Building a Ht Motorized Bicycle or Three.
- Thread starter Theon
- Start date
Getting a bit of riding in this arvo, getting faster on the track behind my place. There's about 1000 Acre of cane padock behind with a track that surrounds it and follows a creek, some nice straights, some nice sharp turns, The bikes gearing and low down are great, letting it crawl smoothly at 2000 RPM and go to a speed that would scare most. Somewhere yust above 4000 if you pull back a little on the bars as you WOT it power wheelies, and keeps lifting as it powerbands until you back off. So was starting to really give it heaps around the corners and spraying mud everywhere with the knobbie back tire when "PING,PING,PING", I broke 6 spokes! and may need some heavier ones.
Bugger! I was having a lot of fun.
Bugger! I was having a lot of fun.
After destroying a couple of spokes on my Goat, I threw the wheels I just built for the Mongoose on with the 36t sprocket, still I get 8600 RPM, same as before, netting 45MPH by the sprocket Bible, but I liked it better before with the wheelie pulling/ spoke snapping grunt of the 44t, so the Mongoose can have it's 36t, and the Goat can keep it's Knobie's.
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Up Date.
I've been slowly plugging away at my case induced Mongoose.
Getting the cases as perfect as I can with file and Dremel.
Also making throttle and clutch adaptors.
The wheels are all together and the disc brakes operational.
I've stripped the Softail's motor and mounted it's crank in the modified cases, spinning freely with nice end float of approx. .5mm.
I'm awaiting a new piston and rings for her and a chrome fuel tank.
Head has been shaved, reshaped and polished.
Exhaust has been made to fit and just needs a few welds tidied up a little for a coat of paint.
So getting close!
I've been slowly plugging away at my case induced Mongoose.
Getting the cases as perfect as I can with file and Dremel.
Also making throttle and clutch adaptors.
The wheels are all together and the disc brakes operational.
I've stripped the Softail's motor and mounted it's crank in the modified cases, spinning freely with nice end float of approx. .5mm.
I'm awaiting a new piston and rings for her and a chrome fuel tank.
Head has been shaved, reshaped and polished.
Exhaust has been made to fit and just needs a few welds tidied up a little for a coat of paint.
So getting close!
I got a morning on the Mongoose.
So I spent some time putting the final touches to the jug.
There has been a lot of interesting discussion here with regard to boost ports, but not much explanation to there construction, size or timing.
I've played with and read a little regarding boost ports on pocket bikes, and now I have case induced reeds I figure to work on similar principles.
One theory I read was that the transfer port that opens first flows last.
So it seems that by opening the boost port first, it helps to pressurize the case for the main transfers to do there thing, then as it starts to flow it's aimed up at the plug. it then does push charge out the exhaust, but that should then be returned to the cylinder by the pipe in power band.
The main transfers are better to have a fairly flat roof, and the boost port a good angle.
I'm still deciding on durations, as I'd like to get an idea of were the pipe works best before I Do another Jug for her.
I therefore have the durations fairly conservative to start with and will raise the jug a little at a time with a thin headgasket. Decking the barrel as I go.
Then when I feel I may have gone too far, I will drop it down a little and use a standard gasket.
So I spent some time putting the final touches to the jug.
There has been a lot of interesting discussion here with regard to boost ports, but not much explanation to there construction, size or timing.
I've played with and read a little regarding boost ports on pocket bikes, and now I have case induced reeds I figure to work on similar principles.
One theory I read was that the transfer port that opens first flows last.
So it seems that by opening the boost port first, it helps to pressurize the case for the main transfers to do there thing, then as it starts to flow it's aimed up at the plug. it then does push charge out the exhaust, but that should then be returned to the cylinder by the pipe in power band.
The main transfers are better to have a fairly flat roof, and the boost port a good angle.
I'm still deciding on durations, as I'd like to get an idea of were the pipe works best before I Do another Jug for her.
I therefore have the durations fairly conservative to start with and will raise the jug a little at a time with a thin headgasket. Decking the barrel as I go.
Then when I feel I may have gone too far, I will drop it down a little and use a standard gasket.
With my 1.2mm alloy spacer I now have 132 Deg of transfer port duration with my boost port opening 2 deg earlier (136 Deg Duration).
A little more than I'd hoped for, But as much as I could want, I am aiming for High revs from this motor, And I can always drop the barrel down a little.
I'm going to run a home made baking dish head gasket in this config, which is so thin you need a micrometer to measure it, which I have but it's in the 'old scale' and is great for small drill bits, but is a pain in the ar*e for comparing with metric measurements.
Anyways, it allows me to drop the barrel back down a little and increase headgasket thickness as I go.
Exh Duration is still at only 156 Deg and will likely be lifted a little more, As I doubt I have enough 'Blow Down' yet. with only 10 Deg between exhaust and boost port. From what I've read 20 Deg maybe a good starting point, with 22 Deg when main transfers open. I don't want to take it too far straight away, but leave some room to experiment.
So my Exhaust Duration with the Jug in it's most raised position should work out to 176 Deg.
Again the most I could want, But I'm looking for Revs.
Dropping back to a .8 base gasket will allow me to run a standard head gasket with 170 Deg of Exh Dur, And Tran Dur of 126 Deg, which is probably where she'll stay.
A little more than I'd hoped for, But as much as I could want, I am aiming for High revs from this motor, And I can always drop the barrel down a little.
I'm going to run a home made baking dish head gasket in this config, which is so thin you need a micrometer to measure it, which I have but it's in the 'old scale' and is great for small drill bits, but is a pain in the ar*e for comparing with metric measurements.
Anyways, it allows me to drop the barrel back down a little and increase headgasket thickness as I go.
Exh Duration is still at only 156 Deg and will likely be lifted a little more, As I doubt I have enough 'Blow Down' yet. with only 10 Deg between exhaust and boost port. From what I've read 20 Deg maybe a good starting point, with 22 Deg when main transfers open. I don't want to take it too far straight away, but leave some room to experiment.
So my Exhaust Duration with the Jug in it's most raised position should work out to 176 Deg.
Again the most I could want, But I'm looking for Revs.
Dropping back to a .8 base gasket will allow me to run a standard head gasket with 170 Deg of Exh Dur, And Tran Dur of 126 Deg, which is probably where she'll stay.
Back to the Goat.
I've reassembled the rear wheel, this time set up with 39t sprocket, but am undecided on this, I think I will miss the wheelie popping torque I had with the 44t.
I've got a brand new $15 15mm barrel carb for her and I've lifted the jug to have a look at how she's running. Obviously rich, But I knew that, but having a closer look at the piston, at the 'wash' pattern in the soot. I can see sure signs of 'short circuiting'. I have ordered two more 'seconds' barrels for a good price and plan another barrel for her.
This barrel was given fairly conservative port timings, not much blow down and was mounted with a .2mm base gasket, Giving me fantastic low down. I only got 8600 Rpm from her, but I liked the way she pulls hard, Idle all the way to 8000, lifting the front wheel on the way!
So it seems that's were my pipe is happy, and somewhere around 4000 RPM must be starting to stuff all that extra fuel back in the chamber, So I'm not straying too far from my conservative port timings just yet, in fact I think with a little more work I can get this barrel working better, I feel I need to flatten the transfer roof, lift the boost ports a fraction as well as lifting the exhaust port, see if I can get a few more revs from her.
Also want to try and redirect the transfers a little more and reaim the boost ports.
I've reassembled the rear wheel, this time set up with 39t sprocket, but am undecided on this, I think I will miss the wheelie popping torque I had with the 44t.
I've got a brand new $15 15mm barrel carb for her and I've lifted the jug to have a look at how she's running. Obviously rich, But I knew that, but having a closer look at the piston, at the 'wash' pattern in the soot. I can see sure signs of 'short circuiting'. I have ordered two more 'seconds' barrels for a good price and plan another barrel for her.
This barrel was given fairly conservative port timings, not much blow down and was mounted with a .2mm base gasket, Giving me fantastic low down. I only got 8600 Rpm from her, but I liked the way she pulls hard, Idle all the way to 8000, lifting the front wheel on the way!
So it seems that's were my pipe is happy, and somewhere around 4000 RPM must be starting to stuff all that extra fuel back in the chamber, So I'm not straying too far from my conservative port timings just yet, in fact I think with a little more work I can get this barrel working better, I feel I need to flatten the transfer roof, lift the boost ports a fraction as well as lifting the exhaust port, see if I can get a few more revs from her.
Also want to try and redirect the transfers a little more and reaim the boost ports.
Honestly Theon? Even the best chinagirl hardly has enough zip to get me excited so I really prefer the reduction in rpm and vibration from a 36 tooth rear. The slightly better speed potential is secondary to me and after running a 36t, I feel totally governed on a stock 44 tooth equipped bike. Makes me want a second gear.
But I guess that's more of a subjective reason anyway.
Just my 2cents.
But I guess that's more of a subjective reason anyway.
Just my 2cents.
The single biggest improvement you can possibly make is to properly aim the ports to get the best retention of fresh charge. Look at some RC model engine Schnuerle porting for tips. Controlling the roll and tumble of the incoming charge will make FAR more improvement than any reasonable port timing change. I've seen custom pistons with ramps and diverters to control the mix. Schnuerle knew his business. His porting is still relevant and cutting edge to this day.
I have raised the exhaust and boost ports a little, and got the transfers hogged out good and proper now.
I tested them with a piece of tube and blowing cigarette smoke through them, with a nice wash across the top of the rear of the piston now which the boost ports will push up.
Just short a 6mm helicoil for the exhaust and she can go back together.
Thinking of trying a nice set of road tyres and building a new dirt bike.
I want Dual Suspension.
Have looked long and hard for an appropriate bike.
Have decided to modify a steel frame mountain bike with parts I've cut from another steel frame Dual suspension bike that did not suit mounting of a motor.
I havn't found a suitable bike yet, but plan to do a trip to the 'Big Smoke' on Tuesday.
I've ordered a hand built 'Screaming Roo' 'Roo Print' motor for this one, It's probably deserving of it's own thread.
I tested them with a piece of tube and blowing cigarette smoke through them, with a nice wash across the top of the rear of the piston now which the boost ports will push up.
Just short a 6mm helicoil for the exhaust and she can go back together.
Thinking of trying a nice set of road tyres and building a new dirt bike.
I want Dual Suspension.
Have looked long and hard for an appropriate bike.
Have decided to modify a steel frame mountain bike with parts I've cut from another steel frame Dual suspension bike that did not suit mounting of a motor.
I havn't found a suitable bike yet, but plan to do a trip to the 'Big Smoke' on Tuesday.
I've ordered a hand built 'Screaming Roo' 'Roo Print' motor for this one, It's probably deserving of it's own thread.
Well after giving my new Roo a go in my Dual suspension bike, I decided to swap motors with the Goat, The Reeded motor from the Goat has better low down for off road.
The Roo has great top end, and revs smoothly, So a bigger carb was in order.
The Roo has great top end, and revs smoothly, So a bigger carb was in order.
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With the Roo in the Goat, and the pipe from the Mongoose now on my 'Frankenstein Dirt Bike',
So I'm working on putting the KTM 'Pro' pipe on my case induced motor.
For which I'm hoping now to get a 'Screaming Roo' Balanced crank.
Dino recon's I 'can't blow one up' with my 'little' reeds.
So it is still happening, just in 'North Queensland Time'.
So I'm working on putting the KTM 'Pro' pipe on my case induced motor.
For which I'm hoping now to get a 'Screaming Roo' Balanced crank.
Dino recon's I 'can't blow one up' with my 'little' reeds.
So it is still happening, just in 'North Queensland Time'.
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I got the majority of the pipe welded today, then when I got home, I have an Email to say there is a Balanced 'Screaming Roo' crank in the mail! So the motor is coming apart again.
Otherwise the motor was ready to run, so it should be a quick swap. I am tempted to fire her up first though. Other than a little final welding to the exhaust, I think she's ready to go.
Otherwise the motor was ready to run, so it should be a quick swap. I am tempted to fire her up first though. Other than a little final welding to the exhaust, I think she's ready to go.
After a couple of Days at the operating table,
I have three complete motors,
The case induced motor got a total strip, clean and repolish, as well as a brand new 'Screaming Roo" 'Computer Balanced' crank, I have been asking for one of these for a while!, And Dino was obviously impressed with my work and has Gifted me this one as 'Research and Development'.
He claims his crank is good for at least 10HP and 10 000 RPM.
I doubt I'll be getting 10HP, but he wants to see if I can break it!
This motor has been given all my smoothest running parts such as clutch and sprocket, I've been over it 3 times now, but I should make sure the brakes on my old Mongoose are ready!
The 'Softtail's motor, which kindly lent it's crank while I was waiting on a 'Roo', now has it's old crank back, with a full rebuild, bearings, barrel, rings and gaskets.
The old piston which has been severely lightened, polished up OK, and so was reused, I tried a Puch head on her, but the pull start wasn't likely to cope, I have a shaved head on her now and I still think the compression may be a little high for the 'longetivety' of the starter. So I have a standard head here than I am going to give just a light shave.
The third motor is from the 'Goat', it has received new Japanese clutch shaft bearings, as the Chinese bearings that I recycled were feeling a little rough.
It got a good flush out and going over, and will likely go back into the Goat when I pull my Screaming Roo motor out and go right over it, ready to put it back in my 'Frankenstein' Dirt Bike with the Reeds and a few mods.
I have a couple of 'Green' barrels from 'Screaming Roo' as well as 2 new pistons, which are the 'good ones' with the larger ports and 40mm inlet spacing. So next I plan to make up two new barrels, one for the case induced motor, and one for the 'Roo' motor when it gets the reeds.
I have three complete motors,
The case induced motor got a total strip, clean and repolish, as well as a brand new 'Screaming Roo" 'Computer Balanced' crank, I have been asking for one of these for a while!, And Dino was obviously impressed with my work and has Gifted me this one as 'Research and Development'.
He claims his crank is good for at least 10HP and 10 000 RPM.
I doubt I'll be getting 10HP, but he wants to see if I can break it!
This motor has been given all my smoothest running parts such as clutch and sprocket, I've been over it 3 times now, but I should make sure the brakes on my old Mongoose are ready!
The 'Softtail's motor, which kindly lent it's crank while I was waiting on a 'Roo', now has it's old crank back, with a full rebuild, bearings, barrel, rings and gaskets.
The old piston which has been severely lightened, polished up OK, and so was reused, I tried a Puch head on her, but the pull start wasn't likely to cope, I have a shaved head on her now and I still think the compression may be a little high for the 'longetivety' of the starter. So I have a standard head here than I am going to give just a light shave.
The third motor is from the 'Goat', it has received new Japanese clutch shaft bearings, as the Chinese bearings that I recycled were feeling a little rough.
It got a good flush out and going over, and will likely go back into the Goat when I pull my Screaming Roo motor out and go right over it, ready to put it back in my 'Frankenstein' Dirt Bike with the Reeds and a few mods.
I have a couple of 'Green' barrels from 'Screaming Roo' as well as 2 new pistons, which are the 'good ones' with the larger ports and 40mm inlet spacing. So next I plan to make up two new barrels, one for the case induced motor, and one for the 'Roo' motor when it gets the reeds.
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I finally fired up my case induced Mongoose.
She kicked in to life before I got out my drive way.
I was having a bit of trouble with the low speed mixture, when I noticed the carb starting to come loose. I need a 5mm helicoil, where I 'stretched' the thread on the reed block.
So I hung on to the carb with one hand, gave her a squirt down the street and back.
Well, she's Loud and she's fast.
This one really does sound like a dirt bike, I didn't try and get top speed or revs, I don't know how fast she's going to go, but fast enough.
She kicked in to life before I got out my drive way.
I was having a bit of trouble with the low speed mixture, when I noticed the carb starting to come loose. I need a 5mm helicoil, where I 'stretched' the thread on the reed block.
So I hung on to the carb with one hand, gave her a squirt down the street and back.
Well, she's Loud and she's fast.
This one really does sound like a dirt bike, I didn't try and get top speed or revs, I don't know how fast she's going to go, but fast enough.
I fixed the carb with a longer bolt, took her for another spin and the speedo didn't want to work, but the Taco read over 10 000 and still climbing. That's with a 36t and 26" wheel. There is a surge of power above 8000 where most motors start to struggle and a nice even flow of power otherwise. But it is rather LOUD.
This crank is silky smooth, with a slight buzz over 9000 RPM. I wasn't sure how far to let her rev? Probably best to be nice to her for a little while.
And did I mention she was loud?
I'll have to get the carb tuned in a little better, it's not easy adjusting this carb under full load while your doing 50MPH, and the exhaust is held in place with zip ties, but I'd say success.
I don't need to go any faster.
This crank is silky smooth, with a slight buzz over 9000 RPM. I wasn't sure how far to let her rev? Probably best to be nice to her for a little while.
And did I mention she was loud?
I'll have to get the carb tuned in a little better, it's not easy adjusting this carb under full load while your doing 50MPH, and the exhaust is held in place with zip ties, but I'd say success.
I don't need to go any faster.
