diagnostic help needed: misfiring at 7500rpm - Honda RC51 Forum : RC51 Motorcycle Forums
 7Likes
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 26 (permalink) Old 07-30-2019, 11:35 AM Thread Starter
Senior Member
 
jondog9's Avatar
 
Join Date: Aug 2010
Location: Northern CA
Posts: 8,653
Mentioned: 15 Post(s)
Quoted: 317 Post(s)
diagnostic help needed: misfiring at 7500rpm

I'm getting an irritating misfire when I'm working the bike hard in the canyons and mountain roads.
Bike temp is averaging 180F, and it starts happening at about 3000 feet elevation.
I live at sea level, but I've been riding my bike in these same areas for years, this problem is new. Same PC3r and same fuel map-Kyle's Sato lowmount map.

Symptom:
Starts cutting out slightly at about 7000-7500. Continues cutting out till about 8000+.
Stops cutting out from 8000 and up, and seems fine below 7000, altho I feel slight occasional surging at a steady speed.

What I've done:
Replaced spark plugs, and air filters.
Honestly, I can't really 'feel' a difference, but they were due.
First pic is the old plugs, with about 7500 miles on them. Second pic is the new plugs with 250 miles on them. Do they look ok?
The fpr is new, but I checked it anyway, even put a little vacuum on the nipple - it held rock steady at 9Hg.

This is where I need help.
My line of reasoning is to check the following:
Bypass PC and ride the bike to see if that changes it.
While I have the tank raised, I'll check all the fuel injector connectors and pulse gen connector. I'll check coils, ECU, and CDI connectors.

Somehow I feel like it's not connectors.

Other facts about my bike:
2000 SP1 that's been well maintained for the last 10 years and 35,000 miles. It's at 51,000 now. Regular fluid changes, valve inspections, etc. My PC3r is at least 12 years old, but is secured snuggly in tail. Not bouncing around.

Suggestions and input appreciated.
Attached Thumbnails
Click image for larger version

Name:	spark plugs 1.jpg
Views:	33
Size:	85.8 KB
ID:	130913   Click image for larger version

Name:	spark plugs 2.jpg
Views:	36
Size:	90.8 KB
ID:	130915  

John, 2000 RC51 #000100

jondog9 is offline  
Sponsored Links
Advertisement
 
post #2 of 26 (permalink) Old 08-02-2019, 06:12 PM
Junior Member
 
Join Date: Jul 2019
Posts: 2
Mentioned: 0 Post(s)
Quoted: 0 Post(s)
Make sure the spark plug tips are tight, and the ends of the wires fully engage the plugs when seated in the bore. Swap out with a known good set of coils. I had a problem in my car where, high load, higher rpm would misfire. Spent quite a bit of $$$ on the fuel system, until I replaced the coils, and no more misfire.
jondog9 likes this.
RC51V-2 is offline  
post #3 of 26 (permalink) Old 08-03-2019, 08:01 AM
Member
 
Join Date: Aug 2014
Location: Tri-State Area
Posts: 32
Mentioned: 1 Post(s)
Quoted: 4 Post(s)
With such an issue I would normally suspect an ignition related problem and would begin by performing a Peak Voltage Test between the Ignition Pulse Generator and the ECM. I would perform this same test twice, both before and after disabling the PC3R, while noting any differences between the two test results. See Page 17-4 of the Service Manual for details. However, your comment about the problem beginning at an elevation of about 3,000 feet would lead me to the fuel system. Have you considered testing the BARO/MAP sensors? See Page 5-57 of the Service Manual for further details.

The BARO sensor is responsible for sensing changes in barometric pressure and alters the ECM behavior accordingly. It accomplishes this by varying its output voltage in response to altitude changes. It is possible that the sensor may fail at a specific point over its intended operating range, causing the ECM to incorrectly adjust the fuel settings at or above certain altitudes. Such a failure may cause the symptoms you are describing.

See the graph on Page 5-57 of the Service Manual to get an idea of how the sensors should behave when operating normally. Page 5-11 illustrates test points on the ECM to confirm output voltages.

BTW, the plugs look fine, though a bit on the rich side.
jondog9 likes this.

Current Rides:
2001 Honda RVT 1000R, SP1 - a.k.a. RC 51
* 90 Degree, Single Pin Crank, V-Twin
* World Superbike Championship, 2000 & 2002
* AMA Superbike Championship, 2002
2010 Aprilia RSV4 R
* 65 Degree, Dual Pin Crank, V-4
2017 Honda CBR 1000RR, ABS - a.k.a. Fireblade
* Flat Plane Crank, Inline Four

Previous Rides:
1990 Kawasaki ZX-10
* World's Fastest Production Bike When First Introduced
And a whole bunch of dirt bikes.

Last edited by Enxss; 08-03-2019 at 08:16 AM.
Enxss is offline  
 
post #4 of 26 (permalink) Old 08-03-2019, 08:34 AM
Senior Member
 
Join Date: Nov 2018
Posts: 150
Mentioned: 0 Post(s)
Quoted: 39 Post(s)
Fueling is rich somewhere looking at the new plugs.
Joe XR is online now  
post #5 of 26 (permalink) Old 08-05-2019, 03:25 PM Thread Starter
Senior Member
 
jondog9's Avatar
 
Join Date: Aug 2010
Location: Northern CA
Posts: 8,653
Mentioned: 15 Post(s)
Quoted: 317 Post(s)
Update.
I reset/zeroed the three buttons on the outside of the PC3r. Then I hooked my computer up to look at the fuel map.
It's been running the Kyle Sato lowmount map, and on the surface, everything looks as it should. I recalibrated the throttle position sensor too.

Then I took a serious ride Saturday morning. It ran very well thru the rpm ranges at all altitudes.
But later that afternoon, when the weather got hotter and hotter as I was coming down in elevation, the misfire started happening again. especially at low rpm. I could hardly keep it running below 4000rpm. Got on the freeway and at constant speed it pretty much smoothed out until I hit the city streets again. Had to keep cranking the throttle some to keep it from dying and it was surging from 1000 to 3000rpm when held at quarter throttle. Made it home.

I believe it's safe to say altitude isn't in the picture anymore, however, heat seems to be. All the times this has happened it has been hot weather and the bike's been working hard.

I'm going to ride once more with the PC3r unhooked and see what happens. After that, as per the advice above, I'll see if I can get a peak voltage adapter for my multimeter, and test the coils and pulse generator.

John, 2000 RC51 #000100

jondog9 is offline  
post #6 of 26 (permalink) Old 08-05-2019, 06:43 PM Thread Starter
Senior Member
 
jondog9's Avatar
 
Join Date: Aug 2010
Location: Northern CA
Posts: 8,653
Mentioned: 15 Post(s)
Quoted: 317 Post(s)
Just got back from a test ride and it's not the PC3r. I'm still getting a terrible stumble when I try to start from a standing stop. Imagine trying to start in second gear with OEM sprockets. That's what it feels like and I have -1+2 sprockets. In first gear, I have to really feather the clutch to get going or it will stumble and die. And of course, then the notorious SP1 clutch judder starts up - complicating acceleration even more.

I realize the symptoms are kinda changing, a little erratic. I'm still leaning towards electrical.
Peak voltage test to come next.
Maybe I'll end up doing the coil over plug mod. Don't know yet, have to (keep trying to) figure the real source of the problem.

Special thanks to Wibbly and Enxss for their detailed advice.

John, 2000 RC51 #000100

jondog9 is offline  
post #7 of 26 (permalink) Old 08-05-2019, 06:44 PM
Senior Member
 
Join Date: Sep 2015
Location: Edmonton, AB
Posts: 1,477
Mentioned: 7 Post(s)
Quoted: 317 Post(s)
It could be a battery/charging system thing as well.

If you have a small multimeter you can install it on the bike and monitor voltages as the issue is occurring.
jondog9 likes this.
Wibbly is online now  
post #8 of 26 (permalink) Old 08-05-2019, 06:53 PM Thread Starter
Senior Member
 
jondog9's Avatar
 
Join Date: Aug 2010
Location: Northern CA
Posts: 8,653
Mentioned: 15 Post(s)
Quoted: 317 Post(s)
Quote:
Originally Posted by Wibbly View Post
It could be a battery/charging system thing as well.

If you have a small multimeter you can install it on the bike and monitor voltages as the issue is occurring.
This is good because the problem occurs most as load increases.

Been considering the charging system too. It's a little lower on the list of possibilities, simply because I continue to have ample cranking power and my battery is only about 6 months old.

I'll include a stator test and reg/rec check on my to do list. Rick's, (the ones that sell the mosfet reg/rec) offer a nice little voltmeter that I've been thinking about for sometime now.

But for the moment, I need to get a peak voltage adapter and see what the coils are putting out.

John, 2000 RC51 #000100


Last edited by jondog9; 08-05-2019 at 07:14 PM.
jondog9 is offline  
post #9 of 26 (permalink) Old 08-05-2019, 09:25 PM
Member
 
Join Date: Aug 2014
Location: Tri-State Area
Posts: 32
Mentioned: 1 Post(s)
Quoted: 4 Post(s)
Have you tried performing a Self-Diagnostic on the injection system since your last ride? See Page 5-7. If so, are you getting any error codes?

Current Rides:
2001 Honda RVT 1000R, SP1 - a.k.a. RC 51
* 90 Degree, Single Pin Crank, V-Twin
* World Superbike Championship, 2000 & 2002
* AMA Superbike Championship, 2002
2010 Aprilia RSV4 R
* 65 Degree, Dual Pin Crank, V-4
2017 Honda CBR 1000RR, ABS - a.k.a. Fireblade
* Flat Plane Crank, Inline Four

Previous Rides:
1990 Kawasaki ZX-10
* World's Fastest Production Bike When First Introduced
And a whole bunch of dirt bikes.
Enxss is offline  
post #10 of 26 (permalink) Old 08-05-2019, 09:47 PM Thread Starter
Senior Member
 
jondog9's Avatar
 
Join Date: Aug 2010
Location: Northern CA
Posts: 8,653
Mentioned: 15 Post(s)
Quoted: 317 Post(s)
Quote:
Originally Posted by Enxss View Post
Have you tried performing a Self-Diagnostic on the injection system since your last ride? See Page 5-7. If so, are you getting any error codes?
The FI light has acted normally, no codes. I haven't done the test yet. Done it a few times in the past, cleared all the codes last time I had an issue that got resolved.

John, 2000 RC51 #000100

jondog9 is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Honda RC51 Forum : RC51 Motorcycle Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in













Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome