Failure to Start After First Service

[The 4th Horseman]

Hi everybody,

I've encountered an issue recently that I've been trying to figure out for a while and I'm running out of ideas.

I completed my first service on my 2018 RC390 about a week or so ago. Measured the valve clearances (3 out of spec: both intake, one exhaust), shimmed em to spec, swapped the oil out for Motul 300V, adjusted the chain tension, etc.. I should mention (in case it matters) this took a while, since I found the tool that KTM provides for hand cranking the engine was incorrectly sized, and had to order a 14mm Allen wrench. All in all, the full service was dragged out over a couple weeks and the bike had been sitting a couple weeks before that. Got everything thrown back together, and even waxed it so it can look good the first time it hits 10k rpm. Piece of cake. No real issues encountered, except for the typical pains of working in tight spaces and fighting with some of the more difficult connectors and such.

Go to fire it up for the first time: I can hear the fuel pump priming, good. Hit the starter, and it churns and churns but the engine won't turn over. Try it a few more times with no luck. No flashing warning light or error codes shown either.

I immediately figure it's the spark plug. I heard the fuel pump prime, and obviously didn't touch that at all, so as long as it's making noise, I know I didn't break the connector during fuel tank removal, so it should be fine at 620 miles. I did however have to disconnect the spark plug connector and remembered being concerned about not having a good way of verifying it was fully seated, way down in that deep well. Seemed like a good starting point. I did check all the fuses first, and they all checked out.

I stripped everything off again, and resistance tested the spark plug connector/ignition coil, just to be thorough. All seemed good. Pulled out the spark plug, cleaned off some carbon deposits, and resistance tested that. Again, seems good. Connected it to the connector, just to see how it seats and to get a feel for what a good seat felt like for my second assembly attempt. While I was at it, I did a resistance check from ignition coil to the plug electrode. Everything checked out. I even measured a resistance back to the battery lead. I had no idea what that should be, but it came out on the order of a Mega-ohm. It was really a half-assed continuity check, which passed.

So I reinstalled the plug and connector, got all the necessities back on, turned the key, heard the fuel pump prime, hit the ignition, and same deal: starter churned and churned but no engine start.

I'm at a loss here. None of the 4 essentials for starting (fuel, air, compression, spark) should have been affected at all during this work, with the exception of the connector de-mating and re-mating, which is tough to screw up. Does anyone have any ideas? What could I have possibly done? Any help would be much appreciated.

 

[ReidMcT]

When you had the plug out, did you check that it actually sparked?

Are you certain you replaced the camshafts precisely?

Most important, are you absolutely certain the battery is good? Have it LOAD tested. Weak batteries can turn over the engine yet not satisfy the ECU.

 

[The 4th Horseman]

I didn't actually check for spark, mostly because I had to remove the battery to get to the plug, and I still had the fuel tank electrically connected and shifted out of the way. I also figured any issue would have been at the connection, as the plug should be fine at 620 miles. So I just did the resistance test, for sanity purposes. I suppose I could check for spark tomorrow, just to be sure. I don't have any better ideas.

As far as the camshafts go, I actually zip tied the timing chain to the gears, so it's unlikely the chain jumped a tooth or anything. I didn't even pull them all the way out, just moved them out of the way enough to get the shims in/out, then slid em back in their slots. Afterwards, both gears were at top dead center, all clearances measured in spec, and the engine hand cranked without issue. I'm hesitant to open that up again, but now you've got me worried that my measurements were wrong. If I don't get this resolved soon, I may try another feeler gauge. Which would cause this issue, too tight, or too loose? I had to loosen the 3 that were out of spec.

As for the battery, that was fully charged on the tender before I even tried to start it the first time. I double checked it with the multi-meter as well, and voltage checked out.

 

[Jon W]

When you adjusted the exhaust was it off the compression release? Just a thought.

 

[ReidMcT]

It is not the shimming. But you have not LOAD tested the battery. Take it to an auto parts store and get it done. Unless you have a pinched fuel line or an unplugged connector, the battery is suspect numero uno.

Numero dos is cracked spark plug insulator, which could have happened when you had it out for the valve work.

I would check the fuel lines, connectors, and battery, in that order.

 

[ReidMcT]

A couple more less likely thoughts: You are sure you had the right crankshaft timing mark lined up when checking the cam sprocket marks? And the cam chain tensioner was reinstalled correctly and is tensioning?

Anyway, valve timing seems least likely because even if it were off, eventually enough fuel would accumulate that the spark would ignite a big back fire or exhaust pop.

 

[The 4th Horseman]

Jon,
You actually bring up a good point. I did hold the compression release when checking the nearest exhaust clearance, and that one had to be adjusted. Do you also have to hold it while checking the far exhaust clearance? Either way, that one didn't need to be changed, so I doubt it's the issue. But I'd still want to get back in there and do it right.

Either way I can't imagine it's the clearances, as I checked them multiple times. Unless the difficulty reaching the exhaust side (did this in the bike) resulted in false, tighter measurements. Maybe larger gauges got stuck trying to make the bend, leading me to believe they didn't fit. I'm skeptical though, and I imagine they would have to be very far out of spec to completely prevent a start. I only adjusted them one shim size (.05mm). Worst case, I'll try buying some pre-bent feelers to double check, but that's probably last resort


Reid,
I'm going to do a load test today. I'd be surprised if it was the battery, given how new it is. I more suspect that I screwed something up or broke something. I had the same thought on the spark plug. I did a resistance test from the connection to the housing and didn't get a reading, but I'm not 100% convinced by that test. I also couldn't visually detect any cracks, but I pre-emptively bought a replacement iridium, just in case. I wanted to check out the other systems before installing it though, since ignition seemingly passed all resistance testing and visual inspection.

The timing chain had tension, and everything measured TDC at reassembly (crank, gears, etc.) with correct clearances. I did have an issue with the tensioner reinstall. The tutorial I watched didn't mention locking/unlocking. So when I reinstalled it the first time, it was all the way out. I quickly realized something was wrong when the chain was too tight to turn, so I pulled it back out found the issue, and reinstalled it. Afterwards the chain had tension, it hand cranked fine, with no noises or visible damage in the chain. Could something more subtle have gone wrong if the chain was over tensioned? If my other checks don't pan out, I'm going to pop the valve cover off and double check clearances, tensioner, etc. anyways.

I think my process today will be to start with the simple stuff mentioned, and then work toward the more painful checks.

1) Load test the battery, just to be sure.
2) Get the tank back off, check all connectors, and make sure none of the fuel lines are pinched.
3) Check for spark against the valve cover - replace if necessary
4) Pop valve cover off and double check clearance, timing chain tension, etc. - Probably won't get to this today.

I'll report back when I'm through.

Thanks for all the suggestions guys.

 

[The 4th Horseman]

Guys. Something very strange just happened.

I load tested the battery and got a steady voltage of 12.73V before start, and a minimum of 10.36V on start (all good). Funny thing is, right before I hit the kill switch, it sounded like the engine may have just begun to turn over. The starter probably cranked for a good 5 seconds with nothing, so I didn't think much of it. I waited a few minutes and went to load test again, just to be sure...Fired right up! I let it run for a few seconds and listened. Everything sounded good, and then I had to cut it off because I'm doing all this in my kitchen (temporarily don't have a garage) and didn't want to gas myself out.

I'm happy it started, but also a little concerned that it took so many tries. I've always done my own vehicle maintenance and repairs, but my vehicles have been fairly reliable, so this is my first time doing this level of engine work. Is it typical to have to crank the starter so much to get it to fire up the first time after doing work like this? As far as starting attempts go, this was my process:

Did my valve adjustment, oil change, etc.
-Tried to start 4-5 times, letting the starter crank for several seconds before hitting the kill switch, or until it cut out on its own (all failed)

Pulled everything apart again and did the spark plug cleaning, reinstall, and troubleshooting mentioned above.
-Tried to start once or twice, let it crank for several second or until it cutout on its own (fail)
-Battery load test one (maybe started at end)
-Battery load test two (Success!)

I'm hesitant to start it again inside, so I'm going to get everything back together and take it out to the parking lot and try again. Hopefully it fires right up. Anyone else have to crank and crank to get that first start after service?

Only other explanation I can think of, is the spark plug was the problem on the initial set of tries, and then I just didn't try enough after solving the problem.

 

[ReidMcT]

There is one possible explanation that does not completely fit the facts as you've laid them out, but which does fit the starting behavior: If air get into the fuel line, it will take many startiing attempts before the engine will fire. I experienced this recently when building a RC390 from parts. Beginning with a completely dry set of fuel lines and filter, it took a total of about 30 seconds of cranking before the engine fired. The fuel filter showed fuel before the first starting attempt, but there was still an appreciable amount of compressed air between the filter and the injector.

You described setting the tank aside with electricals still attached, so it seemed unlikely that you got air into the system. But who knows. It could be as simple as that, which would be good news other than the time and worry you spent.

 

[The 4th Horseman]

Reid,

That is almost certainly it. I only left the tank connected electrically, during the second disassembly to check the spark plug, but I did disconnected the fuel lines. And when I adjusted the valves, I had the tank completely off for a good two weeks while I waited for some tools to arrive. I didn't realize it would take that long to clear out the air, but if you had the same experience with a fresh system, then that's most likely the cause.