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post #1 of 21 (permalink) Old 03-21-2011, 12:12 PM Thread Starter
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☺☺ LΘΘking for Help with RC51 SP1 ☺☺

Its street time here in Illinois. The weather has broken enough to take out these 1 liter Duc eaters and get the attention that only a V-twin rocket gets.
Keep in mind while reading, there was no unordinary sounds before the service. The weather was good enough that a few of us had a day in the middle of the snow to ride a few hours on a couple days. (no noises then) But a couple weeks ago, I started the routine maintenance on the RC (SP1).
Nothing extravagant, new plugs, air filters, oil, coolant, tightening up loose nuts and bolts, light bulbs, dropped one tooth in front and went up two in the rear, lubed up chain, fixed the D/S Radiator mount brackets, (the radiator and the fan were just hanging there, held up by the tension on the hoses. The last problem is, and maybe this is the cause of one problem, I used Sea Foam. just to stabilize the maybe two gallons of gas that it still had in it. (and hopefully to clean any injectors)
So, I had the tank off, (not the first time) and I also removed the air box (this was the first time on this.) But when all the work was done, I put it back together. First time out, rode it until it was warmed up. I went to jump on the throttle in second gear. I had the throttle halfway pinned and held it. Before it climbed RPM's (I’m guessing somewhere between 3.5 and 5k. The bike hiccupped and the FI light came on for a short second. It was like I snapped off the gas and then reapplied it just as fast, within a second. The FI light didn’t stay on nor does it throw any codes. just flashed at me when it "hiccupped" ( I’m using this term because there’s really no other way to describe it) its not a bog.
But still, at this point I didn’t notice the noise. When I talk about this noise, I’m not talking about the Cam gear chatter... No no no... What I’m talking about sounds similar to someone tapping a coin on the exhaust coming out of the head. I have used a stethoscope to try to pin point the "rattle/Pinging/Rack-Tack-tacking" but nothing sounds out of the norm in the motor with the bike idling or stationary rather. When I ride it, it is dominant from the top of the bike. I tried to ride and "probe" hahaha but I couldn’t hear any valve chatter or piston slap. It is the loudest in higher RPM's. Mostly 2nd gear and possibly 3rd. At one point, I thought that the noise was coming from directly under the gas tank, and at the same time, it sounds like the flapper valve... I did remove the foam rubber pads from the top of the air box and when i started hearing this noise, I replaced them, figuring that it may have always been there but these pads dampened the sound. It does speed up when I accelerate and stops when I clutch it. Regardless of the speed. I laid the end to the stethoscope on the top of my tank while moving and the sound was very dominant... but I guess that the liquid and negative enclosure of the tank could have amplified the noise. I am going to go home tonight and try to get it on you tube tonight (or maybe at lunch) and post a link for everyone to listen to it... Its a new noise to me. This is such a vague description on the issue here, I’m hoping that someone may have heard something similar to this before.

Last edited by 51'er; 03-21-2011 at 12:16 PM.
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post #2 of 21 (permalink) Old 03-21-2011, 05:15 PM Thread Starter
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Update☺☺☺

I can not get a clear recording because of the exhaust.. But it definatly sounds like it could be coming from the gas tank. (inside) I have checked the rear valve covers and heads, fronts also. Is there something on the fuel pump that could be rattling? It does not sound like it is internal motor malfunction. I was thinking that I may need to get those valves adjusted anyways..
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post #3 of 21 (permalink) Old 03-21-2011, 07:39 PM
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The hiccup could have been from the fuel pump or poor electrical connections (ground wire or battery posts).

The noise in the fuel tank probably around the fuel pump area unless foreign object got dropped into the tank. What it is, who knows without inspection.

If it's the engine, I'd guess valves, although these engines are good with keeping valve tolerances. And valve clearances tend to shrink not grow with use as the valves gradually wear further into the seats over time.

Hard to say at this time. Need more data.
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post #4 of 21 (permalink) Old 03-21-2011, 10:23 PM Thread Starter
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Thanks sailor... Glad to see a senior member here still... Allow me to reiterate the sound... It sounds not like a pinking or any metal on metal. It sounds like a piece of plastic or if you take a strip of tape and hold it in the wind.. It's not consistent with motor RPM's. It is making me worried though.. I almost have myself convinced that I should take it in and have the top end inspected.. If I lift the tank of of the airbox, I can't find the noise.. The mechanic (and kid with tools) says... I CAN DO IT!!! Hahaha, im torn here.. Anyone with any valve/inspection work here care to ratethe difficulty 1-10?
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post #5 of 21 (permalink) Old 03-21-2011, 11:06 PM Thread Starter
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On a stupid side note, the plugs that I removed from the front and rear cyl's were not the same.. The rear had the NGK FR9BI 11 (iridium) and the back had a NGK 9 V Power.. (a pretty standard plug.) The most noticeable difference is the length, (the iridium's are a couple mm's longer) and the electrode.. I don't think the guy knew where to find the front plug at... hahahah... I did replace them both with the iridiums. No noticeable gain, yet no loss... About the same.. Last plugs looked like it has been running a tad bit lean. Not too bad though... Stay in touch with any thoughts. Thanks
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post #6 of 21 (permalink) Old 03-22-2011, 12:37 AM
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Are you sure there weren't any screws or bolts that fell from the intake into the head? I've seen this happen several times and nothing will be heard until enough air moves through the head to free the object and then it will eat itslef in the engine or get spit into the exhaust and then not make much of a sound until you reach given harmonic resonances in the exhaust or motor for the noise to appear.

I do hope this is a worse case scenario as it usually mars the piston and head pretty good.

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post #7 of 21 (permalink) Old 03-22-2011, 09:39 AM
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Are you saying that when you pull in the clutch the noise stops? If you rev the bike with the clutch pulled in does it still make the noise?
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post #8 of 21 (permalink) Old 03-22-2011, 10:11 AM Thread Starter
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I am pretty meticulous about my mechanics, each screw, nut and bolt get labeled in their baggies about what part they go to. I am 99.9% that there are not any loose nuts or bolts... This "mystery" rattling now, When i removed the oil cooler the first time, I noticed that the crush spacer in the rubber grommet was not there, but the nut was still on the stud. When I started hearing the noise, I also notice that the nut had fallen off of the oil cooler and it was loose on one side. I thought that it was the vibration making the oil cooler rattle. yea, the noise stops when I clutch it, and when the bike is stationary and I rev the motor, 4.5/5k I can’t hear it... this is why it’s really frustrating me. I can’t ride and lean down to see where the hell its coming from. I’m stripping it down tonight and hopefully find something.. I really appreciate the input from everyone. There weather here is supposed to chill down a few deg so that will give me a few days to get it figured out. I will keep the updates coming and if there are any other ideas, please feel free. The only thing that I did different this time when it was serviced was that I partially removed the air box. It was up off the motor about 6-10" only enough that I had to disconnect one of the drain hoses on the P/S side. I did not want to mess with any other of the hoses. Other than the throttle body, is there something under there that could rattle like that?
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post #9 of 21 (permalink) Old 03-22-2011, 05:52 PM
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On the right hand side on the bottom of the air box is a hose that goes into a plastic bottle, did you hook that one back up? Could be the plastic bottle rattling around.
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post #10 of 21 (permalink) Old 03-22-2011, 08:56 PM
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Quote:
Originally Posted by yellow00tlr View Post
On the right hand side on the bottom of the air box is a hose that goes into a plastic bottle, did you hook that one back up? Could be the plastic bottle rattling around.
That's the crankcase vent catch tank. You do want that hose connected.
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