QuestionI was the Arizona state champ small engine troubleshooter my senior year of high school, and have had at least one old jap bike torn down for repair, restoration or modification without a break since I was 10. This year I'm 50 and have 5 vintage classics torn down in various stages of restoration right now, along with a half dozen others awaiting their. So, I'm no dummy... especially not with honda's. well, I've been trying to figure out why I can't diagnose a bad miss in the right cyl of my cb450k7.
I've swapped ign.coils, condensors, hi ten wires/boots
It's getting great spark at the plug (equal to the left side. all timing marks line up (valves and points) compression tests both sides @ 155psi.just had top end apart due to it's been sitting in my shed for over 20years and even though it has only 4,ooo miles it started smoking. when mic'd out I found nothing worn, so I changed out all seals and of course gaskets. cam timing marks verified and cam chain set and adjusted... all marks align as specified (I have 5 different repair manuals on these 450/500 models)in the book ((timing marks/pointer @ the rotor corespond with valve marks @ the cams). I verified all this by using my timing light for final adjustments.. got the timing set right on the "before top dead" mark on both cylinders. satified with correct fire to the plugs on both sides, I made sure the carbs "slides" floated like new (both have all new jets and all oem parts). Still, the right side smokes and backfires and is kept running by the left cyl... which runs perfectly. take the plug wire off the sick side and it makes no change (the left side keeps it running nicely) hold the sick side's plug wire within an inch of the engine and a long blue spark strikes. Try the same thing going the other way (hook the plug wire back to the plug on the sick side)start up with both wires hooked to plugs like normal, and remove wire from good(left) side... just like turning it off... Start it up again (starts up 1st kick and runs good, even idles) but the ehaust is smokey in that side and colder than exhaust from the good side. I've had it running at any throttle setting while spraying starter fluid into the carb intake, and no engine surge, just cleared up that side's exhaust for a few seconds, then it went back to backfiring and sputtering. to elliminate fuel problems altogether I swapped carbs... no change. with every component I swapped (coils condensers and now carbs) I couldn"t get the right side to miss a beat. this all tells me all these components are fine (also pass resistence testing ect.) I'm getting good compression, I can see the gas going into the venturi same as good side when running... so I can rule out gas. the spark is fat and blue at just the right moment, until I put it in the hole... then the only fire it gets is in the form of a backfire... while the other side is just working away like a champ... I've been working on thumpers for 40 years and these 2 lunger's (especially one with this "torque bar" valve sping set up) are always a challenge for me, but this has almost become embarrassing. Anything I'm overlooking that you can think of? I'm about stumped.
AnswerScott,
this happens often on these bikes for various
reasons. Sometimes it's plugged carb jets,
corroded coil or plug wires/caps. Spark
shorting on the points cover. Choke moving
around on it's own, bad contacts in the
ignition switch. Worn cam followers or
torsion spring guides. Sticky ignition
advance unit, faulty fuel petcock,
and fouling spark plugs.
Some of the newer "X" type plugs
with a internal gap may help to
increase voltage to the spark plugs.
There are electonic ignitions available
now for these bikes.
Sometimes the crankshafts rock a bit
on these bikes, adding a .020 shim
to the end float can help to reduce that.
Never heard of a crank going out of phase
on these but maybe a bent rod could
cause smoke.
Lastly, check here for more ideas:
http://groups.msn.com/HondaCB450DOHC
