Hello all, this is my 2nd post. I have done a search and found multiple entries for this type of issue that my brothers bike is having. I did go through a lot of the steps others had already taken, but would like to ask if what I just tested and found today is a big turn in the troubleshooting.
First, what's been done prior to today:
- Found a small animal had made a food storage bin out of the air intake. Good news is it didn't get past the air filter.
- remove carbs, found cracks in the (2) intake boots that mate with the cylinders - replaced them
- sealed up the intake air boots from the carb to the black box. (Those showed openings where leaks could occur)
- drained all gas from tank and bowls
- confirmed fuel pump is pumping into bucket
- new plugs - gapped
- removed bowls and cleaned, removed and inspected/cleaned jets, replaced the needle and seat on the float. (Performed level setting using the U-tube method from the service manual, while
leveling the bike)
- replace fuel filter
- replace air filter
- remove and inspect slides and diaphragms - cleaned aluminum residue and made sure slides were free, no tears in diaphragm
- checked each spark plug connector once disconnected from the plug wire, for the ~5k ohm resistance explained in the manual, both are about 4.6K Ohm
- hooked up the sync gauges and intake vacuum is only 2-3" Hg when manual specs 7-8" Hg @ 1100 RPM warm.
Before the above work, it went from a bike that was rode every year from 2004-2014, then sat for 3 years. My brother tried to start it (once he cleaned the out the animal food and filled with new gas), and it barely made it around the block after it warmed up.
Now after performing the above work here are what is still happening:
-It will idle fine with the choke on but sound like a low RPM Lawnmower, once warm, if you open the choke, the idle screw is maxed out to keep it idling
-Still sounds like it's only running on 1 cylinder, extremely slow throttle response when idling.
-if you crack the throttle, once it does rev up, it stays high in idle for about 2-3 seconds before the RPM's come down, like what would sound like an intake leak or throttle cable issue
Now what I found out today was odd. First, I was going to check cylinder compression, but didn't have the metric adapter. So instead started looking at the ignition system more and decided to just unhook one of the spark plug wires and start it. So with the front plug wire removed it definitely sounds like what it does with both of them in. I reinstalled the front wire, removed the rear, and it still runs. Now I had to pull the choke back out to keep it running on the front but it idled fine and i could rev the engine.
So in doing that, have I ruled out anything by being able to run each cylinder separately, but the front doesn't fire when both are plugged in.
Let me know if I am missing some steps. The one thing I haven't done is entirely disassemble the carbs from each other. I have read stories of throttle plate shaft seals leaking. Maybe that's the next step.