Running rough - Wrist Twisters
 
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post #1 of 12 Old 08-09-2016, 10:43 AM Thread Starter
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Running rough

I have a 2002 919 that I purchased about a year ago with 30K miles and unknown maintenance history. It started running rough last week, and got progressively worse, so I replaced the plugs (NGK) this weekend. Ran beautifully (night and day difference) yesterday, but started stumbling on the way in to work this morning. It stumbles at low RPMs and then clears up as the revs increase. I imagine it'll start stumbling all the time (like last week). I definitely smell unburned gas in the exhaust as well.

So, I'm looking for suggestions from you knowledgeable ones. I'm wondering if the plug(s) are somehow getting fouled - as opposed to there being a lack of spark. Should I invest in an HF noid light to check for spark? Pull the plugs and inspect (I have no experience evaluating them)? Other ideas?

BTW - I did purchase the factory plug remover, and I gotta say, between it, and my wife's midget-sized hands, getting the plugs out was a breeze!

Thanks,
Bob

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post #2 of 12 Old 08-09-2016, 12:00 PM Thread Starter
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After more perusing of other threads, here's my (un)educated guess as to what's going on:

My fuel pressure regulator is bad. This results in rough idle, which clears up (initially on my new plugs) at higher RPMs. Over time (a day for me), the plugs get fouled enough that they stop firing at higher RPMs as well. This theory seems to fit my situation, so I'm going to see if the FPR is bad, and probably replace it any case as it seems to be a weak point in general for the 919.

Feel free to comment, and I'll let you know what I find.

Bob

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post #3 of 12 Old 08-09-2016, 12:18 PM
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This hasn't happened to my bike, but I'd say from my reading of the reports of how this goes, you are right on top of it, here. Hope it's a relatively quick fix.

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post #4 of 12 Old 08-09-2016, 12:35 PM
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It's easy to check, lift the tank and pull the vacuum line off, if it's bad fuel will run out

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post #5 of 12 Old 08-09-2016, 01:19 PM Thread Starter
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Thanks. I'll check in a couple hours when I get home and let you know what I see.

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post #6 of 12 Old 08-09-2016, 02:18 PM
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Also #2 & #3 plugs will be the ones that foul as that's where the FPR gets it's vacuum.

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post #7 of 12 Old 08-09-2016, 03:14 PM Thread Starter
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OK - ready to check, but have a question:
Should I remove the FPR (i.e. the 2 bolts) to make it easy to get at the vacuum line, or is it possible to unplug it w/out removing? It looks like a tight fit back there.

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post #8 of 12 Old 08-09-2016, 03:18 PM
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You should be able to remove the vacuum line without taking anything else off

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post #9 of 12 Old 08-09-2016, 03:37 PM Thread Starter
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Well, no obvious gas dripping out. I guess it could be farther down the line? It has a slight gas smell. I guess at this point I'll just order a new one and see what happens. Preventative maintenance at worst.

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post #10 of 12 Old 08-10-2016, 08:29 AM Thread Starter
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Ordered the FPR (16740-MCZ-013 REGULATOR, PRESSURE (American Honda) $59.87) and O-Ring (16741-PG7-005 O-RING (American Honda) $2.49) from partzilla. I'll update when I have it installed.

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post #11 of 12 Old 08-22-2016, 02:13 PM Thread Starter
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SOLVED!

Good news (so far). I replaced the FPR, and after about 30 seconds of idling, the roughness disappeared. I have put on about 25 miles since then, and everything looks good. I did not change the plugs - as they only had about 10 miles on them (I hoped that wasn't enough time for them to become fouled).

I'll let you know if anything changes for the worse. Thanks for everybody's help!!

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post #12 of 12 Old 08-22-2016, 03:41 PM
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Glad you got her sorted out!

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