1920's Tourer, Rat-style

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twowheeledfox

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Oct 21, 2009
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Houston TX
It's finally done! .wee.

See bottom of this post and the next post for pics.

Now the story and specs... started out wanting a full-on shifter build, but as we all know, money doesn't come easily so I built it with the stock kit.

I used a true rat frame, a 1980's ATB frame with a 1970's roadbike fork, stripped and painted flat black. Wheels off a standard 26 mountain bike, chrome-coated steel. Good ATB tires.

The bars are very nice, chrome risers that make it feel like a motorcycle, but not ape-hanger-ish so it's still comfortable.

I made the headlight myself, would have done a really good welding and grinding job but I have none of that in my garage, so I made do. Here's how I made it: a turn signal housing from an old motorcycle (60's or older preferabley as they have longer, more headlight-shaped housings), sawed off the rear cap, removed the bulb and assorted wiring, removed the lens (no orange headlights of course), insert a round LED flashlight and (here comes the hillbilly part) tape it to the housing on the outside. Glue might work better but I didn't try it. Looks like an old rat bike headlight though and if you have parts lying around it's cheap or free.

The kit is a slanthead 80cc, running double gaskets and an autolite plug, I was impressed bu the quality of the kit this time 'round as opposed to earlier ones, the controls actually looked and functioned well, the motor sounds better and is alot torqueier than my previous engine, and even in break-in rpms (just started running her today) pulls nicely. I have the pullstarter and it works well but is a bastard to use when cold. High compression 2-smoker + low-mounted pullrope = hand problems.

I used various motorcycle bits like the mirror etc.

Brakes are front only but high-quality pads on a u-brake made for severe riding, works quite well at 25mph, will have to see about higher speeds.

Seat is an old springer, looks good and well suspension has to be somewhere at 30mph!

Rear rack is very neat, found it on a crappy bike for $7.50 at the Goodwill. Brought it home and with some clever mounting it will hold a full toolkit, spare oil, and bungee cables on one side and a gallon of spare fuel on the other, plus room above-rack for groceries etc.

I am very happy with it, it rides like nothing else really, sounds like well a homebuilt motorcycle and so far has done good on gas even in break-in. I would like to get an SBP expansion chamber for it when I have the cash but the look doesn't fit the 1920's feel going with this build.

Ah finally, the pedals are non-functional due to the pullstarter. Doesn't bother me much as I don't use it as a bicycle and the pedals are just a formality to fend off cops.

They are hooked up with a chain to the single-speed rear wheel though, put a crawler gear on it so if my pullstarter breaks i can use them like a moped's starter pedals.
 

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happycheapskate

New Member
Nov 26, 2009
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Rockwall TX
Wide 1 piece cranks are fairly cheap, about $20-30, and will add the pedal function back to your bike.

As far as hard starting:
Try my secret. I use a $1.00 store spray bottle filled with 91% (even 70%) Rubbing Alcohol. I spray 2 x on the filter and wait a minute, and the bike will crank easier. Storing the bike indoors or at least under a blanket or tarp out of the wind will help a lot too.

Even if you can't pedal, if you can push the bike or roll down a hill, you can prime the engine by using the momentum to coast a few feet at a time till the engine "pops" or starts.
 

happycheapskate

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Nov 26, 2009
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Rockwall TX
I can't see well how you did the front brake. If its a 27" road fork, how did you get a brake to work with the 26" wheel? If its a 26" fractional size road fork, its still not the same size as common 26" ATB wheels. Maybe its the old 26" size with "mountain" tires?

What are you using for a brake? An adapter plate and BMX brake?

PS Walmart sells some heavy zipper bags in the Office supplies aisle for a couple bucks, that are great for tools, will even hold a full size crescent wrench, mini pump, and small tools.
 

twowheeledfox

New Member
Oct 21, 2009
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Houston TX
I'm using a "U-Brake" or old-style sidepull (they were called sidepulls until v-brakes took the name).

It was made for either 26 or 27" so it has a wide adjustment area for the pads. The fork is a 26" fractional I think, not certain as the bike it came from had no wheels. The 26" wheel, which is from a mountain bike fit perfectly, no problems with width even with the tire which is a low-level "hybrid" type ATB tire, ie for the street and trail in intended use.

Thanks for the advice, I will have to try the alcohol for the filter. The pedals are of fairly low priority right now as it is built with a tiny starter crank gear ratio so without disassembling, adding cassettes etc it won't serve much use other than to keep it relatively legal.

The motor runs strong, smokes a bit due to 20:1 break-in ratio but everything works perfectly... except the chain. Went for the second test run this afternoon and the master link clip fell off, couldn't find it, and of course that rolled the chain between sprocket and chainstay on the frame. had to walk 3 miles back home, but better t work these things out now than when it becomes transport i suppose. Apart from the chain issue it's perfect and seems like it will be reliable (well as much as these things can be). My cheap walmart chain breaker broke trying to "un-master-link" the chain, but it had seen years of hard use before that and had just sucessfully torn apart another 415 chain, should I just buy another Walmartopia brand breaker? Or maybe for a single-use setup a hammer, nail and vise?
 

happycheapskate

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Nov 26, 2009
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Rockwall TX
Get a new one from your local bike shop or Nashbar.com. They have really good tools, cheap, under their house brand.

I say its better to carry a real chain tool, and do away with the master link. If you use a master link, keep needle nose pliers and a small pocket knife with you. (the pliers can help you bend the clip as needed for tight fit, and reinstall. The knife can slip it out of place for disassembly.)
 

twowheeledfox

New Member
Oct 21, 2009
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Houston TX
^Thanks.

First off a small problem: Bogging. When the motor is cold, it's hard to start, and hard to keep running. I have to set the idle high and then lower it after it warms up (3 minutes or so until I can return it to a lower idle). When I pullstart it dead cold, I push the tickler about 2-3 times, pull in the clutch and it will crank in about 1-3 pulls. But the moment with force of the pullrope is not longer applied it will stop running. It sounds fine in the 1 or 2 seconds it is running but then just drops off.

When I bump start it, it will bog at throttle for about 3 minutes or so, than it's warm enough to get to about 3/4 throttle and starts bogging again. Went for a 5 mile ride today and even when warm it would bog down at anything more than 3/4 throttle. Cleaned the carb, check the intake and exhaust and gaskets, decoked the head and checked the headgaskets, now I'm not sure if the bogging-after-warm problem was solved but it still bogs at startup.

I am running 20:1 for break in only, and have taken the motor to cruising at 3/4 throttle for a bit. Have been at full throttle but not for anything longer than 15 seconds. The spark has a cocoa brown colour.

In other news, logged 53 (previously) trouble-free miles at an average speed of 20mph. The headlight works well at night also. Very fun. Only used about 1/2 gallon of gas as well. drn2
 

twowheeledfox

New Member
Oct 21, 2009
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Houston TX
Progress update:

The odo shows 167 miles and I've used just over 1 1/2 gallons of gas. Economy should improve even more when I run through the break-in (20:1) gas mix and go to 32:1. Currently the plug is a very dark brown, so once I will be adjusting the carb as well as the mix.

Currently cruises nicely at 18mph and gets vibration-ish at about 22, top speed on the last WOT run was 28. The rear wheel needs alingment after a trail ride so that is part of the reason for lower numbers, next I will be getting a 36t sprocket to lower rpms at about 25-30mph. I don't seriously trail ride with the MB (except for pushing it :lol:) but I occasionally ride on an unpaved and somewhat bumpy road near my apartment. Will the 36T still do this? It is not on a hill and the bumps are small, if constant. Seems like with the motor in the right cadence it could manage it. I also developed a pedal-less "push" technique to help the motor from a stop; now can anyone with a 36t tell me about what speed you need to human-power the bike before letting the motor take over? For reference the bike weighs about 110lbs and I weigh about 160 including gear.

I have decided to update and simplify the bike; getting rid of the rear rack/baskets and buying a 1 gallon fuel tank so I have decent range without a spare fuel can, and moving the tool bag to the front bars or below the seat springs. I am also replacing the headlight. It should look nice, even sporty with the bike tank, new light and no rack on the back.

Anyway just an update. If you could help with the 36t it would be great.
 

happycheapskate

New Member
Nov 26, 2009
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Rockwall TX
Check your hubs! One might be dragging.

Check your fuel filter as well.

I have a 60-70lb (depending on fuel and bags) beach bike, 1x1. It has a 38tooth and 48cc china. I pedal to about 8-10mph. Not hard with a 36x12 or 14 coaster.
If you use a coaster, make sure its cinched up with a good strap, or it could injure you like a track bike.
 

twowheeledfox

New Member
Oct 21, 2009
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Houston TX
Thanks- checked the fuel filter, a bit of rust from the tank had gotten in, cleaned it out, found my rear wheel has a side-to-side lean spot on it, I think spoke tension adjustment on the 6 or so spokes near it should fix it.

Had some fun tonight, rebuilt her as a cafe racer. While I rebuilt it, it got a new front fork, flipped bars, V-Brakes, a better cable setup, and an under-the-bars headlight and mirror. It still needs a bigger tank to complete the look and of course the 36t sprocket. Pedaling to 8 mph isn't too bad.

Unfortunately the new levers I put on it don't work for the clutch or the brake (clutch drags, brake doesn't grip enough), found out they were for u-brakes, not v-brake compatible levers, which are the only ones with enough pull to be used the HT clutches and v-brakes themselves.

So, the to do list:

1 Gallon tank

36t sprocket

Connect pedal chain

Align rear wheel

Reinstall levers
 

moronic_kaos

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Apr 6, 2010
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Connecticut
What is it like to have pedals that don't function? I find that I can do everything but pop-start the bike (well I can, but it's hard) without pedaling. I was thinking about making some sort of setup with stationary pegs in place of the pedals, since the whole bike will be lowered. Planning on using 16" steel (MAG, or spokeless) moped wheels with some heavy-duty hub brakes. Think it's worth riding pedal-less with a manual clutch if it were to improve the ride significantly?

EDIT: Of course, I'd get a pullstart though...
 

twowheeledfox

New Member
Oct 21, 2009
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Houston TX
Ultimately yes. My rat bike is all apart for a repaint/rebuild right now, but having ridden it for about 2 months without "real" pedals it does fine. Pullstart is necessary of course.

However I would never build one of these as serious transport without pedals-- I have a bicycle already to get around on if this motorbike fails, so I have backup transport. If you can only have one, stick with the pedals- if you want to get rid of pedal drivetrain complexity on a motored build, go single-speed and find a good gear that suits your mid-range pedaling. I have been playing around with single-speed all terrain bicycles as "survival" vehicles lately so the single-speed thing does work fairly well.
 

happycheapskate

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Nov 26, 2009
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Rockwall TX
re: no pedals You can put a Low-rider crank on there, which might be just useful enough to pass laws and maybe start the bike, but will be probably worthless for using coaster brakes or actually pedalling anywhere. I think with a really short crank, it would be almost like having foot pegs.

I'd prefer to have a big old 180mm crank because this thing is a beast if I have to pedal. Right now I'm using 165mm cranks.