Building a Ht Motorized Bicycle or Three.

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Theon

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Jan 20, 2014
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I get carried away,
'I like to have lot's going on in my little workshop' (it's a mess!).
It's The start of our WET season here, so not much to do outside a lot of the time and very little bike riding going on.
So, I've left one of my motorized bicycle complete, The Phantom' a lovely little 24" BMX/Racer Hybrid, Designed by a small OZ Bike building company 'Fourty Bikes'.
She's in a state of tune that will pull from a dead stop with no peddles to 9000 RPM and around 70Kph. She's still not run in, and I'm very happy with the way she works other than a little pinging above 8000 but I don't need to be doing those revs on her, she's a buzz and right in her 'band' between 40-60 Kph. Which is really all a push bike should be doing.

Point Being,
I've pulled everything else apart!
And I'm running out of room!
Motors are one of those things, the sooner they go back together as opposed to being left collecting sawdust, cockroach ****, and rust, the better.
So I need to dedicate a bench to engines here, I need to put 4 Ht's together, as well as a pocket bike motor, scooter motor, chainsaw motor, Re-ring a 500 Quad, Find out what makes the old 250 Quad motors start to rattle?, Rebuild a Carby for my Suzuki Sierra (Sameri), then theres the blown head gasket on my diesel mower..., there's lots of stuff I should be doing.
But I just love building bikes, I love it so much, I put 'em all together, ride 'em around a bit, them pull 'em all apart swap this to this bike, that to that bike, you know how it goes.

I'm going to start though with my Ht motors, I have five.
Three are all ready in bits and once I sort out a bench, The other one is coming apart as well. There's nothing wrong with it, in fact it recently got a barrel upgrade and does 80Kph. However The bike it's in is old it don't have good brakes..
I just want the barrel for my Soft Tail motor. As it has the 40mm inlet to match my intake.

Again point Being,
So I plan to build 3 very different motors at the same time, and therefore figure this may be worthy of a thread.
I just havn't decided yet which bit goes with what...
 

Theon

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Jan 20, 2014
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Re: Building a Ht or Three.

I've set up a bench,
I have all four motors on the bench,
And I've made a few decisions.

1st motor (far right).
Came out of my 'Old Raleigh' test bike.
This is a RockSolid Crank, after taking about 12g from memory from the piston, I lifted it's out of balance point to nearly 9500 RPM this thing flies.
It's been running a 15mm Barrel carb, which works well But I'm tempted to try a 19mm.
The head has been shaved and reworked, And it's just in swapping barrels.

2nd motor.
Is the new motor for my 'Softtail'.
These are my new cases, the crank I've chosen for it is a bushed main bearing, 38mm stroke, never been run, but if it's no good, I'll get a 40mm stroke crank for it from RockSolid.
The Inlet Manifold I've made for this bike requires a 40mm stud spacing, and after asking at RS, Tony doesn't have one, so I've taken the ' Old Raleigh's' barrel.
It will be mounted with a .2mm base gasket, to 'slow it down' a little.
This motor is being mated to a shift Kit, and I'm not looking for revs, I'm looking for nice Mid range, reliable, cruising.
But I also want to get it to pull like a 'Hog' through the gears, so I'm looking for a 'Power band' from say 3500 to 6500 RPM.
And Plan to run a large bore custom exhaust, nothing to fancy, I want it to be a little loud, with out being obnoxious.

No.3.
This one's for my new build,
'The Rat Rod Goat'.
Featuring recently in the 'Ratty Projects' thread.
The Cases are wide mouth and match my Old alloy Mountain Bike Nicely.
I have stripped the shift kit from this motor, and all it's crap GT5 internals.
The New 40mm stroke crank is at RockSolid being 'checked over'.
It will be getting a Rock Solid Reed Valve and Barrel to Suit.
I'm not sure what carb yet,I will talk to Tony and see what he recommends.
I've bought a New 'Blank' Centerfire Head from him for $15 (bargin), Which I'll have a 'play' with.
But Imagine a Puch Head on her one day.

No.4.
These are my leftovers.
There is nearly enough there to put a motor back together,
I'm not sure I can be bothered. As Engine No1. is way to fast for its bike. and so the 'leftovers' will go back in the 'Old Raleigh' and hung on the wall as my 'First Motorized Bicycle'.

And my 9500 RPM motor will be awaiting a new home!

I'll try and go into a bit more detail on each motor as I go, hopefully one at a time!
 

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Theon

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Jan 20, 2014
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Re: Building a Ht or Three.

Motor No1.
The new barrel has been decked by .7mm.
So to get my correct squish and lift my barrel a little,I use a home made .2mm paper gasket under a 1.5mm alloy barrel spacer that I have previously made.
Rather than upset my rings, I use a new piston to check timing and squish.
With the standard alloy head gasket given a rough torque down, I get a squish of .6mm-.7mm
Perfect!
I check my port timings, and I'm happy.
That was easy.
This motor will now go back together and sit on a shelf awaiting use.
Seems a shame really, I might have to throw her back in the 'Old Raleigh' for a bit, just to 'Run her In'.
 

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buba

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Jul 2, 2010
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Re: Building a Ht or Three.

theon

i like your approach -i too seem to like a certain amount of projects inorder to muster the economy of scale to jump in- head first

i wish i had the obvious engine mechanicing skills you have

best
 

Theon

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Jan 20, 2014
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Re: Building a Ht or Three.

Cheers Buba,
I wish I had your creative flare (no pun intended) with the angle grinder.
I hope your keeping safe and I love your work.
I also wish I had your ability to find stuff, I had a great dump near my old place,
Still I have enough stuff already (according to my wife that is).

I've had a Quick look at engine no 2.
It has the 38mm crank which runs a standard piston rod assembly.
With the un-decked barrel, a .2mm base gasket and no head gasket, I get a .8mm squish.
This barrel is too good to deck. As I may want to put a 40mm crank in this motor yet.
So I'm going to make the thinnest head gasket I can or may just try lapping the head to the barrel.
Squish should hardly matter on this motor anyhow as I'm not going for max revs or compression.
Any suggestions on helping seal the head down as thin as possible?
Photo's look similar to last one.
 

Theon

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Jan 20, 2014
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Re: Building a Ht or Three.

I was wondering about using a beer can for a head gasket,
Has anyone tried this?
I'm guessing it would be best to give it a bit of a rub with some wet and dry.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
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Re: Building a Ht or Three.

I have used cheap aluminum roaster pans for head gaskets. They crush down pretty thin although I've never measured one.
 

Theon

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Re: Building a Ht or Three.

That would be a softer metal,
Cheers for that Maniac, That might be better.
Got my Jaw fixed (pinned and plated) today, feels better already.
I'm not too worried about getting the thinnest possible head gasket, as I don't see squish band being of much importance on a slower Revving motor.
But I can see other readers out there might be interested in a combination of gaskets that would allow them to get a little more out of there 38mm crank, without having to take to much of the barrel.
I'm going to run her in on a relatively low compression, and will shave the head a little latter on depending on what PSI I get and how the motor is to start with the pull cord.
The angle fire head I was running had a decomp valve, and a lot of metal taken out of the dome. It felt a bit like a large chainsaw motor to start without the decomp, and I won't have a decomp on my new head.
I would love a twin plug 'Fred Head' with decomp for this. But really postage is a bit of a Drag on something that is already a 'luxury' item.
Besides this ain't a race motor, but It sure would suit her.
 

Theon

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Jan 20, 2014
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Been to RSE today and got a new balanced crank, Reed valve, unmachined straight fire head and High tensile bolt set.
Also picked up a few more 6202 bearings, and am ready to get back to motor building.
 

Theon

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Jan 20, 2014
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This new RSE Crank is quite a bit narrower than my other cranks, leaving about 5mm between crank and case, the difference is that the rods big end is 'counter sunk' into the fly wheels.
leaving only about 6.5 mm between the two fly wheels rather than the usual 12mm.
This is good, as I had planed to stuff the cases and I have some 5mm 'Hard' alloy sheet here.
So this is what I got done this arvo, leaving less than .5mm now between crank and case.
 

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Theon

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Jan 20, 2014
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Doesn't seem that anyone here wants to share there reed valve knowledge, There a secretive bunch these racers/engine builders.
Not me I hate 'secrets', and after doing a bit of research on the subject I'm even more confused.
Still pistons are cheap for these motors so I'll just do my own experiments, and I've ordered a new barrel for the motor as I need the 40mm Inlet stud spacing for the larger reed valve that I got from RSE, and the 40mm inlet barrel I have I wanted to use with my twin carb manifold for the Softtail.
I'm curious about the boost port mod and if this barrel I've ordred turns out to be of decent quality, I'll order another, to play with. Tony at RSE does not have a 40mm inlet barrel to sell me.
Having trouble here in OZ getting good Quality parts from vendors that even know what they're selling. And postage from the States is usually more than the part itself.
So if there is anyone here in OZ reading this who has any recommendations on a good parts supplier please let me know.
I was using "Scr**ming Roo/P*B" but no longer wish to have anything to do with the arrogant ****.
 

Theon

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I seem to be having some trouble with Photobucket and or my SD card.
However today I finished fitting my case stuffing discs installed my new bearings and gave my cases a nice coat of gloss black engine enamel after acid etching them.
The crank is ready to install and now I'm just waiting for the new barrel I ordered yesterday.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
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Honestly, I don't think it's greed keeping people quiet on reeds. There simply hasn't been a lot of technical testing done in a systematic way. It's all "well so and so did this" and "I hear that works" Nobody really knows what works best.
I'd say you would be safe following conventional two stroke tuning guidelines with duration for reed motors. The pipe specs seem to work so the intake should as well.
Gordon Jennings is my personal favorite guru.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
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memphis Tn
Honestly, I don't think it's greed keeping people quiet on reeds. There simply hasn't been a lot of technical testing done in a systematic way. It's all "well so and so did this" and "I hear that works" Nobody really knows what works best.
I'd say you would be safe following conventional two stroke tuning guidelines with duration for reed motors. The pipe specs seem to work so the intake should as well.
Gordon Jennings is my personal favorite guru.
 

Theon

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That's fair Maniac,
Still I'm curious as to what others have done and there results,
I wish I could justify buying a 1/2 dozen piston/barrel sets just to hack up and test.
But I'm going to get two sets to start with, and try a few different things.
Others stuff up's (what not to do) is appreciated, and not using JB to stuff my cases is a valid point. Was also hoping for a little bit of 'This worked for me' also though.
I do come across as a grump, and have had a lot going on of late.
Sorry to those I offend!
People that know me also find me a 'helpful grump' as well as being an opinionated ****.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
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I've had good results using Devcon Liquid steel epoxy for stuffing cases. As long as you buy the complete system and use the cleaner/primer correctly, it sticks like glue.
 

Intrepid Wheelwoman

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Oct 29, 2011
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I'm following your engine mods with great interest Theon. Two stroke tuning has always been a bit of a mystery to me. Give me any kind of flathead and I know what to do, but two strokes have always seemed to run on some kind of esoteric magic as far as I'm concerned.