Bike builders that have machine tools/shops

[Tom from Rubicon]

Out to the machine shop to (shred apart) disassemble top end of the 79cc Predator. Still got the two long studs to remove.
My bench vise did not have enough travel to also use two wood blocks to protect the engine case. Just as well,
I opened up the Bridgeport precision ground vise and firmly gripped the crankcase. (I already had the side cover off).
Holding the engine case firmly is needed as the flange headed head bolts do not loosen their grip easily.
Loosening the bolt is done incrementally to avoid distortion or cracking of the head.
Not so important with cast aluminum, but good practice should you ever encounter a cast iron engine head.

Once head bolts were free, time to free the rocker arm adjusting nuts. Once off, out come the rocker arms, and push rods.
Back to the bench and removed the valve assy. All parts removed to a pristine poly bin.

Thinking of doing all port and polish work before decking the head to ensure a sharp shutoff.
The combustion chamber is rustic as in sand cast texture. I will not mess with valve seats if I can help it.
Tom

 

[Tom from Rubicon]

Out in my shop this afternoon to figure out the best practice for polishing the combustion chamber.
First thought was using a riffler file, but it wasn't cutting it. Literally.
Got the Dremel out, then started sorting through fifty years of bits, burrs, bobs, and brushes used in Die and Mold making.
What I had forgotten was a well organized couple drawers of various Craytex disks and mounted drums. Some of which already had radius profiles. Cratex Shapes for smoothing and polishing hard to reach surfaces - BORIDE Engineered Abrasives (borideabrasives.com)
Holding the engine head at various angles securely so both hands can control the Dremel requires a specialty vise.
A PanaVise mounted in my case on a heavy steel base though I also have the vacuum base. PanaVise Products, Inc.
Started the polish, and am very satisfied with results so far. I think the porting is going to be the real challenge.
I will soon find out. Sorry, no pitchers today.
Tom

 

[Tom from Rubicon]

Done with the porting and polish. Found I had a piece of .750" x 5"x5" aluminum tooling plate all squared up.
Used the rocker cover to transfer punch the bolt hole locations, re-struck the marks with big hammer and punch.
Drilled to .250" dia.,
Tomorrow I'll get some M6x1.0 x20mm bolts to mount the head to the tooling plate and do the .050"+ head decking.
While I was out and about today, stopped at NAPA and bought a tube of engine assy. lube. 8oz. for $10
Still to get, 18# springs, and ARC racing 6671 billet flywheel.
Tom

 

[Ralph hop]

Heck yeah Tom!

 

[indian22]

Tom of course you know that securing and positioning the work piece is key in machine work & hand polishing ports and chamber seems to require both hands during the tedious operation. It's been said that die grinders should be sold only to professionals a tremendous number of great firearms have been ruined by "Dremal gunsmiths" and though engine work isn't in the same league with real gunsmithing & has a bit more tolerance for error; It still requires a a meticulous touch with the die grinder.

I think doing the porting first was a good call. The combustion chamber on most industrial type small motors tend to be really rough. I've seen 4 stroke cart engines with at least an 1/8th. inch of carbon buildup in the cumbustion chamber, especially the L head motors.

Rick C.

 

[indian22]

A bit of happy news: I've a 4" four jaw indepenant adjusting chuck on the way & scheduled for monday delivery! This is a really big deal for me as waiting till June for this piece meant that several, "Need to do projects" were on hold untill summer. Now, with any luck I can get started next week.
I will have to do some machine work on the chuck adapter plate to match the chucks profile at the shoulder & drill the bolt pattern, neither one a problem as I have the three jaw chuck running well (for a three jaw) & I can tap it in for the concentricity required.

With the four jaw, face plate, centers, dogs and clamps I can do a lot of jobs that are typically worked on a mill & that means I can use the lathe to make a small milling attchment for the lathe and fab a cross drill/grind station for the cross slide and with that I can accurately drill a divider plate for the lathe.

Rick C.

 

[Tom from Rubicon]

Truth be told Rick, I went at the combustion chamber first. I figgered if I was going to mangle a valve seat, best to do it before putting a lot of work into the head. I was going to buy a cylinder hone at NAPA to do a pretty finish in the ports.
At 1/4th the cost of the engine and not knowing if it would be used again. It ain't like I do this for a living.
The head looks better than the snagged out job AGK did.
So this afternoon, I mounted the head to the tool plate and tapped it solid onto the vise parallels.
And went at it with my biggest flycutter, .0125" per pass X 4 = .050". Depth mic. says I took .053".
Easter day I will put the hollow dowels in and set the head gasket on the head.
I am expecting a CC variance compared to cylinder bore.
If there is I will use the gasket as a scribe-guide to sculpture the CC. Pitchers from today.
Tom

 

[indian22]

Bridgeport and a flycutter is a very precise way to take off aluminum & doing ports and chamber first was a good decision. I'd think taking 53 thou off will result in a nice bump of compression too. I'd not think you'll have much difference in cylinder to cumbustion chamber match up, but there will be some. Easier to see and correct than to do the math!

Rick C.

 

[Tom from Rubicon]

Your benediction is always welcome Rick, hain't never been or done this small engine monkey business before.
Happy Easter to Y'all.

 

[indian22]

Tom it's strange how memories and names pop into ones head driven by topical references I'd think. One of the machine shops I haunted as a youth was Bartel's Machine shop and a small engine specialist Herman Knight. I'd bought a nice 8 hp Cushman Scooter an Eagle really clean and never dropped, but the motor was really weak and compression was way off and after disassembly (by me) I took the parts to the shop for expert opinion of how to proceed. I'm certain this was the first time I heard the terms mill & align bore coupled with 30 thou overbore and a few other "hot rod" references. Herman with my interference along the way rebuilt this motor to really run. I figure this set my path forward with any transport I owned to the present day. One lesson learned: every motor change made effects the whole and leads to the need for altering other areas of the motor to take any advantage of the first modification. Mill decking & overbore, combustion chamber profile alterations lead to increased fuel & electrical issues. I ended up with a Dellorto carb, regrind camshaft, porting and larger valves with heavier springs. Plug heat range change and increased spark advance. The thing was a beast! It also took all the weight I could muster to get her started, my 110 lb. weight wasn't an advantage in that effort!

Sadly the small engine guys can't make a living it seems in a small town anymore. If it weren't for carts performance parts would not exist either. I think growing up in the fifties and sixties was a great blessing.

Happy Easter!

Rick C.

 

[Tom from Rubicon]

Well after taking Miss Daisey (Mona) for a Easter Sunday drive around the lake country just South of us.
And the weather here was upper 70's. Gorgeous!
Took the 79cc head out of the mill. No burring of the C.C. worth messing with.
After installing the hollow dowels to guide the head gasket and setting it on. I don't know. Fore and aft, there is a 1/16 one side and 3/32 other side of flat unchambered area.
Rick, what is the science regarding timing advance when increasing compression?
Daddy was no engine mechanic either.
Dad's formative years on the farm was seeing and and smelling a horses rear. After the Depression his dad got a tractor.
I.C.E were a mystery. If one stopped in the middle of a field and it had fuel. They just wished it would work.
I remember once, we were half done transplanting a acre tobacco field, when one just stopped. No fire. Chit!!!!
The tractor was a WD A.C. so four stroke. Called the neighbor across the road cuz he was handy with engines.
He come over, looking hard, finally he says "turn the key" with his hand on the distributor cap. Darn distributor cap had come loose. Once the engine lit, he kept adjusting by ear until that tractor hummed, and we finished planting the acre, milked granddads cows, and had supper. Now you know the rest of the story, and why engines are a mystery.
Tom

 

[indian22]

Tom I like to mis-use terminology in my explanations. "Hit & miss" is one that has wide application possibilities, though the definition is typically used to classify a type of small motor. In my experience hit or miss, trial & error...more art than science are frustratingly applicable when dealing with performance motors be they four stroke or two. I should have led with "I don't know" but I buried my lead in order to reveal my process. That there is science behind it all is solid, but as in most formula driven explanations there are multiple mitigating factors, compression is one, fuel type and mix ratio another etc. As I previously posted easier to see than to do the math. That said you asked a great question and it's one that I've chased in the past several times & had some success along the way. Here's my approach: Duplicate the setup of others who've had a modicum of success with a particular engine and if satisfied with the result Bob's your Uncle. Along the way chop the plug repeatedly and you will see what the motor has to say about it's setup. There is some skill required with reading plugs, but it is empirical evidence one can rely on. If change is required try one alteration at a time and read the plug before trying something else. It's a time consuming labor which .most will not endure.

For recreational motor use (not competition) starting is a big deal which involves retard timing compared to peak performance which is more advance and these two must work together for pleasant daily motor use and this is the simple route that I follow and is seat of the pants science. When a motor starts readily and runs sweet I read the plug and memorize what that looks like for future reference. Then enjoy the results you've achieved and ride! Even this simplistic approach takes some time and patience.

Tom I have two bikes that I seldom ride because I went way past the balance point looking for more power, which I found, but I find them way too edgy to deal with day to day one is a 4 stroke the other a two. Both are living room artifacts at this time. I don't see your goal being peak power oriented but rather enjoyment and given the setup parameters that are being used by the "kart guys" for medium stage tune; you should be fine, though fine tuning of jetting & plug range will be necessary to take advantage of your mods. I don't think trying to chase timing past what's being used on recreational motors is a great use of ones effort. Ride and read the plug till the bike feels great and the plug reads right...should sound good also!

Rick C.

 

[indian22]

Four jaw chuck and parts scheduled for delivery tomorrow and I could have used it last night, but a chuck in hand early in April certainly beats maybe delivery in June! Chop saw scheduled for Thursday. My old one gave up the ghost R.I.P. & I've some heavy duty large diameter steel to cut that my 4.5" angle grinders can't manage even if I wanted to expend the effort to butcher through the cuts required.

Patience!

Rick C.

 

[Tom from Rubicon]

Thanks for the come back Rick, I am a expert at over thinking a process.
Tom

 

[Tom from Rubicon]

Anyone know what thread pitch the M8 head bolts of a 79cc Predator are?
Thanks,
Tom

 

[Tom from Rubicon]

ARC 6671 flywheel ordered. scrounge up some heavy springs too.
Tom

 

[Tom from Rubicon]

Ordered AGK 18lb springs. Drives me Bats that mod'ing a 79cc HF Predator amongst bike builders is so rare.
I reckon I will do my best to see it done more often. Starting now. Got a bit of typing to do.
Tom

 

[Tom from Rubicon]

In the mean time;
Show us your shop, your tools, fixtures. Black smiths, your anvils forgings
Lord knows what.
Show us what can be done by hand and hand drill. Show us what you can do.
It was a mistake on my part, so full of my self, and trying to pump up my own self esteem that I titled this thread.
This thread will not survive, without creativity and innovation of all manner.
Thinking, and working with our hands. Learning. Taking what you have learned and applied it to a product............
That you can ride!
Don't be shy. Best practices apply. Otherwise this thread will die.

 

[indian22]

In the mean time;
Show us your shop, your tools, fixtures. Black smiths, your anvils forgings
Lord knows what.
Show us what can be done by hand and hand drill. Show us what you can do.
It was a mistake on my part, so full of my self, and trying to pump up my own self esteem that I titled this thread.
This thread will not survive, without creativity and innovation of all manner.
Thinking, and working with our hands. Learning. Taking what you have learned and applied it to a product............
That you can ride!
Don't be shy. Best practices apply. Otherwise this thread will die.

I don't know if retitling is even possible on the forum, but I personally would use that feature if it's possible. There's been a one and done mentality with forum topics that kills the growth of not just the individual participation and interest in a thread but of the forum overall. I'm probably one of the few that feels this way but I do. There is a big difference in those who post frequently on various themes and those who occassionlly ask a question or make an observation.

Rick C.

 

[indian22]

The 4 jaw came in yesterday and I had it mounted, runouts checked and some one inch aluminum rod chucked, turned and checked for concentricity before six last evening. I'm very pleased with the results and that very little machine work was involved. I did have to borrow some M8 -25 studs from the 4" three jaw chuck for coupling the new chuck to my lathe. I've another box of parts for the lathe scheduled for delivery today.

Rick C.