Hey guys,

Having some issues with my k100 from ‘85. This is my first fuel injected bike project and I am still learning.

Let me describe the situation:
I bought this bike with 68,000 miles on the engine. I bought it non-running and quickly realized she was do for a valve job and decking. I had that taken care of by professionals and have replaced many parts along with it. I have replaced the fuel pump and filter, the head gasket (evidently), miscellaneous tubing and cables and have had the injectors professionally cleaned. 

I finished putting the bike back together today and cranked it over without the plugs in. I am getting really good spark, and what seemed to be solid compression. After doing more tests with cranking it with the plugs in, I did not get any sputtering or signs that she would start except for one very loud back fire that shot a flame 6 inches out of the factory exhaust. 

I then tested for compression and realized that cylinder 1 read 60ish psi, cyl 2 50 psi, cyl 3 10 psi and cyl 4 virtually 0 psi.

Is it possible that I aligned my camshafts timing incorrectly or that my valve spacing is too tight? I followed the manual in setting those up and simply aligned the two cam gears up with their respective marks while the cyl 1 was at TDC. After reading a thread I think it is possible that I wasn’t perfectly at TDC (as truthfully I eyeballed it), but even then I would expect some sputtering. I also checked and the HEC cover was slightly off, I have now fixed it and centered it but that doesn’t not resolve the low compression issue. 

NOTE: I did not feel any resistance after manually turning the engine over several times slowly before I ever tried to crank it. I do not think I bent a valve for that reason. 

Any help would be greatly appreciated, looking for some guidance and thanks for your help

sparkplug69 wrote:I bought it non-running and quickly realized she was do for a valve job and decking.

How did you come to that realization?

Hey Laitch,

I took out the injectors and saw heavy corrosion in the openings. It sat with the valve open on cyl 1, which left some water and debris the ability to get inside the machine. To make sure that I did not have debris on the inside of the engine, I took the head of the engine off.

I put together this document to show the poor condition these valves were in and what it looked like after a professional did the valve job.

http://forum.kforum-tech.com/members-upload/uploads/relevant_pictures.pdf

Check the valve clearances, even a valve riding by a couple of thousandths will give almost zero compression.

sparkplug69 wrote: I did not feel any resistance after manually turning the engine over several times slowly before I ever tried to crank it. I do not think I bent a valve for that reason.

Were you turning the engine over with the spark plugs installed? If so, you should have felt resistance at each cylinder's compression stroke.

Have the valves been adjusted correctly. Too thicker shims could cause these problems.
Regards Martin.

Before you do anything else, go back and carefully review what you did when you reinstalled the head and the cams.  Your problems are screaming valve timing at me.  After confirming beyond the shadow of a doubt that it's all together properly check the things below.

Did the machine shop lap the valves or do any seat work?  If so, I am going to guess that your valves are too tight if you didn't install thinner shims. 

It is also possible that the rings are dry and not sealing properly.  Try putting a shot of oil in the cylinders and doing another compression test.  Also, when you do the compression test you need to hold the throttle wide open.  You would not be the first person to make that mistake.

Last, double check the plug wires for cylinders #3 and #4.  The wire for #4 is longer than #3 and is folded back.  Crossing them will make the engine difficult to start.

sparkplug69 wrote:I also checked and the HEC cover was slightly off, I have now fixed it and centered it but that doesn’t not resolve the low compression issue.

Are you referring to the Hall Effect Sensor? Adjusting an ignition component will not have any effect on engine compression. Is that what you are attempting to convey?

Thanks for all the recommendations, I will be taking your advice and going through valve clearances and ensuring timing was set correctly. I will update everyone once I finish.

Cheers