I went thru checking the spark plugs and I found that the front cylinder one
was fouled (black color). I would assume rich mixture being nebulized. The rear one looked light brown
which I assumed was ok.
This indicates the front cylinder is running too rich, compared to the back. The back might have an intake leak
or the throttle plates are way out of synch. Could also be the sparkplug was not seated (grounded).
The sparkplug insulators on my K2 looked a very light tan at 21,000 miles.
idle speed was very hard to set at 1200 in order to proceed with TBS. The engine would ramp
up to 2500 rpm (fast idle cam doing it of course).
The fast idle (cold start idle) on my K2 drops when the bike gets to ONE temperature bar. It should have
the clearance between the adjusting screw and the stop tab, as shown in the manual, once the bike is
warmed to TWO bars. The TBS is best done with the gauge showing THREE temp bars, that is, at
actual engine operating temperature. I wait until the fan comes on before beginning TBS.
I had to readjust the idle down to 1000 rpms otherwise quick strokes of the throttle would bring
idle speed at 2000-2500 rpms).
Quick response to the throttle is a good thing. When I first did the TBS, my idle was set at 1000rpm.
No joy. Reading on this and the other forum convinced me to use 1250rpm ( Estimated, I'm just using
the bikes tach )for regular idle and for all adjustments. I had to turn the idle down after the first
attempt at TB synching. After re-synching, I had to turn it down a little bit again.
I've read here that 10" of lightweight oil movement is equivalent to 1" of movement on a commonly used
mercury manometer. Sensitive. I can't get stable oil levels closer than 1" at 1250rpm. I've left it with the
front about 1" higher, so the rear would experience the slight richening effect.
I readjusted it twice while having the bike warm (two-three bars) as it would go either above
or bellow the center line.
The TP sensor setting should be the same whether the bike is hot or cold. A mechanical position sensor,
which sends an electrical signal. As you can read on the forums, this sensor can be the cause of a variety
of specific operating woes and testing with a Volt/Ohm meter doesn't always show a problem. Replacement
is the only reliable test, unfortunatlely. I wouldn't replace it unless all else fails.
I revved the engine manually by just opening the throttle a little bit and noticed that the TBS
changes by 5 inches! Is that normal? I tried this with and without secondary plates, same deal. How can
one cylinder "Pull" more than the other one with plates removed thus leaving only the throttle to regulate
the amount of air being sucked in?
You only see the DIFFERENCE in vacuum with a homemade manometer. As engine rpm's increase, actual vacuum
increases greatly compared to low vacuum at idle. 5 inches is a significant difference at idle rpm and low
vacuum. It's insignificant at higher rpm's and high vacuum.
The ST actuator also doen't convince me at all: it takes like 8-10 seconds to bring back idle speed
when it uselessly rises it to 2/3000 rpms.
The ST actuator can be in constant motion at all rpm's. It is the attempt by the ECU at fine tuning. If your
engine is fully warmed (three bars of temp), 8-10 seconds to return to idle speed of around 1200rpm would
indicate that one cylinder is running much leaner than the other at the current idle screw setting.
The reported causes for this are vacuum leaks, unsynchronized Secondary Throttle Plates, out of balance
Primary Plates (TBS) and out of specification valve openings.
Any suggestion is greatly appreciated as riding this bike really makes me miss carburetors motorcycles.
Cheers to all.
I still own and ride a carbureted inline 4. If I could replace with FI, I would do it in a minute. Carburetors
need synching and adjustment every few thousand miles, and are oversensitive to temperature, altitude,
fuel quality and wear.
Since you have dealt with STP, TBS and TPS but still have problems, and since 24,000 miles is overdue
in any case, I suggest that you check valve clearances. Let the engine sit 24 hrs. first, completely cold.
Day before I checked mine, I checked STP, TBS and TPS. They were right on after 11,000 miles. I've been
at the darned carburetors of the inline 4 twice in the same time period because they needed it!
I checked and replaced shims at 22,000 miles. All were at the very low limits of clearance. I replaced all
8 shims one size down to get within the upper limits of clearance. I don't expect a problem until 50,000
miles. After shimming, my STP adjustment was still right on, as was the TPS. I only needed to re-do TBS.
My K2 was running strong and smooth before valve check, and is running well now. I love this bike. I hope
you can solve your problems and have the enjoyment this machine is so capable of delivering.