Honda GX160- 8.5cc

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Basil

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Slow week on the little Honda. I had a big round of aluminum I picked up from somewhere years ago I thought it would make a nice stand. Its solid, heavy'ish and a good heat sink if the cooling is less than adequate. I want the nuts and bolts to look correct for this engine so started with the crankcase drain plugs. Got all the fins done on the head which I'd been putting off and started on the fuel tank which will be moulded and incorporate the ignition coil stuffed underneath out of sight. The tank will be 2 halves joined along the seem.
 

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Basil

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Just before Christmas I decided to get a CNC router. After much research the Onefinity is what I decided to go with. Being in the UK and they are in Canada, I was a little concerned! But all worked out well and all 3 boxes arrived safe and sound. It is their machinist version which has a 406 square machining footprint. I've set it up without the customary spoil board opting to inset a "T" slot plate into a sturdy laminated machine base? Aluminum plate eventually!
I operated a Fadal CNC with Virtual Gibbs for many years and putting a tool into the table would have resulted in a self inflicted fate worse than death.
Fusion CAM is what I am getting up to speed with, Amazing features! and once I get my head around it I will be fine but it is straining the grey matter at the moment. Very happy with the results so far. I was really struggling to figure out how I could reproduce the two levels on the front cover and blend them to the drive flange, it was keeping me awake at night. o_O. Onwards and upwards. 👍
 

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stevehuckss396

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This is so cool! I'm a little bias. I started on a 1/3rd scale Tecumseh 3HP a few years ago. Trying to finish up the current project so I can get back at it. Keep up the good work. I'm really enjoying this one.
 

petertha

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Interesting! I'm not into CNC but I've heard the (OneFinity) name mentioned occasionally. It looks like you have a beefier spindle motor? Can you provide specs & a sense of what kind of cutting DOC/speed you are doing in aluminum. When you say FusionCam, do you mean the cam module/feature as part of Fusion360?
 

Basil

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Cheers Steve. I'm sure there will be a little V8 somewhere in my future. Building a couple of big ones up at the moment and made some good noise today.
Peter, The spindle is, FORAVER Water Cooled Spindle Motor Machining Inverter CNC 2.2KW ER20 Water-Cooled Spindle Motor with 2.2KW Inverter Drive VFD (2.2KW Water-Cooled Motor&2.2KW VFD) : Amazon.co.uk: DIY & Tools
Which seems like I got lucky because it shows no stock now. I have only ran the one (Aluminum) part and crept up on it 0.5mm at a time. Not being used to Fusion 360 Cam I went through and edited the code some where I saw it wanted to plunge the cutter deeper than I was comfortable with. I'm sure I forgot to tick a box somewhere. Tools I used were 1/4 ball, 3mm ball and 2 mm ball Carbide EM. For the small mills I was 750mm/min. and right at the top end of the spindle RPM. Still very early days with it so time will tell.
 

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Eccentric

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Glad to hear you are jumping right in making chips already. 750mm/minute seems fast. that is 30 inches/min which is about twice what I run. Of course it depends on what depth of cut, end mill size, number of flutes, RPM...

Looking forward to your first "real" part. No rush, take your time practising on bits that don't matter.

Greg
 

Basil

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Glad to hear you are jumping right in making chips already. 750mm/minute seems fast. that is 30 inches/min which is about twice what I run. Of course it depends on what depth of cut, end mill size, number of flutes, RPM...

Looking forward to your first "real" part. No rush, take your time practising on bits that don't matter.

Greg
👍 Do you have a pulse generator? I feel it would be a nice addition to my setup. The gameboy remote is a little course when doing tool heights and F.O. on an existing part.
 

Eccentric

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I do not have a pulse generator and likewise think it would be nice to have. I jog my machine with the computer keyboard, I hold down the arrow keys for slow jog, and <shift> arrow keys for fast jog. I often then use the command line to issue a G code, for example I might type G0 X0 Y0 to go to the origin.

I use the command line to issue a G38.2 command to probe for the part to touch off.
 

Basil

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I thought I should get the cam out of the way at this point. Not one of my favorite pieces and the whole thing takes a little while to get my head around, an interesting challenge though! I looked at a few different ways of making cams and finally decided to make a jig and follow the same process as with my Seal Major engine. The cam is EN24T and will be ran with Hardened mushroom type lifters as per the original. I mocked the profile up in CAD and came up with a combination of lobe and lifter face that looked friendly. 3X 2.5mm bolts will attach the cam gear. Slots in the cam gear will allow for fine adjustments.
 

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Basil

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I'm getting very close to finishing the bottom end. The bronze cam bushing locates on a spigot in the rear case. The front runs in aluminum which I may bush later, both have oil supply holes.
While looking for gear cutters, and their prices!! I came across some gears online and located some .8 module, 20 and 40 tooth that were 24mm on centers only .5mm off the scaled original. I had not drilled the case yet so decided to go with them.
The crank gear is light press fit with loctite. I set the crank at TDC and positioned the cam so the gear screw slots are in a fairly centered location. The lifter are mushroom type and machined from tool steel, hardened and tempered.
I resin 3D printed a valve cover up but I think I will make this out of aluminum. My next challenge on the CNC router!
I'm going to machine up bolts to replicate the originals, these will be 3mm. Any advice on a good steel for bolts?, looking for something that will thread nicely with the small die. Machinability over strength. Leadloy?? or not good for bolts? Thanks
Rocker assemblies next.
 

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Basil

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This feel a little wrong. If it bugs me too much I'll make a set! Many years ago (30+) I'd planned on building an inline 4 out of OS parts. We had a great hobby store in Fountain Valley, California that has sadly just closed down, They would have specials from time to time and I loaded up on OS 20 parts and some Saito parts also. Digging through this box ( I hardly ever sell anything hobby related mostly because when I have I have usually regretted it later). I came across some Rocker arms. They were amazing close to in dimensions to what I was about to make.
Only issue! I'd rather buy a Hardened ground pin than make one. They use a 3.5mm shaft.. I had come to terms with making one but then spy'ed my driver set. 3.5mm, hardened ground steel ;) Spot on! It's still usable too!
The hold down bolts are 2mm. Amazingly I had a 3.5mm reamer probably 30+years old! Nice to be able to wrap this top end project up in a day.
I had just received some 1/4" EN1A leaded for hardware I am making and this machined beautifully for rocker arm spacers.
Only 2 attempts on the center post to get the rocker pad smack over the valve stem face. Magic! 👍
 

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Eccentric

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Wow, what a find, those rocker arms look like they absolutely belong. You are a true craftsman, your engine is coming along nicely. I have been in that Hobby Shop if its the one on Ellis.

honda.png
 

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Basil

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Thank you Ray. That's' high praise indeed looking at some of the projects that you and others are building on this forum.
I lived in Costa Mesa for over 16 years starting in the early 80s. Many trips to Mile Square park and would always stop in at the model shop. I was big into RC planes. Looks like it's all a golf course now. :(.
Busy making bolts and getting ready to lay up the fiberglass fuel tank at the moment.
This project has definitely taken over! My wife is getting Jealous!
 

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Basil

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Time to do some balancing. I used the formula that takes the full piston assembly weight and added it to the top end of the connecting rod weight, then divided this by a balance factor (between 50 and 60% for a single cylinder). Add this arrived at figure to the connecting lower weight and make a bob weight to that specification. I crept up on the desired "bob" weight by mounting a drilled piece of steel on a spigot and removing O.D. and rechecking on my scales. Position this weight on the crank pin and carve away until the crank stops on any position. Neutral. I was very surprises how much weight I had to the remove from the pin area. To help with this I drilled the crank in this area also.
My numbers:
Piston/rings/rings etc ..... 13.66 Grams final! (I decided to take some weight out of this item to help reduce the bob weight)
Rod top ............ 2.85 Grams (Supported on cotton and both crank and pin holes on the same plain)
Bottom of rod ....... 8.45 Grams

I decided to start at a balance factor of 50% and I will see what vibration is noticeable. A greater balance factor will require more grinding on the pin area of the crank because the bob weight will be heavier.

13.66 + 2.85 = 16.51 Divide by 50% =8.255
8.255 + 8.39 =16.645. This is the bob weight required. As mentioned I had to remove a lot! of weight from the pin side of the crank to bring it in balance.
 

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Basil

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I decided after much debate to make the fan shroud for the little Honda as a soldered built up assembly. I ordered some different thicknesses of brass sheet and created some CNC programs for the three flat plates required. I had not machined brass yet on my new router so loaded up some thin plywood using 2 side tape for hold down. This way I could also check everything for fit and make small program changes without wasting precious material.
To help with hold down when machining brass I also screwed the plate down after drilling the required mounting holes as a first operation.
Using different sizes of round bar I formed the cookie cutter perimeter component. To hold this to shape I silver soldered the ends together with a small plate on the inside. The outer flat plate is 1.6mm thick, this is so I can get a good radius look imitating the original presses steel assembly.
The round outer ring is also only for appearance, again to mimic a raised portion on the original pressing.
Nice to have another head scratcher component out of the way.
Pushrods next! :)
 

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stevehuckss396

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I try not to rush into that until I have a permanently installed fuel tank and throttle lever. I don't want to knock over a fuel tank or loose control of the throttle while trying to keep an eye on the other half million things that need attention on a first run. Best of luck on the first pop. Post some video of it if possible.
 
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