COmpression low - should I get the spanners out?

waterloo700 · Nov 13, 2009

Tested my cylinder compression (1100 1998 52,000 miles) and it's in the "poor" band at 115/120 psi. I don't have any previous readings for the bike so can't tell if its a sudden drop or gradual deterioration. The bike starts and runs well and I'm reluctant to fix what might not be broke. Previous threads suggest the 5 psi difference left to right is not bad.

Should I overhaul the heads over the winter or leave them alone and see if compression drops further?

Would I see a noticable difference if I did the work and could get the bike back up the the 130/140 psi mark?

Any advice welcome

motobiker · Nov 13, 2009

for me the moral of your post is.. don't go looking for problems.

ride the thing.

Steptoe · Nov 13, 2009

Leave it alone.

Wrigsby1 · Nov 13, 2009

waterloo700 said:
The bike starts and runs well

I have quoted the bit that stood out to me

AberdeenAngus · Nov 13, 2009

waterloo700 said:
Tested my cylinder compression (1100 1998 52,000 miles) and it's in the "poor" band at 115/120 psi. I don't have any previous readings for the bike so can't tell if its a sudden drop or gradual deterioration. The bike starts and runs well and I'm reluctant to fix what might not be broke. Previous threads suggest the 5 psi difference left to right is not bad.

Should I overhaul the heads over the winter or leave them alone and see if compression drops further?

Would I see a noticable difference if I did the work and could get the bike back up the the 130/140 psi mark?

Any advice welcome

If its not affecting performance too much I certainly wouldn't open er up.

It could just be a piston ring gummed up.
Try a shot of Redex in your tank.
Might help. Doesn't cost much and won't do any harm.

Cortina · Nov 13, 2009

Was it warmed up ? Was the throttle fully open ? was it this ? was it that ? ... Just ride the thing and leave it alone !
If the bike was / is running well .... why on earth even do a compression test?
I'll stop now

waterloo700 · Nov 14, 2009

Yes to all that - I'm new to BMW's so "running well" is all relative.

It was running out of steam at 180 two up. Had Kylie Minogue on the back and she's clearly getting a bit of a lard-arse. She'll have to go.

davegs · Nov 14, 2009

Only 180?definatly something wrong was this is top?

Colban · Nov 14, 2009

Sounds like it needs an "Italian Tuneup".

Wrigsby1 · Nov 14, 2009

waterloo700 said:
Yes to all that - I'm new to BMW's so "running well" is all relative.

It was running out of steam at 180 two up. Had Kylie Minogue on the back and she's clearly getting a bit of a lard-arse. She'll have to go.

Welcome to the world of GS's. As you will have already guessed, BM boxers are "kinda different". One of these traits is to take several nuclear half lifes to run in so even at 52k miles it may have been ridden by a pipe smoking vicar (or even a Beemer rider, ahem) at low to no revs for much of its life.

Give it some stick for a bit and you will probably free it up a treat and burn out any crap. Probably use less oil as well. The engine bit is usually very solid and goes on for several owners.

Have fun

COmpression low - should I get the spanners out?

waterloo700

Active member

motobiker

Registered user

Steptoe

What a waste.

Wrigsby1

Well-known member

AberdeenAngus

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Cortina

Well-known member

waterloo700

Active member

davegs

Well-known member

Colban

Registered user

Wrigsby1

Well-known member

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