revtothelimit - motorbike forum

Updating this post to include some previous info and photos.

JAPton on arrival at it's new home: December 2022. Theoretically the JAPton is ready to run, apart from the kickstarter which fell off last time i tried to start it. But it also needs some tweaking.

JAP carb parts in the ultrasonic, (July 2023) before:


And after!


Got the kickstarter filed down a bit today, you couldn't do the clamp bolts up tight enough to prevent it wandering on the shaft. So naturally i fitted it and gave the bike a kick or few......







The stubborn thing will not tick over easily, so im going to have to play with the Monobloc fitted, and probably also check the timing. Its backfiring constantly unless the choke is fully open.

Its fitted with a BTH magneto so I also need to research them.

BUT IT RUNS!

Screwdriver wrote: Sun Jan 01, 2023 7:16 pm Crank seals the most likely culprit….

You'll have to explain that further.....

Its a JAP speedway style 4-stroke single.

The plug is wetting badly so it's more likely to be poor fueling at low throttle settings. That's certainly where I'm going to be looking first.

Oh, and I've no idea how to get the video to show, if it's not showing for you. (Its not showing for me!)

Was moving the JAPton about last night, and noticed a 'bump' as I moved the steering.

I have no idea why the thing has a steering damper on, but it has. And it's nudging the tank at full left lock. I'm minded to take it off anyway, I'm pretty sure the bike doesn't need it.

Then I took a closer look...... The steering damper is held on under the tank with a little bracket, which is bolted to the frame.... THROUGH a hole that someone has drilled in the upper rail! WTF?

I'm not going to say that this is Dad's doing... the frame was mullered when he got it (ex race bike, possibly grass-tracker, cut up, widened, etc etc), so I've no idea when the hole was drilled. But to me, drilling a hole in the tubes of a cradle frame is bloody silly - am I wrong?

I suppose it depends on the size of the hole vs the size of the tube but it does seem a bit wrong. I think you can have holes in tubes without compromising the strength much as long as the holes are small and you aren't attaching something that's going to apply a lot of load at an angle. You can make quite strong, light tubes with lots of holes in.

Count Steer wrote: Wed Jan 25, 2023 10:25 am I suppose it depends on the size of the hole vs the size of the tube but it does seem a bit wrong. I think you can have holes in tubes without compromising the strength much as long as the holes are small and you aren't attaching something that's going to apply a lot of load at an angle. You can make quite strong, light tubes with lots of holes in.

I'll get the tank off when I get a chance (workbench, aka "temporary storage area for parts", is currently in use for something else), and get a better look.

I've seen similar done before,but,it's certainly not ideal.

Frames do have holes drilled in them. With a captive nut inserted and a bolt into that i doubt your losing any structural integrity.

Got the seat off the JAPton last night.....

The electrics are a nightmare of complexity.....

... not! (Needs a bit of tidying though.)

Going to get the tank off soon, once the oil tank has finished draining, the oil tap itself was leaking like a sieve so I've ordered a replacement and a bit more tubing to match, along with a few other bits and bobs from feked.com. (love that company name ) . But there's nothing to stop the oil feed pipe emptying itself - so the bulk of the oil is out, just letting the last few drops drip over night. (hence the jug in the photo).

I got very lucky - I have a 2 litre jug and used it as the first 'catch-jug' when I started draining the oil - without knowing how much was in the tank....

Guess how much was in it?

This is the aforementioned steering damper...


I hadn't realised the tank was actually resting on it!

Also - the head of the fixing bolt on the for clamp was hitting the tank at full-lock.
.

I've ripped the thing off.

Watch out for the 'speed' wobbles ;0

ogri wrote: Thu Jan 26, 2023 11:17 am Watch out for the 'speed' wobbles ;0

Funny thing is.. it's not really a 'quick' bike. Max speed will likely be about 70 (flat out, chin on the speedo, engine on the point of melting), it's only about 400cc. The engine is a mish-mash of 500 and 350 bits (I can't remember the combination).

Oh yeah - also need to find a charger for this :


So have contacted a UK supplier of that battery and hope to hear back from them soon.

For period authenticity, perhaps a SpeedMaster wobble?

Messing around last night it occurred to me that the cross tube on the Featherbed fairing might be usable as points where my Abba stand could fit.....


Nope. The rear brake lever gets in the way, and the cross tube is too high on the bike, so the Abba doesn't lift it much.

Bugger . Might have another go with a thick sheet of ply under the Abba. It would be useful because there's no centre stand and the paddock stand i have (home made), locates on the rear axle rather than the swingarm.

Spent some time this evening tinkering with the JAPton.

I figured the carb probably needed a clean... And i wasn't wrong.


It wasn't terrible, but it needed a clean....

Hopefully this will make a difference when i try running it again!

Gearbox could use some oil.....

Fecking thread in the lower cap hole de-threaded itself too. Gah!

Had some time on Saturday for fettling.... (still not sure how I managed that)



Got a 2BA helicoil kit from RGMNorton and fixed the gear-box inspection plate thread. Stuffed a bit of foam in there to catch all the swarf and it did a good job.
I've a nasty feeling the helicoil may have turned itself a bit too far, but I'll keep an eye on it and pull it out if needed and replace the coil (the kit comes with 10 of the little blighters).

Speaking of little blighters....



I figured I'd just check the engine mounting bolts/studs (it's a rod with a thead at each end - I think that's a 'stud' ?) - and one of them wasn't going tight... obviously it's the one right at the bottom at the back... the hardest to reach!

Oddly it was the nut that lost it's thread, not the stud.

Even more odd - the (perfectly fine) nut on the other end (rhs) doesn't fit onto the (lhs) end? Weird. You'd think they were both the same thread? I need to check the threads on that stud again - they should be the same (at least logic would tell me so).

But - since I don't have any Imperial 'spares' to speak of - it gave me the "opportunity" to invest in a grab bag or 3 from 'Nookie's Nuts'. (I say 3 because I need to cover all of Cycle, BSW and BSF when gathering potential spares for this bike). There's metric on it too in random places, but I've got a fair few of them. I expect to lose at least 1 nut or bolt per ride, so I want to have provisions.....

I also cleaned out the oil tank with some petrol (there was a shitload of burnt carbon bits in there - castor oil does tend to do that I understand), and emptied the gearbox.

I also received a new battery, it charges (yay!), and the brake-light and horn (the limit of the electrics) both work fine. I've also wired in a connector to make charging the battery a bit more easy (it's tucked under the seat-hump so that has to come off to reach it otherwise).

So - once I've got my nuts sorted out, it's going to be a case of putting in fluids and seeing if it'll run again.

You're a brave man, RB. As a spotty clueless yoof, one of the things that turned me towards 'Jap crap' as opposed to old Brit iron, was the multiplicity of incomprehensible (to me at the time) thread pitches employed on British bikes. I remember measuring a nut, going to Dad's toolbox and picking up a spanner with the size stamped on it and wondering why it was 2 or 3 sizes larger (or smaller, can't remember) than the nut it was supposed to fit.

That was my introduction to Whitworth...

By comparison, metric was just so simple and logical.

mangocrazy wrote: Mon Mar 20, 2023 5:21 pm You're a brave man, RB. As a spotty clueless yoof, one of the things that turned me towards 'Jap crap' as opposed to old Brit iron, was the multiplicity of incomprehensible (to me at the time) thread pitches employed on British bikes. I remember measuring a nut, going to Dad's toolbox and picking up a spanner with the size stamped on it and wondering why it was 2 or 3 sizes larger (or smaller, can't remember) than the nut it was supposed to fit.

That was my introduction to Whitworth...

By comparison, metric was just so simple and logical.

I'm perfectly happy doing work on the bike, like you say though, the threads make the mind boggle!

Look up the BA standard one day... it's actually a 'metric' thread but works by taking a starting point (BA0) and reducing (or increasing for larger stuff) each subsequent size by 0.9. wtaf???

That's just bonkers...

A while back on a recommendation from a friend I bought the Zeus booklet. That opened up a whole new world of thread fuckery... But at least I stand a fighting chance of identifying random nuts/bolts now. I finally let Imperial threads into my life when I restored a Startrite Mercury pillar drill - that was quite a learning curve!

mangocrazy wrote: Mon Mar 20, 2023 5:45 pm That's just bonkers...

A while back on a recommendation from a friend I bought the Zeus booklet. That opened up a whole new world of thread fuckery... But at least I stand a fighting chance of identifying random nuts/bolts now. I finally let Imperial threads into my life when I restored a Startrite Mercury pillar drill - that was quite a learning curve!

I think I've got a Zeus book somewhere..... Need to dig that out.

I still have a Zeus book from my apprentice days! Very handy for tapping/clearance drill sizes among many other things. When I worked in the Areospace industry,they happily ran imperial and metric together. I grew up with all the BA,BSF UNC UNF threads as well as the M sizes. I still think in 'thous' rather than 100ths of a mil.