Anything Goes! Another Dutch minibike build from scratch.

#61
Here are some pictures of the broken rocker arm from my previous post.


This is what I found after taking of the valve cover. The lash cap of the exhaust valve had fallen down and could be picked out with a small magneto.


I'm not sure why it broke, because the 18 lbs springs should not be to heavy for standard rocker arms, I guess.
I don't think it's because of coil binding, but I haven't checked that. It's a standard cam and standard ratio rockers.

I have installed a new rocker arm, tonight and the engine ran fine again.
So I took the minibike again for a testride.
This riding with a torque converter is so much better as to with a clutch. Immediate power at the rear wheel, making it spin on dirt roads or lifting the front wheel on asphalt.

The Herbie minibike will be equipped with a stock engine, for now. reason for this is that I want to compare both engines, regarding power, throttle response, balance, etc.
 
#64
I started to work on a stock Honda GX160 engine for the Herbie minibike.


This is the used engine I am using to power the Herbie minibike.
As far as I know it's completely stock. for now I leave everything as it is and will only do maintenance work on it.


The damaged fin on the left is what was on and I have replaced it with the fin on the right hand side.
I also changed oil, set valve lash, set ignition coil gap. It seems to have low compression, which could be caused by worn rings. I'm okay with that for now.
The main goal for now is to compare this engine with the engine I have installed on General Lee minibike (billet flywheel, billet rod, new crank, thinner head gasket). I want to see the difference in performance and balance of the engine, as the General Lee minibike engine seems to be unbalanced.
If there's a noticeable difference in balance between the engines I will try some things when I start to rebuild the Herbie minibike engine.


New intake manifold installed and the engine is now almost ready to mount.

Today I received a new #219 chain and sprocket, which will be mounted on the Herbie minibike.
"Stay tuned"
 
#65
Yesterday I have mounted the new 85 teeth rear sprocket (#219 chain) on the Herbie minibike. I already made a 15 teeth sprocket for the torque converter, which will give it a 1:5,67 ratio. That's the same ratio as the other minibike in this thread.

Assembling of the Herbie minibike continued yesterday:

A fuel pet-cock valve installed in the homemade gastank.


With the Mikuni on 1 side and the exhaust on the other side of the frame, there's an easy accessible valve cover.


With a timing light I checked at which point the spark occurs.


This is the position of the crank/flywheel, where the spark occurs. According to my timing light. Stock flywheel, key and stock ignition coil.


According to my degree wheel the spark occurs at 24-25 degrees BTDC, with this setup.


The kill switch comes standard with some short wiring. And as I don't like connectors in the middle of a wire, I replaced the stock wiring with some made-to-length wiring.


New wires soldered to the kill switch internals.


Kill switch with new wiring installed on handlebar.


Also installed are brake levers, grips and thumb throttle.

Still need to make cables to length for brakes and throttle and install them.
Torque converter, chain, carburator, exhaust and some other stuff also needs to be added, before we have 2 new minibikes running.
With a weekend coming I don't see any problems to make it happen.
"Stay tuned"
 
#66
News!
This single bike project is turning into a twin bike project. We'll be making 2 minibikes, which will be copies of each other. One will be the "General Lee" minibike and the other will probably be a "Herbie" minibike. Herbie, as in the VW beetle with number 53. "Probably", because things are not certain, yet. Because they'll be the same, progress on both minibikes will be reported here.
"Stay tuned".
John
Administrative Note: There was some confusion as to whether this was a single entry, or if the builder was entering two bikes. Since the post quoted above was made on January 20th prior to the entry deadline, this thread does encompass two bikes, General Lee, and Herbie.
 
#67
Administrative Note: There was some confusion as to whether this was a single entry, or if the builder was entering two bikes. Since the post quoted above was made on January 20th prior to the entry deadline, this thread does encompass two bikes, General Lee, and Herbie.
Yes, this thread contains the progress of 2 minibikes. Because they basically are the same (except for paint, decals, tires and some minor details) I thought it would be wise to keep both within 1 thread. Otherwise I would have to make "double posts".
Sorry for any caused confusion. Next time, when I enter more bikes, I will make more threads. ;)


In the meantime, right here in the Netherlands, we are working on the last bits of both minibikes.
Today I helped my daughter in making a lot of decals to trade, so less time spend on the minibikes, but managed to get the following done:


This is the torque converter sprocket for #219 chain, which we've made ourselves. Because of the welding the inner diameter had shrunk and had to be enlarged to fit the torque converter shaft, which is 5/8". I had to take out 0,03mm to make it fit tight.


This is the Chikuni carb for the Herbie minibike. Prior to installation, the #95 main jet is replaced with a #110 to start with.


Frontview with carb, airfilter, fuel line, recoil starter and exhaust mounted. On the side is the, partially assembled, torque converter.

The engine was started and didn't ran so good on idle. I adjusted the slide throttle to lower (less air) and did some adjustments with the little screw which is in the front on the bottom (which was 2 turns out to start with). It seems to run good now on idle.
Here's a video of the engine running, before the adjustments to the carb. >>>Video<<<

Greetings from Netherlands,
John
 
#72
Today has been a productive day; At the end we had both minibikes running and recorded video's of it.

What has been done today:


These are the parts that I used for brake cables and the throttle cable, which has to hook in the slide of the Mikuni carb.
The cables are easy to cut-to-length and the other small parts/connectors are basically plug & play.


Front brake caliper functioning with a cable connected. At this point I adjusted the sideways slide of the caliper and locked the bolts with some blue Locktite.


The same has been done to the rear brake caliper, which is also connected with a cable. The throttle cable is also connected to the Mikuni round slide.


Throttle cable on the other end connected to the thumb throttle (the thumb throttle's that have been modified earlier in this thread).
Here it is at WOT.


The Mikuni round slide at WOT. It is not complete open, but I guess it's less restrictive as a standard carb.


I don't like it when cables are hanging loose, so they have been tied together and to the frame with ty-raps.


To tie the cables to the frame and fork there have been tack welded some small steel rods to the frame and fork, before painting. There's also a small steel rod on top of the center bolt of the neck. Cables have been tied down to the bolt, frame and fork to avoid scratching and damaging.


This is how I mounted the torque converter. In some video's they start with the washer, but the washer doesn't have the chamfer to fit the crankshaft correctly. The bushing does have a chamfer on 1 side, and that felt more "solid" to me. I don't see the point, why the washer should go first if it has no chamfer.
The 4 bolts (1" long) are torqued with 24Nm.


With some pieces of metal I checked if both "pulley's" lined up. They did, which means this is no monday-morning-build torque converter.


The bolt that came with the torque converter, to mount the driver to the crankshaft, is to short. It only threads in a couple of threads. I used a longer bolt and secured it with some blue Locktite (not Locktite, but another brand, half money and also good stuff).
The picture above also shows how little of the crankshaft is used by the driver. It makes me wonder why did they design it like this?


With the torque converter mounted the engine could be aligned with the rear wheel assembly. Goal is to get both sprockets aligned. Nailed it!


There's a saying here in Netherlands: "Goed gereedschap is het halve werk!". Translated: "Good tools are half the battle!".
This chain braker is new to me, but I already like it. I made this chain to length and put it back together with this tool. Not making use of a closing link.
I always seem to damage my hands while working on closing links with a screwdriver...


Completed minibike number 2 of this thread: Herbie!


Both minibikes side-by-side after they have been ridden to record some video's.

The video's will have to wait untill next update.
"Stay tuned"
 
#73
Right on John. I stopped using closing links too. It is the chain's weakest link, and those little gereedschap make it so easy to manipulate the chain. Plus, I save the new bits, and eventually have enough for a whole chain.
 

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