Sluggish performance troubleshooting

Sharif

Member
Joined
May 28, 2019
Messages
114
Trying to find the source of the loss in torque. Recently installed a new air filter, cleaned + inspected the carb yesterday and that was fine as well, changed the spark plug boot cap, checked spark plug, looks pretty clean.

I read somewhere the more open air filter causes the engine to run more rich without changing the jet, also running through fuel quicker as well recently.
Can an air filter seriously cause all this?

Spark Plug currently
89972


Air Filter in question
20190821_144418.jpg
 


extremeodd

Active Member
Joined
Mar 30, 2019
Messages
288
Typically when you increase air flow you need to increase your fueling as there is less of a vacuum and carburetors are purely a vacuum driven system. That is exactly how the choke on the stock carbs work, they restrict airflow which increases fuel delivery. From the sounds of it this filter is more restrictive than your previous one, that would explain the excessive fuel usage and poor power.

Try going for a quick ride with no filter and see if it improves or gets worse. If it gets worse, lower the needle clip. If it gets better, raise the needle clip. If your at the end of the clip adjustments, you'll need to either up or down jet depending on what end of the needle (top: smaller jet. bottom: larger jet).
 

Zak

Active Member
Joined
Mar 21, 2019
Messages
252
I've ran a little rich until recently. My plug is brown and shiny. Yours looks white and dull. Are you running too lean or is that how my plug should look?
 

LewieBike

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Joined
May 21, 2014
Messages
812
A more open filter generally causes your engine to run slightly leaner if anything.

Is the engine 4 stroking and sputtering under full throttle?

The grey color of your plug concerns me, as this could be a sign that your cylinder is shedding it's chrome plating. You also have a lot of speckles on your plug's interior metal section surrounding the insulator, which could be bits of engine cylinder liner.

Also there's a lot of baked on oils on the threads of your sparkplug, are you torquing the plug down firmly, and are you still running 16:1 fuel oil ratio?
 
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Sharif

Member
Joined
May 28, 2019
Messages
114
Typically when you increase air flow you need to increase your fueling as there is less of a vacuum and carburetors are purely a vacuum driven system. That is exactly how the choke on the stock carbs work, they restrict airflow which increases fuel delivery. From the sounds of it this filter is more restrictive than your previous one, that would explain the excessive fuel usage and poor power.

Try going for a quick ride with no filter and see if it improves or gets worse. If it gets worse, lower the needle clip. If it gets better, raise the needle clip. If your at the end of the clip adjustments, you'll need to either up or down jet depending on what end of the needle (top: smaller jet. bottom: larger jet).
I put the original predator one and went to work today, actually did climb the hill normally...makes me wonder if the air filter really is the culprit. To be honest I didn't touch the c clip since I got this kit mainly because I felt like I didn't know enough to mess with that, think it's about time.

The new open air filter is definitely less restrictive, tried blowing through it, there was barely any resistance.
Will play around with that tomorrow morning.
 

Sharif

Member
Joined
May 28, 2019
Messages
114
I've ran a little rich until recently. My plug is brown and shiny. Yours looks white and dull. Are you running too lean or is that how my plug should look?
Mine was a bit browner than that, think it might be how the picture turned out. Don't really know much about spark plug colour charts
 

Sharif

Member
Joined
May 28, 2019
Messages
114
A more open filter generally causes your engine to run slightly leaner if anything.

Is the engine 4 stroking and sputtering under full throttle?

The grey color of your plug concerns me, as this could be a sign that your cylinder is shedding it's chrome plating. You also have a lot of speckles on your plug's interior metal section surrounding the insulator, which could be bits of engine cylinder liner.

Also there's a lot of baked on oils on the threads of your sparkplug, are you torquing the plug down firmly, and are you still running 16:1 fuel oil ratio?
I read about 4 stroking few times, but I am not entirely sure what that means. It doesn't sputter, but rather feels like it loses power, unless I gradually go full throttle on flat ground.

I was having a different issue after cleaning the carb few weeks back (I bent the tang down without realising what I did) and just completely lost power at full throttle, put it back up again now. At the time, before I realised what was the cause I added more oil to my gas can mix to turn it into 20:1, was running 24:1 previously, it did improve the issue, but I was getting at the wrong thing at the time. I am open to a recommended mix, currently got synthetic oil as well, decided to use that to make sure everything is lubricated well and the engine last, getting metal shavings instead is the last thing I had in my mind lol

Regarding the torque, not having a torque wrench, go easy on the twisting in fear of stripping threads with it being aluminium and all. Still working on the "doing it by feel".

Edit
Should add I have a banana pipe without a muffler, fell off, will add after solving this or just give it a go with muffler putty tomorrow. Didn't notice any power increase, but engine runs much smoother overall, minus the engine going back to idle has been hit or miss lately (exhaust gasket has no leak, had that issue with the old exhaust, already checked)
 
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Sharif

Member
Joined
May 28, 2019
Messages
114
I'll check the spark plug again and make sure, colour temperature on the final image matches what I saw, had the camera set to auto and didn't think of it at the time.

Goodnight world
 

LewieBike

Well-Known Member
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May 21, 2014
Messages
812
I'm not saying your engine is 'eating itself", and you seem to be using enough oil....

But that's a very unusual plug color. An opaque battleship grey isn't exactly a color I've seen on any motorbike or car sparkplug I've operated.

Has your compression, the resistance to your pedaling while starting the bike seem to have fallen off? Usually you can feel it by putting your bike on the center stand with the clutch engaged, and set the left crank forward and horizontal, and place about half your body weight on the left pedal.

If the compression is good the crank should not easily rotate forwards.
 

Sharif

Member
Joined
May 28, 2019
Messages
114
I'm not saying your engine is 'eating itself", and you seem to be using enough oil....

But that's a very unusual plug color. An opaque battleship grey isn't exactly a color I've seen on any motorbike or car sparkplug I've operated.

Has your compression, the resistance to your pedaling while starting the bike seem to have fallen off? Usually you can feel it by putting your bike on the center stand with the clutch engaged, and set the left crank forward and horizontal, and place about half your body weight on the left pedal.

If the compression is good the crank should not easily rotate forwards.
I feel pretty certain at this point the problem is gone after using the old air filter after a day, was working on getting disc brakes installed on the front today and didn't have time to fiddle around with the clip, will do that tomorrow and update.

I will be going to the petrol station to mix oil for the next month tomorrow and was wondering what ratio do you reccomend?
Was thinking of going back to 25:1 again
 
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