Poor Compression

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Brigadoon · #1 Unread post by **Brigadoon** » Tue Oct 04, 2005 4:28 pm

I am thinking about buying a 1979 Kawasaki KZ650 SR. There are a few minor things that need to be fixed, but the seller (my friend) said that it has compression problems in two of the four cylinders. He is not sure what is going on but I am just wanting to get an estimate on the range of how much it is going to cost to fix? I know it depends on what is wrong, but i just want a general idea on what it might cost! Thanks!

Gadjet · #2 Unread post by **Gadjet** » Tue Oct 04, 2005 4:37 pm

Poor compression could be the result of worn out rings or stuck valves.

If it's rings, you will need to pull the cylinders off and replace the rings. You'll also need to give the cylinders a light honing.

If it's valves, it could be a case of replacing the valve springs and lapping the valves to get them to seat correctly and get rid of any buildup and pitting.

Worst case is worn lobes on the camshaft or holed pistons. If this is the case, you're talking big bucks.

Rings and valves can be done by you, in which case your only expense will be the new parts and some time.

Brigadoon · #3 Unread post by **Brigadoon** » Tue Oct 04, 2005 5:54 pm

Is there anyway to tell without taking everything apart? I am going to go look at this bike in the near future, so some pointers would help! Thanks!

BuzZz · #4 Unread post by **BuzZz** » Tue Oct 04, 2005 6:21 pm

Remove all the sparkplugs and take compression readings on all cylinders.

Pour a thimblefull of motor oil into the spark plughole of the weak cylinder(s) then retest each bad hole one at a time. If the oil brings back the compression to the same levels as the good ones, it is probably bad rings(unlikely). If it only helps raise the compression a little bit, it is probably the valves(more likely).

Good luck with it....