SP2 - TPS or ECU? Tell me what's wrong... - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 19 (permalink) Old 01-22-2016, 04:51 PM Thread Starter
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SP2 - TPS or ECU? Tell me what's wrong...

Hey guys / gals,

Quick update on any previous threads:

ITS ALIVE

Many thanks again to members here with help and parts. It ended up being a combo of a FPR / Coil / Plug problems. To top it off my fuel pump died in the middle of all that troubleshooting, so it's been a long road. I didn't let the bike win though

It starts and idles fine now.

However, I'm not out of the woods yet: Sometimes, when I crack the throttle just a little bit, it jumps to 5k rpms and sits there. Like, even when I let go of the throttle, it'll sit at a solid 5k for a bit and then eventually drop back down to idle. When I say solid @5k I mean a 10 second or more rev. Randomly happens too.

It's a little unsettling, and I'm afraid to really ride it hard in the twisties if it's going to act that way.

Throttle cable is lubed, checked the action on it, not sticking.

Due to previous issues with the bike, it's as stock as it can be right now. Still have the TurnOne carbon box, but OEM exhaust, no PC3, solid battery.

Thoughts?

The adventurous don't live forever, but the cautious don't live at all...
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post #2 of 19 (permalink) Old 01-23-2016, 09:20 AM Thread Starter
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Just thinking out loud here, but maybe the contacts need some cleaning around the TPS? Or since I still have that ridiculous airbox, maybe too much air? Should I hook the PC3 back up and see if that solves it? Hmmm.
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post #3 of 19 (permalink) Old 01-24-2016, 12:04 AM
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i can't see a tps making an engine rev to 5000 rpm. lift the tank and try to replicate the behavior, i can almost guarantee your throttle plates arent fully closing.
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post #4 of 19 (permalink) Old 01-24-2016, 08:25 AM
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^^^ what Wib says....double check throttle butter flys and make sure they are not restricted at all.
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post #5 of 19 (permalink) Old 01-24-2016, 10:04 AM
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Make sure both throttle cables have plenty of slack in them when conducting this test. The other thing I would look for is an air leak.

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post #6 of 19 (permalink) Old 01-24-2016, 10:58 AM
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Since it only happens sometimes it would first look at everything with the cables and routing of them as well as linkage.
I have had bikes do this and it was because of a cable routing.

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post #7 of 19 (permalink) Old 01-24-2016, 01:46 PM Thread Starter
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Linkage and cable routing are good to go.

Throttle bodies close correctly.

I had it start, idle, then when I just barely started to move the throttle, it jumped to 5k, sat there, then came back down and eventually died. The throttle and rpms seems real jumpy.

Upon restarting, the bike felt like it was going to fire, and right before it caught it 'reset' almost like a weak battery.

I have one of those LiFe lightweight batteries. I started googling and found that some bikes (like ours) don't get along well with those. Anyone seen an alien motion battery wreak havoc like this?
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post #8 of 19 (permalink) Old 01-24-2016, 03:00 PM
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The RC51 takes a lot of power to start and run.

Something i have found especially true with 1st gen fuel injected bikes.
If you have a regular battery i would try and start and run it with that first.

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1988 FZR1000R
2013 YZ-450f
1974 Yamaha RD350
1971 Honda CB500
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post #9 of 19 (permalink) Old 01-24-2016, 03:01 PM
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Oh, or if you dont have that you could run some jumper cables from a car battery.

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1988 FZR1000R
2013 YZ-450f
1974 Yamaha RD350
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post #10 of 19 (permalink) Old 01-24-2016, 05:01 PM Thread Starter
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Tested with standard battery. Same behavior. The bike will stumble around at 2 or 3k like it's 'hunting' if I'm holding the throttle steadly, or (occasionally) rip itself up to 5k and hang there. I literally was watching the bike rev itself, throttle closed, standing there scratching my head.

Out of curiosity, I pulled the plugs out of both cylinders. They were both black, sooty, smelled like gas. The rear plug is now fouled. I have two FPRs I've tested, so I know it's not that issue.

I'm really starting to lean on TPS/Throttle body at this point: 'hunting' for revs, essentially revving itself to 5k for no reason, dumping fuel in both cylinders. Hell, how else would the bike get to 5k with a closed throttle plate? I envision raw fuel just getting blasted into the pistons.

Unless someone has another idea or wants to blame the ECU? I have a spare throttle body I bought a while back so I might get cracking on this. At least I'll know this bike top to freakin bottom soon...

Hell this could have been my problem in the first place.

The adventurous don't live forever, but the cautious don't live at all...
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