Anything Goes! Another Dutch minibike build from scratch.

#6
Hello again.
Thanks for the nice words.
@mrpat: I got the engine from grabcad.

This will be my second build. (My first build in this thread.) Since the first bike build, I've purchased a manual tube bender with dies. In my opinion a must have, to make some nice bends. This bender will be used to make the bends for this bike/project and future builds.


Here in the Netherlands I'm still in designing progress, when time allows it.
My 17 yo daughter wants to have a "General Lee" minibike, that's why it's orange. And no, her name is not Daisy...
It's hard to get some "lines" of a Dodge charger into a minibike, but I've made an effort to do so.
The bottom of the fueltank is rounded, like a Charger's hood. And the frame rails below the seat are angled, which makes it a bit more the same way as a Charger's rear posts. Designwise that's about it.

The minibike will have a torque converter installed. First time for me and not sure what to expect from it.
The engine will be mounted on the frame with a 5-10 degree angle, which will give enough space between the torque converter and frame rails. This way, there's no need to cut in the torque converter or design a frame "around" the torque converter.


Wheelbase and tire size of this bike will be the same as my first build. And that's about it what will be the same.
Some data off this minibike:
Wheelbase: 890mm.
Rake angle: 25 degree.
Trail: 57mm.
Offset: 25mm.
Tubes to be used: 22mm diameter, 3mm wall thickness.
Fuel tank capacity: 2,5ltr.
Tires: 145/70-6
Torque converter: Chinese Ebay.
Engine: Honda GX-160, with some aftermarket parts this time;-)
Fenders: Homemade steel fenders.
Exhaust: Homemade, like everything else in this build.


This is an exploded view of the re-designed homemade rearaxle/hub assembly which will find it's way in the minibike. "Re-designed", because the basics are also used in my first build. Except this one is 22% lighter in weight and will be easier to make.
The rearaxle/hub assembly will hold the wheel centered, just like the sprocket and brake disc. When the brake disc is removed, the wheel can be removed. On my first build I also have it like this and everything lines out perfect.

The 3-D design progress is about done; time to make files a lasercutter can handle and start the actual building process!
"Stay tuned"
 
#9
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.

What happend since last post?
One Mikuni/Chikuni carburator arrived.
I have imported the carb from the USA (will this give me some likes?:D)

Because the Mikuni jets don't fit in the jet holder/emulsiontube (M5x0,75 thread doesn't fit in M5x0,8 thread), I will modify the jetholder/emulsion tube in a way that I can use Mikuni jets.

With the use of this carburator the governor will also be removed from the GX160 engine. Because of that, I have ordered a 1.75Lb billet flywheel.
A billet connecting rod, 18Lb springs, gaskets, etc have also been ordered at GX tuningstore UK. That's in Europe.

At the moment I have 4x GX160's (3x QMDS, 1x QX4) and 1 GX140 (SE). And after a compression test on all of them, I took the worst performing engine for this project(s).
This will be my first Honda GX160 to tear down (by the way).


This is engine nr. 2; it made only 5 bars (75psi) compression. After taking the valve cover off, I noticed the exhaust-valve to slightly open on compression stroke. This afternoon I had no idea what could cause it to open, during compression stroke. Now I know. (Keep reading...)
Compared to the new Mikuni VM-22 the original carburator has a tiny hole. That will make some noticeable difference, when the Mikuni is installed.


This cylinderhead came off. After some searching on the interwebs and OMB, I think this is a 18CC head? I could be wrong...
I've seen a lot of GX parts go by on internet and this engine seems to have a flat top piston. Or this is standard on a GX160 of this age (prior 2003).


Flywheel removal; well that went easier as I expected! A prybar and a hammer (with the nut on the crankshaft) did the job.
Thanks to an earlier thread here on OMB I knew there is a lighting coil in the 3 QMDS-type engines I have. This is one of those QMDS type engines. I took the lighting coils off and they won't go back.


At this point I did find why the exhaust valve opens during compression stroke. I thought the engine might have a damaged/bend camshaft or something, but it appears there's a decompression mechanism on it. Another lesson learned on this sunday afternoon. Perhaps this caused the poor compression testresult, too. I have another engine, which makes 8 bars (116psi) compression. Makes me think that engine's decompression mechanism isn't working? Or stuck.


I know...; no gloves for me, as I'm no surgeon.
I took out the piston, connecting rod and crankshaft and started measuring.
Crankshaft O.D. measures 29,90 and 29,92 mm (1.1771" and 1.1780"). According to the Honda service limit and the connecting rod instructions, this crankshaft needs to be replaced.
Piston also needs to be replaced as it's to loose in the cylinder. With the piston almost at the top, I was able to put the tip of a feeler gauge of 0,008" between the piston and cylinder. According to the .pdf document I have; the piston to cylinder clearance service limit is 0.005".
This could also be because of a worn cylinder, but I've measured the piston with a caliper and a micrometer and both measurements indicates that the piston needs to be replaced.
With the bore gauge I was not able to measure the cylinder, because I need some washers for it. I will get those this week. A measurement with a caliper, indicated that the cylinder was within specs. But I want to measure it with the bore gauge, which is more accurate.
The cylinder needs a little hone job. It is to smooth.
Pistonrings; will be replaced, too. Piston ring end gap was to big.

Well...and that's just for 1 engine. The "Herbie" minibike also needs an engine. I think I'll tear that one down pretty soon. So I can safe on shipping costs! Don't feel sorry for me, I like this kind of work. It gives me more satisfaction as to buy a new engine and run it.
If you have any comments, remarks; feel free to post!

"Stay tuned".
John
 
#11
Today I have measured things again, because I have made a mistake yesterday. I didn't measure the piston skirt yesterday, but the top of the piston... Today I measured the piston skirt and the piston to cylinder clearance. Piston doesn't have to be replaced. I also measured the cylinder today with the bore gauge and it's within specs, but will get a little hone job, as the piston rings will need to be replaced.
I am not sure what to do with the crankshaft. It measures 29.92mm.

Stay tuned.
 
#13
I have made a timing/degree wheel. It is 250mm diameter.
First I made a fullscale design of the degree wheel on the computer, with logo of my company. At a signshop they made a couple of decals/stickers of it and I sticked it to a stainless steel part, that had been lasercut at work.

Perhaps a timing wheel isn't really necessary, but I just like to know when things happen in the engine.

The drawings for both minibikes are almost ready to be send to a lasercutter. And in the meantime the package arrived with the billet rod, 1.75Lb billet flywheel, 18Lb springs and gaskets. Pictures will follow. Also a lot of other parts have been ordered. Some from Europe and some need to come from China.
Tomorrow the 2nd torque converter (for the "Herbie" minibike) should arrive, which I've ordered at a US seller on Ebay. According to the pictures and description it is the same torque converter as the one I already have.
Today the bill came in for the import duties on the carburator, which I've ordered in US. The carburator and 6 main jets had cost me $105,- in total, that's for the parts ($58,-), shipping costs ($22,-) and import duties ($25,-). I knew it was going to be expensive, so this was a one-time-only for now.
I have ordered 2 more carburators by now, but now in Europe (no import duties for me) for a total of $73,-.

Tubes (22x3mm) for the frames have already made it to the workshop. And for the front- and rearaxles I already have a piece of 50mm CrMo tube.

"Stay tuned"
John
 
#15
I was just admiring that cylindrical gas tank you have on the Honda. Really cool!

Just curious if the parts were a gift, would you have to pay import duties?
 
#16
I was just admiring that cylindrical gas tank you have on the Honda. Really cool!
That picture shows the engine as I purchased it, along with 2 other engines, also with those gas tanks. Maybe I will use the tanks for another project.

Just curious if the parts were a gift, would you have to pay import duties?
You are welcome to make me a gift.:)

I have found this info:
1€ = $1,15
Importing goods from outside Europe:
Under €22,- (value of the package); There are no extra charges.
Over €22,- (incl shipping costs); Taxes (21%) and handling costs (around €15,-)
Over €150,- (incl shipping costs); Taxes (21%), handling costs (around €15) and import charges (for these kind of parts it's around 4%).
Gift... No taxes, no handling costs and no import charges. But the value of the package must remain below €45,-. I think customs are allowed to open packages if they suspect something. If I was a selling compagnie, I wouldn't want any trouble with customs and wouldn't send anything as a gift, while payments have been made online.

Better option:
If I would travel to USA and back, and I take goods with me in luggage they are tax free, if the value of the goods is less then €430,- (gift or no gift). And that's per person.
A ticket is more expensive...and I don't know if it's allowed to have all sorts of minibike parts in my luggage.

Best option:
Make my own parts. And when they have to be bought, buy them from within Europe.
 
#17
Here is a picture of parts that have arrived.

2 more carburators, for other yet to build, minibikes. ARC flywheel, ARC connecting rod, new fan, 18lbs springs, gasketsets.

I will be making my own manifolds, so I started the drawing process.

First I take over the contour of the gaskets on paper, scan these drawings and then insert the rasterimage in the 3-D design software and take over contours. Print it out, check, modify, print out, check again...
 
#18
Today I cleaned the Honda engine and found a date marking on it made by the previous owner. According to that, the engine began life in 2002. And it was still in running condition, before I took it apart. After the clean up it will not look as good as a new (clone) engine. Just like people; older people have character...

I've honed the cylinder, as I will replace the piston rings and the cylinder was to smooth/shiny.

The cylinderwall looks good and feels good. (The flashlight of the camera makes it look worse as it is.)

"Stay tuned"
John.
 
#19
Hello,
Short update on the projects;
Some more parts have arrived and others are on their way.

Both minibikes will be equipped with torque converters, so now I have 2 at home. In the background (on the box) is 1 of 2 seats, that we'll be using.

Both minibikes will be using thumb throttles. These aluminium throttle housings came for €4,-/each.

I'll modify them to make it more comfortabel to operate. And to meet my quality standards.
They standard Chinese clearance/play on the shaft is resulting in poorly behaving and sticking throttles.
I'll replace the cast aluminium shaft with a stainless steel one (cut off part of 14 mm bolt). And with a reamer I'll make the housing bore 16 mm. In the housing I'll place some thin wall sliding bearings. They will not misbehave themselves anymore...

For a total of €6,- (=approx $7,-)! I have ordered, all new, quality, hardware for:
Cylinderhead studs + nuts
Side cover studs + nuts
Valve cover studs + nuts
Exhaust manifold studs (SS) + brass washers + brass nuts.
Intake manifold studs + nuts
And a new M14x1,5 nut for the flywheel.

"Stay tuned"
 
#20
Yesterday I started to modify the thumb throttles, which came from China. There were plastic and steel ones, I have ordered the steel ones. (with steel they mean aluminium). I have ordered 6 of them, 2 to be used now and the others for spare/other projects.

This is how they came. Placing of the handle in relation to the housing will be modified and I will also replace the green bolts with some stainless steel ones.


A lot of clearance/play between the cast aluminium shaft and housing. This resulted in poorly behaving and sticking throttles. Also the feel you get, when applying the throttle was "not so good"... It had a cheap feel to it.


Drilling out the bore to 16mm.


Putting in 2 PTFE coated sliding bearings. 16mm OD and 14mm ID X 15mm wide/each. The 14mm stainless steel bolt is what will be used to make a new shaft for the throttles. Here it is used to hammer down the bearings.


6 Thumb throttles equipped with sliding bearings. At this point the clearance is reduced by approx. 0,7mm. As mentioned before I will also replace the (out of round) cast aluminium shaft with a stainless steel one. This also gives me the opportunity to adjust the handle in the correct place/degree in relation to the housing. As they came standard, the handle was to far away from the grips, because I will also be using a seperate brake lever, which will be placed between the grips and this throttle housing.
If I would have bought better quality throttles, I would have to modify them, too. Because of the handle placement.

Next step is to make the shafts and handle placement.
 

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