compression psi

HELP! Can someone give me the compression PSI for 1982 SECA please?

 

155 is high side and anything under 100 psi is not so good. My Seca 750 has a reading of 135 lowest cylinder 145 on others but that was last year. Be cautious if all are low it could be the gauge so don't panic . The other thing if you put a little oil in cylinder if reading goes up it could be the rings. Good luck

 

every thin you need can be found here
The Information Overload Hour


XJ650 and XJ750 air-cooled engines:
Minimum: 128 psi
Standard: 156 psi
Maximum: 171 psi
Max. variance between lowest and highest: 14 psi

 

She may have a 550 Seca.........so here's the whole nine-yards:

Cylinder Compression Gauge:

Yamaha recommends that you perform a compression test every 5,000 miles or so, and that you should record the readings, per cylinder, for future comparison and evaluation. The acceptable readings (specified at sea level) are as follows:

To do a compression test properly, you should first make sure all of your engine valves are properly adjusted to their recommended clearances, as valves that are too "tight" (not enough clearance) will allow the intake or exhaust valve to be open more than is necessary, or at the wrong time within the compression stroke cycle, thus bleeding off compression that would otherwise be developed.

Do not use thread adapters or the like on your pressure gauge, as the added volume of air space within the adapter will reduce the indicated pressure readings.

a) make sure the engine is cool/cold, 60F is the ideal temperature to take measurements at,

b) remove all spark plugs, and then stick the plugs back into their caps and make sure the plugs are grounded to the cylinder head (or even better, disconnect your TCI unit).

c) remove the airbox filter lid and the air filter.

d) make sure the battery is FULLY charged, and remains so throughout the course of these tests! It is actually recommended that for purposes of compression testing that the TCI be un-plugged and jumper cables to a large capacity battery (i.e. car battery) be used to make sure that the cranking speed remains pretty constant between each reading. Slow or sluggish cranking speeds will reduce the indicated compression pressure.

e) open the throttle FULLY and keep it open during testing.

f) crank the engine over until the needle stops advancing.

g) Let the starter cool down for a minute or so, then do the next cylinder, etc.).

h) If the readings are below spec, then shoot about a teaspoon amount of motor oil into each cylinder, crank the engine over a few revolutions with the starter (to spread the oil around), and then re-test each cylinder using the above procedure.

i) compare the two results and analyze.

j) keep all of your figures, and note the date and mileage from your odometer, so you can compare the next time you take readings (every 5,000 miles or so).


The specified compression pressures should be:

XJ550 engines:
Minimum: 100 psi
Standard: 121 psi
Maximum: 135 psi
Max. variance between lowest and highest: 14 psi


XJ650 and XJ750 air-cooled engines:
Minimum: 128 psi
Standard: 156 psi
Maximum: 171 psi
Max. variance between lowest and highest: 14 psi


XJ700 non-X (air-cooled) engines:
Minimum: 128 psi
Standard: 156 psi
Maximum: 171 psi
Max. variance between lowest and highest: 14 psi


XJ700-X and XJ750-X (water cooled) engines:
Minimum: 154 psi
Standard: 159 psi
Maximum: 165 psi
Max range allowable between highest and lowest readings: 14 psi


XJ900 engines:
Minimum: 114 psi
Standard: 142 psi
Maximum: 171 psi
Max. variance between lowest and highest: 14 psi


XJ1100 engines:
Minimum: 128 psi
Standard: 142 psi
Maximum: 156 psi
Max. variance between lowest and highest: 14 psi


NOTE: for readings taken at locations that are above sea level, the following correction factors should be applied to the readings that your gauge obtains:

- 1000' above sea level, multiply your readings by 1.029 to get a "true" compression reading.
- 2000' above sea level, multiply your readings by 1.060 to get a "true" compression reading.
- 3000' above sea level, multiply your readings by 1.093 to get a "true" compression reading.
- 4000' above sea level, multiply your readings by 1.126 to get a "true" compression reading.
- 5000' above sea level, multiply your readings by 1.160 to get a "true" compression reading.
- 6000' above sea level, multiply your readings by 1.196 to get a "true" compression reading.
- 7000' above sea level, multiply your readings by 1.233 to get a "true" compression reading.
- 8000' above sea level, multiply your readings by 1.272 to get a "true" compression reading.


Also, be aware that barometric pressure differences (during testing events separated by more than just a few hours) will cause changes in indicated compression readings. Basically, higher atmospheric pressures translate into higher indicated compression pressures. Although it is rarely of major consequence, in order to be "dead-nuts" accurate you should also record your local barometric pressure at the time of each test.


Now Analyze This!:

1) If one or all of your cylinders are too low in pressure, it means that:

a) you did the compression test incorrectly
b) the tester gauge is inaccurate, or was not used properly.
c) your engine has piston ring, piston wall, or valve leakage problems.
d) you valve clearances are too tight, and should be adjusted, or aftermarket camshafts have been fitted that have altered the camshaft timing.
e) if a cylinder or cylinders have NO compression at all, that typically means your piston has been catastrophically damaged (i.e. a hole in the piston crown, broken piston, etc.)
f) if a cylinder or cylinders have good compression that rapidly "leaks away" (best determined by the use of a Leakdown Tester gauge as listed further below), this points to burned or otherwise problematic valves.
In order to further analyze a low-compression condition, you should squirt a small amount of engine oil into the suspect cylinders (about a teaspoon), crank the engine over for a few revolutions to spread the oil about, and then re-test those cylinders.

g) if the compression pressures RISE by a large amount after the infusion of oil, then this typically means that the pistons, piston rings, or cylinder walls are damaged or worn in some way(s). However, be aware that if you introduced a significant amount of oil into a cylinder (1 teaspoon or more) when conducting this test, a small rise in pressure may occur, and it may instead mean that your valves are the problem, since the introduction of that much oil in a small cylinder will naturally cause the compression to rise.
h) if the compression pressures do NOT rise after the infusion of oil, then this typically means that the valve seats or faces are worn, or a valve is hanging up within its guide, or your valve clearances are way too small.
i) if two adjacent cylinders (cylinders 1 and 2, or cylinders 3 and 4) have low compression, and the oil treatment produces no greater pressures, this points to a damaged cylinder head gasket, warped head, etc.
j) it can be very useful to introduce 20-30 psi of compressed air into the cylinder (thru the spark plug hole) to help identify the source of low compression: the escaping air can pinpoint the source of the leak (air hissing out of the intakes or exhaust points to valve problems, while air escaping thru the crankcase breather indicates ring-seal issues).


Of course, many other situation may cause low cylinder compression, including valves that are out of adjustment (too tight, thus holding a valve slightly open all the time, losing compression), cracked pistons, cylinders, or cylinder heads, but those situations are the not all that common.



2) If one or all of your cylinders are too HIGH in pressure, it means that:

a) you piston domes (tops) and/or the cylinder head combustion chamber have a significant accumulation of carbon upon them, which should be cleaned via some type of chemical treatment or engine dis-assembly and manual removal methods. Note that higher cylinder pressures caused by such build-up may be "masking" or hiding other problems that might cause LOW cylinder pressures, such as worn rings, etc.

b) your engine has been fitted with aftermarket, high-compression pistons, or has had the cylinder head "shaved".

NOTE: high cylinder pressures are NOT a good thing, as they tend to blow out head gaskets and can cause accelerated piston, piston ring, or bearing wear.


You can also test for piston ring and cylinder wall condition by performing a "leak-down" test, which consists of forcing a measured amount of compressed air into a cylinder, and then seeing how long before this air "leaks" out of the combustion chamber and down into the crankcase (past the ring seal):

http://www.dietersmotorsports.com/Compression-leakdowntest.htm

 

her first post
Love the new bike...Handle bars and instrument panel... not so much!

 

Well then........nevermind!

 

@Nyeema

For the sake of keeping things easy on the troubleshooting front, would you mind if I merged your two threads?
The preference here is one thread per-bike.