Building a Ht Motorized Bicycle or Three.

[Theon]

Thank's Maniac, I don't actually 'need' one, however would like to find a good source.

The Barrel.

This barrel will do quite fine, for the engine I'm using it on, and it times nicely, too nice infact, and the 2.5mm I cut from the piston is no longer needed.
I have included a few comparison shots of the barrel I was after compared to the barrel I got, both have been ported, the one on the left is the '40mm stroke barrel'(which also has narrow inlet studs, but same casting as the 40mm inlet version I was after.)
The 'bigger' barrel has larger fins, much larger port castings, and there is a difference noticeable in the transfer port from the 'outside' of the jug, the 38mm barrel has a flat top to the casting where as the 40mm has a tapper to the casting.
However, this new barrel looks to have a wider transfer port, and very good port timing (for a 40mm stroke) from standard, It still has the ramped transfers, and opening a little later, which should help my low down.
I use a .2mm Base gasket, and get a squish of .3mm(without head gasket), perfect.
I just need a new piston, lol. As I now have 70 deg on the inlet, more than I wanted(60).

 

[Theon]

The Head.

Answering I.W. (and I was about to do this anyway.).
I made it, the Decomp valve is from an old chainsaw, and with a bit of careful Dremel work, It's a neat fit. I have also 'Reshaped' the head to reduce compression, widen the Squish band, give better flow, and gave it a polish.
I have not shaved this head other than 'a lap' , as, with correct squish these heads have way to much compression standard.
They usually come on the 38mm stoke engines, with a squish of around 3mm.
Included in the photos are (from left to right).
The standard 'center fire' after polish and small squish band.
The modified 'angle fire' with decomp, widened squish band, excess plug thread removed and a polish.
My 'Shaved Center Fire', I have taken 1.5mm from the head with a belt sander, checking for evenness with veneers as I go. Then a light fine and clean 'smooth' file. I have given it approx' 5mm of squish band, a polish and am yet to remove excess plug thread.
I have not cc'ed these heads, but probably should.

 

[Intrepid Wheelwoman]

Well Theon, the conversion you did on the cylinder head was so good I thought it was some kind of aftermarket conversion head. Adding a decomp is something I'm keen to do on my next China Girl build

In fact all your heads are beautiful pieces of work and it's great to see the pictures.

 

[Theon]

Got a bit more done on,

The Pipe for the 'Goat'.

She's a tight fit,
and might be a little loud without muffler,
I'll work something out.
It's taking a couple of 'adjustments( Gentle with the Big hammer)' .
And I will need to install the rear sprocket next, to make sure that clears also.
I may have to put the 'road wheels' on her 'cause I'm starting to get curious how the top end is going to be affected by the reed conversion.

 

[Theon]

So a little tight, and the cranks still rub, nothing a bit of 'panel beating wont fix though.

 

[Theon]

No.4

I think I may have found the right home for Engine No.4.

'The Fat Stingray'.

OK it's not a real 'Stingray',

I'm not sure I can be bothered with pedals on this one, I kind of like the idea of a 3 speed box.

With the other bikes being close to finished, time to drag out some of the 'other projects'.

 

[Intrepid Wheelwoman]

That's a cool looking bike Theon. Your twin carb setup is just great and suits the bike very well.

 

[Theon]

Thank's I.W.,
The 3 speed gearbox, is what's holding me back on this one, I have an old 3 speed hub, but it goes the wrong way for what I wanted it to do, I'll work something out, it may not need a gearbox, I havn't worked the gearing out yet.
But I'm trying to get all my Lathe Jobs together, so that I can get them all done at once, and move on with a couple of my other projects.
So for this one, I need to make a longer Jackshaft, and will run just two chains, Until I 'work out a Gear box.

 

[Theon]

My wife didn't seem quite so impressed that I had a 'new' bike project and this one will get 'stashed' for now.
I 'm that close to getting my other two going, but it's good to take your time towards the end.

The Softtail.

Well I found that the other new barrel I had with the narrow inlet, the one that came with my latest kit, which is a slightly better barrel than the one I just received, gave me perfect port timing with an alloy spacer, it had already been decked, and was a little less than 2mm shorter than the barrel I was planning to use, my alloy spacer is 1.5mm. and so worked out nice.
I took a little time to match the inlet and exhaust manifolds and make new gaskets, I reused a copper exhaust gasket that I had already made, loctited the studs, gave the frame a touch up and installed the motor.
It mostly just needs the right throttle cable now.
I'm glad I've got the Decomp valve, she lifts the bike trying to pull her over without.

The Goat.

got a set of road wheels.
It still has a few finishing touches to take care of,
But I want to get the Softtail done first.

 

[Theon]

The Softtail is going!

It's a little rich with a .65mm jet, so I just gave her a no. 6 plug for now.
Compression test gives me spot on 150 Psi.
She's obviously got a lot more torque than the old motor, pulls strong, and cruises in top gear,
I gave her a litre of 25:1 I mixed for the chain saw the other day, to run her in, then will be going to 40:1 Penrite Synthetic, and try a slightly smaller jet.
After a test ride she's showing 150 deg c.
Starts first pull and idles nicely.

 

[Intrepid Wheelwoman]

And I bet you had a big smile on your face during your first road test too Theon

 

[Theon]

Just took it for second road test, maybe 10 Km or so. Will have to go down in jet size, I know its good to run things a little rich at first, But she's 4 stroking a bit too much as I get the revs up. She's holding 150 Deg c. Head temp, and its a warm day here. So I'll try the next smaller jet I have, retorque and adjust the chains.
But a great bike to ride, handles nicely on the rougher bitumen roads out here and cruises happily at low revs in top gear.
This will be my 'main ride'.
Once she's run in, I may have to look at peping her up a little, but not much need for what she is and how she goes, a smaller jet will make a big difference. I took the smaller jet that I was running in this carb out when I put her on this motor, but this ones to big.
Will hook up a Taco and see what revs I'm doing for the next ride.

 

[Theon]

Ok,
So swapped from a .65mm down to a .6mm jet, Much better, she happily revs out to 8000+,
She got a bit warmer though, and now reads 190 deg C. and could do with a better head, but I believe under 200 deg C is all good.
When I go to 40 to 1 oil mix that should richen her up a little, which she needs to run a little rich with the shift kitloading her up in higher gears.
She cruises at 6000 to 6500 in top, not sure what speed, but fast enough(over 60 Kph),
Speedo next.

 

[Theon]

After a lot of maths I worked out that for every 1000 RPM in top gear I get 9 Km/hr (Aprox but very close.)
So at 6666 Rpm I should be doing 60 Km/hr.
Which is what my speedo read, so at 8000 should be doing 72 Km/hr, again what my speedo read.
Not bad for a standard pipe, Rt Carb and a motor that's not run in yet.

 

[Theon]

Engine No.4

I want this one to be a 'screamer'.
Fed by a 'Tilly' with a choke of 19mm and throat of 22mm.
The Barrel has Quite nice timing, with a 'standard' base gasket, however has a squish test of 2.5 mm with head gasket.
So, I will need to Deck the barrel, by a little under 2mm.
I'm thinking to get a squish around .8mm, I'm just considering lifting the barrel a little more.
I have exhaust opening at 104. I'm thinking 102.
Ramped transfers opening at 120, I'm thinking 118.
At BDC my piston will fully clear the exhaust port floor,
Standard gasket is .8mm so I'm gessing I want another .3 or .4 of a mm.
I have an alloy spacer at 1.4mm, that gives me 98 on the exhaust so ideally a base gasket of 1.1mm.
Might be better to just lift he ports a little and stick to the standard gasket.
I'm thinking to flatten the ramp in the transfers a little by widening the port to the inlet.
As well as lifting the exhaust port by .3mm , it's not much really is it?
This is where you need to measure your port timing fairly accurately before 'diving in with the Dremel'.
The barrel has already had inlet and exhaust ports widened, but I'm going to go a bit wider,
to suit this carb.
Plan is to go with a compression of around 165 Psi, and probably have to use mixed gas in her.
The next door neighbor just got a KTM 50 with a power pipe as well as standard exhaust, so I plan to borrow the old exhaust and study the new one a little to get a bit of a pattern from.
I'm not sure it will go in the 'stingray', I'm starting to see a four stroke in it.

 

[Fatandre]

This engine of yours. How fast is it going?
Its a 2 stroke right?

 

[Theon]

2 stroke ,yes.

 

[Theon]

Cheers I.W.
First ride I had a couple of small things to sort, but by my second ride I was smiling, when I swapped to the smaller jet, then I was Grinning, Now with the Pipe in place, I am getting really excited.
She sounds like a motor bike now.
I think I'll have to lose the decomp valve head, It's not keeping her as cool as I'd like, and ditch the RT as It won't like the pipe.

 

[Theon]

I only got a quick ride in today, but the Softail went and sounded good with the new(from the Phantom) pipe, I backed of at 8600 RPM and she was still wanting to 'climb'.
The RT went quite well, so it can stay for now,
But the angle fire head is going to have to go, it just doesn't have the cooling capacity for this motor.

 

[Theon]

With my Soft tail going,
And the Phantom having overheating problems, due I suspect from the angle fire head and with not enough room in the frame for a straight fire head, I have decided the best option is to detune her.
Although she handles well, she is a little twitchy at high speed, as well as a little harsh on narrow tyres and so has lost her pipe to the Softtail will lose the 'Big inlet' Barrel, and also her flip flop hub.
I picked up a pink full suspension bike today with discs, to wreck for parts for the Goat, so the Goat's getting front shocks and disc brakes.
I also got a 'mower' plug for the Soft tail, and I'll get Tony at RSE to mill the spark plug seat down a couple of mm on a center fire head so that the plug 'fills' the thread.
Have also decided the best spot for engine No 4. is in my old black chrome Mongoose, and she'll be my next 80 Km/hr 'Road Racer'.
Photo prob's again?