Back in the Saddle

Discussion in 'General Questions' started by Timbone, Dec 4, 2015.

  1. Timbone

    Timbone Active Member

    Here's a recap of my latest trials as a motorized bicycle owner/operator. I think this will show the newbies how complicated things can become, even when you have decent mechanical skills and good understanding of how to solve problems.

    I finally got my motorbike out on the road today, running smooth and relatively vibration free. But, man, it took me quite a bit of work to get there. The story:

    About three weeks ago, I was gonna run a quick errand on the moto. The bike had been running good, but there was a safety issue with a twisted half of the rear V-Brake. Braking was decent, but not really where it should have been. Oh, yeah: a very worn rear tire. I have a new one ready to go but changing out the rear tire is a tedious and dirty job!

    Pedalling away for the bump start, the thin crankarm on the right side broke. Bam! No ride today! Broke right off that the pedal. crankarm interface. No way to ride without getting a new one piece crank. Fed up, and mindful of the less than optimal brakes on the rear. I just went to the garage, removed the pedals and crank, along with the bad part of the rear brake. Wouldn't even give myself a chance to risk riding this thing in an unsafe condition.

    Pedalling this bike is very hard once the clutch is dumped and you have to fight the engine compression. I would estimate about 400 watts is necessary to get it going on flat ground. This kind of effort led to the failure of the crankarm.

    So where am I gonna get what I need? Strangely enough, I FOUND a V-Brake equipped mountainbike. Yes, I found it! Somebody had stashed it behind my workplace and I found it first and nobody fought me for it. It was a cheap bike, but I see two good tires, cables, brake levers, wheels, and V-Brakes! Evidently, someone had stolen the bike, rode it until they got a rear flat, then dumped it. Their hardship is my good luck! Yea for me!

    I have a free brake fix, but where to get the old school one-piece crank?

    There's a inner city bicycle mission in town that takes donated bicycles and parts and, through volunteer work, reprocesses them to provide very low cost bicycles to those in need. You have to be a member to buy any parts or bikes. How do you get to be a member? Sweat equity. I donated 9 hours of my time there refurbishing old bikes (I completed one bike from scratch) which allowed me access to their treasure trove of collected one piece cranks. I got a super stout crankset with sealed bearings and cups for $10. Score!
    Yesterday, I went to work. Fixed the rear brake which was easy enough, but I wasted a lot of time trying to recycle my old cables. Eventually had to use a new, pristine brake cable.

    The one piece crank went onto the bike so easy. Gravy. To optimize the length of the motor chain, I slid the rear tire back just a bit. That means a new chain. No biggie: I went to WallyLand and bought a 1/8" wide chain for about $6. But this gave me two problems! One, the chain was much to short (Bell 300). But worse, the chain would not feed onto the chainring. This thing was stout: much too beefy to allow the thin half of the link to settle in.

    My previous chainring was a triple that I had no mechanism for shifting. The chainrings where riveted together and I fiddled for too long trying to find a simple way to get them loose. Forget that. All I got for my effort was filthy hands!

    I had a perfect ring attached to a square tapered BB bike that I have in my pile of stuff. I removed the crank after a prolonged search for my rarely used crank pullers. There was a kind of retaining ring on the inside of the chainring that I could not get to move. After a fight I gave up and decided to just grind the thing off. No joy there! I ground all the way down but the chainring would not bulge. I have no idea what's holding that thing on. Had to give that up.

    So I had to remove the new one piece crankarm and it was an extended battle. The sealed bearings did not want to get out of those cups. I used a long, thin screwdriver and very slowly persuaded them out. OK, so what to do with the too beefy chainring? I took it to the grinding wheel. Very slowly and carefully, I worked each tooth of the chainring, a little off each side, until my test chain would fit nicely. With 44 teeth to work, that took quite a bit of time. But I got it just about perfect.

    I replaced the crankset, then removed the rear wheel to change the rear tire. I had used a generic Bell cruiser tire with Kevlar that served me very well. No flats and despite lots of missing tread, the tire could have seen more service.

    About 6 months ago, I bought a Bell tire at WallyWorld and saved it for this. It has a very thick rubber, with a flatter contact patch. I didn't notice at the time, but this was a 1.75" wide tire - not nearly as wide as the used one. It was hard work for me to get the thick, flat resistant tube into the thinner tire. I had to make sure remove nearly all the air in the tube before replacing it in the new tire, and I had to slowly work the tube around the rim until it settled nicely. Another task that took much more time than I anticipated. I put the rear wheel on the bike and then had to pause, needing to go back to WallyWorld to get another chain to have enough links to make the circuit.

    I optimized the motor chain length and locked down the position, THEN cut the pedal chain to length. I had two masterlinks which made it easy. My first pedal chain cut was one link too long, so I cut one more off and went with that. Homemade chaintugs allow me to perfectly set my rear axle and after considerable adjustments to the tugs and to the chain tensioner on the motor chain, I finally got it optimized.

    OK, I am ready to ride now. It's chilly out and the bike has been sitting in the cold. The carby is jetted at .65, a lean run at WOT. This i a DAX F80 engine with a RT carb. After several attempts, I could get nothing but sweat on my forehead. My technique was as always: drop the clutch with wide open throttle and pedal hard down the soft hill on the street. Nothing. After a long day behind me at this point, I gave it up for the day.

    Today was sunshine bright and much warmer. I had to get the bike started. No way I could fail.

    First I changed out the old style CDI (that i am pretty sure is functional) for an older "upgraded" CDI I bought from Bikeberry (the one with the NGK plug wire). Opened the petcock and made several high energy attempts to start. Nothing.

    I set the bike in the sun and changed the CDI back. I had examined the spark plug before changing the CDIs and the plug was WET. Flooded. Great. I left the plug out as I changed back to the older stock CDI. Off I go for more attempts. Again full throttle and high energy pedalling. Brappppp! It kicked! Lots of white smoke! Nothing then Brappp! Short runs and stops. it wants to go. I rode it down the street, still more off than on, but it will idle now, but not a good run yet. I stopped, pulled the clutch and revved the motor. it ran for about 8 seconds then stopped. More attempts to start yield nothing. I walked it back to the garage and got an idea: use some WD40 as a kind of starting fluid. I sprayed that directly into the air intake and tried a few more times. No go. Back to the yard where I removed the spark plug and allowed the engine to dry out. Time for a break and a clean up.

    About a half hour later, I rolled out the driveway and drop the clutch. This time, the motor kicks while under full throttle but this time, I close the throttle and work to find a sweet spot. The engine responds nicely and after kicking out big clouds of white smoke, the piston finds good rhythm and consistancy and I have the power to take off. What a feeling! I flew around for a few miles in very chilly air and got good heat into the engine. I rode back to the house, stopped the engine, and went inside to get my tool backpack. The bike started right up and I rode about 2 miles to the coffeehouse.

    I had some trouble again getting her started after my coffee break, but once up to speed, the bike performed wonderfully. I think the tighter, more rubbery rear tire makes a huge difference. Very little vibration either from the engine through the bars or through the road. And I had a good high peed cruise at about 28-29 mph with no hint of 4 stroking.

    I'll gas her up and go for a ride in a few hours. My next steps are to get some kind of shock absorbing front fork on the bike and attach a high lumen 12V headlight on the front.

    Now you see why my mantra is Never Give Up!
    Last edited: Dec 4, 2015

  2. jaguar

    jaguar Well-Known Member

    I've warned people for years about excessive high compression.
    you admitted that was the cause of the beginning of your woes and yet never said anything about wanting to bring down the compression to a reasonable amount.
    yeah you'd better have a Never Give Up motto if you're going to keep from correcting what is incorrect.
  3. Timbone

    Timbone Active Member

    Jaguar, I truly appreciate all you do for this forum. I've read countless posts of yours and I have taken a lot away from it. Maybe I am somewhat at fault here but let me be clear: I am running a completely unenhanced HT China Girl engine with no modification whatsoever. Just a stock head with no fiddling at all with the innards.

    This bike is somewhat hard to pedal, though I can climb fairly steep hills under leg power only provided I stand on the pedals and grind it like I would a tough climb on my pedal road bike.

    So, it is quite a good bit of work to pedal through the compression. And all of the recent issues I've had with starting the bike, especially in cold weather, I did several miles of simply pedalling through the compression with no joy (and by "no joy" I mean no ignition in the cylinder).

    I am happy to report that my many trials and errors have led me to a very successful starting method: I simply pedal through the compression with zero throttle input and keep going. I got a good cold weather start this morning with temperature just above freezing. After about 200 yards of steady pedalling and slowly working in the throttle the engine gets some heat and it takes off. I am very happy!

    I have been served notice and I make you this promise: if I ever decide to go with a cylinder head that yields high compression I will certainly make sure that your Jaguar CDI fires it up!


  4. bakaneko

    bakaneko Active Member

    I learnt to give it a few extra presses of the "primer" for cold weather conditions. You would be surprised how much one or two extra presses results in a much faster start time (engine starts moving). In fair weather, I usually just press it once but now in extreme cold weather (at or below freezing) I give it 4 presses and it starts very quick. Sorry, this is for a first start of the day. No need to press it after its warmed up or between errands.

    And, sure you found the bike. :rolleyes7:
  5. jaguar

    jaguar Well-Known Member

    even when I first started out with the stock carb I didn't have that much trouble getting it started. Maybe you do because you haven't planed the head flat and then installed a new gasket (since the old one conformed to the previous irregularities and thus needs to be thrown away).
    Then I put the first version of the Jaguar CDI on it with a Dellorto SHA carburetor. It ran great till I moved down from 8000ft to sea level. That's when I got the fully adjustable Mikuni carb (18mm).
  6. bakaneko

    bakaneko Active Member

    Aye, I didn't do anything with the head and gasket. I am in Wisconsin and it gets cold and dry in Winter. It really dries up the engine :annoyed:
  7. Timbone

    Timbone Active Member

    The old NT carb I used had the primer button. But I am running the RT carb that has the slide, but not the primer button.

    As for bike theft, some of my worst memories are of the bikes I had stolen when I was much younger. To wit: a early '70's Schwinn Collegiate (from my garage) and my worshipped '74 Schwinn Varsity. I know of so many others victimized. There is definitely a special place in Hell for bike thieves.

    I work in a commercial/industrial area and there is a large community of folks who get around by any means they can find. This is the THIRD bike I have found stashed on my work premises. We even had a trashed motorized scooter that ran on a little 25cc engine. I am not sure who took that as I had no interest in it. I gave one of the bikes, a 24" wheel model, to a kid down the street. These guys will literally ride their bikes till they can't go anymore and dump them. Bike maintenance costs money that many of them do not have.