|
So Your bike wont run?
TOP TEN TROUBLE
SHOOTING TIPS
WHEN IT WON'T RUN RIGHT, FIND THAT PROBLEM!
by: Rick "Super Hunky" Siemen
Nothing is more frustrating than when your bike won't run, or runs goofy.
So, what I will attempt to do here is to give you a genuine, hands on type
of troubleshooting guide that you can use.
No confusing high-tech talk or impossible-to-understand charts. Just the
basic kind of grunt information that I have accumulated through more than
three decades worth of messing around with some screwed-up dirt bikes.
Don't expect scientific delving here; instead, you can look for common
horse-sense reasoning and, in many cases, oldfashioned chasing of hunches.
DIFFERENT KINDS OF GRIEF
You can divide motorcycle maladies into a number of different categories:
1. The stupid thing won't start, even though it ran okay the last time you
rode the bike.
2. Your bike is really hard starting. Maybe you even have to tow it to get
things fired up.
3. It starts okay, but runs ratty.
4. Bike will not start, but you don't have a clue why. Maybe it's not even
your bike, so you don't have any history to go by.
5. The bike coughs, hesitates, sputters or backfires while it's running.
6. Erratic running.
7. Pinging, detonating or odd sounds come from the engine.
8. Bike runs for a while, then dies.
9. Bike stalls easily.
10. Overheating.
1. THE STUPID THING WON'T START, EVEN THOUGH IT RAN OKAY THE LAST TIME YOU
RODE THE BIKE
Few things are more irritating. The last time you rode, the bike ran
great. You parked it in the garage, and a month later it just won't start.
As with most troubleshooting, yank the spark plug. If it's wet, or oily,
slip a new plug in the cap, ground it out against the head and push the
kickstarter through. If you see a nice fat blue spark, chances are the bike
will start okay now.
A plug can foul from a leaking petcock, or just be cause it was tired and
heavily coated with carbon.
With a new plug installed, stomp it through a few times and see if it
fires, or tries to fire. If it doesn't bark to life right away, yank the
plug. If it's wet again, your bottom end might be loaded with gas. This
happens with older bikes that sit for a while. Some crankcases have a drain
plug on the bottom. If this is the case, remove it and let the gunk drip
out.
So you say your engine cases are loaded up just a little bit? Wonder where
all that premix came from?
If not, then you can gently turn the bike upside down, remove the plug,
put the bike into gear and cycle the engine by slowly rotating the rear
wheel. If you see a lot of mist and gas blowing out of the plug hole, you
have found your problem.
After that, it's just a matter of putting in clean plugs until the bike
lights off. When it does, it will be accompanied by a huge cloud of blue
smoke that will kill every mosquito within two blocks.
Just remember, if you can get a nice spark out of a plug, you should be
able to get the bike lit off. However, let's say you have that big fat
spark, and it still won't start. Where do you look?
Chances are nine out of ten that something is preventing gas from getting
to the engine. You need a few things to let an engine run: fuel, spark,
compression and exhaust. Always look in the carb first, and check for crud
blocking the jets.
If you washed your bike before you put it away, there's a good chance that
water is in the float bowl. If the bike's been sitting in a cold garage
after a hot day of riding, condensation can form in the bowl. All it takes
is a little bubble of water to clog a jet.
Remove the float bowl, check for water or debris, then blow out not only
the jets, but all the passages with some contact cleaner or compressed air.
While you are wallowing around in that carb, check for fuel flow. Turn on
the petcock and make sure that gas is getting into the carb. A float needle
can stick if it's worn, or some gummy deposits make it stick to the seat.
Couple of places to check: leaky petcock is one source.
Having checked all these things, the bike should now start.
2. YOUR BIKE IS HARD-STARTING
It takes a zillion kicks, or maybe even a trip on the end of a tow rope,
to get the bike started. This is not the way to begin a day of riding or
racing. First steps, naturally, should be the regular plug check and
replacement, if necessary.
Hard starting can usually be traced to crud or water in the carb float
bowl or, failing that, lame jetting. Without getting into a major jetting
story, here's the basic things you need to know:
If a bike starts okay cold, but is hard to start when hot, the pilot jet
is too rich. If it starts fine hot, but gasps like a hooked trout when cold,
the pilot jet is too lean. One good test is if the bike still runs decent
with the choke partially on. That's a solid clue that the pilot is way too
lean.
You can also find freaky things that make a bike hard starting. Once I had
a Maico 450 that was driving me nuts. The jetting, I knew, was perfect, but
it gave every indication of hard starting and running rich. After two ruined
motos, I found out that the pilot jet was backing off in its seat and
letting excess fuel leak by the threads.
3. YOUR BIKE STARTS OKAY, BUT RUNS RATTY
Again, look at your plug for clues. If there's a buildup on the tip,
replace the plug and try again. Common sense checks get the first nod. Make
sure your timing is spot on, the carb is clean and all electrical
connections are tight and corrosion free.
Logic aside, small things can make a bike run ratty. Check the fuel filter
and see if it's clogged. Make sure the fuel line isn't pinched. Don't take
anything for granted. I'm reminded of the Can-Am enduro rider of a dozen
years ago. The 370 Can-Am ran like a moped with desert gearing in deep sand.
This puzzled everyone, as the engine was fresh and the jetting was spot on.
Just a few weeks previously, the bike ran great.
Naturally, the ignition was suspect, so bench checks were run. The bike
still ran like a toad. In desperation, all of the ignition components were
replaced. Twice. Still hopeless. Air leak checks were done. Everything was
tight. The engine was taken completely apart, triple checked and put back
together. Crank seals were perfect, so no power was being lost there.
In total desperation, a perfectly good running engine was taken out of
another Can-Am and slipped into the chassis. The bike was still a pig.
The crew sat down and made a list of everything that had been checked or
replaced. One of the people had just finished a Sherlock Holmes novel, and
in it the great detective noted: "No matter how strange it seems, Watson,
whenever all the possibilities have been eliminated, whatever is left, no
matter how improbable, must be the answer."
Well, the only thing that hadn't been changed or checked was the
SuperTrapp muffler. It was taken off and a new SuperTrapp installed. The
bike then ran like the proverbial striped ape. Careful examination of the
old SuperTrapp showed that there was a carbon buildup on the Trapp discs
that was the same color as the disc material enough buildup, in fact, to
strangle the engine.
Other things that will make most any bike run ratty are air leaks, worn
rings, head gasket leaks, bad engine seals, clogged air filters and worn
engine bearings. Worn bearings? Sure. When the end of the crank is allowed
to wander, the ignition will vary as the mag end of the crank wobbles
around.
Two things that will make an engine run ratty and defy detection are worn
reed valves and intermittent electrical shorts. A visual inspection of the
reeds will solve the first problem, but a frayed coating on a wire can drive
you crazy. Look underneath zip ties for shorts, or places where a wire could
be making contact with a hot part, like an exhaust pipe. Normal vibration
will often let the wire jiggle and kill or weaken the charge to the spark
plug.
Check every connection on your bike to find shorts or interrupted power.
There's so much vibration on a dirt bike, things can come loose . like this.
.Stock reeds can (and will) take set or get warped, cracked or frayed.
Replaced them with quality items like Boyesens.
4. BIKE WILL NOT START, BUT YOU DON'T KNOW WHY
If it's a strange bike, you are starting from scratch. Do all the usual
stuff, start
ing with the time honored plug check, carb cleaning and so forth. If it
still won't bark, start using the Sherlock Holmes approach.
A buddy of mine bought a new KTM and brought it over to my house one day,
in complete dismay. I ran all the regular checks. The bike still wouldn't
start. After two solid hours of head scratching, the only thing we hadn't
checked was the airbox.
The saddle was removed and we did a double take when we saw a bright red
shop towel stuffed into the air inlet tract. When my friend washed his bike
the last time, he removed the filter, pushed a rag into the air inlet to
keep water from getting in the carb and replaced the saddle after forgetting
to put the filter back in. It's pretty hard to light off a bike without air.
You want more weirdness? I once worked on a bike for half a Saturday
trying to get it started, only to find out later on that the curb had
literally been put in backwards. Don't laugh. Many carburetors have inlets
and outlets very close to the same size.
Once a neighbor came over with a tale of woe about his bike. An hour
later, we found out that he had installed a new set of Boyesen reeds and
left one of them out.
I can't tell you how many European bikes that I have tried to start that
have driven me to distraction, only to find out that the kill buttons had
gone south.
No spark? Always suspect the kill button, especially on European bikes.
Then there's the clincher for the weirdness award. My buddy bought an old
enduro bike real cheap to set up as a trail riding machine for his wife.
Because it wasn't running, he got it for a few hundred bucks. After spending
an entire weekend trying to get the bike running, he gave up. An offer of
unlimited beer got me and Big Jim over to the house to assist.
After doing all the usual checks, the bike had us well and truly stymied.
It had spark, timing was right on, the carb was clean, and we even took
apart the entire top end to check for mechanical problems; still the bike
refused to fire up.
Big Jim solved the problem; he took a long piece of welding rod and
inserted it into the end of the exhaust. Thunk! The rod stopped dead against
a non-metallic surface. The muffler was removed and taken apart. Inside was
a plug of mud that had hardened like pottery.
A phone call to the previous owner later revealed that he had looped out
trying to climb a muddy stream bank and injured his shoulder. The bike had
not been started since then, and had sat out in the hot California sun.
Hence the kiln dried plug in the exhaust, and the explanation of a most
definitely puzzling non-starting problem.
5. THE BIKE COUGHS, HESITATES, SPUTTERS OR BACKFIRES WHILE IT'S RUNNING
It drives you nuts to have the bike hiccup while you are passing the guy
in front of you. If you have done all the usual basics, then it's time to
check for air leaks, specifically in the carb or inlet tract. Common sources
of sudden air leaks are the carb coming loose in the manifold, the top of
the curb loosening and a leaking head or base gasket.
However, more often than not, you will find water or debris in the carb
float bowl causing the problem. How does it get in? Think about gassing up
your bike between motos, with the wind blowing airborne grit all over the
place and don't think the gas you bought the day before doesn't have water
in it. One of the best insurance policies you can have is a good in-line
fuel filter; change it often.
6. ERRATIC RUNNING
If the bike runs well for a while, then runs bad for a while, and keeps
going back and forth, chances are that the problem is not mechanical in
nature, and surely not jetting. More often than not, the hassle can be
traced to a loose wire or connection, or a frayed wire shorting out via
vibration.
One other logical place to look is that old devil carb float bowl once
again. A tiny piece of grit, or a minuscule drop of water, can and will
dance around the main jet and cause the erratic running.
Another is a bad float needle/seat combo, or perhaps just a poorly adjusted
carb float. In fact, most engines that run erratically can have the problem
traced to crud or water in the float bowl.
When the offending matter is off to one side of the main jet, the bike
will run perfectly, but when it moves to directly under the main jet
orifice, fuel flow gets strangled. The normal on/off of the throttle will
let the grit or water move around, as the pressure changes with power on and
off.
7. PINGING, DETONATING OR ODD SOUNDS COME FROM THE ENGINE
If your bike starts to emit a death rattle under heavy power, you should
immediately do all the carb checks for cleanliness. Next step will be
inspecting for air leaks in and around the carb. Specifically, inspect the
main jet for a foreign substance stuck up inside that will make the bike run
horribly lean.
Major sources of air leaks: reed cages, reed blocks and card inlet housings.
If all these things check out, you might have pump gas with way too low an
octane rating. It never hurts to have some octane booster or a gallon of
pure racing gas with you.
8. BIKE RUNS FOR A WHILE, THEN DIES
This always seems to happen at the worst time, like when you are running
up front. More often than not, this sort of problem indicates a failing
ignition system. The bike will start and run okay for, say, 20 minutes,
until everything gets good and hot; then the engine will die and refuse to
start, and after a half hour or so it will fire up again.
Get back to the pits ASAP before the ignition takes a complete dump and
strands you 40 miles from the nearest rock.
Once, while racing an XR500 Honda in an enduro, the classic symptoms of a
dying black box started. However, being a resourceful sort, I didn't wait
for the electrics to cool back down. Instead, I poured some water on it from
my enduro jug to cool it down and managed to limp in without "houring out."
9. BIKE STALLS EASILY
Simple. Turn up the idle screw a bit. If your carb doesn't have an idle
screw, chances are it's a bit too lean on the pilot jet. Richen it up one
size and see if that helps. Also, get in the habit of squeezing in the
clutch when you brake hard.
10. OVERHEATING
Bad things happen to bikes that run hot, things like seizing and turning
pistons into ashtrays. Since most modern bikes are liquid cooled, you can
tell when they start to run hot. Steam starts to come out of the cap and
vent hose.
First things first: Let the bike cool down. Don't even think about taking
the radiator cap off when things are cooking, or you can get severely
scalded. While it's cooling down, check the radiator fins for mud, leaves or
dirt blocking the air flow.
Then remove the gas tank and see if any tubes are cracked, split or being
pinched by the gas tank. Also inspect lower hoses that lead from the water
pump area, and check for moisture at the water pump cover.
Temporary fixes are limited: You can remove the mud shield louvers to
increase air flow, and you can even take off the front number plate to move
more air to the cooling area. This is essentially a get back to the pits
fix.
If you are out on the trail and the water level is down, just about any
liquid will work temporarily to help cool down the engine. Once I poured a
quart of oil into a nearly empty radiator to limp home. Don't laugh; it
worked.
Some overheating is self induced. A few bikes (like Huskys) will not pump
water when the clutch is held in, so if you abuse the clutch a great deal in
tight woods, you will see your Husky start to run hot and blow steam.
The answer? Get in the correct gear to allow clutch-free riding and the
bike will cool right down.
Let's say you ran hot in the first moto and need to cool down the bike for
the second. First, drain all of the coolant out of the system and replace it
with regular water. Yes, we know that the system is designed to run with
anti-freeze and that extended use of water will cause scale and corrosion
buildup, but your bike will run slightly cooler with water than with a
coolant/water mix. When you get back home, drain out the water and clean and
flush the system.
Most bikes can also be cooled down by altering the timing slightly. The
closer to TDC you move the timing, the cooler the bike will run. It's not a
permanent cure, but will often do for a quick in-the-field
Four-strokes especially modified ones tend to run hot when pushed hard.
For the life of me, I don't know why big four-strokes don't come with an
engine oil cooler. The single best thing you can do to cool down a
four-stroke is to drain out the hot (and thinned!) oil and put in fresh oil.
Don't skimp and use cheap oil. Get the good stuff.
One of the biggest culprits that makes four-strokes run hot is a
restrictive ex haust system. Keep carbon out of the silencer/spark arrester
assembly, more so on stock items than with aftermarket units.
.Many problems with poor running bikes can be traced to clogged mufflers.
Four strokes are especially sensitive in this department.
Other things to check on a hot running four-stroke are low oil level,
clogged oil filter and any sort of air leak. Again, oil is the most crucial
source of engine heat, as most four-strokes have the same oil doing the
cooling and lubricating for both the transmission and the engine. On my per
sonal four-stroke, I drain the oil after every ride while the oil is hot;
cheap insurance to stay cool!
Most engine problems fall into one of these ten categories. Later on,
we'll do some chassis related trouble shooting.
Add your link here
.
Add your link here
|
Maybe your having trouble staying on top of things?
This is some descriptive text. |
