Engine Misfire - Honda CBR 300 Forum
 6Likes
  • 1 Post By kiwi rider
  • 3 Post By IslandRider
  • 1 Post By kiwi rider
  • 1 Post By r100
LinkBack Thread Tools
post #1 of 9 Unread 07-31-2019, 06:28 PM Thread Starter
Junior Member
 
Join Date: Oct 2018
Location: Vancouver Island
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
(Thread Starter)
Engine Misfire

Hello,


So as the title implies, I'm trying to solve an engine misfire issue.


The bike is a 2015, cb300f. Riden daily, rain or shine. However the last week or so it started to misfire under low speed acceleration, gears 1 through 3. Once up to cruising speed there did not seem to be any problem.



The issue has progressed and now misfires under acceleration and load, such as going up steep hills, also in higher gears while accelerating.


I put some injector cleaner in tank....still misfire.

I took the tank off and checked for water in the gas....none.
I checked the air filter.....clean.
I checked fuel filter....blew fuel through it from both sides and seems ok.



I then put the tank back on, put some gas in and tried riding and still had misfire.



I have now taken the tank back off, and changed my spark plug, however the old one looked OK.



One thing I noticed was that it was easy to take the spark lead boot off, and with the new plug in, the spark plug boot does not fully seat down around the lip of hole in the engine. ( am i describing this clearly ? ) I seem to get good connection to the spark plug though with a solid feeling connection. I also seated the spark plug as per the NGK guidelines. How loose or tight does the spark plug boot seat onto your engine ?


I have yet to try and ride with a new spark plug. If this does not solve the issue, my next plan is to buy a new coil pack and see if its that.


Anyway, any thoughts ? It seems like it could also be a fuel flow problem....injectors ?


Thanks.
IslandRider is offline  
Sponsored Links
Advertisement
 
post #2 of 9 Unread 07-31-2019, 08:19 PM
Senior Member
 
kiwi rider's Avatar
 
Join Date: Aug 2014
Location: Southland, New Zealand
Posts: 5,050
Mentioned: 58 Post(s)
Tagged: 1 Thread(s)
Quoted: 1765 Post(s)
Sounds like you've tried most of the obvious/easy stuff. Does it misfire when your cruising at speed or only under load?

2014 CBR300 (sold)
2018 Ninja 400
kiwi rider is offline  
post #3 of 9 Unread 08-01-2019, 01:08 PM Thread Starter
Junior Member
 
Join Date: Oct 2018
Location: Vancouver Island
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
(Thread Starter)
Only while accelerating under load. There does not seem to be misfire while cruising. This is why I susspect fuel or air flow problem and not spark plug, as its not just all the time random. But to be safe, I thought I would change the spark plug anyway. Just to try a go through a process of elimination.


I guess the next thing would be to test the flow rate of the fuel pump ? I see in the manual there is a spec for flow rate. has anyone ever tried to measure this ?
IslandRider is offline  
 
post #4 of 9 Unread 08-01-2019, 07:26 PM
Member
 
airhead83's Avatar
 
Join Date: Apr 2019
Location: Burke County, NC 28601
Posts: 94
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 40 Post(s)
Quote:
Originally Posted by IslandRider View Post
Only while accelerating under load. There does not seem to be misfire while cruising. This is why I susspect fuel or air flow problem and not spark plug, as its not just all the time random.
While you're trying to figure the fuel rate, take a looky-loo at the rubber fuel and air vent hoses to be sure none have kinked or collapsed. A bad fuel hose will feel really soft and mushy, and allow the interior to close off, but outwardly look OK at a glance. So you need to put hands and fingers on the length of the hose to be sure. No need to over think it, it'll be really obvious something is amiss if the hose has gone bad. Good Luck.

To ride or not to ride? What a stupid question.
airhead83 is offline  
post #5 of 9 Unread 08-01-2019, 07:39 PM
Senior Member
 
kiwi rider's Avatar
 
Join Date: Aug 2014
Location: Southland, New Zealand
Posts: 5,050
Mentioned: 58 Post(s)
Tagged: 1 Thread(s)
Quoted: 1765 Post(s)
Quote:
Originally Posted by IslandRider View Post
Only while accelerating under load. There does not seem to be misfire while cruising. This is why I susspect fuel or air flow problem and not spark plug, as its not just all the time random. But to be safe, I thought I would change the spark plug anyway. Just to try a go through a process of elimination.


I guess the next thing would be to test the flow rate of the fuel pump ? I see in the manual there is a spec for flow rate. has anyone ever tried to measure this ?
No not personally but generally it involves lifting the tank and removing the fuel out line that goes to the throttle body and putting an alternative hose on the outlet that runs into a suitable size container. Turn the key on for the perscribed time (usually a minute) and then measure how much fuel you have in your container.

Wild card: Possibly it is some electrical component breaking down only when a certain amount of load is reached. Ignition coil?
airhead83 likes this.

2014 CBR300 (sold)
2018 Ninja 400

Last edited by kiwi rider; 08-01-2019 at 08:34 PM. Reason: sp mistake
kiwi rider is offline  
post #6 of 9 Unread Yesterday, 03:27 PM Thread Starter
Junior Member
 
Join Date: Oct 2018
Location: Vancouver Island
Posts: 5
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 2 Post(s)
(Thread Starter)
Cool

OK so the update is that I have fixed the problem ! Yes so happy that the bike is running smooth again : )


It was one of two things or a combination, I checked my new battery and it was low...reading just over 12V, so I charged it up to sit at 13V. And I replaced the spark plug. For the spark plug I also tightened up the fittings on the coil and used some dielectric grease on the coil contacts and plug contact. Put tank back on and now we are good again.



Thanks for the input and ideas.




Island Rider
IslandRider is offline  
post #7 of 9 Unread Yesterday, 08:27 PM
Senior Member
 
kiwi rider's Avatar
 
Join Date: Aug 2014
Location: Southland, New Zealand
Posts: 5,050
Mentioned: 58 Post(s)
Tagged: 1 Thread(s)
Quoted: 1765 Post(s)
That's good your running smoothly again. Hard to know what it was as you did three things at once, but I'd put my money on the low batt voltage.
It would be worth checking your alternator output with a multi meter incase it is not charging the battery sufficiently. You should expect to see around 14 to 14.5 volts going in.
shisoshin likes this.

2014 CBR300 (sold)
2018 Ninja 400
kiwi rider is offline  
post #8 of 9 Unread Yesterday, 08:34 PM
Senior Member
 
r100's Avatar
 
Join Date: Feb 2016
Location: Burlington Ontario Canada
Posts: 102
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 38 Post(s)
+1.
What KIWI said.
kiwi rider likes this.

I've spent most of my money on women, motorcycles, and beer.
The rest of it I just wasted.
r100 is offline  
post #9 of 9 Unread Today, 03:43 PM
Senior Member
 
Gromit's Avatar
 
Join Date: Jun 2017
Location: Anglesey, U.K.
Posts: 297
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 87 Post(s)
Garage
Check reg/rec also. If they are going faulty they can destroy your battery.

Don't worry about old age - it doesn't last that long.
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

2016 CBR300RA



To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Gromit is online now  
Reply

User Tag List




Posting Rules  
You may not post new threads
You may not 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