Engine braking question

Discussion in 'Whizzer Motorized Bicycles' started by Dannt D, Aug 5, 2008.

  1. Dannt D

    Dannt D New Member

    I have 125 miles on my new 07 NE5. Sometimes I turn the 'run / stop' switch to stop when I need to slow down instead of riding the brakes. I also figured out that if I hold the compressino release and give about 1/2 throttle it pops real loud and blows flames out the pipe. Will this hurt anything other than my relationship with the neighbors? Could this poping cause oil leaks in the engine?

  2. stude13

    stude13 Active Member

    hi d; itll probably only blow the head gasket if your lucky.
  3. WZ507

    WZ507 Member

    Engine braking

    If you are holding the throttle half open with the ignition switch off, the carb is feeding gas to the engine at the same rate it would if the ignition switch were on, which causes the cylinder to load up with gas, which in turn washes the cylinder bore free of oil, which in turn is a very bad thing as it wears the rings and bore excessively. If the compression release is pulled it's not quite as bad, but still a practice that I'd have difficulty condoning. My advice would be don't do that any more if you like your engine.
    Last edited by a moderator: Dec 15, 2015
  4. RdKryton

    RdKryton Active Member

    WZ507 Covered it pretty well. Throwing the kill switch off while riding is not good even if your not giving it any fuel. You still have raw fuel going into the cylinder that will cause premature wear by washing the oil from the rings and cylinder. Also doing the flame thing with the compression release will cause you to blow your head gasket. It might be fun to watch but in the long run but you are destroying your investment. I know the brakes on these Whizzers are a weak spot but those two things your are doing will cause you problems and cost you money.

  5. ren

    ren Guest

    I have a 2007 NE5, and this question might fit here. Is it ok to hold the compression release to push the bike forward a short distance with the engine not running. If not then one has to pick up the back end of the bike to move it forward because the back wheel will not roll but slide.

  6. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Ren, You can push the bike forever with the compression release as long as the motor isn't running.

    Whizzer OuterBanks LTD
    A North Carolina Corporation
  7. ren

    ren Guest

    Thanks Quenton, it's good to know I haven't been doing harm. By the way I'm waiting for it tool cool off a little before I make the mods I purchased from you. Will post results when done.

  8. mmmmm flames.... ive never heard of a motor doing that!
  9. smitty

    smitty Guest

    I don't see how opening the compression release with the engine running (and a little throttle) will blow the head gasket. There will be less pressure in the cylinder with the exhaust valve open, than when the engine is running (especially accelerating). I agree about the fuel washing the cylinder walls promoting wear. The popping and flames would be raw (burning?) fuel entering the pipe and muffler.

    On restarting my bike after a short stop, it will often 'report' (pop) just as I release the compression release. I figure it's the unburned fuel that passes through the engine into the pipe and muffler, after the ignition is switched off. Sometimes it's loud enough to make pedestrians jump.
  10. Dannt D

    Dannt D New Member

    I understand washing the oil off cyilnder walls when the engine is cold. Starter fluid can do this in a bad way. I would think when the engine is at opperating temp the vaporived gas would not condense on the cylinder walls and would not dilute the oil. With the throttle being closed there would not be much fuel going through anyway. I am talking about doint this at speeds of over 10 MPH. The engine is still oiling itself as it turns through. I may be wrong here so please feel free to post a follow up. Thanks, Danny
  11. del

    del Guest

    OK, Danny, I'm beginning to get it now... I think...

    You seem to have two questions, which need to be addressed separately: The first about turning off the kill-switch ("Run Stop" switch). And the second about opening up the compression release valve and opening up the throttle. I'll attempt to address them separately. And I have little doubt that others on this forum might have different opinions...

    First the kill-switch... I don't think it's a good idea to turn off the ignition while running the bike at any speed above idle. Yes, the crankcase is still having oil splashed around in it. But it's not diluting the oil in the crank case that's the problem. Even when the engine is up to temperature the fuel is not fully vaporized. Running it at speed with the ignition off will introduce droplets of raw fuel into the combustion chamber. It won't run down the cylinder wall, but it will dilute the thin film of oil at the top of the cylinder. And thus, increase cylinder, ring and piston wear. So, I don't shut off the ignition until the bike is at idle. (And, truth is, I should probably stop the engine by shutting off the fuel like I was trained to do when I was learning to fly...)

    And pulling the compression release at speed, and hearing a BANG... I'm presuming that the explosion is coming out of the exhaust..?? But it doesn't matter much... Explosions are a bad thing. Fuel is supposed to burn, not explode. If you open the compression release and get an explosion, guess what? You're _still_ pumping fuel into the engine. That's a double no-no. Not only will there be unburnt fuel in the cylinder, but you'll be adding stress to other components that were most likely not designed for that sort of abuse. Unless you like spending money and time on repairing the bike, or paying someone else to do it, more than riding, it's not a behavior that I would advise..

    Does that make any sense?

  12. RdKryton

    RdKryton Active Member

    Well said del. I could not have said it better. Thanks

  13. What are you thinking?

    Dannt, would you pull out the choke on your car going down the road? Would you turn off the key (IF you had a manual clutch car) while going down the road?

    When I was in High School a guy I know did that, he was tickled spitless with the noise it made, till it blew the muffler right off the pipe into the street and he had to pay someone for a new muffler and labor. As I remember, it was his Mom's car!

    I would NOT honor the warrenty on ANY engine that was being treated that way, and amoung the guys I know, no-one else wouild either.

    Engine braking on simple 4-stroke vehicle means to let off the gas, and let the engine naturally slow the vehicle, NOT to try to blow it up with fuel dumped into the system.

    Be careful with your new Whizzer, and it should serve you well, Abuse it, and you'll spend money and time fixing it.

    If you want more noise, why not buy a louder horn?

    Stay safe,

  14. Mountainman

    Mountainman Active Member

    no reason to tear it up.. Caught my son doing something like this with a motor bike I had bought him -- not a happy dad !!! Happy Riding from - Mountainman
  15. Dannt D

    Dannt D New Member

    I understand the pop and bang trick is not beneficial to an engine and exhaust systen however the switch off engine braking thing may be open to debate. Keep in mind I am talking warm engine, opperating speed, throttle closed, no choke and switch off. Here is a posting on the topic from a machinist forum.; "IMHO you're always going to get gasoline in the crevice by the top ring land of the piston...otherwise automakers wouldn't be pulling every trick in the book to reduce the volume there. (It adds to hydrocarbon emissions).

    How much is certainly debatable, and how much lube dilution would lead to something catastophic like piston scuff is another issue to be debatable.

    IMHO it's directionally incorrect although probably doesn't hurt anything for short distances. If you upgraded to fuel injection you could simply switch off the injector pulses :rolleyes:

    Another data point...tests are purposefully run on vehicles with 1 spark plug grounded...the idea here is to simulate a failure mode of a plug or wire or coil module, etc. One cylinder is pumping raw air + fuel (important distinction between extra air + fuel and extra raw fuel only). Fed an air + fuel mixture*, the catalytic converter brick, which is already searing to start with, starts resembling something close to the surface of the sun (!!). Newer catalytic converters are well-insulated and so the heat is concentrated internal to the gas stream and so the tailpipe on back will usually turn purple all the way to the back end Spare tires and vehicle underbodies get thermal loads they generally never see...but could possibly under the freak failure condition. This is approx 10 miles @ 50mph on a climbing grade-load with vehicle only, no trailer. The engine is unharmed.

    * overfueling as in running richer than stoichiometric 14.7:1 will cool the catalyst brick as the hydrocarbons vaporize (phase change/latent heat). The important difference is that fresh air isn't available for combustion."
  16. Warrantee and theories??

    Dannt, I can assure you that many things are done in tests that are not good for the "overall health" of the machine.

    If you have problems understanding, or believing, what I have said, perhaps you'd be more comfortable to hear it from Whizzer?
    You could always call them and tell them your theories of how dumping excess fuel into the engine, and lighting it up with a pop and a bang don't hurt a thing?

    I would expect, however, that you would find this activity will void the warranty on your whole bike.

    Give it up, your practice is neither beneficial to the engine, nor is it harmless, and in some juristictions you will find yourself ticketed for excessive noise, and potentially causing traffic problems with your intentional explosions.

    How does your dealer feel about this, and is he fully ready to warranty anything you damage by improperly operating your bike?

    Mike Simpson
  17. KilroyCD

    KilroyCD Active Member

    Well said, Mike.
  18. fsprandy

    fsprandy Member


    What you're doing is a time honored tradition and while not the best thing for an engine it isn't likely to hurt it much either. I don't think you need to worry about blowing your muffler off on a Whizzer. Worst case is probably accelerated cylinder wear. It's your bike - have fun!
  19. del

    del Guest

    Well, Mike,

    All Whizzer dealers are not creaeted equal.. The "mechanic" at the dealership where I bought mine slowed down the engine by shutting off the kill switch just before we loaded it up in the pickup to take home; as if he did that all the time... I cringed at the sight.. But that's the same "mechanic" who, in the process of "fixing" a problem with stripped threads in a rear-view mirror mount managed to mess up the electrical system so bad that it took weeks, and several calls to Whizzer, for me to get fixed...

    Needless to say, I won't be going back there..

  20. del

    del Guest

    OK, Danny,

    Now that the question of opening the compression release (exhaust valve) to get a Bang! seems to be off the table. Let's go back to using the kill switch to slow down...

    You bring up several interesting points. Since nobody runs an engine at 14.7:1, to avoid detonation, pre-ignition, and overheating, we're all gonna be running a bit rich. So there will still be a bit of unburnt fuel in the process. There's not a whole lot we can do about that. It's a fact of life in the internal combustion engine.

    I'm not sure why you brought up Catalytic Converters... If there's one on my Whizzer, I haven't noticed it. But, what you say about them seems to be true. However, if running on the slightly rich side means that fuel will cool the converter by evaporating, what does that tell you? Even when the unburnt fuel reaches the converter, it's _still_ not fully vaporized. Otherwise, there would be no latent heat of evaporation absorbed from phase-change to cool the converter. And that's in one of the hottest sections of a modern car system.

    When I think about this sort of thing, I like to think in terms of extremes. If you're running a Top Fuel Dragster, 1/4 mile between engine overhauls means you're having a good day. If, on the other hand, you're flying in a single-engined airplane and the engine blows, you're having a bad day.

    So, yes, I agree that it most likely will not hurt the bike _much_ to slow down by hitting the kill switch (unless you get after-fire). But, considering the extremes, and the prospect of having to pedal the Whizzer home, I tend to err on the side caution.

    Last edited by a moderator: Aug 13, 2008