Lowish pressure under compression testing

I've finally got a hold of a compression guage that actually works (don't buy cheapies with red boxes off fleabay.. They're rubbish)

The pressure on all 4 cylinders is around the 110 mark. I would think this is just due to the engine being quite old, and since it's still above the magic 100psi, I don't really feel the need to rebuild the engine.

Is there anything else likely to be causing the low pressure that's easy to fix? Are there any longer term consequences of leaving the bike with low pressure, orhter than poor accelleration? I know the guage is working find because my XJR is showing a much higher reading.

 

How are all the cylinders in relation to each other? If they're all right around 110 without any wild variance between them, then I wouldn't worry about it all that much.

Just make sure all your valves are in spec and keep fresh plugs in it, and run it.

 

They're all pretty much the same..118-115-115-112 Cylinder 1 having thehighest and trailling off to Cylinder 4

Valves a re all ok.

Ok, well I'll ignore it then, if it isn't going to cause me troubles then why try to fix it.. I've enough problems with my carbs

Thx

 

At what altitude do you live? Pressures are different at higher altitudes so you need a correction factor if you are at high altitudes. For example I live above 5000 feet so I have to apply an 87% correction factor to the published values.

 

I live at 500m - About 1650 feet. What kind of corrections? Can you give me an example ?

 

Youre good..
Keep good plugs in there and work on those carbs...
Worry about compression when you ain't got none.
I tought your best reading was 110 but with 118 to 112 you should ride all day!!!

 

Ahah... I've found this on another website.. It's a compression correction value for altitude, thought it might be useful for others:
Elevation Multiply by:
1000' ----- 1.029
2000' ----- 1.060
3000' ----- 1.093
4000' ----- 1.126
5000' ----- 1.160
6000' ----- 1.196
7000' - ---- 1.233
8000' ----- 1.272

That puts me on around 120 average, which is acceptable.

Also managed to sort the carbs today.. Running perfectly now, perfect balance, perfect mix (according to my Colortune) going to take her for a ride tomorrow to check everything out, if it's all hunky dory, I'll sit back for a while and enjoy my handywork.. I've got to get my XL125 backon the road, so Pepe (and I've christened the XJ750) is going to stay in 1 piece for a while.