8 speed 79cc revival

[xXNightRiderXx]

Ok, I got the wheel off the bike, and it turns out it's the pawls that broke. It freely turns to the rear, and catches to the front when turned by hand. I got the axle off, and need a 12mm allen wrench to remove it. I'll post a photo of the damage when I pull the thing off.

 

[xXNightRiderXx]

Ok, I got the wheel off the bike, and it turns out it's the pawls that broke. It freely turns to the rear, and catches to the front when turned by hand. I got the axle off, and need a 12mm allen wrench to remove it. I'll post a photo of the damage when I pull the thing off.

I was wrong. It wasn't the freehub itself at all. It was the threads in the wheel itself holding the freehub to it.

Time to build myself a wheel that I can actually repair, instead of one that I have to replace every time something goes wrong.

 

[xXNightRiderXx]

I found a double wall mtb rim with a welded joint and eyelets, a mtb hub with 6 pawls, no threads in the hub to strip out, and thanks to mbrebel, 12ga spokes measuring 254mm. Not only does this mean I'll be able to repair the thing when it fails, it also means that my bike can accelerate and stop faster because there's less mass to impart inertia to and remove it from. Who knows, I might even be able to go faster.

I think I'll also add a 203mm brake rotor to my rear wheel. Interestingly, my current system is 180mm with a 160mm is to post adapter, and it'll be 203 with a 180mm post to post adapter.

PS: this will be a 36 spoke setup, front and rear.

 

[xXNightRiderXx]

I'm also planning on building me a trailer I can use to haul my mtb or my gas bike around, depending on what I need to do.

 

[xXNightRiderXx]

Ok, so here are my plans for the future:

Rebuild the battery box for more efficient use of space and better wire routing.
Port and polish, with another mild head sanding
Build new wheels
Build a tow trailer for my mtb
Craft an engine cover to block mechanical noise
Have a new exhaust pipe with a glass pack muffler made
Buy and install a one wire alternator
Buy and install the bored and reworked carb install from agk
Buy and install the agk flywheel
Buy and install a new spark plug for more efficient burn
Get a vin, insurance plan, and registration
Buy and install a longer intake for more low end power
Avoid losing my bike to inattentive or malicious drivers. (Ongoing)

I shall post photos as soon as each item is accomplished.

 

[xXNightRiderXx]

I probably could have made this better. I'm the one who wrote it, and after all this time of not even thinking about it, I'm having a hard time deciphering it. So, I'm going to streamline my wiring representation once I've redone my wiring. And yes, I do need to redo it. It's a rats nest and barely fits into a 1" split loom.

Anyway, I'm going to get some tools and parts month after next, which is after I pay my legal fees. Gonna get those wheels built, and my cylinder head spiffed up. Gonna angle my valve seats, lap my valves, port and polish, and do some more sanding for more compression. Then I'm gonna install that flywheel, then take a center punch, and pop out that blasted governor. I'll be free and clear to do other mods after that. At some point, I may decide to do a cam upgrade and 22lb springs, but until then, it's on the back shelf. Has anyone ever spun these engines up above 8k for an extended period? Maybe close to 10k? If I do a shorter air intake and bigger cam, that's where I'll want to spin it up to. Between 6k and 9k. Alternatively, I'll keep the small cam and a long intake and keep the power around 3k. I would like to advance my cam timing just a few degrees. Any way I can do that without paying for a custom cam?

 

[xXNightRiderXx]

I found a company that has done custom cams for this engine: performancecams.com

$135 for a custom welded profile. What I'm thinking is offset timing, but maintaining the intake opening position and making the closing position a few degrees later, and maintaining exhaust duration, but moving open and close a few degrees later. The idea behind this is the later the intake stays open after bottom dead center, the more the intake velocity can be used to charge the cylinder, and the more compression I can get. The later the exhaust opens and closes, the more the exhaust can be pushed out and replaced with the intake charge. The intake will be opening just before the exhaust closes to take advantage of scavenging. If I'm mistaken, tell me straight up, and let me know about anything that would be better.

 

[xXNightRiderXx]

Alrighty! I got a class action payment which I used to purchase an alternator, two #35 20t sprockets, a pulley for the crankshaft, and a set of glass and alloy mirrors that won't shake as much as these damn plastic ones. They even have a much higher range of adjustment to get the perfect angle to properly see behind me.

I have the new hubs on the way, which have 6 pawls, and the teeth the pawls engage are on the hub itself. The freehub body pulls away from the hub, so there are no threads that can be stripped away. Next step: Rims and spokes, 93 octane stickers for the tank, carbide burrs and sanding spirals to do some port work, and a set of valve seat cutters for a 3 angle seat job. With the intake, I won't use the sanding spirals much. I'll just let the burrs run around the intake port (light pressure with the Dremel, no resistance against the rotation of the burr), lightly using the sanding spirals to remove any peaks obstructing the charge. This will produce a rough finish in the intake port to keep the charge atomized without reducing the amount of fuel and air entering the cylinder. Any objections to this method?

I'm also thinking of turning the engine around and using an idler sprocket system to reverse the jackshaft rotation. This will allow me to mount the engine level and get optimal cooling, leg clearance from the exhaust, and oil level. I will also be able to route the exhaust down and back, keeping it away from the saddle and my thigh. Not sure how easy that will be, however, I'm sure I can do it, since cars and cameras did it. I'll just be using nuts and bolts instead of welds.

 

[xXNightRiderXx]

No objections? Alright then, I'll get goin on this. The pulley, hubs, mirrors, alternator, sprockets, and chain have all arrived, but it turns out that I left the stock jackshaft plate in the weather too long, so the shaft and most likely the bearings are all rusted and shot now. Time for a new one. Screws were falling out of it anyway. There are 3 things I will need to do to make this stage successful:

1: I will need to fabricate a mounting bracket for this alternator. It's a beast of a thing compared to the size of the engine. The steel I use will have to be at least 1/8" thick to support the weight, and one bracket will go onto the truss rod mount and twist to mate up with the alternator. The other bracket will bolt onto the engine side cover and bend around it, preventing the bracket from rotating. There won't be any adjustment for tension here, so I'll need to make the belt a little bit tight at first. It'll loosen up in the first couple hours of operation, and then I can tighten it with an idler pulley mounted somewhere.

2: purchase a new jackshaft plate to relocate the clutch. This is so I can turn the clutch with the two sprockets I bought, making room on the crankshaft for the pulley.

3: build the new wheels with a minimum of 92% max tension in the spokes. Because they're 2.6mm spokes, I will also need to drill out the hub flanges to 2.8mm and countersink the holes. This is why I bought MTB hubs. They can handle that extra load on the spoke flanges without breaking. The hubs I bought seem to be based on the older Industry 9 hubs, which are top of the line when it comes to durability and speed. High speed sealed bearings will help reduce the rolling resistance, maximizing acceleration and top speed. These wheels will also be lighter than the mag wheels, and so carry less inertia, making it easier to slow them down.

As far as turning the engine around, it's not feasible. To do so would require shifting parts around in a way that would create greater load on one side of the bike, where currently, the load is spread in a diagonal. That one sided load concentration would increase the risk of bending the frame under the torque of the engine. Cars and cameras did it in a way that would keep the load in a diagonal distribution, where I have no such option if I'm to keep using the cassette. Yes, I understand that on most builds, the load is concentrated on one side, and it works fine, but that diagonal force distribution spreads the load throughout the frame, rather than one side of it, maximizing longevity. That's my aim.

I will be replacing all of my chains, and likewise replacing my cassette. The cassette shows wear, and the chain has slipped off the inner chainring and jammed into the nuts, likely causing damage and stretching the chain. The chainrings show no wear. I will search for an ebike compatible cassette, since they are built a bit more rugged and will resist wear better. All of my chains have become dirty, and have probably worn a bit, so I want some known reliable chains and will lubricate them using a dry wax based/Teflon based lubricant. This keeps the dust off, preventing wear so long as I keep it out of the weather. If I take it out in the rain, I'll lubricate them using the proper lubricant.

I will also be disassembling my clutch and lubricating that as well, keeping all lubrication away from the bell and pads. Until I get more power, I'll stick with the 42-11 cassette. Once it starts outpacing the low gear range, (e.g. 2 seconds or less before full sync) I'll swap it out with a 36-11 cassette. That will ensure that I can reach higher speeds per gear and maintain clutch sync time. It is currently at 3 seconds.

Once I get everything all together and working well, I will disassemble the bike and repaint the frame with a metallic red paint and a gloss clear enamel, after fully stripping all paint off the frame using a citrus based stripper.

Thankfully, my seatpost is long enough that it prevents the seat tube from being crushed, though I will probably replace it with a slightly longer one just to be safe.

 

[xXNightRiderXx]

My hubs have arrived, and I've got to say, they're even better than I expected. I'll be running 14ga up front, and 12ga on the rear. Cuts down on cost and machine work. I've already got 36 holes to drill out for the 12ga, I don't need 72. As it is, I'm lucky I have a friend that has a drill press, so I can get a nice, straight cut. If he doesn't have a 2.8mm bit, I'll be getting my own hss double cut bit. I'll also be using a pair of wooden 1x2 blocks to prevent damage to the finish of these hubs.

Time to buy the rims and spokes, and a couple pieces of scrap steel plate.

 

[xXNightRiderXx]

Alrighty, I've got the new wheel/hub drilled and laced up. time to make it run true and tight. It looks great.

 

[xXNightRiderXx]

Alrighty, a few updates to lay out here.

1: I got one wheel finished and the other going on the truing stand tomorrow. I matched the polished spokes on both wheels, so they look like they belong together.

2: Now that my wheels are taken care of, I'm going to be focusing on performance. I'm going to finally purchase the billet flywheel, a manifold kit, a carb, and a new spark plug, along with a few cheap ones for chops. Unfortunately, removing the spark plug involves removing the engine, so it's going to be a hassle doing chops. If anyone's got another method for checking mixture, lemme hear it please.

3: Once all my performance stuff is taken care of, I'll be redoing the wiring. I'm going to use motorcycle harness plugs and 2 inch split loom to make maintenance easy. I'll also be rebuilding the box, not out of bloodwood, but out of mahogany. This is probably the most consistent thing I've said lately, lol.

4: A full strip down and repainting is in order as well. I'll be stripping the frame down to bare metal (protecting the steel from oxidation with some bacon grease until I'm ready to lay down the primer if I don't have it ready beforehand), laying down some rust preventing primer, the color coat, and finally, a durable clear coat, maybe a thin layer of clear epoxy over that too, idk. Either way, this bike is going to get a makeover. This, of course, is the final stage because I want everything working, easy to remove and maintain, and aesthetically not clunky before I paint literally everything except the box, the wheels, handlebars, fork, headlight, turn signals, you get the point. I'm torn between a metallic emerald or a candy apple finish. On one hand, the red accents on the bike would pop against the green and draw the eye to the bike, but on the other, going red would reduce the contrast and make everything seem blended together, and a little more boring.

Anyway, the reliability stage is almost complete. I just need to replace my fenders (one got mangled and the other is in bad shape), tires (2 year old rubber that's just been sitting for most of its life), and my grips (need more grip on the grips). I have one more thing to add before I go: my gearing is optimal for my purposes. With a maximum possible top speed of 105mph, a 5th gear speed of 65, and a first gear speed of 16, all at 5800rpm, this bike is well geared for both range and torque. I calculated the equivalent cadence at 397rpm at the chainring and used a bicycle gear calculator to reach these speed quotes, which takes into account the wheel size.

The problem is this: do I have enough power to even realize my 5th gear speed, and can my frame handle the power needed to reach that speed? I'm fine if 45mph is all I can do, I'll just build another bike that can handle that design speed and more.

This, my motorbicycling friends, is my 4 stage plan for building any bike: Get it working, get it roaring, get it lit up, get it looking good.

Thanks for reading another NightRider post, and keep the rubber side down.

 

[MotoMagz]

Sounds like a nice project. Seat post may not be enough to stop frame from collapsing. I’ve slid a sold piece of 5/8” round bar in a older frame to prevent this. Get some pictures up!!! Good luck!

 

[xXNightRiderXx]

Sounds like a nice project. Seat post may not be enough to stop frame from collapsing. I’ve slid a sold piece of 5/8” round bar in a older frame to prevent this. Get some pictures up!!! Good luck!

It's been a pain and a cash guzzler, but it's fun. I've had this engine mounted up for over two years now, and I've not seen any sign of the seat tube buckling. This is a 90s MTB, so they were less concerned about weight than durability, so the tubes are naturally thicker and stronger.

Here's some photos:

 

[xXNightRiderXx]

Ok, here's another update. I just had my final drive chain break, and found out that the nuts bolting the chainrings to the freewheel are all kinds of mangled because the jumpstop, having a plastic clamp, is failing to do its job. I'm going to replace that plastic clamp with a steel one so it won't move around anymore. I'm also going to replace the bolts and nuts while also adding space between the chainrings so the chains have zero chance of binding if one of em comes off.

It's also quite cold here right now, so my engine experiences a bit of throttle lag until it warms up, not sure why that is. I am running a little lean to handle our summer temperatures though, so it could simply be the increased air density. I should probably think about using a choke on my intake during our winters.

I'm going to buy agk's intake manifold kit and have it welded so the carb is facing straight out of the block, so I can keep using my air filter.

Oh, I also bought some Finish Line ceramic based wet lube for my chains, so they'll shed water like a spillway. I also bought some White Lightning Clean Streak degreaser, and that stuff eats through my super sticky motorcycle chain lube, which is made to stick to the chain like flies on food, so I'm going to give all three chains a solid cleaning and relube. I'll probably have to lube my sealed bearings too, since everything's been out in the weather this whole time.

I suppose reliability is still something I need to figure out.

Anyway, thanks for reading another NightRider post, and keep the rubber side down.

 

[xXNightRiderXx]

I just tested my engine with the choke on, and hoo boy, it's got strong low end, but can't spool up very well. I'm going to increase my jet by one size.

 

[xXNightRiderXx]

Hey guys, I found a thing:

Amazon.com

It's supposed to be used with reed valves, but I figured it would work with my engine if I used my two stroke intake manifold. 19mm 4 stroke carby, here I come.

Oh, I got the front wheel all laced up too, and both are now mounted to the bike. Apologies for the image quality, it was a photo taken with low battery using a porch light at night.*

* Cropped to make two separate photos since the original was too large to upload

 

[xXNightRiderXx]

The bike is out of commission once more, though I can quickly get it running again. I bent one of the sprockets on the cassette, so I pulled the wheels off to replace the whole cluster but then decided to use them on my MTB for efficiency. I'm going to put them back on the bike tomorrow so I can ensure proper chain alignment. I'm also going to swap my two chainrings to have the jackshaft chain closer to the frame and the cassette chain centered on the cluster better. Thankfully, these adjustments are free except for the nuts and bolts holding the chainrings together.

 

[xXNightRiderXx]

Alright, I finally mocked everything up. What you see in these photos is not how it will look when finalized, but will give a general idea. The alternator is up front, though I could potentially mount it under the engine. However, doing that means I would be worrying about oil getting on it and not only making a mess, but also ruining the alternator.

The clutch will be driven by 23t sprockets for a 1:1 ratio between the input shaft and the crankshaft. It should have plenty of torque to engage that clutch at 1800 rpm, but if not, I will have to wait until agk has their flywheel back in stock so I can increase the engagement rpm. All that would be is swapping the input 23t sprocket with a 28t.

I did this mock up so I can figure out where I need to drill and mount brackets. For the threaded mounting hole, I can probably just use 1.25" clamps and connect them with a thick aluminum bar. For the belt tension, I'm going to drill and tap two holes to mount a tensioner on the transmission plate. This should ensure a constant tension once the belt has worn in. For the drive chain from the clutch, I'm going to buy a #420 x ring chain and set it's length before I cinch down the transmission plate so both it and the #35 transfer chain are properly tensioned.

As for the exhaust: I found a worm gear hose clamp that will slide over the braided section. I'm hacksawing off the expansion chamber section to get rid of that excess back pressure. The muffler itself provides plenty as it is.

Of course, before all of this is put together and finished up, I'm going to tear it all apart and clean every last piece with some degreaser, a pressure washer, and a stiff brush. Then I'm going to apply some heavy oil to every surface that requires lubricant and put it all back together. I'll spray my shafts with some light oil to protect them from corrosion.

Anyway, here's the photos:

 

[xXNightRiderXx]

Ok, so I took a hacksaw to my exhaust pipe today to get rid of the expansion chamber, and decided to measure the inside diameter of my pipe... To my chagrin, it was 4mm under the size of my exhaust port at 16mm. I will be trying to find a 22mm pipe to replace it with and bending it to flow along my desired path, then welding everything together. Shouldn't be too hard with a 1.5mm wall thickness.

I also pulled the engine today. I'm going to be pulling it completely apart to clean and inspect it before I do the internal work. I'll give my valve seats a 3 angle grind and lap the valves to it, port and polish the head, cut away the compression release, and I'll do a little oil management trick: drill and tap through the engine casing near the bottom and add a hose barb, then put a clear length of hose on it and cap the other end, making sure to clamp both ends.

When I fill the engine, I should then have a nice visual aid for determining my oil level and I can mark the hose for "full" and "refill immediately," or F and RI. I WILL be finally removing the governor completely on this teardown as well. I'll be waiting to do all of this though until I have the valve seat cutters, the lapping compound and grip stick, the aluminum stuff and bar clamps I need to mount my alternator, the flywheel, the intake manifold and 19mm carb, and finally, a proper exhaust pipe for this engine. I feel like this little thing is pushing 4, maybe 4.5hp even with a super restricted exhaust and a poor intake just because of my compression increase. Doing all of these mods could possibly bring this thing up to 5.5 almost instantly.

Honestly, I'm amazed BBR could get away with a 16mm ID exhaust pipe and call it a performance part. The only engines I can see that working on are the 49cc slowboys, the ones who cruise around at 15mph and 2400rpm.

I would not be surprised if my fuel efficiency actually significantly climbs once I get the intake and exhaust figured out, especially considering how much exhaust gas can remain inside the cylinder with that crappy exhaust pipe. I'm very likely not getting a complete burn because of it and I'm seeing a lot of carbon deposits in the port and pipe, so it's off to the cleaners and the welders.