New to Minibikes, Old to Small Engines

#1
Hello, there, folks. Today, I found myself a few mini bikes for $50 on craigslist, so I bought them. They're in a city a little while away from me, so I haven't gotten the chance to pick them up, but a friend has them. I had her take some pictures for me. What do I need to do to identify it?

So far, I know that they are both K&S Hornets. One of them has the "ape hangar" style bars, a belt-drive torque converter, and a white engine. The bike is complete, aside from an air cleaner.

The other bike doesn't have the ape hanger bars, and it has no belt. I believe it has a centrifugal clutch on it, but the pictures she sent were not that great.

Assuming they're original, how do I ID the engines, years, etc.? Where can I get decals for it?

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#2
Welcome to the OldMiniBikes..I would say the one is defintly a Hornet. Not sure about the blue one, but somebody will be along to tell you what they are. Good luck with your mini's and have fun ! :thumbsup:
 
#3
They're definitely both Hornets... Or at least, they both have the Hornet decal on the fork bar. I know nothing about them, though. Who made the engines? How big were they? How much of a pain is it going to be to find parts?
 

capguncowboy

Well-Known Member
#6
They would have tecumseh engines on them originally. They were made in Texas (I'm pretty sure anyway). Parts are here and there. Your best bet is here or ebay. Nice little bikes.
 

markus

Well-Known Member
#7
Nice finds, by the looks of them they are pretty original and not cobbled up.....that's getting hard to find anymore! Both those engines are Tecusmseh H (small frame) probably both h35 (3.5hp) if you look below the fuel tank on the shroud/recoil side you will see a tag on each of them that is riveted to the shroud, the set of numbers stamped in under "serial" will give you the build date for the engines, That will give you a roundabout time frame for the bikes build date as well. Looking at the shape of the throttle assy and the tank and exhaust I would say they are both 1971-73 engines. if found together I would bet they were bought as a pair and have been together all these years.

To decipher the serial code the first number is the last digit of the year, the next 3 numbers were the day it was built on in that year, the last number or digit if there is basically just something that would have determined maybe the assy line it came off of or shift etc... nothing really important at this point and time. The other set of numbers under "model" are the engine and setup of it. to look for parts (for the engines) use those numbers....easiest thing to do it type them into google just as they are stamped and you can usually pull up Partstree or Jackssmallengine or even Sears parts, which will bring up parts explosions and lists as a good start for part numbers etc.. Typical wear parts are mostly available still some things can be harder to find but they are very common engines.

The bikes may have something like this somewhere as well, I spotted this K&S ID decal on something that was for sale recently and saved to my files for reference. but may be stick on the bikes somewhere

K&S decal:
 

Scottessey

Active Member
#9
I just finished a Hornet. They're fun to ride. The gold one has a belt driven V-plex clutch which gives it both a lot of spunk on the take off and decent top speed. I have some spare parts around. Holler if you need anything. :thumbsup:

 
#10
Nice finds, by the looks of them they are pretty original and not cobbled up.....that's getting hard to find anymore! Both those engines are Tecusmseh H (small frame) probably both h35 (3.5hp) if you look below the fuel tank on the shroud/recoil side you will see a tag on each of them that is riveted to the shroud, the set of numbers stamped in under "serial" will give you the build date for the engines, That will give you a roundabout time frame for the bikes build date as well. Looking at the shape of the throttle assy and the tank and exhaust I would say they are both 1971-73 engines. if found together I would bet they were bought as a pair and have been together all these years.

To decipher the serial code the first number is the last digit of the year, the next 3 numbers were the day it was built on in that year, the last number or digit if there is basically just something that would have determined maybe the assy line it came off of or shift etc... nothing really important at this point and time. The other set of numbers under "model" are the engine and setup of it. to look for parts (for the engines) use those numbers....easiest thing to do it type them into google just as they are stamped and you can usually pull up Partstree or Jackssmallengine or even Sears parts, which will bring up parts explosions and lists as a good start for part numbers etc.. Typical wear parts are mostly available still some things can be harder to find but they are very common engines.

The bikes may have something like this somewhere as well, I spotted this K&S ID decal on something that was for sale recently and saved to my files for reference. but may be stick on the bikes somewhere
Holy crap, that was the single most informative post I've ever read. Thank you. I should actually have my hands on the bikes on Tuesday when I can take better pictures. When I do, I'll have a better idea of where I'm going with these. I did buy them as a pair, so I doubt they've ever been separated.
 
#12
So, I got my hands on one of the bikes. It runs... kinda. The linkage was really messed up. The needles were corroded in the carb. The whole thing was a giant mess, but the engine runs. Next up, I need to buy a new carb. Here are some pictures of the before state.
 

Attachments

jrzmac

Active Member
#13
if you wanted to get the right linkages, you can find them here:

Governor-Linkage
Tecumseh Governor / Throttle Linkage - 32698

Governor-Spring
Tecumseh Extension Spring tec 31426

also, is it idling a little fast? the screw that goes into the throttle plate is in a little too far I think. Be careful when starting the engine. Dont know if it's still on the bike but, if it is, it can go flying out of your hands. That carb looks to be pretty old too, probly original. If it's too far gone you might want to get a cheap aftermarket carb like these:

Carburetor for Tecumseh 631921 632284 631070A Fits Many H25 H30 H35 Engines | eBay

Tecumseh Replacement Carb Carburetor 631921 632284 631070A | eBay

Amazon.com: Tecumseh 632615 Carburetor: Patio, Lawn & Garden

http://www.ebay.com/itm/New-CARBURE...864?pt=LH_DefaultDomain_0&hash=item3cb7ab74e0

The top 2 carbs are nicer because of their swivel fuel inlets!
 
#14
Well, I got a new carburetor. Two of them. The bike would only idle at WOT after I tightened down the mixture screw on the bottom... right up until the head snapped off. Now, I just have to wait until the show up. I got some sort of linkage figured out, but I have no idea if the governor is going to allow for it. We'll just have to see.
 
#15
Alright, so I got new carburetors. I stuck one of them on the more complete hornet, and it runs! I feel like I could get a little more performance out of it, though. I've done what I could with tuning the carburetor, but I feel like I'm missing something important. I have the needle on the side of it turned out 1 1/2 turns and the needle on the bottom is turned out 1 full turn from seated. That seems to be a good running spot for it. Of course, on a single cylinder with no manifold vacuum, I'm kinda lost when it comes to tuning...

I also replaced the spark plug with an E3.10. I've heard good things about them in small engines, and I'm not a fan of Champion plugs. What else can I do to get some power out of this little guy?
 
#16
A couple of things I do:

Make sure you're getting WOT. Sometimes with new carbs, the throttle plate stop prematurely hits the case, keeping the butterfly from coming all the way open.

Adjust the governor by loosening the 1/4" bolt on the arm, and at WOT, ensure the governor shaft is all the way to the right, clockwise. Tighten adjustment while holding it there. Check and make sure your throttle plate returns to the idle stop.

Using a new condition governor spring, put it in the top hole on the arm, and the last hole on the throttle actuator where the cable is. Adjust, or fabricate a throttle actuator (wire) to achieve WOT with the hand throttle. Check for binding. (This setting should give you 4000-plus RPM, so warning)

The biggest improvement on a Tec is getting the shortest, most open exhaust you can find. A six inch pipe works great, and you feel it in the response, but that's not always possible when they're on a vintage bike.

Your carb trim on both high and low speed sounds about right. They can be all over the place though. Once I have all the above done, I ride it and slowly increase or decrease the bottom jet, (high speed) until it accelerates best, and runs best at the top end.

After that, it's gearing. (and don't blow up the motors while over-reving) :)
 
#17
I did some fiddling with the governor, and now I'm running great. The next thing I want to do is lighting, speedometer, and a tachometer. For the speedometer, i'll probably get one of those cheap bicycle ones from Wal*Mart. I've been looking at a TinyTach for the tachometer. SDoes anyone have any experience with them?

With lighting (Everything will be LED), can i run a lighting coil off of the spark signal, or do I need a special flywheel with a second magneto?
 
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