Compression Test on a R1150RS

[Eddiem]

Hello

Does anyone know what type of numbers should I see when I do a compression test on a 2002 R1150RS?? I know what the compression ratio is on the bike but don't know what type of PSI numbers should I see when doing a compression test.

Regards!

Ed

[snowprick]

Is this what you are after

[Eddiem]

Rod

Yes that is what I was looking for, the PSI results 145 Pounds is the number that I was looking for!

Thanks so much!

Aloha

[itimna bundok]

Dang! Rod, you've only been on a BMW for a bit and now you're the "go to guy!" BINABATI KITAL!!!

[snowprick]

Dang! Rod, you've only been on a BMW for a bit and now you're the "go to guy!" BINABATI KITAL!!!

People who buy BMW usually are, diba. ha ha

I got a lot of help during my pre-purchase period. Everyone was very helpful. Lets call it payback time.

Some time ago I was directed by a fellow fourmer to a download site that hosted BMW Manuals. I believe they are a "must have" item and that is where I found the limits for the comp test.

Now where the hell did I get them from!

[CycleRob]

Eddiem,

This would be a good time to outline the SOP for doing a compression test.

1--Even though it might set a (who cares) trouble code, I disconnect the Motronic relay so there's no spark (to ground out) and full throttle fuel is not injected into the cylinders. The excess fuel will alter the ring sealing and give a false reading. Unlike carburettors, which are physically not able to add full throttle fuel quantities during the slow engine speed, low airflow, zero manifold vacuum while running on the starter, EFI will do so.

2--Use full throttle when the starter cranks. Count about 6 to 8 "pumps", usually when the gauge's needle stops increasing significantly, then use that reading.

3--Unplug the (unnecessary) fuel pump relay too.

!!!WARNING!!! Do NOT open fire the ignition system. Open fire is a firing spark plug secondary lead hanging in open space, where spark energy has no place to go but destructively back into the coil. Either de-power the coil -or- insert the plugs into their wire terminals and ground the spark plug metal to the engine. Be sure the ground exists (paint) and it's reliable, as if $$$ was at stake (it is).

EXTRA CREDIT: On a multi cylinder engine I hook up a 10 Amp charger during the test. Also, on carburetted engines, because the accelerator pump shoots a stream of fuel each time the pedal is put to the floor, do it only once and keep it there until all cylinders are tested.


I posted this because occasionally someone will not use any throttle and then wonder why his/her engine is so bad. Also, you can permanently damage expensive components if you open fire the ignition system.

You're welcome.

[boxermania]

I could not match my steemed colleague CycleRob explanation as it is all true and precisely accurate, however, there is a simpler/faster test that will tell you not only the mechanical condition of the engine but where the trouble might be located.

It is the Leakdown Test, since I'm unaware of your mechanical skill level I'm going to dispense with the explanation as you can Google it.

With the bike on the center stand, one of the pistons at TDC (the one to be tested), put the bike in first gear and apply the rear brake (tie it down with something or get an assistant) install the Leakdown Tester and proceed with the test.

The rule of thumb is that 5% or less leakage is very good, up to 10% acceptable and beyond that it bears looking into addressing the problem.

The nice thing about the Leakdown Test is that by listening to the scaping air, it will pinpoint the source of the problem.

In our bikes, barring broken rings, the valve seal in the exhaust valve would be the first thing to show.

I purposely left a few details out.....as if you are interested and want to assume a greater role in your bike's operation, I feel that some research on your own will be required.....call that my homework....

I'm assuming that an air compressor is available.....if not......an air tank will suffice.......if not......this test can't happen.

[Eddiem]

All

Thanks so much for all your help, Boxermania, Cycle Rob and Rod you guys have been very helpful! BTW I do know about the cylinder leak did not perform it cause the bike had just Ok compression on both cilynders.

Aloha!

EM

[CycleRob]

I have both the leakdown & compression testers. Eddiem already had the compression tester so I gave him the fun do's & costly don'ts. A leakdown tester is more expensive too, but if you're "in-the-business" it's a necessity.

Yes, the leakdown test is much better because it tells you what component is leaking and the pressure gauge tells you just how bad. If you get a low reading, then the . . . . .
--Hiss in TB=Intake valve
--Hiss in the exhaust pipe outlet=Exhaust valve
--Hiss in oil fill hole=Piston rings or scored cylinder walls