Jump to content

Kawasaki BigHorn F-9 Lost Compression

Recommended Posts

Hello,

Been a long time since I've been active on this forum but recently got back into it and now I need some help. I recently purchased a 72 Kawasaki bighorn 350 with 6500 original miles and the bike ran awesome. I put about 300 miles on it and then the plug went. Threw a new plug in started on the first kick and made it about 10 miles before the bike quite out again. Now the bike doesn't seem to have the compression it first did. After inspecting the bike I noticed a slight amount of seepage between the jug and the cylinder head. I though I found my problem put a new gasket in but still the same issue bike can easily be turned over with one hand on the kick starter. Bike has a strong spark, cylinder head and jug are flat and should be creating a solid seal between the two. My question is do two stroke rings go out this quickly? Most if not all my experience is 4 stroke and they tend to slowly start dropping of compression and get Smokey before they go completely. To add to the equation this is a rotary valve motor and is a little different from my 2 stroke sleds I've worked on. I panned to have klemm rebuild the motor this winter but I was hoping to enjoy it a little more before the seasons over. If the group verdict is a simple re-ring and go ill order the kit and be on my way but I first wanted to check in and see if anyone might have had one of these and knows if there could be something else wrong with it.

Thanks for the Help

Share this post


Link to post
Share on other sites

I would skip straight to pulling the head off.  Easy on an old air cooled motor like that.  Inspect the cylinder wall for damage.  It is not at all normal for compression to go away like that without a mechanical failure or loss of lubrication causing engine damage.

Share this post


Link to post
Share on other sites

Do you have a compression tester? How about a vacuum / pressure tester? I would try those before disassembly.

 

On a lighter note, I PERSONALLY GUARANTEE the problem is not one of the following:

 

reed valve failure

radiator / cooling system

power valve system failure

 

  • Like 1

Share this post


Link to post
Share on other sites

turbodan- I pulled the head when I threw a new head gasket at it, no major scoring but cylinder is definitely glazed.

KDXGarage- Its a rotary valve 2 stroke and its air cooled.

This system is also supported by a oil injection pump as its not a pre-mix bike. Im looking into how to test the pump and make sure its still working and didn't cause the failure.

Share this post


Link to post
Share on other sites

Since the bore isn't scarred, it is possible the rings are stuck from carbon deposits and the oil injection pump is probably working. Pull the pipe so you can see the rings and side of piston; this will likely indicate your next step. To test the injection pump, disconnect the outlet hose and run the engine on some pre-mix. Unless you are certain of the injector oil quality, drain it and replace it with a type designed for air cooled engines. FWIW, I bought a '74 off the showroom floor and had a blast with it.

Edited by DaveCR

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×