circa 1970 Honda Monkey Bike- Project/Resto

Managed to find and resurrect some photos in the OP :D

Before:
Monkey2.jpg


Here she is as she is now. Need to get some tank badges, not sure what ones to get yet though!!

monkeylegal.jpg


Since that pic, I have managed to get ne cone air filter, as getting parts for the original can are quite expensive, and it's a bit fiddly. Looks a little cleaner.

Want to tidy up the wiring a bit, and see if I can make it look a bit neater on the other side. I think i also need to adjust the float, as it seems to suffer a little from fuel starvation after a lot of full throttle.
 
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Had a small fire the other day. Had been adjusting the float and the carb for quite some time, and got it running very well.
Filled up the tank, and headed off for a long ride down to the new forest to meet up with some Honda c90 peeps.

Got about 2 mins down the road, and the fuel hose popped off the carb and set it alight :D

Q me standing on the side of the road holding up a flaming bike, the flames were quite high! Managed to pat it out with my gloves after about a minute. Took me a little while to turn off the fuel line in the flames, so it was on fire for a lot longer than I would have liked!

It was not starting after I put the flames out, and the wiring loom was looking like the culprit, a bit crispy, and worse for wear. Lobbed it in the garage and considered my next move. Then I pulled the wiring loom last night, and have inspected it carefully. The loom is very simple, and surprisingly seems in very good nick. It looked like a couple of wires from the ignition were popped out of the back of the connector block. So, they were probably not connected, and i expect i might have tugged on them a bit during the fire flapping. The wrapping around the loom seemed to have protected it quite well.

Continuity is fine across all connections, and the coil is still giving out a spark. So, seeing as I now I have it in parts, and understand the loom a bit better. I am looking at how I can add a 6v gel battery to the mix to make the lights and electronics a bit more stable. Then once this is done, and it's getting colder, I will strip it down again, and see if I can get the frame stripped and re-painted :)
 
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Pulled the motor yesterday, it would not start and the compression was coming in around 50psi, and adding oil to the cylinder saw it rise to 70ish, so it's clearly rings/cyclinder knackered.
Plan is to replace the piston and cylinder, trying to see if I can get a bore up kit.
I do also have a spare head that I wrongly bought a few years ago. It was the small valve version (for later bikes). Only reason I could not use it last time was the domed piston would crash into it, so stayed with the original head. Using this new head will mean I can avoid having to change the valves, as they look like toast on the old head. I think it also means I can run the flat-topped piston kits, so might be able to get a cheaper replacement kit as a result.
 
Been looking into the options for this engine, and have finally decided to go for the kitaco 75cc kit. It was a little more expensive than the unbranded kits, but come from a known uk seller, and has many good reviews. I am going to use the original head, and have started to clean this up. On closer inspection, the head does indeed look ok. Once I cleaned up the valves, they look, and seal well enough, For the mileage it will do, its not likely to burn through them in the near future. I will probably look for a new head in the by that time anyway :)

So, the kit is ordered, engine is stripped ready to fit, and I also ordered a new plug cap, as the old one was annoying me :)

https://www.shirebikes.co.uk/collec...-z50a-z50j-6v-z50j1-st50-dax-6v-cf50-chaly-6v

All in £105 with shipping. Going to pull the bike apart in the next few days also, and just clean/tidy it up a bit, Might look at getting the frame painted before re-fitting everything too!

This kit should mean I keep it looking fairly standard, as it does not require an external oil cooler, or high volume oil pump.
 
Ok, kit is installed :)
Went together very well.
Had to resist the urge to run it up tonight, but it's late and if I woke up the kids, i would be for the high jump!

I kicked it over and it spluttered and then I killed it straight away to keep the noise down, so it should start when I get home tomorrow from work.

Not able to find valve clearance settings in the kit's Japanese instructions so I will have to see if I can get the values from the kit seller.

Still, the access is very easy on this bike to adjust them, so not too worried about that.
 
Will do! Just got it started tonight after a bit of a saga.. Had to kill it again as it's too late to start it up indoors and it's raining....

Kicked it to death and it would not start, checked the spark, compression was great, it would kinda choke once in a while sorta tempting me to keep kicking.
I even pulled out the wiring and put it back to basic one wire setup (just connect black wire from stator to coil), still would not start. Was sparking well though. Hmmm...
Ended up pulling the carb to clean it in desperation.
Then noticed the damn choke slide was diagonally jammed across the inlet inside the carb!
No wonder it would not start.. Choked to death.
Pulled it apart, added a tiny washer to take up the slop for the sliding lever, reinstalled the choke slide and boom, started first kick :)
I had set the valves with some figures I got from the monkey bike Facebook group.
It's never started so easily ever before :)
Somewhat excited to see how it goes!

Hoping to get the wiring loom back in, tidy up the spark plug cable, it's about 3 times the length it should be. Also want to resolder the coil connector as I ghettoed it together to bodge the wiring earlier.

Still got a couple of wires on the loom I have no idea what they do. The wiring diagrams I have seen just don't seem to match up either. I think I have some sort of hybrid harness, or at least one from another year bike confusing me.

Got a rectifier/regulator to see if I can get a battery on there to make the lights more reliable. Just got to work out where in the harness to stick them!
 
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Great work, really intrigued to hear how it affects the performance.

You got me thinking with this little bike so I started looking on ebay, talk about scene tax :eek:
 
Excuse the drowned rat look, it was raining and I had been outside for a while!

http://maltopia.co.uk/monkeybike.mp4

Just a quick run down the driveway. Got to get the MOT renewed next week, then I will get go tuning the carb and valve clearances for the new bits.

FedUpWithMaths said:
Great work, really intrigued to hear how it affects the performance.

You got me thinking with this little bike so I started looking on ebay, talk about scene tax :eek:
Click to expand...

Thanks:)

I know, the prices are mental! Get on Facebook and look for monkey bike groups, lots come up for sale there, and pricing is normally fairly keen as the people on there know the real values of kit.


I feel like I know a bit more about the wiring after redoing a lot of it last night. So going to have a poke about with the regulator and see where I can slot it in so I can run a battery and keep the LED lights lit. Otherwise I am just running down the street as a mobile strobe light. The camera makes it look worse than it is, but you can tell.
 
Regulator was a bust, it worked, but it seemed to reduce the lights brightness. I guess I need to ensure the battery is on the lighting circuit to get proper light brightness. I was only working with the bike on idle, so its possible that the battery would take over at that point, and only charge on higher revs.

I also need a new multi-meter. Mine is a bit of rubbish, and seems very unreliable!

Wiring, tidied up a bit:
20180324_102319.jpg


20180324_102326.jpg


Done a bit of polishing on the engine block when it was out, along with a lot of de-greasing, but the flywheel cover is going to need some work, along with the exhaust. Otherwise, I think its getting close to be ready for a full strip down, and re-paint :) I even cut down the coil - plug cable length, and added a new NGK plug cap.

Oh, and some tank badges are needed! I also have a new rear brake cable coming, in black, to fix the rear brake light switch, and get rid of the old brown one!

I am still waiting on a fork-rebuild kit, with some up-rated guides from America, along with some. I already go some ct70 fork sliders to get rid of the top end fork slop, and the usual seals to replace on a fork rebuild. But, I think I might do that after paint, as I will be pulling the forks off for that anyway.
 
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I have all the parts I need for the fork rebuild kit. I FINALLY have the tank badges on, and have been requesting quotes to get the frame and forks resprayed.

I put on a larger carb with an offset manifold, as the 75cc kit was struggling with the stock carb. However, even with the upgraded carb, the kit is not breaking 30mph on the flat. It seems to be down to the limited bore size on the original head. Which I kind of think makes the 6v 75cc kit pointless? I am emailing the kit seller to ask if other people have similar experiences with this kit. It does run well, but its not really much of a performance increase!

Next up, I am going to have to learn how to polish/port the standard head i think!
 
Malt_Vinegar said:
I have all the parts I need for the fork rebuild kit. I FINALLY have the tank badges on, and have been requesting quotes to get the frame and forks resprayed.

I put on a larger carb with an offset manifold, as the 75cc kit was struggling with the stock carb. However, even with the upgraded carb, the kit is not breaking 30mph on the flat. It seems to be down to the limited bore size on the original head. Which I kind of think makes the 6v 75cc kit pointless? I am emailing the kit seller to ask if other people have similar experiences with this kit. It does run well, but its not really much of a performance increase!

Next up, I am going to have to learn how to polish/port the standard head i think!
Click to expand...


Four strokes are a nightmare to tune. Even the YZF R125s upgraded to 180cc offer very little improvement over the stock engines. Such a shame really, two strokes are so much more tuneable :(


50cc to 70cc goes from this:


To this:

 
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