Question about 1991 Honda CBR 400 RR

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Compression tester reading on cbr 400rr

What should the compression be on this engine

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In general, as high as possible. But the real test is how close the readings from the cylinders are to each other.

Posted on May 09, 2009


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On my Ryobi BC 30 I have done a compression test and the pressure will not hold.

When testing engine compression it builds up when the engine is turning over and when you stop turning it over the compression tester has a valve in it to hold the pressure reading I think your tester is defective and not holding the pressure reading

Feb 05, 2016 | Cars & Trucks

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How do you check if you have compression on a 84 porsche 944

You have to buy or borrow a compression gauge tester. It threads into the spark plug hole; so you pull all the plugs out, then check each cylinder's compression. The proper way is to first disable gas and spark, put the tester into the first cylinder, then crank the engine over a set number of times- the same amount of cranking for each cylinder, so all get a balanced test. While cranking, hold the accelerator pedal all the way to the floor-this lets the engine breathe normally, getting all the air available. then compare your compression readings: a good healthy engine will have all cylinders pretty even, in the range of somewhere between 150 psi-200 psi. Low compression readings means compression is being lost somewhere, like worn piston rings, bad head gasket seal, or valves not sealing.

Wondering if you have any compression at all? Hold your finger over a spark plug hole while someone briefly cranks the engine over. You can tell if there's any compression at all-you will feel the pressure build up under your finger. Rent or buy the gauge tester to get a true reading of your compression.

Jan 17, 2016 | Porsche Cars & Trucks

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I've a Pulsar 150cc bike bought in may 2009, roamed around 70k kms. Problem is it is exhausting white smoke only when it is started, mechanic at a Bajaj showroom says it has come to bore and had to be...

Hi, if the smoke really is white smoke and is only present when you start then it COULD be just water vapour which once exhausted (after warming up) would result in normal exhaust gas colour from then on.

If it is burning white smoke all the time then it could be piston ring failure. As this is a single cylinder engine you would need to find out what the normal compression reading should be and then check your reading with a compression tester. You probably don't have one but most motorcycle garages should be able to test it for you for a reasonably small fee.

From what I can find out online your compression ratio should be 9.4:1 which means your psi reading on the gauge should be around 124 psi - this may be a little lower due to engine wear.

If you can get hold of a compression tester, make sure you have the bike sized fitting on it (same thread size as your spark plug) and then warm up the engine for a few minutes then turn it off and remove the spark plug. Then fit the compression tester into the cylinder head in place of the spark plug.

Turn the engine over using the electric starter if you have one or the kick start if you don't (it wont run without the spark plug but it will turn over) and note the reading on the gauge of the compression tester. If you have a friend with a similar bike then you can check his and compare it with yours.

Regardless of the reading, now remove the tester and then put about a couple of squirts (teaspoon full max) of engine oil into the cylinder head and then repeat the compression test.

If there is a noticeable increase say 20-30 psi then I am afraid its your piston rings or valve guides which are leaking pressure, the oil temporarily sealed the leak and gave a higher reading.

BUT if the pressure is about the same then its probably not your rings and like I said earlier it could be steam caused by water vapour in the engine burning off at start up. If you smell the smoke what does it smell of?

Hope this helps,

Steve B

Feb 17, 2014 | 2007 Bajaj Pulsar 150

1 Answer

Popping on acceleration

It could be a problem in the valve train. For a car that old, before putting new parts in, you could buy a compression tester for about $30, and do your own compression test. It should tell you if the engine is good enough internally to warrant proceeding. If compression is low on any cylinders, that problem must be addressed first. If a valve is not sealing and causing the popping, that cylinder will show low compression.
For the test, the engine should be at normal operating temperature. Then pull all the plugs out, connect tester to #1 spark plug hole. Have a helper hold the throttle wide open while cranking the engine over about 5 seconds. Watch the gauge-the first revolution or two will cause the gauge to jump high at first, and successive revolutions during the 5 second span will cause the needle on gauge to climb a little each time. Record or note the compression on #1, then do each cylinder. Try to do the same amount of cranking on each cylinder, and keep the throttle wide open. What you want are compression readings on each cylinder that is well above 100 psi, and all should be close. The lowest reading should be within 75-85% of the highest reading cylinder. Example: say your highest reading is 135 psi. 85% of 135 is 115-so your lowest reading should be at least 115 psi. Some general guidelines: any cylinder with compression below 100 psi is definitely a problem-that cylinder will not have hardly any power output, even if it is firing. Worn piston rings or poor valve sealing is causing compression loss. A newer engine should have compression readings above 150 psi. As the engine wears, compression will drop. In general, for high mileage engines, you would want to see compression in the range of 125-150 psi, the higher the better, but remember, it should be balanced-the lowest should be at least 75% of the highest reading cylinder.
Post back if you have questions-good luck.

Jan 26, 2014 | 1983 Oldsmobile Firenza

1 Answer

How to preform a compression test on a valkyie

Remove the spark plugs. Using a screw in compression tester, screw the tester into a plug hole and tighten it slightly. Open the throttle and crank the engine about six full revolutions. Record the reading and proceed to the next plug. Do the same on all the plugs, recording the readings and cylinder number each time. That is all there is to it. If you can only obtain a press in type compression tester it becomes a two man job as one person has to hold the tester while the other holds the throttle open and cranks the engine.

Mar 22, 2011 | 2001 Honda Valkyrie Interstate

1 Answer

Battrey gets very hot on my cbr 400rr

most likely you have a shorted cell, replace the battery.

Mar 09, 2010 | 1990 Honda CBR 400 RR

2 Answers

What compression should my poulan pro 42cc engine have

The compression reading for a chainsaw is greatly impacted by where the schrader valve is installed on the tester too. It is a very small volume and needs to be be on the plug end of the tester. HTH

Dec 06, 2009 | Poulan Garden

1 Answer

Wont start

the old petrol has buggered up the jets a good carb cleaning will fix the carbs now drain the old petrol out and get new dont try to mix old and new gas it does no good please give us a rate hope this helps

Jan 03, 2009 | 1988 Honda CBR 400

1 Answer

Timing belt broke changed it engine is missing. could it be

The easiest way to test this is to carry out a compression test. This test will determine if any valves are bent. The test is very easy to carry out. 1.obtain a compression tester. 2. remove all spark plugs. 3. screw tester into spark plug hole. 4. with your foot on the accelarator, crank engine. 5. read the tester reading and write it down. eg. cyl 1 175psi cyl.2 170psi etc. if you have a bent valve one cylinder will be very low compared to the rest.

Dec 21, 2008 | 2001 Chrysler PT Cruiser

1 Answer

Spark plug gap

Don't change the setting on the plug. The 400's are happiest when you just plug in new ones and ride. They like NGKs the best. There are two types for the 400. One runs hotter. This choice will depend on which country you live in and what the ambient temperatures are.

Nov 10, 2008 | 1998 Honda CBR 400 RR

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