Question about Honda CB 250 Motorcycles

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Hello I have a 1985 big red 250es. it runs great has plenty of power but it smokes and keeps fouling plugs. could it be rings or valve seal troubles

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If it only smokes when starting up and when pulling away, the valve guide seals need to be replaced. If it smoking constantly, the rings are bad. If you replace the rings, hone the cylinder walls and replace the valve guide seals at the same time. You may want to go to a hotter plus also. Please rate my answer. Thanks.

Posted on Sep 12, 2010


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What does blue smoke mean

Burning oil. Could be a couple of things. Possible your valve guide seals are warn out. If its blue smoke mostly when you first start the car, its likely valve guide seals. If its continuously smoking blue, its more than likely a broken or warn out piston ring. If its just every so slightly blue in tent, it might be worth a try to replace your PCV valve first. When the PCV valve gets completely gummed up, the pressure inside your valve covers has no way to vent other than forcing its way through the valves into the cylinders often times taking oil with it. Since PCV's usually only run out about $10 its worth a shot. Other wise, you've got a decent overhaul ahead of you for either piston rings or valve seals...on a 12 year old car most folks would either choose to scrap it, or live with the blue smoke while monitoring oil levels and watching for fouled plugs. Hope that helps and good luck!!

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I have a problem with my econovan, i havent had a service done to it in over 6 months and now when i took it to a guy to service it, its been blowing blue / white smoke only on cold motor so i did some...

Hello, I have several suggestions for you. Your problems can still be with the cause of the blue smoke. You need to get a compression test done on the motor either with an elaborate test machine at a Dealer or Tune-up shop or use an old-fashion compression gauge. With the valve cover off and engine running you can also push on the valve spring with your thumb and weak valve springs will cause the engine to miss. Sometimes the weak springs can be detected with a Vacuum gauge, showing a bouncing needle. Your valve stems may be gummed up from the bad oil seals you changed.

The blue smoke is also a sign that the oil rings for the pistons are worn out or have rotated to give a bad seal. When the engine warms, the rings expand and helps eliminate the smoke. Check your sparkplugs for oil staining. Your sparkplugs may be fouled and this condition is called "blow-by".

You can check and clean your EGR valve because it needs to seat or your engine can not idle smoothly. Check the Intake manifold for loose bolts, then use a water mist around the seams to see if the Intake gasket is leaking. Just use an old spray bottle filled with water and spray the engine while it is running.

I hope my solutions are very helpful to you in finding the problem.

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My 95 tahoe seems to be burning oil. #3 cylinder had a fouled plug. i fixed that but it smokes when i accelerate hard & i dont know where the oil keeps going.

Do a cylinder leak down test

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I have a 98 Ford Tarus LX, I change the spark plug on the car and now it is blowing smoke out the tail pipe, what could cause this? I thought a vacuum line might be the problem, could you assist me with...

The plug was fouling, when you changed it, it started working again. You have either bad rings or valve seals on that piston. You can buy an anit-fouler from most parts stores which will keep the plug from fouling, but it will not cure the underlying problem. In order to find your underlying problem, You will have to use a compression tester. If the cylinder has less than 80lbs. of compression, the rings are probably bad, if it has good compression then it is possible the valve seal.

The problem is more than likely going to be rings if it smokes all the time.
Bad valve seals typically smoke when you start the engine.
Either way, you will have to have a mechanic fix it, knowing is only half the battle.

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you have bad seals in the valves or bad piston rings.

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It was throwing white smoke out of ex now it dont run

In my experience, white smoke is oil burning. Question is Why?

Could you have put too much in the engine? You might have broken rings. You at the very least have fouled plugs now. Clogged crank case vent?

Check the oil level and adjust as appropriate. Rings is a big deal. Plugs are pretty cheap and easy to change.

I hope this helps you solve your trouble.

Thanks for using

Positive comments welcome


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