Running
- I prefer the words "run in" to "break in" because it
sounds less destructive. During the first couple of
minutes a fresh engine is running I like to lightly blip
the throttle - between idle and about twice idle speed.
It is my intention to warm the engine and feel the
tightness of the freshly assembled mill. A couple of
minutes running like this with an air cooled single is
plenty of time. I then let it cool completely and perform
a compression test so I can use the information as a
benchmark to compare against some time later. A static
compression test is kind of like checking the blood
pressure of the engine - it checks its current state.
Drops in pressure can mean things are starting to show
wear (rings-piston-bore), while increases in compression
are more likely due to carbon build up on the piston
crown or combustion chamber dome. In either case, even if
the compression is fine and the hours have stacked up -
change the piston and associated parts out at a specific
interval. For this engine I feel safe with 45 hours.
Metals are elastic materials that can only withstand a
certain number of stress cycles. Going beyond that number
is not wise. Unfortunately, that number is determined by
experience - the driver is the only person who knows what
conditions he/she has subjected the engine to. Unlike a
baby that will start crying when its diaper needs
changing, the two stroke engine will start spewing parts
to indicate its "feelings." It's better to change the
"disposables" a little early to prevent them from getting
s(p)oiled.
I'm not one to add more oil to the gas during run in
because I'd rather not mess with the jetting that much and
it's not necessary in most cases. Some oil injected engines
require a small boost of oil - by adding it to the raw gas.
Usually the piston manufacturer will include any special
startup or "first tankful" instructions along with the
piston kit - there was no such instructions with this kit
anyway. I have seen the additional oil requirement on a few
engines - the Suzuki LT80 comes to mind as well as the
Yamaha GP760. I'll mix 5 gallons of fresh 92 octane gasoline
at a ratio of 50:1 using the AmsOil Series 2000 synthetic
oil. This will be the ratio during startup, run in and it's
running life. As it is right now the interior of the engine
was assembled using a very light coat of two-stroke oil on
its piston and associated parts, B.E. and main bearings and
cylinder wall. There's more than enough oil available for
start up during the kick starting procedure.
I don't "go for it" right after starting up a fresh top,
but I don't baby it either. I'll spend more time warming up
the engine before taking off and I'll avoid running under no
load but that's about it. It's probably best (especially
with a forged piston that has to grow more to fit the bore)
to fully warm up the engine before taking off - it takes a
few minutes if the engine is stone cold. The purpose is to
get the internals up to operating temperature - or at least
a temperature that's safe to take off from. Failure to do
this can result in a cold seizure - not a good thing, though
more typical of a liquid cooled engine. For the most part I
run in an engine the way I ride it - hard! Running in a top
end means letting the rings wear against the bore in a way
that leaves the bore smooth and the rings with an area that
is smooth and will seal well. It is the bottom side of the
rings that provide the sealing of combustion pressure. The
pressure of the rings against the bore determine how well
that seal will be. Experience has shown me that the "run in"
period occurs quickly with two strokes and waiting too long
for "it" to happen takes too much time away from the
available life expectancy of the parts. One tank of gas is
all it gets to do its duty. During that tankful I'll take it
to all operating speeds - including full throttle, though
it'll not be subject to sustained periods at any RPM.
If you click on the Thread
Spread link within my web site you'll come across a
short response I gave to someone some time ago regarding
what oil ratio to use during break in - it just happens that
the person was asking about it for his Blaster. I've copied
it here for easy reference.
- If you add more oil to the gas
during break in - it WILL lean out the mixture of fuel to
air throughout the whole rpm operating range. You must
compensate for it by richening up all mixture settings.
Drop the clip one or two notches (to raise the needle),
increase the size of the main jet a couple of sizes and
adjust the idle speed air screw to let the motor idle at
its fastest rpm - then turn the idle speed down. You
could skip all of this by just keeping the same amount of
oil in the gas as you normally run. Once your new top end
is broken in - in a tank full of gas or two - you will
need to change the jetting again. That is - when you
change back to the amount of oil you used to
use.
-
- If you get the opportunity to
take apart an engine very often you may notice that the
bottom end of a two stroke almost always has a
substantial amount of oil laying in the cases. Even in
engines that have been run at leaner oil to gas ratios
(50:1 to 100:1) there is plenty of oil. The other
internal parts of the engine also are well coated wet
with oil. It doesn't matter if the motor is air cooled or
liquid cooled - the internals of the engine are still
coated. Much of this oil may accumulate at idle and
during periods of low rpm running. Once you get the motor
spinning faster and it is under load, that extra oil in
the case may finally have a chance to become suspended
again in the fuel and air mixture and perhaps be
burned.
-
- Many people will rev their
engine to clear that oil (that plume of smoke they get at
startup or after idle) and refer to it as "cleaning out"
the engine. And that is exactly what is happening. That
oil - which has become separated from the fuel has
gathered in the cases and is standing by waiting for some
serious turbulence to get it up the transfer ports and
into the cylinder where it can finally be burned. Too
much oil in the gas can lead to additional problems like
carbon deposits on the piston crown and cylinder head,
sticky rings, fouled plugs and wet drippy black gunk
(unburned oil) coming out of the joints of the exhaust
system.
-
- It is probably best to avoid
sustained periods of idle, or very low rpm running under
no load. It is also probably better to choose a lower
gear (for instance 3rd at 5000 rpm instead of 4th at 3800
rpm) and let the motor spin faster when driving at slower
speeds since there in less likely a chance of the oil not
finding its way to the combustion chamber. It is my
opinion that if you use top quality oils (synthetics are
the best) you are only throwing away money and making
more smoke by running more oil through the engine than it
needs. I have had good luck by always using the same oil
to gas ratio and the same oil brand.
-
-
-
- I receive a lot of mail from people asking for
specific recommendations for the oil to gas mixture as
well as the brand of oil to use in their two-stroke
engine. I always start my response to these inquiries the
same way - by telling the person that I'm not going to
tell them what oil ratio or what oil brand to use. There
are simply too many engines purposes, oil brands, running
conditions and circumstances to make broad based blanket
statements about them. However I have posted on my
Glamis Sand Dunes page the oil
brand I prefer and the ratio I mix at - as well as the
fuel I use. This works for me - with my setup on my
TRX.
The jetting kit I received from LRD for the stock
carburetor of this engine contained a new needle and clip
(the needle was received with its clip in the 3rd position
from the bottom - of 6 grooves) - it appears to be made from
stainless steel though I did not verify that. There are no
identifying numbers on it so I'm guessing the company either
made it or had it made. I doubt it is a Mikuni part since it
doesn't have the company logo. Also included as part of the
kit is a Mikuni #30 pilot jet and 2 Mikuni main jets, a #300
and a #310. When I ordered the jetting I informed them I was
running a .50 mm over bore cylinder that had its porting
specs changed to the new numbers I established. I let them
know I was running a K&N air filter without an air box
lid and that the engine uses a tuned exhaust pipe. I told
them I was switching to premix at a ratio of 50:1 and that
the static compression was about 160 lb. at sea level and
the quad would be ridden at or about sea level too. They can
use all of this information to determine the jets necessary
to include in my kit. I'll swap in the new parts - start
with the #310 main jet and the clip of the needle in the
position it was received in - 3rd from the bottom. This will
be my baseline setup - any changes I make will be taken from
this point.
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The Blaster finally gets to go off road -
November 1999
Here's a small thread detailing the first outings with
the new power.
I understand you took the Blaster to Hollister Hills SVRA
over the weekend for its maiden voyage. How was it?
Rick
- Well, I am not going to be
riding for a while. I crashed the Blaster and I bent the
axle. I bent my handle bars. I broke the plastic. I bent
the light frame. I deflated the front tire somehow, but
luckily I am OK and so is the engine. We went to Holister
and I was not use to the hard pack. I went up a steep
hill and I had to downshift at the top. When I did it
took off and did a pop-a-wheely. When I did this it went
up and looked like it was going to fall up-side down on
top of me. So I let go. When I did it landed on its end
and stayed there. But then it was going to fall backwards
(I thought it was going to fall on me and take me with
it) so I moved out of the way and watched my bike roll
down the hill end over end until it stopped at the
bottom. So not only am I in major debt - I can not ride
for a long time. I would like it if you could keep an eye
out for the parts that I listed. If you find them please
tell my dad. Thank you,
-
- Jay
- BUMMER.
-
- All that and you didn't even get hurt (heh)?!? It's a
good time to get a Dura-Blue axle and some Renthal
handlebars! It sounds like there was too much engine and
not enough kid. I can't believe you let that thing get
away from you. I'll bet if it was a football you would
have caught it!
-
- Rick
-
-
-
-
-
- On the Dura Blue should I get
the stock width or the 4 inches wider? 2" on each
side.
-
- Jay
-
-
-
-
-
- I would do some research before I made that decision.
Maybe there's an axle that is adjustable so you can be
wide when you need to be wide and narrow when you need
narrow. I would have a hard time committing to a wider
axle - I think adjustability is "key" here.
-
- Rick
-
-
-
-
-
- The engine ran great. It
definitely has more power than before. It ran well and
seemed to be jetted okay. The plugs fouled at the end
because Jason was having to ride back at about 2 mph due
to the bent axle (the tire lightly rubbed the inside of
the fender). Jason's crash was avoidable but with his
inexperience it is also predictable.
-
- He ran up a steep grade (I had
just come up it and turned around to make sure he made it
okay, so I saw everything) and when he was almost over
the top onto the flat trail at the top, he downshifted
(like you might have to on a steep dune) and just as he
hit the lip of the grade he wheelied. It went up so far
that he slipped off the back of the seat. The bike rested
momentarily on the grab bar on the back (like when on the
trailer, standing on end by itself). Jason was on the
ground and looked up at the bike standing up. If he had
put his hand up and lightly pushed, the bike would have
fallen forward. He didn't and the bike began to fall
backward toward him. Remember all of this was on flat
ground. As the bike fell Jason dove out of the way, the
bike landed with the seat on the very edge of the lip of
the grade, it then flipped end over end down the entire
grade. As I drove over to Jason he was crying like a baby
on the ground. I thought he was hurt until I realized
that he was crying over his bike being
wrecked.
-
- A new Yamaha axle is $199. A
new Dura Blue eliminator is $299, but is lifetime
warrantyed. I haven't found a used one yet but have sent
out several E-mails.
Bill (Jasons dad).
- The axle purchase presents a touch choice.
Conventional thinking says that an axle guaranteed for
life is a very strong unit - and that may be the problem.
In some circumstances it may be better for the axle to
bend rather than having it being the strongest link of
the chain. A weaker axle might bend, to absorb some of
the energy of the impact rather than bending the swingarm
it attaches to or the frame that attaches to that. I
think buying replacement handle bars present a touch
choice as well since they have the ability to
absorb-and-protect as well.
-
- There might be some advantage to an adjustable after
market axle - especially if it can go as narrow as the
stock length and a couple inches wider by spacing it out.
If I remember right some companies sell two or three
different quality level replacement axles. Maybe one with
a shorter guarantee would be stronger than stock but not
stronger than the obstacle it might encounter.
-
- A quick glance at a magazine found the Eliminator at
the top of the list (lifetime warranty) but a heavy-duty
(six month warranty - 2 1/2 time stronger than stock)
part listed too. It seems the difference in price between
the two axles is as little as $20 - it seems too close. I
wonder if 1-800-pac-parts is still in business for stock
parts.
-
- A long time ago when I flipped my TRX in Hollister
the $70 Renthal bars (1986 price - triple now) bent as
well as the steering stem. I can remember thinking maybe
if I had the stock bars on it might not have ruined the
$200 stem. I replaced them with the stock ones I took
off. On the flip side of that during the incident the
rear axle was bent a little bit. A stronger axle might
not have bent if subject to the relatively light impact
it suffered - but who knows if it would have ruined
anything else. I'm still running the slightly wobbling
axle.
-
- If it were a decision I had to make I would have to
consider all the miles, circumstances and conditions my
TRX has encountered. Maybe what's needed is an adjustable
strength axle - one that's strong when it needs to be and
weak when it needs to be. I'm thinking smart metals - you
remember T2 don't you?!?
Rick
Jason and I are going to go to
Pismo on Friday after Thanksgiving. Do you want to come?
We'll be back on Sunday.
Bill
Unfortunately, I can't go then. Le tme know how
everything works out for you though.
Rick
- Rick, It ran great. In fact my
dad even rode it and I think was kind of impressed. We
did have to change something in the carb because it was
pinging inthe mid range (needle clip position). It wasn't
when I rode it but it did when he did.
-
- Jay
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