compresion down or is it ?

[peterhankinson]

hi all
hope you can help fitted replacement engine and have done a compression check its reading 120psi on all 4 pots is this low ? milage is 54,000 miles.... thanks inadvance...peter

[Nessism]

120 is getting down there but serviceable. Did you check with the engine hot and the throttle wide open? If not, your values will come up some when properly tested. Also, did you verify the proper valve clearances? If not you could be loosing some compression through the valves.

Hope this helps.

Good luck.

[Dave8338]

If the test was run on a cold engine...you're in good shape. Hot WOT not terrible, not perfect. :?

[peterhankinson]

engine was hot with throttle open valve clearence average 2 to 3 thou just had new head gasket would that cause drop?

[Dave8338]

No, if anything that should raise the #'s (assuming that there was a leak)

[catbed]

how did the bores look when you replaced the head gasket? if the bores are glazed, you may need new rings, but not likely with numbers 20 psi above service limit.

did you take the cylinders off when the headgasket was replaced? if so, the rings not have had a chance to re-seat.

[peterhankinson]

yes striped down to check pistons no wear seemed prettty good nick reground valves re shimed best i could get them with available shims. only ran it on tickover after rebuild for ten minutes before i checked the compresion, might recheck the timing over weekend? having said that it runs well no knocks smoke ect. ah well back to the drawing board, wont let the so and so beat me! thanks for your help, very grateful...peter

[catbed]

its because you took the jugs off. once the rings seat after 100 miles or so, the numbers should go up. if it runs fine, dont worry about it. might want t reclean the carbs if you left gas in them like i did. make sure all of the valves are spec. z1 has shims for like 4 bucks. dont take shortcuts because you'll just end up having to fix it later. just ride that sucker!

[chef1366]

Ride it for a couple of more seasons worry free.
Then a hone and ring job. Why didn't you do this when you had it apart?

[psyguy]

one other thing...

the gaps on the piston rings have to be in a particular position

however, your readings are not bad for a 54k engine, and still above the serviceable limit, so id just ride it

[peterhankinson]

should of changed them but finances ect ect and in my defence the p/o said it had all been done about 1,500 miles ago looking at it seemed to be some truth to it. but hind sight is a wonderful thing. anyhow had a tinker with it today seems to be running well apart from the petrol tap? replaced the seals ect with new and its a bit hit/miss in the on postion , hunts for more fuel. on the reserve runs a bit better on prime ticks over nice but dosent rev to good, one step forward 2 steps back! ah well at least the great british summer is near..... thanks for all your help and advice its a great help ...peter