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Discussion Starter #1
Who out there has dealt with a leaking head gasket on their K12RS?
I have no power on cylinder two. I pulled the Injector rail and injectors this morning. I ran one injector at a time into a soda bottle, all injectors work fine. I have new plugs in 2 months ago. Plug number 2 looks wet and sooty, plug 1 looks sooty, plugs 3 and 4 are tan and clean.
I have good spark in all plugs.
Ok so I did a compression test, with throttle closed - #1 150psi; # 2 150psi; #3 190psi; #4 220psi.
With throttle held wide open the test showed #4 240psi; #3 240psi; #2 180psi; #1 210 psi.

Next I did a vacuum test using the ports on front of throttle bodies for each cylinder.
All showed low vacuum and rapidly fluctuating needle 10-4 inches at idle.
 

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I've never seen or heard of head gasket problems on a K bike but anything is possible.

have you checked valve clearances?
 

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invest in or rent a leak down tester. It may help distinguish if the lost compression is into the crankcase (rings), the intake (intake valves), the exhaust (exhuast valves).

Are you burning a significant amount of oil?
 

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Never heard of head gasket problems. Usually if you get one there are issues with the cooling system getting pressurised and puking coolant.

Your compression readings don't look bad enough for a gasket leak or burned valve.

The fluctuating vac readings may be because you didn't have a small pinhole restrictor in the vac gauge line.

Perhaps you've got gummed up rings, the cylinders need some of that Techron stuff or the bike needs a good blast?

Try and get to the engine breather. If you have a ring blow back problem you should get a lot of back pressure from the vent and even oil coming back into the throttle bodies.



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Discussion Starter #5
OK good news. Thanks Voxmagna. I pulled the breather hose off at the block and stuck a long straight hose on the port to outside of the bike. No pressure coming from the block.

I was thinking about my test with the vacuum gauge and decide to check to see where those ports on the throttle bodies came out. Well the ports go to opening just past the throttle plates. Not a good spot for accurate vacuum readings. You really need a vacuum port at the intake manifolds.

I decided to use the high voltage test light I got at Harbor Freight, goes between spark plug and boot. Checked cylinder 2, good spark. Let the bike run awhile with tester on and cylinder 2 was getting warm. Wow. I put plug boot back on plug went for ride, cylinder 2 dead and cold. You can check by checking temp at header pipes.
So I put the high voltage tester back in between and cylinder 2 started running.

I have a plug boot and wire that grounds out when down in the spark plug well.

My test yesterday was using insulated pliers holding boot with plug in it to a good ground and watch spark. Looked good, but plug not in so did not know boot was grounding out.
Cylinder 1 is not as bad but fires poorly.
So using the high voltage tester, cost like 3 bucks, saved me some grief.
Now I just need to order some plug wires. Ain't cheap.
 

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Good find and relatively cheap to fix. :clap:

At least it made you check a few things. The cold header was a definite pointer to non- firing.

I broke a plug top once and had to replace the complete lead. I seem to remember they used 2 different manufacturers, so you need the No. 2 lead same manufacter as the rest. They can also be swapped about for testing. I've got one of those spark gap voltage testers, but I also still have my old Colortune with metric adapters. You don't hear much about those now, but I still use mine.

Before fitting the new plug top, dust it with talc powder and only pull them on a hot engine when they are easier to get out.



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