PUMPING GAS
You hear the words and you read the stories. “THE ENGINE IS A PUMP”. We don’t think much of it and just acknowledge and move on . SURE , I know. Pistons, pressure, air, fuel, spark. Boom. Boom Boom.
Over the course of the last 3 months, I’ve played the role of detective in the curious case of the #2 cylinder engine misfire. What started out as a fine running, high revving 4 cylinder quickly turned into a poorly running and sputtering 3 cylinder.
Following a high spirited and entertaining ride with a long time friend (who was riding Tiger almost 35 years newer) I noticed that my engine was misfiring under load. A quick and short run around the block was all that I needed to confirm that SOMETHING was wrong. There was an engine misfire.
Considering it had been around two years and eight thousand miles since i’d torn the carbs down, MAYBE it was time to practice what i preach and CLEAN MY CARBS.
After 3,4, and 5 times taking things apart and cleaning , more cleaning, poking, soaking, and spraying, i still could not sustain a steady 4 cylinder fire. I studied the forums and the GS holy bible site https://thegsresources.com/
I realized that i had cleaned my carbs to a surgical precision. Every passage clean. Every O-Ring replaced. It was NOT the jets. I started at the top and checked my valve clearances. BINGO (i thought). Intake on #2 was too big. After a short waiting period for a new shim , i was back (i thought) and ready to roll .
Nope
The engine did appear to run better. Even on all 4 cylinders . The engine misfired the more it ran . The more it started to foul and show signs of an engine misfire. AND SMELL …..
DRIP DRIP DRIP
As I looked down to the floor of my garage, i noticed drips. Ok, maybe carb cleaner making its way off the bike. Maybe..
Or MAYBE it was gas, leaking out of the exhaust.
After another online search , I discovered that one likely culprit in this pump system I was trying to problem solve was the very beginning of the process. The petcock. The fuel flows into the carbs from the petcock via a simple tube. However there is a second hose that connects the carb to the petcock. This one , showing in the picture , is what applies the vacuum to the petcock to suck fuel into the carbs.
At the end of the day, a simple diaphragm , showing signs of wear and even sporting a couple of holes, was causing my petcock to push fuel directly in the #2 intake and flooding that cylinder with fuel (then into the exhaust). Had I started my detective work at the tank, and worked my way through the system, I would have saved myself a few hours of work.
The plus in all of this is that removing and installing the carbs is NO LONGER a challenge. Do anything enough times , you get pretty good at it.
This long and nasty winter is coming to an end and soon I’ll have this old bike back out on the road. Racking up more stress relieving and soul cleansing miles. Thank you to the folks at Old Bike Barn for the quick fix !
