KFX 450 HQ Forum banner

1 - 16 of 16 Posts

·
Registered
Joined
·
25 Posts
Discussion Starter #1
Had been running great and then injector stuck. It ended up filling pipe with fuel trying to get it to start. So bought a new oem injector and now it wont run right. It starts idles fine and will rev up if you ease into and threw the throttle. If you accelerate hard it cuts out and pops/ backfires and will stall out then takes a bit to start. I've checked valves, {within spec} tps is based set at .62 and wide open 3.98 readings are smooth threw the throttle no spikes or jumping of volts. Fuel pressure is showing 48lbs and holds steady even when it acts up. The roll over sensor has bypass kit in it. Tried a different coil also. Not sure on what is causing this now
 

·
Registered
Joined
·
21 Posts
How old is the battery? Low voltage and/or capacity could be an issue. You didn't mention the spark plug, did you check gap?
 

·
Super Moderator
Joined
·
9,699 Posts
Ok!

List your upgrades unless it completely stock...?

Standard fuel pressure is 43 psi.

Back firing & cutting out is a sign of a lean fuel mixture.

Bogging down motor, really sluggish to accelerate is a sign of too rich fuel mixture.

"Stating your motor flooded prior to replacing your injector" now running crappy...Check/replace your water temp sensor...

Water temp going faulty will enrich your fuel mixture & flood your motor, when it goes bad it's causes a too lean fuel mixture...
 

Attachments

·
Registered
Joined
·
25 Posts
Discussion Starter #4
Battery is only about 2 months old showing 12.8 volts. Plug was new before this happened and have checked gap since it happened.

How old is the battery? Low voltage and/or capacity could be an issue. You didn't mention the spark plug, did you check gap?
 

·
Registered
Joined
·
25 Posts
Discussion Starter #5
Has hmf slip on, hmf optimizer, ltr intake tube into dasa box. Fuel pressure shows 48lbs on my gauge and holds.The injector had actually stuck and was always allowing some fuel by. I did replace the water temp sensor already thinking that may have been it. Plug color shows that its not running lean, its a nice dark color maybe showing a tad rich.

Ok!

List your upgrades unless it completely stock...?

Standard fuel pressure is 43 psi.

Back firing & cutting out is a sign of a lean fuel mixture.

Bogging down motor, really sluggish to accelerate is a sign of too rich fuel mixture.

"Stating your motor flooded prior to replacing your injector" now running crappy...Check/replace your water temp sensor...

Water temp going faulty will enrich your fuel mixture & flood your motor, when it goes bad it's causes a too lean fuel mixture...
 

·
Registered
Joined
·
25 Posts
Discussion Starter #6
Forgot to mention, have tried it with optimizer unhooked also and have tried different settings and still the same.
 

·
Super Moderator
Joined
·
9,699 Posts
Forgot to mention, have tried it with optimizer unhooked also and have tried different settings and still the same.
Service manual...states...
Fuel Pressure (High Pressure Line):
With Engine Idling 294 kPa (3.0 kgf/cm², 43 psi) with fuel pump running...

48psi is too high and will damage/wear out the injector's internal spring, causing it not to close completely, Thus allowing fuel by & reason for a rich fuel mixture..A rich fuel mixture will cause carbon build up on the piston & valve surfaces & can cause pre ignition/detonation to occur...Might explain the cutting out & poor performance..add seafoam motor treatment to a couple tank fulls to clean up fuel pump regulator & system..

Also low compression can cause your symptoms you have as well...!!

Does the motor start right up cold but it's harder to start hot...???

If yes..Check your valve clearance
Valve Clearance: between cam and valve lifter
Standard:
Exhaust 0.17 ∼ 0.22 mm (0.0067 ∼ 0.0087 in.)
Inlet 0.10 ∼ 0.15 mm (0.0039 ∼ 0.0059 in.)
If the valve clearance is not within the specified range,
adjust it.
 

·
Registered
Joined
·
25 Posts
Discussion Starter #8
Motor starts right up and valve clearance is set right in does with manual. Compression test out at 66lbs. The fuel pressure has read that before it started doing it. I'm not sure that is the issue though. As every aftermarket pump that people install that I've seen comes with a 350kpa regulator which equals roughly 50 psi. So I've thought about it being too much pressure also but, how is everyone else running these aftermarket pump setups with out a issue?


Service manual...states...
Fuel Pressure (High Pressure Line):
With Engine Idling 294 kPa (3.0 kgf/cm², 43 psi) with fuel pump running...

48psi is too high and will damage/wear out the injector's internal spring, causing it not to close completely, Thus allowing fuel by & reason for a rich fuel mixture..A rich fuel mixture will cause carbon build up on the piston & valve surfaces & can cause pre ignition/detonation to occur...Might explain the cutting out & poor performance..add seafoam motor treatment to a couple tank fulls to clean up fuel pump regulator & system..

Also low compression can cause your symptoms your have as well...!!

Does the motor start right up cold but it's harder to start hot...???

If yes..Check your valve clearance
Valve Clearance: between cam and valve lifter
Standard:
Exhaust 0.17 ∼ 0.22 mm (0.0067 ∼ 0.0087 in.)
Inlet 0.10 ∼ 0.15 mm (0.0039 ∼ 0.0059 in.)
If the valve clearance is not within the specified range,
adjust it.
 

·
Super Moderator
Joined
·
9,699 Posts
Motor starts right up and valve clearance is set right in does with manual. Compression test out at 66lbs. The fuel pressure has read that before it started doing it. I'm not sure that is the issue though. As every aftermarket pump that people install that I've seen comes with a 350kpa regulator which equals roughly 50 psi. So I've thought about it being too much pressure also but, how is everyone else running these aftermarket pump setups with out a issue?
Those who drag raced with built motors didn't use the higher pressure regulator because it will damage/wear out the spring of the fuel injector..
They used the STI Denso pink 550cc injector....the KFX OEM injector is 440cc

The Standard is 3.0 bar..But you can get 3.5 bar regulator to improve your pressure to 50 psi...!
(Standard 3.0) 3,0 Fuel pressure regulator KAWASAKI KFX 450R KSF 450 FUEL PUMP 49040-0020 | eBay )

(Upgraded 3.5 WARNING in the description ) 3,2 Fuel pressure regulator KAWASAKI KFX 450R KSF 450 FUEL PUMP 49040-0020 | eBay
Warning
Fuel pressure regulator - with raised operating pressure of 350 kpa
increased pressure. improves the atomisation of fuel in the engine compartment. which will improve the characteristics - engine operation


    • increasing the maximum speed
    • increasing the acceleration of the vehicle
    • faster reaching the maximum speed
With the increased pressure you'll need a dyno to properly adjust your A/F ratio

What's the fuel pressure @ 9000~10,500 RPMs / 3/4~full throttle...Does it drop below 43psi...?
 

·
Registered
Joined
·
25 Posts
Discussion Starter #10
No it holds, that was one of the first things i checked and was hoping for to see. But it holds steady no matter what i do throttle wise.
What's the fuel pressure @ 9000~10,500 RPMs / 3/4~full throttle...Does it drop below 43psi...?
 

·
Super Moderator
Joined
·
9,699 Posts
No it holds, that was one of the first things i checked and was hoping for to see. But it holds steady no matter what i do throttle wise.
What are the HMF optimizer setting your running...?

Test the optimizer for being faulty...Disconnect the optimizer, start it, throttle up, take it for short ride (under load) and see if it clears or worsen...??
 

·
Registered
Joined
·
25 Posts
Discussion Starter #12
Think im at 2.5 ,4,3 right now but have been up and down and tried all combinations along with unhooking it. and no change.

What are the HMF optimizer setting your running...?

Test the optimizer for being faulty...Disconnect the optimizer, start it, throttle up, take it for short ride (under load) and see if it clears or worsen...??
 

·
Super Moderator
Joined
·
9,699 Posts
Think im at 2.5 ,4,3 right now but have been up and down and tried all combinations along with unhooking it. and no change.
If there's is no change to your motor with the HMF optimizer hooked up or disconnected then the optimizer is faulty/not working...
Your symptoms are that of a Lean fuel mixture...I recommend you at least try another HMF or different fuel controller due to LTZ intake tube...!

"Back firing, cutting out & hard starting is lean fuel mixture...!!

Sluggish & slow acceleration bogging down & no performance is a too rich fuel mixture...!!

But also check...?
Check for loose clamps & leaks around the throttle body...also check the vacuum hose to the pressure sensor for cracks...!

What color is your spark plug "spark"...?

Check your harness ground fuel tank mounts for being loose ...?

Also check your harness for any wires installation rubbing against the frame...And check all your harness connection for moister, corrosion, dirty or loose...
 

·
Registered
Joined
·
25 Posts
Discussion Starter #14
how do you tell/check if the optimizer is working? It lights up goes threw all the settings and adjustments.
 

·
Super Moderator
Joined
·
9,699 Posts
how do you tell/check if the optimizer is working? It lights up goes threw all the settings and adjustments.
See if you can boost your optimizer to a richer A/F and see if your motor becomes sluggish & bogs when you throttle up..If there's no change then it's bad...

I'm thinking it was your optimizer that held your injector open & flooded your motor when it went faulty...
 

·
Registered
Joined
·
25 Posts
Discussion Starter #16
Feels like optimizer is working, even with just having throttle cracked a bit and increasing values I can hear tone change. It also feels though it's starting to run better the more i putt around. Maybe a take l tank of bad gas. Gonna try and run it some more tonight and see how it acts
 
1 - 16 of 16 Posts
Top