Bump - Can't find any apparent air leaks.. I'm running 147.5/65/20 jetting with a .9mm o-ring shim on the needles. With 3 turns out it still burps through the carb

I did notice some fuel in the outlet hose running from the lower T off carbs to the petcock. Not sure if its coming from the carb or petcock side though

Next shop session I'll pull the carbs and break them back open to inspect

Quote from: Dirtbox on February 26, 2014, 05:16:31 AM
I have a noise on the carbs where there is a shockwave, coming back from the inlet valve when revving through 2000 RPM. Below and above that it's fine.

I found it by holding the carbs with my hand and you can hear the sharp clack and feel it on the carb. I think its on the Left hand carb more.

I suspected weak valve springs but stuff I have read on line suggest that weak spring problems get worse at higher RPM but mine don't.

The problem is very pronounced when warming up if held at 2000 rpm but gets a bit better as the carb gets warm.

The bike has had a top end overhaul the valves have just been ground in and the valves are spot on for clearances. The garage reports that the valves are sealing very well on vacuum test.

Has anyone had this problem.

By the way the bike has a drop in K&N, a Delkevic Zorst and is re jetted 140 with the needles on the second position. It goes like a rocket compared to when it was standard.

I have a GS500 K2.

The re jetting has only just been done the power and responsiveness is great and the plugs look perfect but could this be a symptom of being a little too rich.

Has anyone got constructive advice ??

I had exactly the same...  I started by adjusting the valve's clearence...some were too tight ... but did not solved...
I clean the carb (roughly) and did my first equalization on the carbs....  did not work

then I start to play with the mix screw... but never got the right feel of the engine.. and continued sneezing (popping from carb)...

I was convinced that was the mixture (lean).. and was considering changing the slow jets....

I later founded that one screw mix had an oring missing.. |I changed both...  things got better.. but not perfect

Checked the timing o the chain and valves marks

Made a complete clean on the both carbs... (again)

Then I had an idea... instead of equalizing the carb only from the vacuum point of view  I put the engine running about 1700 rpm.. and pulled the spark plug connection... and I realized that one cylinder was holding the engine running and other not that much...

So I kept playing turning the right  or left cylinder on and off and adjusting the mix and the "equalization" screw... (check the service manual.. it has how many turns you should start with.. mine is 3 turns)

later I noticed that one coil was not under the service manual specs.. I bought a used one...

Since then the engine stopped sneeze...

Was along work...  and to be honest, I cannot pinpoint your issue...

Start cleaning and check your carb.... thoroughly!!!!

Check..as I did one cilinder at time separately...

But was a long shot form me

Gave advice on a 3 year old thread... lmao I love these.