CBR F4 cranks but does not start - Help | GTAMotorcycle.com

CBR F4 cranks but does not start - Help

K

k2p2

Active member
I’ve been working on my CBR F4 for the past two weeks but have run out of ideas so I’d be grateful if anyone could point me in the right direction.
The bike wasn’t winterized properly so I started with draining my float bowls and gas tank and then added new fuel (6L) and about half of a can a Seafoam. The bike would crank and the exhaust would pop and a little white smoke would come out here and there but no start.
Next I removed the carbs, took apart the float bowels and the vacuum chambers, cleaned them with carb cleaner and put it back together ( Note: I didn’t take out the retaining pin on the float as it was my first time cleaning carbs and didn’t wanna break anything). It made no difference and the occasional spark out of the exhaust and the white smoke were no longer happening.
Here are my questions:

1) Should I take the carbs apart again and try cleaning the float valve ( I should mention that I had my carbs cleaned by a mechanic last season and they looked clean when I took them apart; however when I would drain the bowls I noticed a lot more fuel would come out of the leftmost bowl than the rightmost one [sorry if I’m not using the technical terms])
2) I realized (a little too late) that half a can of Seafoam is too much for 6 L of gas. Do you suggest discarding the fuel in the tank and using just gas (no seafoam) ?
3) What are the next steps if the issue isn’t the carbs

As always I appreciate your help :)
 
You seem pretty knowledgeable but it wasnt mentioned so I will ask.

How's the spark?

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I have no experience with seafoam. Does it degrade the octane or affect the gas? I once had a tank of gas with generic carb cleaner in it do exactly what you are saying. The bike would pop, backfire, sputter, but wouldn't go. I drained it and put in clean, untreated gas and it fired up.

When you initially drained the float bowls what was the gas like? Did it smell like varnish? With the float bowls off did you see any rings of sediment from evaporation of the gas?
 
peterm15 said:
You seem pretty knowledgeable but it wasnt mentioned so I will ask.

How's the spark?

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Click to expand...

That’s what’s next on my list. I’m going to perform a spark test this evening. I’ve only put about 5K on the bike since the spark plugs were last changed so I doubt that’s the issue but I will report back tomorrow morning.
 
Plugs may need a cleaning.

My suggestion is to remove the plugs, give them a wipe with gas to get any junk off, check the gap and reinstall.
Drain the gas and add fresh. (The above degrade comment makes sense)
Try again.

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doozerdave said:
I have no experience with seafoam. Does it degrade the octane or affect the gas? I once had a tank of gas with generic carb cleaner in it do exactly what you are saying. The bike would pop, backfire, sputter, but wouldn't go. I drained it and put in clean, untreated gas and it fired up.

When you initially drained the float bowls what was the gas like? Did it smell like varnish? With the float bowls off did you see any rings of sediment from evaporation of the gas?
Click to expand...

Thanks for the reply. I’ll empty the tank and put new gas in today and see if that makes a difference. Any idea why I’m not getting the pop and the spark out of the exhaust after carb cleaning ?
No rings of sediment in the bowls at all. They looked pretty clean (which was expected as they were serviced last season).
 
peterm15 said:
Plugs may need a cleaning.

My suggestion is to remove the plugs, give them a wipe with gas to get any junk off, check the gap and reinstall.
Drain the gas and add fresh. (The above degrade comment makes sense)
Try again.


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Click to expand...


Thank you. Will definately try that and report tomorrow morning
 
Just clean the plugs while the gas is draining. It takes 5 min. Kill 2 birds with 1 stone.

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Ha! 5 minutes... LOL... Assuming the coils are easy to get off, it might take you 15 minutes if you're quick. Still not bad.

If the carbs still looked clean inside then I'd blame the gas.
 
Took the spark plugs out, cleaned them and they all tested ok.
The bike still doesn't start.

The manual says to reach the spark plugs by moving the radiator to the side which is an absolute nightmare. All you gotta do is remove the air cleaner housing and they're right there. Wasted 2 hours trying to swing the damn radiator to one side.

Any ideas guys ?
What's next ?
 
So visually see a spark when cranking? Is the choke cable operational?
Battery voltage test?
fuel pump priming?, petcock on or off?
 
Jayv said:
So visually see a spark when cranking? Is the choke cable operational?
Battery voltage test?
fuel pump priming?, petcock on or off?
Click to expand...

Yes I could visually see sparks when cranking.
Checked the choke cable as well. Petcock is on. I will test the battery voltage and report back but the battery is only one season old so I doubt that's the issue.

As for the fuel pump: after draining the carb bowls and giving it a couple of cranks, I have gas in the bowls again so I'm assuming the pump is functional. Correct ?
 
If there is gas in the bowls and spark it should at least fire a few times. There is a flow test that can be done on the fuel pump, but if the bowls are filling then it's most likely okay. Certainly okay enough to run an idle for a bit.
 
Is there a way to check whether the same amount of gas gets to each bowl ?

When I drain them, it seems like a lot more gas comes out of the leftmost bowl than the rightmost one. I assumed that's because the bike is on the stand and is at an angle but apparently the same amount of gas needs to go to each bowl. Am I overthinking this ?
 
Last edited:
Drain each, one at a time, into some sort of measuring vessel?
 
Swap gasoline for propane ... just route a hose to the air box. Turn the gas on for about 15s, turn the gas off. Start the bike. If it fires (it will run only for few secs) your problem is the gas supply. If it doesn't, it's something else mostly electric related.
 
k2p2 said:
Is there a way to check whether the same amount of gas gets to each bowl ?

When I drain them, it seems like a lot more gas comes out of the leftmost bowl than the rightmost one. I assumed that's because the bike is on the stand and is at an angle but apparently the same amount of gas needs to go to each bowl. Am I over thinking this ?
Click to expand...

Even if your levels are off, the bike should still fire, unless you have way too much gas getting through (due to failing carb valve seals) ...
 
The fuel is not getting to the carbs anymore.
When I push the starter button the fuel pump just makes a single click but I cant feel the continuous pumping of the fuel.
I took the fuel pump out and ordered a new one but am now thinking maybe it’s my relay and not the fuel pump.
Is there a way to test the fuel pump itself ? Can I connect it directly to the battery ? How do I check the relay ?
 
mxs said:
Even if your levels are off, the bike should still fire, unless you have way too much gas getting through (due to failing carb valve seals) ...
Click to expand...

I did a similar test. I injected some fuel into the carbs and the bike started for a second or two which led me to believe I wasn't getting fuel to the carbs.
Hopefully it is the fuel pump
 
Yes, you can connect it directly to the battery. You should connect it to a fused battery terminal to be safe. If you slip and short something, or if the motor is already shorted you could get some sparks and if you're lucky some welding. LOL

Test the relay by connecting the coil to the battery (again a fused line). You should hear the contact click firmly.
 
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