not just because it wasn't fully engaged.

Can you get your hands on another CDI to see if that cures it?
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Old 11-20-2014, 07:51 AM   #13
effensteve
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Side stand safety switch? I try to err on the side of easy first.
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Old 11-20-2014, 08:33 AM   #14
stealthtiger OP
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Originally Posted by ICERIDER View Post
Well, If your pump is doing the "put put" when you turn on the ignition I would say you don't have a problem with it. Although 18,000 miles does seem to be a problem time for some pumps. The other thing that says your pump is probably ok is that you can red line it. I know it's tricky with speed limits etc but can you maintain full power for a reasonable period to verify max fuel flow? The other way would be to connect a pipe to the pump outlet and switch it on to see the flow. The corrosion would be on the pump plunger shaft, but to be honest this is probably unlikely in your case as your pump is mounted high up unlike the Adventure which is under the engine and can get wet.

Did the engine cut out only in 1st or 2nd gear and not in higher gears? As you probably know there's a system on 1st & 2nd connected to the CDI to tame the power. You also mention mid-rev performance drop. If fuel and air is unchanged from before this problem then it is very likely an ignition problem. By the way my coil problem was an actual failure and not just because it wasn't fully engaged.

Can you get your hands on another CDI to see if that cures it?
Thanks for your response. I believe the engine cutting out and the midrange lean quality are two different issues that I initially mixed up. I think that the cutting out was related to the ignition and not the fueling as I once thought. Hopefully the new spark plugs solved that and I'm really hoping that once I have a warm enough day, at least 40F, that I can pull the carbs and reset the fuel mixture screws to where they were when I opened them up the first time. If there is still an issue once the carbs are back where they were and the plugs are replaced then I'll start looking into the coil and the CDI.
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Old 11-20-2014, 09:11 AM   #15
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The cutting out then able to re-start are classic, well documented cases of a fuel pump exiting stage left.
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