Question about 2002 Honda CRF 450 R

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2002 crf450, rough running, back firing, hard start

Hard start, back firing, sudden onset problem, valves? coil? replaced sparkplug but same.

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  • wsg29 Feb 20, 2009

    difficult to kick start, back firing, dificult to start when hot

  • Anonymous Mar 15, 2014

    it run good until gets hot then it starts to cut out like starving for fuel it back fires shut down but it will start up again run for a while and cut of again

  • Tony Young
    Tony Young Jun 14, 2015

    Rough idel?



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Would that cause a rough idal?

Posted on Jun 14, 2015

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Classic valve train issues. Sounds like the valves are tight. One thing that concerns me is the "sudden onset". Valves usually tighten over time.
Make sure you also tighten the cam chain as well.

Posted on Dec 27, 2008


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2000 Expedition is idling badly and stalling.

Have you changed your fuel filter? When is the last time you changed your sparkplugs? Have you had any codes on the computer? Heres what I would do. First change your sparkplugs. This is a 4-6 hour job. You have to unbolt the cop(coil on plug assembly). After you change the plugs your truck will run rough. Drive it around the block then back to your house. It will take 3-5 restarts before your truck quits running rough. Reason for this is because your computer is trying to "relearn" the firing order. I have done this several times so i know what i am talking about. You can even look it up. Your 2000 expedition is a dang good truck with a great engine. After your computer relearns the firing order then the rough idle will be gone. Then I would take it out on the freeway and run it hard for 5-10 miles. If you experience a miss or two then that means you need a new cop(s). Get a code reader and it will tell you which cop is bad. Cops are expensive. I bought 6 new ones on ebay for $40. If you buy from autozone or ford dealer then you are looking at about 80-100 bucks a piece. Tell me if this helps. Ford makes a good truck and the expedition is a great truck. Mine is a 2000 expedition also. I have 248,000 miles on it and running strong with no burning oil. Good luck.

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Why does my vehicle stall when at idle.

Intermittin Engine Stall
Engine No Start
MISFIRE IN motor cylinder is more likely the cause to engine stall and hard start.
You will have to fix this problem first,
A misfire, most the time, is caused by, incorrect cylinder firing order (diagram at bottom). Or no or low cylinder compression
no or low compression is the result of A Vacumm leak.
If the timing chain was recently replaced, the valve cover had to be removed, the valve cover gasket could cause a huge vacumm leak which would effect some if not all 6 cylinders,

Lack/loss of power
Hard start
Engine hesitation

For Now
check firing order( coil pack to sparkplug)
check sparkplugs


I hope this helps for now
If you have any questions, you can email or post back

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if you spark a little starting fluid to it does it fire?if so then fuel is the problem then is the gas older than 30 days dump it out and try fresh gas if new gas then open the carb and clean it if it does not fire on starting fluid check for spark if no spark pull the top cover from the engine and look for wiring damage unplug the coil from the engine side of the coil and check for spark if no spark then the coil is bad and if its a riding mower the carb might have a anti back fire valve that could stick closed

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1 Answer

Does not rev up

first- if you have not performed a tune up- do that. I have had vehicles do exactly what you describe due to carbon tracking in the distributor cap. Make sure to lay out the plug wires in a manner where they cross only once, and try to avoid side by side cables for any distance. It also would not hurt to fire it up in the dark of night to see if there are any arcs to ground, Itis possible the ignition coil is breaking down.

When the car is at idle- carefully look down the carberator throat and see if there is gas dribbling out of the venturi- use a mirror and flashlight. A slight dribble is okay, if it is streaming out- replace carb float and needle valve/rebuild the carb.

In 85, they were still rather basic, so as long as you have spark, you can reasonably assume the electronic modules are okay, but it is still possible for wires to fail, for the magnetic pickup to develop an intermittent condition, or even corrosion.

If this was a sudden onset, replace cap and rotor at a minimum. Check baeline timing too. Also check to make sure the vacuum advance and centrifugal advance system are functional. A defective advance system can just aggravate the situation.

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No codes rough idel fills like running on 4 cly exhaust smells good feul pressure new plugs coils firing hard start

You could have a bad spark plug wire, not allowing all your cylinders to fire. make sure the spark plugs are gapped correctlly, they don't always come pre-gapped,check your timing, and your firing order, if just one sparkplug wire is out of place it can make your car sound like its falling apart. good luck!

Aug 19, 2011 | 2002 Jeep Grand Cherokee

1 Answer

This is a 1984 1200 that will not start and back fires thru the exhaust and carbs

Back fire is an indication that the bike is firing incorrectly.
Your timing chain is probably stretched, due to the year.
inproper valve timing due to stretched timing chain will make the bike backfire.

I have other thoughts like stuck valves or inproper sparkplug wires on wrong plug,
i always start with easier and less expensive method.
1st check your sparkplug wires to make sure they are on the right plug.
2nd pull sparkplugs and do compression and leakdown test.
3rd pull componets to see if valves are opening and closing, (valve clearance check)
4th if valves are good, then timing chain is probably stretched.
5th if timing chain and timing marks are good, and valves are good, then proceed to
testing the signal generator to make sure your getting a signal to the cdi,
6th if you have a signal to cdi, the cdi tells which coil to fire. either # 1&4 or # 2&3.
if signal generator is working, but coils aren't firing right then its the cdi.
obviously your coils work because its firing, just back firing.

Thats all it could be from easiest to hardest.
Good luck and have a great weekend.
Big Al

May 21, 2011 | 1987 Honda GL 1200 Aspencade Gold Wing

1 Answer

Every so often or especially when it rains heavy my car looses power while driving and cuts out when i loose speed. it will start again straight away but will cut out again instantly blowing a lot of smoke...

unsure if your engine model is same as ours here,but rain or heavy dampness usually shows up leakage in sparkplug wires and insulators.They give this exact problem.this model here has long extended rubber/plastic insulators that run through the valve cover to the sparkplugs.If the sparkplugs havent been replaced for a while(some of these have platimun or iridium plugs that should run 60-100,000km).the current needed to fire them will always take the easiest pathway to earth,and often it is through the side of these long insulators.Itg will be hard to see as the hole is only pin sized but will have a small build up of black carbon around the hole.'Also when the fault is evident,you should be able to lift the bonnet and hear little crack sounds as they leak and the engine will misfire when this occur.Hence the loss of power,the plugs wont be firing each time that they leak.
A new set of sparplugs and leads should fix this.If it is the direct fire model that has an individual coil over each sparkplug,you can purchase the insulators separately.The coils should be fine or they would fault in any weather.Hope this helps you

Mar 22, 2011 | 2001 Audi A4

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