What's This 45 Mph Talk?

Discussion in 'Whizzer Motorized Bicycles' started by Hal the Elder, Dec 27, 2008.

  1. Hal the Elder

    Hal the Elder Member

    I've opened up my intake restrictor to match the venturi opening of my carb and opened up my muffler baffles to 1" diameter. My camshaft has also been advanced one tooth.

    I don't think I can make 35 MPH, let alone 45 MPH. I've had it to 33 MPH on level ground with no headwind and 40 PSI in the tires, and there didn't feel like there was much reserve.

    I live at 3000 ft. elevation...would that have an effect on power?

    Frankly, I don't even like going as fast as 30 MPH! Those 2 drum brakes don't have that much emergency stopping power for a 104-pound motorbike and a 225-pound rider.


  2. RdKryton

    RdKryton Active Member

    Hi again Hal
    Your engine will gain power as it breaks in. This will take about 500 miles. You will be able to hit 45 mph if you are jetted correctly. I have hit 40+ on mine and I don't like going that fast on a bike. 25-30mph is fine by me. I just like having the power to carry the hills here.

  3. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Hal,
    "opened up my muffler baffles to 1" diameter" ? Why didn't you replace the defective Whizzer muffler? Opening the original muffler insert will never equal the Hi flow insert, never! If the replacement wasn't quickly available, maybe Whizzer was out of stock. Don't plan on your Whizzer breaking any speed records with the original "modified" insert. My tests have revealed the center flow tube must go all the way through the insert and equal the size of the holes in the mounting ends.

    Have fun,
  4. Hal the Elder

    Hal the Elder Member

    Hey Jim:

    25-30 MPH is fine by me too, but I really feel cool at 20-25 MPH!

    How do I know if I'm jetted correctly?

    My idle mixture screw doesn't seem to make any difference whether it's turned all the way in or backed out 5 turns!

    I would like a little extra power, but not for speed; just for accelleration and for the few mild hills in my area.

  5. Hal the Elder

    Hal the Elder Member

    Hey Quenton:

    Didn't you read my post that said my Hi-Flow muffler fell apart after 10 miles?

    The Whizzer muffler wasn't defective...the Hi Flow was! The stock Whizzer muffler has proper, substantial welds on the baffle plates, but the Hi-Flow had small, inadequate welds, which is why it failed right away!

    I opened up the baffles on my stock muffler to the EXACT DIAMETER (1.015") as the Hi-Flow muffler, which now provides the same unrestricted exhaust flow. I used rotary files to do the job.

    You and others may be getting 45 MPH performance, but I don't!

    Last edited: Dec 27, 2008
  6. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Hal,
    I remember the bad luck with the Whizzer muffler insert you had, and I will admit I am somewhat surprized. I have sold hundreds of the inserts and not a single one failed. I will tell a story about exhaust sytems on the NE Whizzer motor that may help your lack of power. I once agreed to modify a new motor for someone in Texas, but was having real problems making it run like all the other motors I had modified prior to this one. It was real important that this motor produce a lot of power because like I said it was going to a company in Texas. I won't mention the company, but everyone should be able to figure it out. The person that ordered the motor might have worked for a motorbike company and the first name might have started with the letter "D", or maybe not. Anyway the motor ran really poor, and I was having a hard time getting it up to 35 MPH. After exchanging the head, cylinder, carburetor, ignition system, and camshaft, I just couldn't seem to find the problem. By accident the problem went away and I proceeded to continue the break-in process. Still unaware of the accidential fix, it was time to box up the motor and the exhaust pipe. I suddently realized I had accidently installed a different pipe during one of the earlier changes. I took the muffler insert out of the original pipe and exchanged it for the one I had just tested, guess what! the bike started running like carp again. After careful inspection I noticed the insert didn't have the long center pipe installed and in fact was trapping the exhaust in the center and distrupting the exhaust pulse. I exchanged the insert again and it ran great.
    Moral of the story is; the long perferated tube in the center makes a major difference in performance.
    BTW if one of my NE Whizzers only went 45 MPH I would consider putting it out of its misery. If the head is milled, the combustion chamber is re-worked, the carburetor jetted close, mushroom lifters, correct tappet clearance, and the exhaust flow is correct it should easily take a 200 pound rider past 45 MPH on level ground.
    I will gladly help you get the most from your motor, but I strongly suggest you re-consider the exhaust insert you use. If the insert has broken welds, consider getting a warranty replacement, because I don't think it is a common problem.
    Are you still using the soft lifters? Did you re-work the combustion chamber in the head? Are the lifters set at .006" intake, and the exhaust at .008"? Are you using a 90 MM clutch?
    Let me know, and I assure you I can help you pull a bunch of power from the motor.

    Have fun,
    Last edited: Dec 27, 2008
  7. Hal the Elder

    Hal the Elder Member

    Here's my story:

    The first thing I did was to open up the intake restrictor spacer to match the I.D. of the carb and the intake port of the engine.

    This made a small, but noticeable difference in performance.

    Then I ordered a Hi-Flow insert from Mike Simpson. I installed it, and it made another moderate improvement in performance, but it lasted for only one 10-mile ride before the weld broke loose on the rear baffle. I threw it away, because it was junk.

    I couldn't get a warranty replacement on the Hi-Flow insert, because IT ISN'T A WHIZZER PART! Instead, I asked Mike for a refund.

    Then I bored out both baffles on my STOCK WHIZZER MUFFLER to match the diameter of the Hi-Flow baffles. This is what I am running now.

    To reiterate, the stock Whizzer muffler never had any problems...it was the Hi-Flow insert that failed!

    That's it!
    Last edited: Dec 27, 2008
  8. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Bad news Hal,
    The insert was in fact a Whizzer part! Mike purchased it from Whizzer and would be under warranty. You shouldn't thrown it away, now Mike can't warranty it and you shouldn't expect him to eat the money. He didn't make the part! See if you can find it as I am sure he could and would replace it under warranty. The part had a one year warranty from Whizzer.

    Have fun,
  9. Hal the Elder

    Hal the Elder Member

    I Still Have The Bad Insert!


    I still have the failed insert, with the rear baffle broken off.

    I didn't realize THAT was a Whizzer part...I thought it was made by a small manufacturer as an aftermarket accesssory to fit the Whizzer.

    You mean that was a "performance" part made by Whizzer, and would be under warranty even though it didn't come with the bike?

    This is really getting confusing!

  10. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Hal, It is not considered a performance part by Whizzer. It is however the best choice for good exhaust flow. Contact the dealer for the best way to warranty the part, it will be in your best interest to do so. Really happy you found it.

    Have fun,
  11. Hal the Elder

    Hal the Elder Member

    Hey Quenton:

    The dealer I bought Oscar from is not a Whizzer dealer. He's a Used Car dealer who occasionally sells a Whizzer Motorbike as a sideline, and does not stock any Whizzer parts.

    So what do I do now? You or Mike Simpson should know...

  12. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi Hal, Contact Mike for the warranty exchange.

    Have fun,
  13. WZ507

    WZ507 Member

    How Fast Should My Whizzer Go?

    Motor bikes and fishing have a lot in common. The stories never diminish in any detail with repetitious telling, but quite the opposite, the salient details tend to creep ever greater with repetitious telling. If we tell the stories often enough we actually start to believe them after awhile. And that is where I want to bring us all back to reality.

    I'm talking about Whizzer speed here, and want to set the record straight regarding what a person might realistically expect. I feel this is important to air out so that any new Whizzer performance enthusiasts have realistic expectations of what sort of speeds well prepared Whizzers might achieve. I wouldn't want to see someone labor for years trying to figure out why his flathead bike won't go 65-70 mph, when no one else has either. I questioned people for years trying to figure out how fast a flathead Whizzer will actually go and the more I asked the more confused I got. Below are my opinions on the subject.

    There have been reports in various threads here of flathead Whizzers going up to 70 mph on a dyno, and I have personally seen OHV Whizzers run up to 84 mph on a dyno, but in both cases this is way outside the performance envelope of what these bikes are capable of in terms of real road speed, and the dyno in these cases was simply a test fixture employing a large squirrel cage fan for resistance, that does not relate well to real road speed. I own a OHV Whizzer, and 60 mph on the real road is being pretty generous on the best of days.

    No one has said anything untrue on these pages, and my intent is not to question what others have said, but rather to simply bring us back to the "real road" of reality. I think we've stretched the truth about as thin as it can be stretched without breaking. Perhaps the thing least appreciated by readers here is the extrapolation from "dyno speed" to "road speed". We tend to think of them as one and the same and they certainly are not. Dyno's vary from home grown devices to highly sophisticated machines that provide highly reproducible results. But even among high quality dynos reproducibility from one brand to the next can always be an issue. And certainly a quick pull on a dyno is not a good predictor of real road speed.

    For those toiling in the Whizzer performance arena here are my opinions regarding performance benchmarks for well prepared flathead Whizzers running on level road, in calm air, with the rider sitting upright (26" bike, 7.5:1 gearing).

    50 mph - you've done a great job and should be really proud of your project
    55 mph - you've outperformed 90% of Whizzer performance enthusiasts
    60 mph - you're in an elite group exceeding 99+% of Whizzer performance enthusiasts

    In the same performance ballpark as mentioned above, the July 2008 Whizzer Newsletter reported ΒΌ mi speeds of 3 different OHV Whizzers that ran at the Four Ever Fours Antique Drags event in June 2008. The speeds? 55-62 mph.

    The bottom line - you get your flathead Whizzer going 60 mph and you've really done something. Hope this helps.
    Last edited by a moderator: Dec 15, 2015
  14. Hal the Elder

    Hal the Elder Member

    HEY WZ507: (wish you had a name)

    As a retired Aerospace engineer, I know something about hydrodynamics as applied to air resistance vs speed, and I know that horsepower requirements vary as the square of air resistance on a frontal surface area.

    Thus, if a motorized vehicle is capable of a given limiting speed through the air, with air resistance being the limiting factor, then to double that speed it will require FOUR TIMES the horsepower.

    To illustrate, if the limiting speed of a 3 HP motorbike is 40 MPH THROUGH THE AIR, NOT ON A DYNO, then to achieve double that speed (80 MPH), it would require 12 HP.

    I'm personally not interested in any speed over 30 mph, but it would be nice to know that I had sufficient reserve power to aid in accelleration from a stop and to handle some grades in my High Desert area, NOT for any extra speed potential.

    I get a bit nervous when I go past 30 MPH on my stock Whizzer, and feel more secure in the 20-25 MPH range!

    Thanks for your technical dissertation, Mr. WZ507!

    Last edited: Dec 28, 2008
  15. WZ507

    WZ507 Member

    Aerodynamic Drag Vs HP Requirements

    Hal - Your comments about aerodynamic drag, as it relates to HP requirements, are not correct, and under estimate the HP requirements by a factor of 2. Your comments are correct for relating wind drag to changes in speed, but not HP.

    The drag, not the HP, increases as the square of the speed, i.e., if the speed doubles, the drag increases by the square of the speed, or a factor of 4 (2^2 = 4). The HP requirements are also affected by speed, but in this case even more so, as HP = drag force x velocity, or restated, as speed increases the HP required is now the cube of the change in speed. So, if the speed doubles the HP required increases by a factor of 8 (2^3 = 8).

    Let's make an assumption and apply this to some of the numbers I provided earlier. Assuming it takes 5 hp to go 50 mph, how many HP does it take to go 60 mph? The speed changed by a factor of 1.2 (60 mph/50 mph = 1.2). Cubing the speed change gives a factor of ~ 1.73 (1.2^3 = 1.73), and applying this factor of 1.73 to 5 hp gives ~ 8.6 HP (1.73 x 5 = 8.6).

    Think about that for a moment. You've done lots of work on your engine and say you've increased the power from 2.5 HP to 5 HP (100% increase is a huge change!) and moved you from 40 mph to 50 mph. Now you want to go 60 mph which will require 8.6 HP. Where in the world are you gong to find an additional HP increase of 72% on top of the 100% you've already gained? That's why I said previously that 60 mph is a very challenging target.
    Last edited by a moderator: Dec 15, 2015
  16. Hal the Elder

    Hal the Elder Member

    You're Absolutely Right, Mr. Nameless WZ507!

    I was confusing aerodynamic drag with horsepower requirements!

    You are correct: Horsepower requirements increase as the CUBE of the speed increase ratio, therefore to double the speed from 40MPH supplied by a 3 HP engine to 80mph would require 2^3 (2 cubed), or 8 times the horsepower, or 24 HP, not 12 as I had erroneously stated earlier.

    Doing the comparison on a Dynamometer, where wind resistance does not enter the picture at all, doubling the Dyno speed would require only a modest increase in horsepower, NOT eight times!

    Thanks, John, or Bill, or Tom, or Bob, or Frank, or...?