Question about Honda VTR 1000 SP-2 (RC51 Motorcycles

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1000sp2 2003 model.running lean &backfireing top end+-7000rpm .fuel press.ok...plugs new...valve clearens 100%.injectors test& throttel cdi unit...only part not change is ECU....

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It must be the ecu get it tested buddy

Posted on Sep 28, 2009

Testimonial: "Thanks i will test the ecu.and thanks for your help"


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1997 opel corsa 14i while drive if I depress accelerator car backfires,how do I fix that

Tune it up. New spark plugs if they are over 50,000 miles old.

Backfiring is typically a symptom that occurs with a gasoline engine that has spark plug wires crossed, spark cross firing inside the distributor cap in dust or condensation or an over lean condition.

If it runs smoothly when normal cruise it wouldn't be crossed wires so that leaves an over lean condition or cross firing in the distributor cap as the most likely causes. So check the inside of the distributor cap for moisture, dust etc and clean it if you find it.

Next, to check for over lean on acceleration the most likely is partially plugged fuel filter so renew it. Next step is to clean the fuel injector (s) with the good breed of fuel injector cleaner that you add to the fuel.

Sep 05, 2015 | Opel Cars & Trucks

1 Answer

Engine keeps backfiring under load motor is an enduro xl 13.5 hp

Need Make/Model/Year/Engine Model/Deck Size, and hours on meter if you have one. A short description of the events preceding the beginning of the problem is also helpful.

Several possibilities:
1. Needs a valve adjustment or a valve job. Start with adjustment.
2. Needs new plugs. Start with new plugs.
3. Shear pin under flywheel is slightly damaged throwing off the timing. Remove flywheel examine shear pin for any damage. Just go ahead and replace it; if it even looks nicked or sliced.
4. Coil, or spark plug wire, is going bad. Very hard to test a coil for weakness without test equipment that the average person doesn't have. Check the first 3 problems, first. If it still backfires, then replace coil.
5. The other thing that causes backfire is fuel mixture too lean. On a small engine this is not usually an adjustment problem. It may be the fuel system/carburetor is dirty or partially clogged. It may also be an air leak in the gaskets of the intake manifold. If nothing else solves the backfire, remove the carburetor and clean or rebuild it. This is the least likely of the options so save it for last.

If compression is good and cylinder leakage is minimal, but a cylinder is misfiring or shows up weak in a power balance test, it indicates a fuel delivery or ignition problem (fouled spark plug or bad plug wire). A power balance, or cylinder balance, test should be run on a twin cylinder engine.

If an engine is hard starting, runs rough, misses or lacks power, run a cylinder balance test to determine if both cylinders are operating to their full potential. You will need an engine tachometer, a spark tester, and an insulated screwdriver.

1. Using the spark tester, with the plugs in, start engine and verify spark is equally good on both cylinders. Remove spark tester.
2. Connect engine tachometer.
3. Run engine at top no load speed. Note rpm.
4. Ground one cylinder spark plug with screwdriver. Note rpm.
5. Ground other cylinder with screwdriver. Note rpm.

The difference in RPM between the cylinders should be less than 75 rpm. If the difference between the two cylinders is greater than 75 rpm, the cylinder with the least rpm loss is the weakest and is a potential problem.

Note: If the spark plugs are new this could be an indication of a weak coil. Of course it could also be compression (rings), or valves.

Mar 24, 2015 | Garden

1 Answer

Fix cracking & popping in engines backfires in exhaust

This could be anything from bad ignition to timing to bad fuel supply (lean) to bad valves in engine. Run compression test to eliminate worst case, check both ignition and cam timing, vacuum leaks, ignition module.

Jan 19, 2015 | Cars & Trucks

1 Answer

I have a 95 chevy K3500 7.4L TBI, when cold it misses a little but as son as it warms up it runs fine. Plugs & plu wires only have about a year on them

if it only does this cold until it warms up it sounds like carbon build up on the back of the valves. this causes fuel to be absorbed when cold before the fuel enters the combustion chamber causing a lean condition. have a top end fuel service done this will clean the carbon off the valves. depending on how bad the carbon build up is you might have to do this a couple of times.

Sep 21, 2014 | 1995 Chevrolet K3500

1 Answer


Back firing is caused but lean conditions suggest a fuel injector volume test. This requires a injector pulse generator. pulse each injector for same interval usually 100ms and record pressure drop and re prime line between each test for accurate values. If all is fine. remove valve cover check for broken valve spring or flat camshaft lobe. low rocker arm movement.

Nov 09, 2013 | Jeep Cars & Trucks

1 Answer

Why my 1997 f150 4.2 runs bad

Fuel supply or valve-train issues come to mind.
If the fuel mixture is lean, that will cause backfiring and loss of power. Poor fuel atomization caused by incorrect pressure or plugged injectors should be considered.
Cam timing is a possible issue. Has the cam drive slipped?
Best wishes!

Dec 25, 2012 | Cars & Trucks

1 Answer

95 chevy 1500 pops and backfires doesn't want to shift into overdrive when cold when it does the truck runs real rough

Have you checked the fuel pressure under a load, low pressure will cause these symptoms. The test port is on the top of the engine in the fuel supply rail to the fuel injectors, the fuel pressure test port looks like a large tire fill valve. You will need a fuel pressure test gauge to do this test (about $20), the pressure must be watched while you accelerate, it should never go down on hard acceleration just up about 6-8 PSI

Mar 14, 2012 | 1995 Chevrolet K1500

1 Answer

The reason I'm checking the timing belt is that there is mis-fire in 1 & 2 cylinder. If the firing order is 1,2,3,4. I have continues fire out of 1 & 2, when plug wires are pulled out of head. 3...

unplug the fuel injectors, check the olhms on all. the readings should all be the same, around 11-11.5 olhms. Any readings that are higher is a sign of a bad injector which is what your problems sounds like., putting to much fuel to a cylinder causing different fuel amounts to each cylinder and causing it to backfire out of the throttle body , excess fuel . Also remove the throttle body and clean with cleaner and a toothbrush after replacing any injectors. Or there's a simpler answer and that the cambshaft is worn-out/round causing the lifters not to open enough to let in all the fuel. A worn belt would not cause misfires only on select cylinders but rather jump timing, slipping a notch on a gear and possibly bending a valve or valves and this cause a loud clacking or a really a sign to quit running the motor because it's broke! Good luck.

Oct 16, 2010 | 2004 Kia Rio

1 Answer


The problem is almost certasinly that dried gas residue has plugged the injector spray tip, most likely they are ruined and will need to be replaced, the only way to determine this 100% is to have a dealer run a injector flow test, they may be able to power clean them, here is the price of the replacements.

ACDELCO Part # 217296 moreinfo.gif {#17112982}
INJECTOR KIT,SEQ M/PORT FUEL REQUIRES O-RING P/N 217-1379 217-296.jpg $95.79

Apr 14, 2009 | 1991 Cadillac DeVille

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