Vintage bike with 16" wheels- Will it work with a HT?

Discussion in '2-Stroke Engines' started by Fletch, Mar 2, 2011.

  1. Fletch

    Fletch Member

    I'm thinking about motorizing this bike bellow, but it has 16" wheels. Can it work? Should I do it?


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  2. professor

    professor Active Member

    Of course it will work.
    If you do, the short wheelbase will be squirlly, brakes minimal (meaning dangerous).
    There really are kid bikes- how much do you weigh?
  3. retromike3

    retromike3 Member

    Question: What do you want to do with it?

    If you are using it as a pit bike, Maybe. If you want to actually go somewhere Look for something else.

    When I was first looking at making a motor-bicycle I was thinking about using 24 inch wheels, but after checking out this sight and the other one I went to a 26 by 1.5 tire and I have been very happy with this set up.

    I don't have any suspension other than the "give" the steel has and I am quite comfortable when I even go downtown (over ten miles over a hill.

    the problem with little wheels is that they have a tendency to stop when they hit a good size pothole or rock but bigger wheels just roll over those type of obstacles.

  4. Fletch

    Fletch Member

    I just saw it on craigslist and I was thinking about adding a motor and selling it. I think it's a 1969 Sears Screamer which is supposed to have a larger rear wheel. It would definitely be more of a novelty item than transportation. I would have to use a larger rear sprocket (gear down? Or is that gearing up?) right?
  5. retromike3

    retromike3 Member

    gear u[ with little wheels

    Since each revolution of the smaller wheel only moves you forward a small amount you have to use a smaller cog or "gear Up"
  6. motorpsycho

    motorpsycho Active Member

    why not? sure it'll work, but i'd put the correct 20" rear wheel on it.
    Do you have any idea what a mint condition, all original sears screamer is worth?
    both of my bikes are 20" frames with 20" wheels and i'm running 41 tooth sprockets on both of them.
    if you plan on keeping that 16" rear wheel, you will have to go down to a 36 tooth sprocket or smaller to get any decent speed out of it.
    if you put a bigger sprocket on it (like a 44 tooth or bigger), with that 16" rear wheel it might wheelie like crazy because it will have so much bottom end torque.
    I would get it and put a 20" rear wheel on it with a 20x2.00 cheater slick and run a 44 tooth sprocket.
    both of my 20" bikes will get up to 30-32 mph with this size sprocket.
  7. Fletch

    Fletch Member

    Well I have a general idea how much a Sears Screamer is worth, but as you can see from this picture of one bellow, it is nowhere near original condition.

    If you check out this value guide:

    It would be "#5 Complete original needing full restoration." #5=$200-$300.

    But it is obviously not "complete" so I don't know. They are asking $150 for it assuming they still have it. Do you have any idea what it may be worth, or what I should offer for it?


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  8. motorpsycho

    motorpsycho Active Member

    I have seen mint complete, original sears screamers got for a $300-$400. they are definitly expensive, but not in the schwinn Krate category.
    I can tell you right now tho, that the engine that has the intake manifold will be a problem. There won't be much (if any) clearance between the air filter and the seat post tube.
    I have the version of the 50 c.c. 2 stroke that does not have the intake manifold (the carb is bolted right to the cylinder) and it is still a tight fit on my 20" frame.
    if you look close, the bottom frame tube and seat post on my bike are at about the same angle as the ones on the screamer. look how close the air filter is to the seat post tube on my bike.
    I have a low profile air filter on it and no intake manifold tube.

    Last edited: Mar 3, 2011
  9. Fletch

    Fletch Member

    That's an awesome bike! What kind is it? I'm not even a big fan of small bikes either. The guy sold the bike apparently because he didn't reply. Was it worth $150 based on the pic IYO?

    I've seen those 49cc with no manifolds, and remember reading that customs snagged a bunch of them so they haven't been around?

    What kind of carb did they come with? Are the bolt holes spaced to equip more aftermarket carbs? Any problems with blow-back?
  10. motorpsycho

    motorpsycho Active Member

    well, it's a generic "schwinn" stingray frame. It's actually a newer re-pop of the old style stingray, but not made by schwinn. I did put a schwinn headbadge on it tho.
    Yep, i got the 50 c.c. w/o the intake manifold in the summer of 2009, and i have not seen any being sold since then.
    the carb that it has on it is slightly different than the standard n.t. carbs that come on the h.t. 80 c.c's. the bad part is that it is not easy to get the carb off to make mods or to change the jet. the carb is mounted to the cylinder with long studs & nuts. the nuts are in recesses in the carb, so they are almost impossible to get to. as far as i can tell, the bolt holes on the cylinder for the carb are spaced the same as on the engines with the intake tube, but i'm not 100% positive on that. this carb is shorter than the standard n.t. carb because the part that bolts to the cylinder is flat.

    I have no idea what that screamer may have been worth because it was hard to tell exactly how it was in the pics. I'm not an expert on these things, but i would guess that it was probably worth $100.00 - $150.00.
  11. Fletch

    Fletch Member

    Is that the Grube exhaust? I heard it's really loud? Looks awesome on your bike though. What exactly did you do on the end of it? Those little bikes look fun to ride.
  12. motorpsycho

    motorpsycho Active Member

    no, the exhaust is an expansion chamber from spooky tooth.
    I used the stock muffler and modified the baffle inside for more flow.
    Yes, the pipe is very loud without a baffle or muffler on the end of it.
    Mine is just a little louder than it was when i just had the stock exhaust on it.
  13. Fletch

    Fletch Member

    Ok I see the stock exhaust on the end now. so you just welded it on? I'm pretty sure that expansion from Spooky is the Grubee chamber: It's hard to see but it's almost all the way to the bottom. Part E-ECES. What kind of performance gain do you notice with it? Have you tried a SBP chamber to compare the two?
  14. motorpsycho

    motorpsycho Active Member

    yes, it looks exactly like the grubee pipe but mine is labeled as A SKYHAWK CHAMBER.

    As far as a performance gain, i think i gained about 2-3 mph on the top end, and the low-mid range pulls a little better than the stock exhaust. it's not a night and day difference, but it did make an improvement through the entire rpm range. I think the sbp chamber works better, and it's also tuneable.....but is more expensive and trickier to mount on certain bikes.
    Well, i took the stock baffle out of the stock muffler and modified it by drilling 3 holes in the baffle plate for better flow. then i stuffed the baffle up inside the stock muffler housing, hiding it up inside so it looks like a big straightpipe.
    I welded on a 4" length of pipe between the chamber and the muffler, which added a slight amount of lower end torque than running the chamber with no muffler at all.
  15. Fletch

    Fletch Member

    Nice... Yeah Grubee makes the "Skyhawk" engines. I have a SBP pipe and I like it aside from the fact it isn't chrome and all one piece. I really need to learn to weld. I have a stock pipe that broke loose and I will post a pic where the small welding broke. It would be easy to fix if I new how. Is it cost effective to rent welding gear just for something like this? I know it is really expensive to buy your own right? There's a welding class at the community college I may take next semester. I saw some disposable welding torches at Harbor Freight when I was there last. I have no helmet, but maybe there are goggles?
  16. motorpsycho

    motorpsycho Active Member

    well, renting welding gear may be more expensive than just buying a new pipe in my opinion, Unless you have more stuff to weld.
    yes a good mig welder will run you around $400.00 - $500.00 depending on what you get. you don't want welding torches for this sort of thing. you need a wire feed welder that uses gas to cool the weld (usually argon) but now they make then where no gas is required, and the wire has flux built in it to promote good weld adhesion. welding torches are good for brazing (which is like high heat soldering usiung brass rod as the "solder". this is good for light weight repairs where there is very little stress and/or heat after the area has been brazed.

    You can pick up a cheap wire feed welder for a couple hundred dollars, but you will only be able to weld fairly thin metals. (like sheet metal) If you never plan on welding anything thick, this would be fine.
    Actually, i use my neighbors welder, i don't own one.
    I took welding classes way back in high school in the 80's, and if you are taught right, and practice on occasion, welding is almost like riding a bike. You may becainse rusty if you don't do it for a long time, but you never really forget how to do it.
    I'm not an expert at welding by any means, but I know how to make a nice weld bead and i know how to get the job done.
    It takes years of welding to get those professional looking welds.
    The key to a good weld is metal penetration. you should be able to butt weld 2 peices of steel together (just 2 peices of steel butted up end to end). after the weld is cooled, you shoudl be able to put the 2 peices of steel in a vise, and hit it with a hammer several times. the steel shoudl bend before the weld breaks. The weld shoudl be as strong as the actual steel. If the weld breaks then there was not enough penetration.
    a welding class would be a good idea if if you only plan on welding a few things here and there because one day you may decide to weld up your own frame from scratch.
    IN this case, it woudl pay to know what you're doing.
  17. retromike3

    retromike3 Member


    they have been making very strong brazed bikes for a hundred years. I remember a test that was done for a bike tech magazine were they had a TIG bike, a filet brazed and silver brazed bike and out them on a jig and stressed them till they failed. In each case the tubing failed before the weld.

    One of the things you can do with a bike that has been brazed together is fix it. I have replaced head tubes and drop outs on brazed bikes but if its bin TIGed if you dent it or bend it you toss it.

    I used to own a mountain bike that was TIGed together but it was finished with brass. That was an old Jamus I had converted to my first motorbicycle.

    I started out with a set of tanks because I had a limited set of funds(still do) and I could get a good TIG welder with a high frequency circuit or a frame jig and a set of tanks.

    Beware of over-generations sometimes they are less than they appear.

  18. Fletch

    Fletch Member

    Thanks guys for all the insight... I'm really considering that class. I never took it in HS but I know many people do. I will post a pic when I get a chance.
  19. HeadSmess

    HeadSmess Well-Known Member

    opinions differ as to best jointing to use.

    if its mild steel, use a mig. set, point, pull... too easy.

    anything else really should be brazed if you value your life.

    TIG welding, oxy welding... ANY welding, in a hiten or cro mo frame, really requires post weld heat treatment....meaning expensive! and invariably, warping... (tig welding seems to have this aura of "magic" about it, but anyone that does it knows its no different to anything else and all up to the operator...)

    this also applies to alloy frames, and in fact, is even more crucial! aluminum is like cheese....

    now brazing, or even nicer still, silver soldering...the way to go.

    unfortunately most good brazed frames are also "lugged", ie, the sockets at each junction...these are hard to fabricate. some arent though... watch for cracks!

    and never mind the fact your mounting a vibrating engine into it...

    meh. if you go oxy need gas. go mig, you really should use gas...gasless wire sux... so you need gas...get an inverter stick/tig...youll need gas for the tig...

    you need gas :( sorta expensive, sorta not... reminding me i got another bill :eek:
  20. motorpsycho

    motorpsycho Active Member

    Like i said, I'm no welding expert or authority, but i know how to mig weld, braze and stick weld.
    There is a ton to learn about welding so the more info i can pick up, the better.