learnings, motorcycles
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Lessons from disassembling a motorcycle engine

For a long time, I wanted to work on an actual motorcycle engine

Theory is great but as it is said theory is theory and practical is practical. No matter how many times we watch Sanjeev Kapoor and Tarla Dalal cooking and memorise each ingredient to mg, can we vouch that we would make the next dish as good as him/her? Certainly not impossible but surely not so confident yes.

I had a deep interest to break down the engine to its last bolt and learn the complexities first hand.

All these years, I have read and watched the workings of all sorts of motorcycles but never got to try my hands-on with engine internals.

How did I go about doing this?

I was looking for a scrap motorcycle engine for some time. Luckily one day I got my hands on an old engine, not a scrap but good enough for the workout. A good connect of mine Shyam Bhai handed to me Honda Unicorn engine for Rs. 1000. Bolts were hard and rusted as it can and it didn’t seem it was opened before.

After spending more than 45 days on it, working mostly during weekends in my spare time and several lessons, the engine was disassembled to the last bolt as far as I can go.

Kept the engine internals and sold the casing and bolts to kabaadiwala in Rs. 750. Turned out to be a good deal to me.

Looking decent after scrubbing kilos of dirt

Tools

  1. Opening an old engine may not be that easy and quick. Bolts and screw are tight and some may be just very hard to unscrew or unbolt. In the process to open them, some may become flat and free. I had an experience with an oil pressure pump screw getting flat. Tried lots of ticks (rubber bands, balloons, impact screwdrivers, cutting it and opening with Phillip screw) none worked, unfortunately. Finally, I had to use a drill machine and drill across the screw. In case of drilling out of option, mechanics get the flat screw soldered to another metal piece and use the soldered top to unscrew.
  2. Keep in mind, we cannot work on a motorcycle engine with a star screwdriver and round spanner. Without a doubt we need more than that, let’s go one by one in below points.
  3. I purchased tools on the go as and when required and I suggest you to do likewise so that you don’t end up spending money and accumulating useless tools.
  4. I bought 1/4 inch socket spanner toolkit (Force toolkit). I won’t say I am quite happy with it but the variety I get in this toolkit turned out useful in working on my Dominar 400 too. Still, the usage as of now is no more than 50-60%.
  5. ¼ inch toolkit is good but soon I felt that I need more specialised tools for opening 10-12 mm bolts. Fixed ‘T’ spanner is the best. I would highly recommend purchasing 10mm and 12mm fixed T-Spanner. Taparia fixed ‘T’ spanner costs around 300 Rs. for both 10 and 12mm.
  6. ½ inch socket wrench is good to have but it’s costly (Rs. 2000). I could perfectly work with ring spanners for bolts greater than 14mm. I bought 15-16, 17-18, 19-20 mm spanner. Though I had 8 sided ring spanner but recently came across a youtube video by Jeet Bhaskar recommending 6 sided spanner. According to Jeet, 8 sided slip on the bolts and sometimes makes the bolt flat worsening the situation.
  7. Next lesson, a hammer is must. If you are working on a running engine, dead blow hammer is recommended. Since dead blow hammer does not have metal face it does not damage components.
  8. Get a C-clip remover if you want to save your nails and clips flying around.
  9. I tried to get around without a clutch holder, unfortunately cant. Clutch holder costs Rs 500-600. I wanted to do with less than that hence used pipes and welded them to make a custom puller. Pipes (Rs.90) welding (60).
  10. Magnet/alternator/flywheel (all are same) puller. You need to buy or borrow magnet puller. Jugaad doesn’t work as the magnet has a crescent moonlike key inside to hold it.
  11. Valve opener. Garage mechanic uses hollow pipe and place them on the valve spring then hitting it with a hammer, this releases the valve spring key. Removing and assembling without valve compressor tool requires practice or expert aid, I would recommend buying or borrowing one.
  12. Leverage on spanners works magic as the physics behind it. Make full use of them.  A couple foot long iron pipe works as good leverage. Mechanics use shock-up pipes.
  13. Buy a tough screwdriver which you can use with a hammer.
  14. Toolkit drivers may break.
tools for motorcycle repairing

Some of the tools and items I used in the process of disassembly. That welded iron pipe with 2 small 90 degree pipe rod is what I used to remove the clutch.

Toolkit for motorcycle

Broken drive of my toolkit 🙁

Practical learnings

  1. Expect cuts and blows during the disassembly. I had several cuts on my fingers, palms and lower legs as I worked putting a paalthi/sukhasan. Use cut-resistant gloves in case you need to avoid these. Don’t forget to get a TT (tetanus) injection in case you are pierced 😀
  2. Visualise the working of parts, question why something was designed like this. Research and try to explore as much as you can.
  3. Take photographs, shooting video is better to remember the position of parts. This would help you big time during assembling.
  4. Use cardboard to place the engine and work. Cardboards absorbed the grease, oil and saved my tiles and myself from my mother.
  5. I use to clean the parts with cotton cloth as I pulled them out. Later placed bolts, screws in a plastic ziplock and catalogued them for future reference. Use paper pieces to catalogue the parts. If you think you’ll remember them then you are wrong, you don’t know how easily we are fooled by our mind.

Some pictures from the disassembly.

Honda unicorn engine disassembly

top: gear assembly, drum shifter and crankshaft bottom left: magnet side of the engine casing bottom right: engine bore. Observe the amount of carbon deposits 😛

honda unicorn engine repairing

some images from the opening-up. bottom left: centre casing, everything pulled out bottom right: camshaft, rocker arm pulled off. Valve springs is what we see.

motorcycle engine self repair, honda unicorn engine parts

Some of the parts from the engine. First column top to bottom – crankshaft, flywheel, coil. 2nd column top to bottom – camshaft, rocker arm and timing gear, timing chain, chain tensioner. 3rd column top to bottom – clutch assembly, centrifugal oil filter, piston. 4th column – oil pump, gear drum shifter, gear forks. 5th column – kick rod, gear shift plate, input and output gears.

Honda unicorn engine disassembly, motorcycle engine honda unicorn

Closeups of some parts.

Filed under: learnings, motorcycles

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Hello, I am Niraj. I define myself as an amateur photographer, biker and seeker. I like to connect with like-minded friends and share even the tiniest experience raw in nature, ever felt of the place, people or time. I believe life is an endless journey and our actions no matter how small affects this infinite universe in some or other way. So don't stop and keep up your work going.

2 Comments

  1. Jay K says

    Really loved the learnings. Being a grease-monkey myself, I am feeling excited and eager to undertake such a task 🙂
    Thank you for sharing this Niraj!!

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