78/81 Honda Express buildup help request

chad dixon /

This is our first post folks. Kalli and I bought a pair of Honda Express ped's a couple summers ago.

We've decided it's time for an overhaul. I'm fortunate to have at my disposal a very well equipped cnc machine shop. I own it. What I lack is the general background knowledge on what parts interchange etc. . .

So, that said. If there's a kind soul out there who's willing to take the time to navigate us through the sea of parts, we would be very, very grateful.

I would like to consider this a higher end project. I want maximum performance from these bikes on all fronts. Suspension, engine, braking, etc. I'd like to go fringe on mine and possibly entertain the idea of forced induction via either a turbo or nitrous.

It's a fun hobby/toy thing for the wife and I. We work together at our business so this is a way to cut loose a bit. The bikes are completely tore down right now.

The direction I plan to take this is to build triple trees for actual forks on these bikes. I also want a programmable shock for the rear. I'm looking long/hard a down hill mountain bike forks/shocks. Adjustable rates, compression/rebound, the works. For brakes I'm again looking at mountain bikes. Hydraulic disk setups for sure! I've already found better rubber so that was easy.

Engine. BB kit. 75cc+ along with a nice pipe. I'll machine the intake from scratch most likely and will buy a prepped Mikuni. I do want to convert to an electronic ignition and a hotter coil pack. I've only seen these for the Hobbit models. Again, if I have to machine an adapter plate so be it.

Paint and what not we'll take care of in house. I've got a booth, oven, etc. (we are custom firearms manufacturers -www.longriflesinc.com)

I'm a serious guy with this project. Please don't feel like this is a "dreamer post". Your help will be deeply appreciated and I'll be happy to post pictures as this progresses along.

Thanks and I look forward to any offerings.

All the best,

Chad and Kalli

LongRifles, Inc. (edited)

Re: 78/81 Honda Express buildup help request

looking forward to this, please post pics and info as you go

Re: 78/81 Honda Express buildup help request

chad dixon /

Will do Chris. First though I've got to get the parts situation squared away.

Soon I hope.

Re: 78/81 Honda Express buildup help request

You need different bikes.

Re: 78/81 Honda Express buildup help request

chad dixon /

It's kind of the point. The fact that these aren't "mainstream" for hot rodding is why I find it attractive.

Under dogs. . .

Re: 78/81 Honda Express buildup help request

No, it's the fact that doing exorbitant amounts of work to them will not net you a result that another bike could. Call it a faster diminishing return, I would call it a waste of time.

Re: 78/81 Honda Express buildup help request

Tyler Dead Possums /

I was always under the impression that forced induction doesn't work on a traditional 2stroke, since the exhaust port is open after the intake is closed, so any boost you built goes straight out... Unless the reverb air forces from the pipe keep the boost in?! Idk, I'm no scientist.

I've heard of some specialty 2stroke engines that have a valve controlled exhaust, which would work with forced induction! But have never personally seen one.

Regardless, sounds like you got some cool projects in the works!

Re: 78/81 Honda Express buildup help request

chad dixon /

I'm aware of the same. with no mechanical means of retaining the boosted intake charge, it pees right out the X port.

I've considered a rotary valve of sorts to manage this. I've also considered just scrapping it and sticking a bottle on the thing instead. (bombs are cool too right??)

Re: 78/81 Honda Express buildup help request

chad dixon /

Were getting off track here. The point of this is to request assistance with parts selection. -Not debate whether these bikes are the best option for what I'm interested in doing.

As stated, I own a well equipped machine shop. I'm not opposed to using it to get what I'm after.

Parts are what I need. Wisdom, although appreciated, isn't.

Re: 78/81 Honda Express buildup help request

chad dixon /

Just ordered a pair of these. It begins. . . :)

Re: 78/81 Honda Express buildup help request

Tyler Dead Possums /

I believe Honda Express and Honda Hobbit have the same stud pattern and stroke, so the top ends would be interchangeable.

I'd say grab a 70cc hobbit kit, 19mm or bigger carb, and a nice expansion chamber exhaust. Since you have access to machining tools, you should be able to make your own intake and modify any exhaust to fit the bikes.

Re: 78/81 Honda Express buildup help request

Moby Express /

You're going to need to use that machine shop and make new gears for the final drive in order to get past 48ish mph

Re: 78/81 Honda Express buildup help request

chad dixon /

Would a Hobbit stuffer crank fit in the express cases?

Re: 78/81 Honda Express buildup help request

Moby Express /

crank should "fit" but it'll need some love on the ends to make it work

Re: 78/81 Honda Express buildup help request

chad dixon /

What'I'm kinda hoping to do is be able to fit up a clutch disk setup from a Kart. Then I can go straight to chain/belt and have almost infinite range for speed/acceleration.

Re: 78/81 Honda Express buildup help request

chad dixon /

Fair enough! Love I can handle. Sweet! Thanks.

Re: 78/81 Honda Express buildup help request

chad dixon /

K, much as I'd like to continue chatting about this, I gotta get to work.

More later.

Re: 78/81 Honda Express buildup help request

The final drive is lubed by the oil in the chaincase so a dry kart clutch is out. You see now how by design thos bike is going to make unnecessary hurdles for you?

As mentioned the final drive ratio is going to the end of your party when the bike simply won't go any faster no matter how much chain snapping power you manage.

Re: 78/81 Honda Express buildup help request

chad dixon /

Just got off the phone with a good friend of mine. Danny Fitzmaurice. Danny owns Zipper cycle out in Maryland. He's gonna take care of porting the Athena jugs. They'll arrive probably Saturday, then they go to Maryland.

I'll be sending them out to Millenium Tech in WI afterwards to be recoated with Nikisil. Porting is sure to nick the edges. I imagine the ring won't like that much along the port openings.

More to come!

Re: 78/81 Honda Express buildup help request

If the guy has a clue about porting it won't touch the edges in any way that will need re coating. Send him your heads and have him cut a squish band into them, they will not clear the larger piston domes.

Re: 78/81 Honda Express buildup help request

chad dixon /

Thanks Ryan, will do.

Re: 78/81 Honda Express buildup help request

If you want to get crazy you should put a stroker crank in.

Re: 78/81 Honda Express buildup help request

chad dixon /

Who offers a stroker for the Express?

Re: 78/81 Honda Express buildup help request

I feel like this thread is just going to be an absolute mess.

Sorry OP, but everything you've asked/said had been answered many times, or the information is already out there. These aren't really under dogs either. You'd need to build a beta, solo or solex to be an underdog.

Yes. During your intake you will lose fresh charge through the exhaust port. Yes, the resonance of the pipe will knock it back in. Different lengths/chambers will determine when the power band is at its peak or how long it occurres. Read up on expansion chambers. Don't need to be a scientists, just read up.

If your using an Athena kit there's no need to stroke the crank. It's designed for a stock stroke.

Re: 78/81 Honda Express buildup help request

chad dixon /

Fact:

The only guidance I've asked for is parts interchangeability. What made for this will fit on that.

That's it.

I have a good understanding of internal combustion theory and execution. A very good one. I'm attempting to be polite because I don't know the depth of the gene pool here.

What I don't need is keyboard crew chiefs telling me how much time I'm wasting by venturing into this. THIS is what I AM doing. I don't need the lecture (2x now).

Point 1:

The assumption regarding an external clutch setup being impossible due to the wet sump lubrication requirement of the rear end. Think I haven't thought of this? As stated, I own a very well equipped machine shop. The drive train/swingarm assembly also serves as the left side of the cylinder case right? Right? So what's stopping me from replicating that part from a length of forged billet 7075 and converting it into a dry clutch drive train?

Nothing. It's a couple hours on the computer to model it and a few more to program it. My Kitamura VMC will make quick work of this. Trust me.

This isn't my first rodeo with engines or bikes folks.

Not trying to be a pompus dick here, but I get so sick of lectures telling me what I can and cant do. Live in your own box if it suits you, but don't expect me to squat there with you.

To the rest who've been helpful, thank you. It's appreciated.

Enjoy your weekend.

Re: 78/81 Honda Express buildup help request

Moby Express /

If you do make a new side case. make it longer. The rear wheel with a nice 2.75x14 tire barely fits.

Re: 78/81 Honda Express buildup help request

chad dixon /

Thanks. Will consider that.

Re: 78/81 Honda Express buildup help request

Tyler "Gary" Dead Possums Wrote:

-------------------------------------------------------

> I was always under the impression that forced

> induction doesn't work on a traditional 2stroke,

> since the exhaust port is open after the intake is

> closed, so any boost you built goes straight

> out... Unless the reverb air forces from the pipe

> keep the boost in?! Idk, I'm no scientist.

OP, I read this and thought I read you had typed this! My fault.

It's mopeds, so do what ever you want. Get wild I guess.

Re: 78/81 Honda Express buildup help request

chad dixon Wrote:

-------------------------------------------------------

> http://cdn2.bigcommerce.com/server5100/v2bmlqo/pro

> ducts/722/images/1315/Honda_Hobbit_PA50_Athena_70c

> c_Cylinder_Kit_009300__91341.1405435680.1280.1280.

> jpg?c=2

>

> Just ordered a pair of these. It begins. . . :)

Good choice, keep us updated.

Re: 78/81 Honda Express buildup help request

Remove the oil pump. Make a block off plate. Premix fuel.

Boysen dual stage reeds. Cut the middle spacer out of the reed block and enlarge the port.

Mikuni VM 20 with high flow air filter.

If your making a custom intake, you already know its value.

Athena is a great choice of BB kit.

The Hobbit and Express are very similar animals. I have both. The drivetrain is the main difference. I would bet that a a Hobbit HPI setup could fit or be made to fit. CDI too.

There are fewer pipes that are made specifically for the Express. You could get away with most Hobbit pipes with se level of modification. One of the best is called the MLM H95. Like I said though, it will require mods.

I'm not the biggest moped expert, but that's my experience. I've never attempted any drive train modifications or forced induction methods. Hope that helps.

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