Great detective work.  This is helping me move forward with a generator that only runs in choke

Cold compression testing is different from hot. When cold there is no oil on the cylinder walls therefore compression is very low as well as lack of thermal expansion doesn't allow for proper ring to bore sealing. You put the oil in the bore, it sealed it nicely and compression shot up. That's normal reading you got from the cold test.

Defenetly rings mate, that oil test just confirms. What about a leak down test ?

I have a honda GX120 that has low water pressure,  runs ok, any ideas what it could be?

These engines have automatic decompression centrifugal lever on the camshaft opening the exhaust valve just a little bit putting that much oil in it will also raise the compression because the oil will seal that little Gap in the valve at decompression the only way to properly check the compression is to make sure the intake valve is set to the proper gap I believe that's .015 but you could check your engine specs for valve tappet clearance to be sure. Once you have got the intake valve set at the proper clearance remove the rocker arm on the exhaust valve this will eliminate the decompression now redo your compression test. Sometimes the decom on the cam gets froze up or the spring breaks causing permanent decompression.

I have a gx160 and I have low pressure will not go higher than 10 what do I do

read some more it has a automatic decompression .
remove pusrods en try again.

Id recommend that you pull the piston, give the cylinder about 15-20 seconds of ball honing, put new rings on the piston. its possible there some leaked around one of the valves, maybe its not fully seated or cracked.

You need to seat the exhaust valve loosen it up then do a compression test

Rings

You have low compression because you rebuilt it with the deep dish style of gx piston. The older gx's have flathead pistons.

On my dads Honda GSV190 push mower engine I'm going to try to replace the valve stem oil seal first before pulling the engine down.

Even though the compression tested at 75 PSI ,above Hondas recommended 71 PSI,the general consensus online with lawnmower mechanics is  piston rings which no longer seat on the cylinder walls cause the engine to burn oil in the Honda engines.

I want to do a leakdown test on my 3hp Briggs & Stratton engine as it uses a fair bit of oil when mowing with it,it burns a bit of oil,the maximum amount burned in a couple of hours has been 200 mLs of oil so 1/3rd of 600 mLs just got burned off.

I was a bit worried that the inlet valve guide was a tad worn when I lapped the valves in so I would like to confirm that it's not rings & perhaps that it may be a worn valve guide.

So a $111 USD valve guide installation kit might come to the rescue because it's usually a case of throw the cylinder & crankcase out because the valve guide is drilled straight into the aluminium !

saving my ass at work here hahaha

better off to replace with a power fist motor on sale. unless you have too much time on your hands lol. can't go wrong one year over the counter return policy

I read that GX160 engines have auto decompression that makes a normal engine compression measurement inaccurately low.  The exhaust valve rocker arm should be turned sideways or removed to do the compression test, otherwise you'll probably get around 60 even with a good engine.

Thank You! iv been working on my 7 hp brigs and straton, "off a genorator" now on my go kart. cleaned a entire hand full of oxidation out of the carburetor and it still only runs on chock, "better though" I appreciate your passion. i know its not the head gasket so i bet its the rings after all that powder getting in the engine for all those years.

ps clean gas en carb .

Id say rings too. And im not sure if low compression would cause the lack of fuel. Thats an interesting one.

You sound Canadian.

I think I mentioned my dads GSV190 powered lawnmower before on here well,Honda says that 71 PSI for that engine which runs the decompression camshaft is o.k. but it's hard to start & it usually burns oil when the engine is cold,once it warms up it's o.k.

I've ordered new rings for it but I still need to order the newer piston to suit the 014 rings (it's a 2003 model with 004 rings & matching piston) but I would like to do a leakdown test on it to find out how badly worn it is.

I added oil & the compression went from 71 to 125 PSI but I want to confirm that Hondas figure is correct !