OX-66 No Start, long storage

[Loral123]

pull the pumps and see if you can clean and free them up.

We be in some cold snap and snow here in new york. I will take them off next sunny day. Hopefully soon.

I hope this works. Two options - Yamaha OEM pump. Could be $900 each or aftermarket at $69 bucks. Both scare me - both prices are insane. One too high one too low.

Pat

[99yam40]

hope you did not burn them up trying to start them if the did not turn.
not sure if those DC motors pull overcurrent if not turning like the AC motors.
Never thought about DC motors much

[boscoe99]

That info has been around before the web was even invented.
How did you monitor exhaust gas temp?
Makes sense that if the engine didn't have the compression to burn it all it would leave carbon behind

Exhaust gas temperature meter.

Why wouldn't it all burn? I did not see any difference in the burn rate. Or burn temperatures.

Octane has nothing whatsoever to do with burn rate. Octane is a measure of gasoline's resistance to auto-ignition at temperature. The higher the octane the higher the temperature before auto-ignition occurs.

[boscoe99]

pull the pumps and see if you can clean and free them up.

Boscoe have you ran 93 in a low compression 2 stroke motor to compare to 87?

I believe most F motors are high compression, even the 4 stroke weed eaters and leaf blowers

heck I heard about the speed of burn /octane thing way back before there was a web.

Nope. Have not. Only tried it in the three models that I did because I had access to them. They have ports into which probes for the air/fuel and EGT meters can be inserted. Don't think any two stroke Yams have that port.

Yea, I also heard the octane myth long before the innerweb. The innerweb makes the dissemination of crap information faster and more widespread.

[99yam40]

Higher compression causes higher heat from what I have heard. that is why they recommend higher octane on those motors.
now with low compression there will be less heat to start out with due to less heat of compression, and the burn could be slower to move through the complete cylinder.
At least that is what I was taught or understood back in the day

[TownsendsFJR1300]

My Yamaha 600cc motorcycle (95hp, in-line 4, 14,000 red line, water cooled) has 12.2:1 compression ratio.

Yamaha spec's call for using regular fuel, (with two cats, no knock sensors)... Runs like a top and never had an issue...

Now my friends BMW motorcycle has a much lower compression ratio BUT requires high test...

Spec's, (note the compression PSI itself):

[rodbolt17]

it is not all about mechanical compression ratio.
it is all about combustion pressure.

my 455 in my old 442 was running with 12.5 TRW forged slugs yet I ran it on regular.

the camshaft desighn lowered combustion pressure.
the higher a fuels octane means the slower it burns.
the higher octane is less likly to explode.
kinda like the difference between red dot and accurate 4350.
both are smokeless but they burn at different rates but used in the wrong way they explode.

[Loral123]

Compression

Seems like big 2 stroke yamahas run at about 6:1, slightly lower on the bottom two pistons-something about cooling equalization.

[boscoe99]

Higher compression causes higher heat from what I have heard. that is why they recommend higher octane on those motors.
now with low compression there will be less heat to start out with due to less heat of compression, and the burn could be slower to move through the complete cylinder.
At least that is what I was taught or understood back in the day

Exactly. The higher the compression ratio the higher the temperature of the air/fuel mix when it is time for the spark plug to ignite the fuel. Which is why at some particular compression ratio, gasoline with a higher octane rating is specified. To help to prevent detonation.

Same thing with a supercharger. The air being compressed by the compressor gets much hotter than normal. Even with the use of an after cooler. That hotter air, when mixed with the fuel, will be more prone to detonation.

But I still say that octane is not about and has nothing to do with the burn rate of the fuel once the fuel is ignited.

[scofflaw]

But I still say that octane is not about and has nothing to do with the burn rate of the fuel once the fuel is ignited.

Not sure why you think the flame can't go out once started, the cylinder pressure that creates the heat must be sustained through the complete cycle. In a low compression engine the heat just isn't enough to complete the burn.

[rodbolt17]

it is ALL about the burn rate.
it is also why Yamaha specifically stated not to run premium in the old 220 excel and a few others.

it simply burned to slow and led to power loss at WOT. this was documented by a Yamaha tech bulliten as well as owners manuals.

my coworkers Honda 750 wont run well at all with premium it much prefers regular.

I can remember 85 octane that my Studebaker inline 6 liked but ran like crap on the 98 ethyl super shell.
yea I worked at a shell station in Vallejo CA at the time.

the higher the octane the slower it burns making it less likely to detonate.

that valve rattle you hear is NOT valve rattle at all.
it is the cyl head vibrating due to detonation.

kinda like the burn rate of black powder is rather instant and smokeless has a variable burn rate depending on what it is used for.
just as in an articulated rod piston engine it is all about maintain peak pressure until it is time to start the next cycle.
same as smokeless powder in a rifle. my 6.5 swiss likes IMR4350 shoots very well,way better than myself with that powder and a 140gr jacketed hollowpoint boattail.
move up the burn rate to 4064 and it shoots a pattern.
my 7mm mauser is just the opposite.
it likes IMR4064 and shoots a pattern with 4350.

it is all about a con*****ed burn rate and constant and consistant pressure.

just like a piston engine.

it is also why methanol and ethanol have an arbitrary rating of 100 octane.
you simply cannot detonate alcohol fuels.
that is why when we got much above 13/1 we ran methanol and some added the oxygen bearing fuel of nitro methane.

it is kinda how nitrous oxide works. you add fuel and nitrous oxide and you just increased the amount of fuel and oxygen in the cyl without making the displacement larger.
the oxygen seperates from the nitrogen and burns with the added fuel. nitrogen is an inert gas so it actually helps cool things.

[boscoe99]

Not sure why you think the flame can't go out once started, the cylinder pressure that creates the heat must be sustained through the complete cycle. In a low compression engine the heat just isn't enough to complete the burn.

I suppose the flame could go out. Don't know why it would however. Not sure why that has been brought up.

Piston coming up, the air is compressed and the temperature rises. The fuel/air mix is ignited before the piston reaches top dead center. The fuel/air mix being ignited then causes the temperature to rise even further. As the fuel/air mix burns the pressures within the cylinder continue to rise and creates even more of a temperature rise.

Ideally, all of the fuel will be burned in a con*****ed manner before the temperature could rise high enough to cause any unburned fuel to auto-ignite. That auto-ignition is referred to as detonation. That is what octane is about. To keep the air/fuel mix from detonating before it can be burned normally.

[rodbolt17]

nd just like various smokeless poiwder burn rates it is con*****ed by slowing the burn.
my co workers Honda on premium will barely idle and you can almost see the raw fuel dripping.
he tried it.
had to drain the tank and refill with regular. bike actually calls for 86 octane.
my old stude ran at 6.5/1 and hated shell 98.


however in the original posters efforts it is not an octane issue, most likely a locked up fuel pump.
sometimes you can soak the pump in a jar of combustion chamber cleaner and break them free on the bench with jumpers and reversing the polarity.
to do this DO NOT hook it to a battery continuously it will burn up the pump.
strike one jumper on a terminal then reverse the polarity and hit it again and reverse again.

the issue with premium fuel in the OX66 motors is the O2 sensor.\
it can and will detect the unburned fuel and trim the injector on time. leads to a reduction in power.

[scofflaw]

[QUOTE=

Ideally, all of the fuel will be burned in a con*****ed manner before the temperature could rise high enough to cause any unburned fuel to auto-ignite.[/QUOTE]

At that point in the burn cycle, any unburnt fuel will be exhausted out the pipe.
No harm there, except carbon buidup.
The detonation issue happens before the spark plug ignites the mixture. High compression with the lack of octane ,in the fuel, results in the mixture igniting on its own before the spark occurs

[rodbolt17]

not high COMPRESSION.
it is high COMBUSTION pressure.

big difference.

like I said camshaft selection also plays a part.
my 455 olds with a luanati w-30 cheater cam and 12.5/1 trw forged pistons ran well on regular.
my buddies 455 Pontiac had to run 95 minimum.

best thing to do is run the fuel it was desighned for.

you can find it in the owners manual.

anything else is simply wasting money.