How To Train Your Night Furry

FurryOnTheInside's first build, part deux:
Dawn Of A New Error

There was me thinking I would be working on the second build shifter mountain bike by now haha. I'm just getting the Night Furry tuned up to hopefully take it on a proper long distance trip. I can hear the beaches calling me from the west.
I have collected a few parts to hopefully improve the performance and reliability of the Night Furry (touring MB) while it was winter and while I was busy with boring non bike stuff. I have started getting the bike together again in the last week or two, though.
So here's a few of the things I have been working on..

Firstly I needed to upgrade my front brake. Awesome stopping power just wasn't enough. I needed a black lever and caliper haha. No but seriously, I wanted a similar shape lever to the rear brake, so I got this Magura MT2 which is not too dissimilar to the Magura HS33 rear lever.
View media item 61342And the caliper is quite nice too. A bit chunky perhaps but seems to be good quality. I fitted it to the adapter that I had previously had to cut down for the Shimano Deore caliper to fit properly with the 220mm Hope rotor. The MT2 is different though so I needed washers to get it spaced out enough.
View media item 61311I thought I might as well buy a new adapter, that hasn't been cut down, so I won't need the washers. But then I checked how wide the pads actually are and the MT2 has a wider pad surface, needs a wider brake track on the rotor than the Deore, so I had to get a new rotor too. Not that it wouldn't have worked, but it's best to do things correctly. :)
So I got this Hope rotor that is newer and wider, but it is also a floating rotor and slightly larger diameter at 225mm
View media item 61319It really is quite huge. I'm used to seeing the 220 now so it looks normal to me but everything else looks puny!
View media item 61313
So that's brakes sorted, next thing is I got a new narrower handlebar because I really wasn't getting used to the 720mm mountain bike bar. The new one is 610mm but it still has room for all my controls, just doesn't have a load of unused space and I can put my hands more under my shoulders so I am more comfortable on the bike for long periods of time, which is what this build is all about after all.
I really need to have music when I'm riding for hours, too. A bit of kickass neuro or some thumping goa to smother the engine noise lol. :p There was room for my little 10W Bluetooth stereo speaker with a "handlebar extension" to support it. I could add lights to that extension too if I don't put them elsewhere.
View media item 61318
I want to be able to choose/ change to the best gear ratio while I'm out on the road, and so I need to have multiple sprockets mounted together on the left side and some kind of system for chain tensioning that will allow bump starting. I have not got that up and running yet but I have made a start..
I saw that there was probably room to squeeze two sprockets in behind the spider that I put behind the rear rotor mount, meaning that I should be able to get the second largest sprocket to line up with the engine output sprocket (10T).
View media item 61314It was tricky getting them to fit.
View media item 61317I had to change the M10 bolts and nuts to proper chainring nuts that are thinner and source some M8x0.75 bolts, then shorten them as there was only one size (40mm) and make some 15mm long 10mm OD spacers. I was able to get these parts all in stainless steel. Took ages to do it neatly.
View media item 61316I did have to use a few shim washers to get the sprocket stack spaced just right, hopefully I will keep them oiled enough to not rust a lot. Most of the washers I used are stainless though, but those only come in 1.25mm which is a bit limiting.
View media item 61334Anyway I managed to get four sprockets mounted. 38T(steel) 40T(Al 6061) 42T(steel) 44T(steel)
There is apparently no steel 40T available in the 104mm BCD standard.
View media item 61331To make the chain bend to all four sprockets (actually three of them probably wouldn't be a problem anyway, the way I've lined it up) meant switching from the 1/8" (#410) bmx single speed chain to a 3/32" multi speed chain. Actually what I chose was the KMC X9-93 which is an even narrower 11/124" nine speed chain.
Such narrow chain means that the front sprocket had to be even thinner, but that gave me the opportunity to grind it on the right hand side again, and thereby move the chain line further left. I had ground it down to 3.2mm (0.120") for the bmx chain. This time I went to 2.2mm with the teeth slightly tapered to 2.0mm to help ensure that they engage smoothly.
View media item 61322In order to do this safely without burning or ripping off fingers I mounted the 10T on a bamboo cane and secured it with a softwood wedge hammered in. This meant I could hold it against the bench grinder and rotate it easily.
This technique was even more helpful for the second stage, though. I put the cane through a hole in my little folding workbench and was able to rotate the cane from underneath the table top with one hand while using the rotary tool with my other hand. Total control and safe too. :)
View media item 61321While I had the sprocket off I relubed the bearing on that side of the clutch shaft (it didn't need it but best to do it now) and took a photo of the epoxy chain retainer I made during the initial build.
View media item 61320
I'll have to see if I can make the four ratios system work with an automatically adjusting tensioner too. It would be quicker to change ratios if I don't need tools or even really touch the tensioner/s at all. I'm hoping this Shimano Zee (Shadow Plus) derailleur will do the trick. As this is Shadow Plus technology it has the one way clutch drag system, meaning the resistance to allowing chain slack is much greater than the tension it applies. Science! :p
View media item 61339
While I was working on the drivetrain I thought I would upgrade the rear derailleur for the pedal chain. Acera is okay, functional but not great, old tech. I had this Shimano SLX Shadow derailleur for a while now. Fitted it to the bike today and I'll dial it in when I have the chains back on.
View media item 61341
Lets see what else am I doing? Okay next is the exhaust muffler. It is nice and quiet with the long soft silicone hose added behind the muffler, but I worry that it adds restriction to the flow of exhaust gasses. So today I cut half an inch off the internal side of the stinger and I drilled the lower baffle in the muffler even more to flow faster. I stuffed a steel scourer inside just so it hopefully isn't any louder. I had already opened the baffle a bit, but this time I went further and drilled five 8mm holes.
View media item 61338View media item 61337
When I took the muffler off the engine the exhaust gasket crumbled and left a rough layer on the exhaust flange and the rest on the cylinder. I was expecting trouble but not quite this.
View media item 61335I'm wondering what to replace it with. Could I just wet it with oil and clamp it back together for now? I expect not.
I have a silicone brownie baking tray, hoping that will work. Idk.
I probably have a spare stock gasket but I would like this problem to not happen again so I'll give the silicone a try.
View media item 61336The other thing was the RED Loctite completely disappeared from the threads of the left stud hole in the cylinder. Somehow. That one is puzzling because I know that I put plenty in the hole and on the stud. I might try the blue when I put it back together but this means I can't trust any of the red loctite I have used on the engine, so I can expect to be pulling out the wrong parts when I unbolt things that have red one end and blue the other, like my exhaust studs did. :/

The only other real change was that I got around to changing the jet size in my NTTC stock carb. I got a Delorto DO style 5mm jet kit from KMT (English company, Swiss machines) in sizes from .65 through to .74 so I have put the .68 in for now. I noticed that the new KMT jets are 1mm shorter than the stock jet, so I have bent the prongs on the carb's needle valve (fuel inlet valve) upwards by 1mm to make up for the difference. I'll be testing soon.
View media item 61323

Well that's it for now. I might take a photo of my temporary air filter box tomorrow. It's super junky, but hopefully will increase my stealth a little bit. :)
 
Last edited:

FurryOnTheInside

Well-Known Member
Joined
Sep 23, 2013
Messages
3,926
How do you plan to run the derailer on the wrong side?
Okay, sorry took a little longer to get it ready for a photo. Things are rarely as straightforward as you expect. I had some trouble finding the right length bolt for the B screw and had to get the rotary tool out.

I am running the Zee derailleur as a tensioner, not as a derailleur, so I'll just type Zee instead of derailleur lol.

View media item 61343
The Zee has some advantages over other types. Firstly this Zee has a short cage, so it has less freedom of back and forth movement and the spring is not fighting such a long lever. This should help when it comes to bump starting the engine in the smaller sprocket ratios.
But the really big advantage is the "Plus" in Shadow Plus technology. The Zee contains a one way clutch drag system which can be switched on and off to allow me to pull some slack and change sprocket. This drag will hopefully be enough to make the bump starts work quite smoothly without creating a lot of slack in the upper run of chain. I have to see if I can increase the drag to practically fixed, as that would no doubt be better.
View media item 61344
View media item 61346The mech hanger for the Zee had to be bolted fairly high up on the engine sprocket cover in order to clear the pedals. A lower engine, or a cruiser build, and this might not have worked at all. As it is I'll probably catch my shoe on it but I had to try. :)

View media item 61347The stub of an old gear cable fixes the lateral position of the Zee. It is about a micron away from its maximum inboard movement. It is not limited by adjuster screws, it's at the limit of the parallelogram.
View media item 61345The B screw sets the height of the Zee. It stops the lower run of chain touching the upper run of chain.
The trouble with the B screw was that even if I use a very long bolt it will miss the B screw stop with the Zee pulled into this shape. So I had to put nuts on to fatten it, and then take them all off and use my longest bolt and then chop that off. A lot of two steps forward two steps back, unscrewing bolts and tiny nylocs lol :rolleyes: but I got there in the end. :)

View media item 61348Now I have to figure out where to put the rear pulley wheel and what length to cut the chain. Then after that, figure out the best way to mount the chain slider for the upper run of the chain.
 
Last edited:

dmopedMA

Active Member
Joined
Apr 14, 2017
Messages
176
It's looking good, keep us posted!

I see a problem when you are running and you try to "motor brake", the Zee will extend the chain and maybe problematic on the top part... a freewheel on the sprocket will solve it but you won't be able to bump start it... let's see how you deal with that :)
 

FurryOnTheInside

Well-Known Member
Joined
Sep 23, 2013
Messages
3,926
It's looking good, keep us posted!

I see a problem when you are running and you try to "motor brake", the Zee will extend the chain and maybe problematic on the top part... a freewheel on the sprocket will solve it but you won't be able to bump start it... let's see how you deal with that :)
Same goes for any of the spring tensioners that other builders are using. Except this will have a lot more slack to pick up and potentially release during the bump start and engine braking.
I try not to do engine braking and I'm not too worried about that but I have to hope that the one way drag system, and the chain slider, will handle the bump starts.
I have deliberately used sprockets that are close in tooth count so there's only six teeth (3") of potential slack when the chain is on the smallest of the four sprockets.
 

FurryOnTheInside

Well-Known Member
Joined
Sep 23, 2013
Messages
3,926
It's looking good, keep us posted!

I see a problem when you are running and you try to "motor brake", the Zee will extend the chain and maybe problematic on the top part... a freewheel on the sprocket will solve it but you won't be able to bump start it... let's see how you deal with that :)
View media item 61351
I have increased the drag setting on the Zee to as much as I dare. The on/off lever is plastic so too much would risk snapping the lever when I operate it. The lever is connected to a cam which engages (tightens) the steel band which is like a band brake. The ratchet means this only drags in the direction the chain is pulled. I think the drag is tight enough now that it is practically locked up when the lever is in the "on" position and it will hopefully take the strain of bump starting the engine without allowing the upper run of chain to go slack. :)

View media item 61356
I fitted a chain slider (RSP chain controller) at a funny angle that means it swings in the direction that the chain has to be moved when I change rear sprocket. The 11/124" chain fits just fine even at this odd angle, it seems to function well, it just looks wrong. I considered making a big cone shaped chain slider to catch any slack chain but I think or hope there'll never be a problematic amount of slack chain with the Zee locked up as it is.

View media item 61357
I got my fixed pulley on the lower run of chain too so it is lifted over the chain stay even when the chain is on the furthest left (38T) sprocket.

The issue still unresolved is that the upper run of chain doesn't clear the seat stay of the frame when it is on the 38T. It isn't way off but it's touching and would make a hole in my frame pretty quickly.
I could make the sprocket stack narrower, but really there isn't much room for that. The chain only clears the next largest sprocket by 0.1 or 0.2mm so that narrowing the gaps between sprockets could potentially cause ghost shifts.
I don't think that shimming out the rear axle to force the stays apart will do it either. The difference at the point where the interference is occurring will be less than at the axle, so I'd have to shim out ~5mm to make 2.5mm more clearance.
The most practical option, even though it is something that I would hate to have to do is actually dimpling the seat stay. I'll have to make some special jaws for a vice so that I can do it carefully and only make the dimple where I want it and not crush or damage the whole tube. This would be no problem on some wider frames but the Specialized Sirrus is a "hybrid" which is shaped rather like a road bike frame with the stays swept in quite close together.

For now I plan to test with just the largest three sprockets. 40T, 42T, 44T is quite a decent and useful choice of sprockets anyway. :)
I have some fine tuning to do on the front disc brake and fender and I have to fix and finalise the new tailpipe muffler design but I'm close to going for a test run now.
Supposed to be a heatwave here this week! :cool:
 

FurryOnTheInside

Well-Known Member
Joined
Sep 23, 2013
Messages
3,926
I just did a first test of the new features and got two interesting results. As this is science I would not call them good or bad results.

View media item 61362View media item 613521.
The exhaust system was just as noisy as before I added the extra muffler, there was a small amount of leakage at the gasket which I believe was the cause.
I concluded that the Teflon coated fabric (oven liner) is not a suitable exhaust gasket material.

Next I will try silicone baking tray! :D

2.
After five successful bump starts there was a derailment at the front sprocket which somehow also caused the chain to escape the cage on the Zee. The chain was apparently not damaged.
I have concluded that the sprocket cover needs the epoxy filling closer to this narrower nine speed chain, that it was not okay to leave it the same as it had been when I was running the bmx chain.

I will empty the fuel tank or just remove it, drain the carb, and put the bike on its side to do the epoxy. I will also look at moving the chain slider forward or adding another chain slider close to the front sprocket. :D

View media item 61364

I also still need to make some side covers for the engine, to make it more discreet.
 
Last edited:
Top