detonation - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 7 (permalink) Old 04-01-2016, 03:41 AM Thread Starter
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detonation

Hey!
I have a 2004 with Yosh RS-3 pipes and a PCIII. When the bike arrived here in South Korea it had a massive detonation issue. It would start knocking at around 4500, taper off and come back on around 6500. A very unsettling sound, as in I hope the engine doesn't blow.
The seller said it had a full Yosh system, but contacting Yosh revealed that they only made a full system for the SP1. I tried different maps (the PCIII had a Yosh full system map) and it didn't make much difference. I used the PCIII push buttons to richen it, which reduced the detonation but also the performance. The bike sat for a year or so in the US while I was trying to make shipping arrangements (a very long story). When the shipping arrangements were complete the seller had to drive it 10 miles to a pickup location,. I was thinking the nasty old gas might have plugged the injectors, further complicated that the seller replaced the locking gas cap with another cap that doesn't seal perfectly (I can smell the gas leaking), and this 1 year sit and evaporation probably further skanked the gas.

So lately after reading an issue here about an issue resolved by cleaning the ECM pins I opened it up and yes the pins were somewhat corroded. I cleaned them up holding the ECM in the air with the pins pointing down and dousing with WD-40 and tap it on the ground to get as much WD-40 out. Then I used some fine sandpaper and a knife to try to clean up the pins. Amazingly, the cleaning reduced the detonation, but it's warmed now since the last time I rode it (winter). So I went through the service manual checks to try to narrow down the issue. When I turn on the ignition, the FI light comes on for a few secs and turns off, no blink. When I tested the ECM using the shorting plug, it continuously blinked (did not stop at 20 blinks). I reset it and tested again with the shorting plug, which now gives a normal indication (on continuously). I don't know why the different results. Anyway, no blinks normally.

I tested the MAP, BARO, IAT and ECT portions of the ECM and all tested OK. I did not actually disconnect any of these (I'm adverse to unnecessary work if I can find a work around), I just stuck multimeter leads through the ECM connectors and took voltage and also ohm readings on all pins relating to the above. All looks good.

So any advice would be welcome. I was thinking maybe the throttle bodies might be loose causing an air leak, but that's more work than I want to do. Besides, I would think that Honda has this stuff so engineered that they couldn't possibly have worked loose. Hoping anyway. Thanks for any insights.

I previously had a 2004 but it got stolen. Korean police are a joke, they didn't do anything to find the bike. We have CCTV in our area that everyone has to drive through. I would expect that if you give them a time frame that they could hunt down any vehicles that passed through. Especially if it's an enclosed truck.
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post #2 of 7 (permalink) Old 04-01-2016, 07:56 AM
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try replacing Fuel Pressure regulator

check all the grounds and wiring harness for any corrosion/breaks.


2003 SP2: Everything I could find.
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post #3 of 7 (permalink) Old 04-01-2016, 09:44 PM
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Make sure the gas is of high enough octane too, once you purge the old out.

I'd run a bottle of Seafoam through it too. https://seafoamsales.com/

Best of luck to you.



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Last edited by madbuyer; 04-01-2016 at 09:49 PM.
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post #4 of 7 (permalink) Old 04-03-2016, 08:48 PM
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You're probably talking about pre-ignition, not detonation.

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post #5 of 7 (permalink) Old 04-04-2016, 11:25 AM
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Quote:
Originally Posted by meballar View Post
Hey!
I have a 2004 with Yosh RS-3 pipes and a PCIII. When the bike arrived here in South Korea it had a massive detonation issue. It would start knocking at around 4500, taper off and come back on around 6500. A very unsettling sound, as in I hope the engine doesn't blow.
The seller said it had a full Yosh system, but contacting Yosh revealed that they only made a full system for the SP1. I tried different maps (the PCIII had a Yosh full system map) and it didn't make much difference. I used the PCIII push buttons to richen it, which reduced the detonation but also the performance. The bike sat for a year or so in the US while I was trying to make shipping arrangements (a very long story). When the shipping arrangements were complete the seller had to drive it 10 miles to a pickup location,. I was thinking the nasty old gas might have plugged the injectors, further complicated that the seller replaced the locking gas cap with another cap that doesn't seal perfectly (I can smell the gas leaking), and this 1 year sit and evaporation probably further skanked the gas.

So lately after reading an issue here about an issue resolved by cleaning the ECM pins I opened it up and yes the pins were somewhat corroded. I cleaned them up holding the ECM in the air with the pins pointing down and dousing with WD-40 and tap it on the ground to get as much WD-40 out. Then I used some fine sandpaper and a knife to try to clean up the pins. Amazingly, the cleaning reduced the detonation, but it's warmed now since the last time I rode it (winter). So I went through the service manual checks to try to narrow down the issue. When I turn on the ignition, the FI light comes on for a few secs and turns off, no blink. When I tested the ECM using the shorting plug, it continuously blinked (did not stop at 20 blinks). I reset it and tested again with the shorting plug, which now gives a normal indication (on continuously). I don't know why the different results. Anyway, no blinks normally.

I tested the MAP, BARO, IAT and ECT portions of the ECM and all tested OK. I did not actually disconnect any of these (I'm adverse to unnecessary work if I can find a work around), I just stuck multimeter leads through the ECM connectors and took voltage and also ohm readings on all pins relating to the above. All looks good.

So any advice would be welcome. I was thinking maybe the throttle bodies might be loose causing an air leak, but that's more work than I want to do. Besides, I would think that Honda has this stuff so engineered that they couldn't possibly have worked loose. Hoping anyway. Thanks for any insights.

I previously had a 2004 but it got stolen. Korean police are a joke, they didn't do anything to find the bike. We have CCTV in our area that everyone has to drive through. I would expect that if you give them a time frame that they could hunt down any vehicles that passed through. Especially if it's an enclosed truck.
If an air leak could be causing your problem, you may want to reconsider checking the connecting boots under the throttle body. The clamps can work loose over the years. I remember being a little surprised at how loose mine were when I bought my bike. Same thing on my VFR.
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John, 2000 RC51 #000100

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post #6 of 7 (permalink) Old 05-29-2016, 03:59 AM Thread Starter
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Thanks all! Problem solved! I postponed the work because I knew it could take a day to take care of business. The clamp for the back throttle body had worked loose, much looser than the front. I tightened it up pretty tight, and about the same amount of thread was showing compared to the front clamp. The front clamp was at an angle that I could not get to the screw to tighten. But it appears to be tight. I really didn't expect this to fix the issue, but I guess the connection on the rubber piece between the throttle body and head has enough slop to leak air.

I also reseated all the electrical connections to the throttle bodies and any other connectors I could find.

It also appeared that the PCIII cable was pinched by the tank so I rerouted it.

With the confined space I couldn't get enough torque on the Allen wrench to loosen and remove the fuel hose banjo bolt, so after removing all other fuel hose connections I just added more tool parts at the front of the tank to prop up the the tank further. I was able to prop up the tank enough to remove the air box so Life Was Good.

After putting it back together I gassed her up and uploaded a Sato Low mount map and took her on a ride. I was ready to hear the detonation cacophony come back but the ignition/fuel system behaved like a church mouse!

Thanks again, I had just about given up on the bike.
Mike
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post #7 of 7 (permalink) Old 05-30-2016, 11:13 PM
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Noyyyycce! . .

John, 2000 RC51 #000100

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