my friend asks a question

John,

Here is a question for you and your metalhead group.

Q: Say you had a 2 CYCLE motorcycle and you wanted to push start
it. Suppose that you got on it and turned on the ignition but didn't
hit the start button. Instead you depressed the clutch lever and put
it in 1st gear. Then four of your not so bright friends, two on each
side, pushed you and the bike BACKWARDS!! Remember there are two each
side so they should be able to keep you from falling over. After the
bike gains some momentum you pop the clutch. Now, the question is:
WILL THE BIKE START WITH THE ENGINE RUNNINGBACKWARDS??!? If not, why
not? The reason that it comes up is that I read about a new class of
ULCCs (UltraLargeCrudeCarriers -- Way big mutha oil tankers) that
have 2 cycle diesel engines with NO transmission, clutch or reduction
gears of any sort. The drive shaft comes out the back of the engine
and goes out the back of the hull and the propeller is bolted directly
to the end of it No gears, no clutch, no nothing. The way that they
reverse it is by shutting of the engine and then restarting it
BACKWARDS!!?! It is designed to do this, I'm wondering if all 2
cycle engines will run backwards or not? Inquiring minds want to
know.

Bill

From Engineman

On Sat, 29 Oct 2011 18:22:51 -0700 (PDT), "
> wrote:

>John,
>
> Here is a question for you and your metalhead group.
>
> Q: Say you had a 2 CYCLE motorcycle and you wanted to push start
>it. Suppose that you got on it and turned on the ignition but didn't
>hit the start button. Instead you depressed the clutch lever and put
>it in 1st gear. Then four of your not so bright friends, two on each
>side, pushed you and the bike BACKWARDS!! Remember there are two each
>side so they should be able to keep you from falling over. After the
>bike gains some momentum you pop the clutch. Now, the question is:
>WILL THE BIKE START WITH THE ENGINE RUNNINGBACKWARDS??!? If not, why
>not? The reason that it comes up is that I read about a new class of
>ULCCs (UltraLargeCrudeCarriers -- Way big mutha oil tankers) that
>have 2 cycle diesel engines with NO transmission, clutch or reduction
>gears of any sort. The drive shaft comes out the back of the engine
>and goes out the back of the hull and the propeller is bolted directly
>to the end of it No gears, no clutch, no nothing. The way that they
>reverse it is by shutting of the engine and then restarting it
>BACKWARDS!!?! It is designed to do this, I'm wondering if all 2
>cycle engines will run backwards or not? Inquiring minds want to
>know.
>
> Bill
>
>From Engineman


This is just a GUESS on my part. The big difference I see is that a
2cycle motorcycle engine is designed to run at med to high speeds so
I'm guessing it's designed for single direction running. I'm thinking
it also has reed valves and port valves and those might not work
backwards.

The Oil Barge Engine, on the other hand, is surely designed to run at
very low speeds, possibly as low as 200 rpm and no faster then perhaps
800 rpm. I suspect it uses valves similar to a typical car engine
too. So I can imagine it might be fairly easy to design one that runs
in either direction.

wrote:
> John,
>
> Here is a question for you and your metalhead group.
>
> Q: Say you had a 2 CYCLE motorcycle and you wanted to push start
> it. Suppose that you got on it and turned on the ignition but didn't
> hit the start button. Instead you depressed the clutch lever and put
> it in 1st gear. Then four of your not so bright friends, two on each
> side, pushed you and the bike BACKWARDS!! Remember there are two each
> side so they should be able to keep you from falling over. After the
> bike gains some momentum you pop the clutch. Now, the question is:
> WILL THE BIKE START WITH THE ENGINE RUNNINGBACKWARDS??!? If not, why
> not? The reason that it comes up is that I read about a new class of
> ULCCs (UltraLargeCrudeCarriers -- Way big mutha oil tankers) that
> have 2 cycle diesel engines with NO transmission, clutch or reduction
> gears of any sort. The drive shaft comes out the back of the engine
> and goes out the back of the hull and the propeller is bolted directly
> to the end of it No gears, no clutch, no nothing. The way that they
> reverse it is by shutting of the engine and then restarting it
> BACKWARDS!!?! It is designed to do this, I'm wondering if all 2
> cycle engines will run backwards or not? Inquiring minds want to
> know.
>
> Bill
>
> From Engineman

Its possible but the electronics won't let it
and the cooling fan would not work right.
Most 2 cycle engines have spark plugs and need timing
of the spark.
A pure diesel engine, non electronic, can run backwards.

wrote:
> John,
>
> Here is a question for you and your metalhead group.
>
> Q: Say you had a 2 CYCLE motorcycle and you wanted to push start
> it. Suppose that you got on it and turned on the ignition but didn't
> hit the start button. Instead you depressed the clutch lever and put
> it in 1st gear. Then four of your not so bright friends, two on each
> side, pushed you and the bike BACKWARDS!! Remember there are two each
> side so they should be able to keep you from falling over. After the
> bike gains some momentum you pop the clutch. Now, the question is:
> WILL THE BIKE START WITH THE ENGINE RUNNINGBACKWARDS??!? If not, why
> not? The reason that it comes up is that I read about a new class of
> ULCCs (UltraLargeCrudeCarriers -- Way big mutha oil tankers) that
> have 2 cycle diesel engines with NO transmission, clutch or reduction
> gears of any sort. The drive shaft comes out the back of the engine
> and goes out the back of the hull and the propeller is bolted directly
> to the end of it No gears, no clutch, no nothing. The way that they
> reverse it is by shutting of the engine and then restarting it
> BACKWARDS!!?! It is designed to do this, I'm wondering if all 2
> cycle engines will run backwards or not? Inquiring minds want to
> know.
>
> Bill
>
> From Engineman


The 2 cycle bike won't start and run backwards. The port timing in the
engine along with the ignition timing won't allow it to happen.

The diesel on the other hand will run backwards easily BUT that is
because it is designed that way. Very common in marine and some
machinery applications.

The common method is a selectable valve train and port system. On the
BIG engines they usually use either a 2 or 4 cam system with 4 valves
per cylinder. One set if for forward and the other reverse. On the
smaller engines such as Detroits there is a sliding valve train system
and different controls to switch fuel timing and oil flow.

If the engine is built for it the operation is simple and very common in
marine engines. Used with both 2 and 4 stroke diesels commonly. There
are also many twin engine smaller boats that run two identical engines,
except one is set up to run in reverse of the other.

On gas engines this is simple, you replace the cam with a reverse grind
and the timing chain gets tossed in favor of a two gear drive. On some
you also need to replace the oil pump with either a dry sump or just a
remote pump.

--
Steve W.

Ashton Crusher > wrote:
>
>This is just a GUESS on my part. The big difference I see is that a
>2cycle motorcycle engine is designed to run at med to high speeds so
>I'm guessing it's designed for single direction running. I'm thinking
>it also has reed valves and port valves and those might not work
>backwards.

I know that the 2-cycle Briggs and Stratton on my old lawnmower would
start backwards because once I mis-assembled the pull cord assembly
and managed to do it.
--scott


--
"C'est un Nagra. C'est suisse, et tres, tres precis."

I didn't know Briggs & Stratton ever built any 2 cycle engines.
cuhulin

On 10/30/2011 05:13 AM, Steve W. wrote:
> wrote:
>> John,
>>
>> Here is a question for you and your metalhead group.
>>
>> Q: Say you had a 2 CYCLE motorcycle and you wanted to push start
>> it. Suppose that you got on it and turned on the ignition but didn't
>> hit the start button. Instead you depressed the clutch lever and put
>> it in 1st gear. Then four of your not so bright friends, two on each
>> side, pushed you and the bike BACKWARDS!! Remember there are two each
>> side so they should be able to keep you from falling over. After the
>> bike gains some momentum you pop the clutch. Now, the question is:
>> WILL THE BIKE START WITH THE ENGINE RUNNINGBACKWARDS??!? If not, why
>> not? The reason that it comes up is that I read about a new class of
>> ULCCs (UltraLargeCrudeCarriers -- Way big mutha oil tankers) that
>> have 2 cycle diesel engines with NO transmission, clutch or reduction
>> gears of any sort. The drive shaft comes out the back of the engine
>> and goes out the back of the hull and the propeller is bolted directly
>> to the end of it No gears, no clutch, no nothing. The way that they
>> reverse it is by shutting of the engine and then restarting it
>> BACKWARDS!!?! It is designed to do this, I'm wondering if all 2
>> cycle engines will run backwards or not? Inquiring minds want to
>> know.
>>
>> Bill
>>
>> From Engineman
>
>
> The 2 cycle bike won't start and run backwards. The port timing in the
> engine along with the ignition timing won't allow it to happen.
>
> The diesel on the other hand will run backwards easily BUT that is
> because it is designed that way. Very common in marine and some
> machinery applications.
>
> The common method is a selectable valve train and port system. On the
> BIG engines they usually use either a 2 or 4 cam system with 4 valves
> per cylinder. One set if for forward and the other reverse. On the
> smaller engines such as Detroits there is a sliding valve train system
> and different controls to switch fuel timing and oil flow.
>
> If the engine is built for it the operation is simple and very common in
> marine engines. Used with both 2 and 4 stroke diesels commonly. There
> are also many twin engine smaller boats that run two identical engines,
> except one is set up to run in reverse of the other.
>
> On gas engines this is simple, you replace the cam with a reverse grind
> and the timing chain gets tossed in favor of a two gear drive. On some
> you also need to replace the oil pump with either a dry sump or just a
> remote pump.
>

what he said. [great response]

--
nomina rutrum rutrum

On Sat, 29 Oct 2011 18:22:51 -0700 (PDT), "
> wrote:

>John,
>
> Here is a question for you and your metalhead group.
>
> Q: Say you had a 2 CYCLE motorcycle and you wanted to push start
>it. Suppose that you got on it and turned on the ignition but didn't
>hit the start button. Instead you depressed the clutch lever and put
>it in 1st gear. Then four of your not so bright friends, two on each
>side, pushed you and the bike BACKWARDS!! Remember there are two each
>side so they should be able to keep you from falling over. After the
>bike gains some momentum you pop the clutch. Now, the question is:
>WILL THE BIKE START WITH THE ENGINE RUNNINGBACKWARDS??!? If not, why

I would guess that it woudl start.

>not?

I have a motorcycle, that I fixed and ran for 5 minutes, but haven't
been able to work on more.

I certainly havne't adjusted the timing. If the spark timing is like
a car, set BEFORE TDC, then running it backwards would have the timing
after TDC. That would make the engine a lot less powerful, But if
all you neede r everse was to back into a parking place, it might
still do it It wouldn't run for long and wouldn't waste that much
gas.

Maybe there are other reasons a moto wouldn't run well in reverse.

The reason that it comes up is that I read about a new class of
>ULCCs (UltraLargeCrudeCarriers -- Way big mutha oil tankers) that
>have 2 cycle diesel engines with NO transmission, clutch or reduction
>gears of any sort. The drive shaft comes out the back of the engine
>and goes out the back of the hull and the propeller is bolted directly
>to the end of it No gears, no clutch, no nothing. The way that they

No nothing? No adjustment for the spark timing, to make it BTDC, even
though the entine is runing backwards?

>reverse it is by shutting of the engine and then restarting it
>BACKWARDS!!?! It is designed to do this, I'm wondering if all 2
>cycle engines will run backwards or not? Inquiring minds want to
>know.
>
> Bill
>
>From Engineman

On 30 Oct 2011 09:29:33 -0400, (Scott Dorsey) wrote:

>Ashton Crusher > wrote:
>>
>>This is just a GUESS on my part. The big difference I see is that a
>>2cycle motorcycle engine is designed to run at med to high speeds so
>>I'm guessing it's designed for single direction running. I'm thinking
>>it also has reed valves and port valves and those might not work
>>backwards.

I don't see in what way the valves would be running backwards even if
the engine was. All they know is if the piston is going up or down.

>I know that the 2-cycle Briggs and Stratton on my old lawnmower would
>start backwards because once I mis-assembled the pull cord assembly
>and managed to do it.

Good to know.

But I'm amazed; you could mis-assemble the B&S pull cord backwards!!
Did you put something on upsdie down, and drill a hole so it would go
on!

>--scott

On 30 Oct 2011 09:29:33 -0400, (Scott Dorsey) wrote:

>Ashton Crusher > wrote:
>>
>>This is just a GUESS on my part. The big difference I see is that a
>>2cycle motorcycle engine is designed to run at med to high speeds so
>>I'm guessing it's designed for single direction running. I'm thinking
>>it also has reed valves and port valves and those might not work
>>backwards.
>
>I know that the 2-cycle Briggs and Stratton on my old lawnmower would
>start backwards because once I mis-assembled the pull cord assembly
>and managed to do it.
>--scott

Did the grass get longer as you ran it across the yard?