JAPton blog

Discussions and updates on your new bike, your new build, your wishes, wants and desires
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Rockburner
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Re: JAPton blog

Post by Rockburner »

mangocrazy wrote: Fri Jul 24, 2026 9:42 am Well done, that man. Perseverance pays! The exhaust sound with no silencer was enough to wake the dead. What's it like with the silencer?
Cheers!

TBH, err... not a lot different! :D :D

IIRC the story goes that it's off an old BSA M21 (or something similar) and was only chosen by my Dad because it's the correct bore to fit the enormous downpipe! :D
crust wrote: Fri Jul 24, 2026 9:56 am Fantastic!!!

What an excellent reward for all your hard work and perseverance :thumbup:
Thanks!
JackyJoll wrote: Fri Jul 24, 2026 12:52 pm I have never found those nylon bases prone to leak, so it should be fixable, maybe with a replacement gauze.

Any piece of Hylomar that comes off downstream of the gauze will roam around the float bowl like the Flying Dutchman, until it causes trouble.

I mounted a small resin-filled coil too close to an iron cylinder head and the coil cracked.
I do still have the old coil, and I know where to source them if I need a new one. I think it's far enough away, but given that I want to do another slight mod... it may well get moved.

Re the nylon filter - I've been scouring the photos I can find online and none of them seem to have that lip - so I think I've just got two very old, work filters and will buy a couple of new ones at the earliest opportunity (Sunday at Ardingly if I make it, Sunday evening online if not. :) )


Thanks everyone for the replies, tbh there were times I wasn't sure we'd get this far. :D I can't wait to get it on the road... :D (It's currently still registered and insured, and doesn't even need an MOT iirc!)
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Re: JAPton blog

Post by Rockburner »

Actually, one thing I should admit to... if only for recording the idiocy for future referral....

When I did the ignition timing I didn't check the documentation for the Mag.

The mag shaft actually has a direction indicator on it (in the document it's an arrow scratched onto the end of the shaft, on mine I think it's a punch mark that's distinctly off-centre). The arrow indicates the desired orientation of the shaft when setting the time... it must be pointing "down" when you're setting the timing so that the spark occurs at the right point in the 4-stroke cycle (the mag is driven by the camshaft, which turns at half engine speed)



....




I completely forgot about that mark, and so didn't check it when I did the ignition timing. :roll: :? :? :?

I had a 50% chance of getting it right.... :D :D :lol: :lol:
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Re: JAPton blog

Post by Count Steer »

Rockburner wrote: Fri Jul 24, 2026 2:11 pm Actually, one thing I should admit to... if only for recording the idiocy for future referral....

When I did the ignition timing I didn't check the documentation for the Mag.

The mag shaft actually has a direction indicator on it (in the document it's an arrow scratched onto the end of the shaft, on mine I think it's a punch mark that's distinctly off-centre). The arrow indicates the desired orientation of the shaft when setting the time... it must be pointing "down" when you're setting the timing so that the spark occurs at the right point in the 4-stroke cycle (the mag is driven by the camshaft, which turns at half engine speed)



....




I completely forgot about that mark, and so didn't check it when I did the ignition timing. :roll: :? :? :?

I had a 50% chance of getting it right.... :D :D :lol: :lol:
Probably find the engine was running perfectly....backwards. :D
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Re: JAPton blog

Post by Noggin »

Mate, I'm sitting here (in the last throes of a migraine) and grinning like a raving loony !!!! How bloody awesome!

I'll be honest that I mostly. just look at the pictures cos I don't really understand most of the words!!!

But seeing that start and the noise . . . . WOWOWOWOWOW Bloody freaking awesome :) :)

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Re: JAPton blog

Post by JackyJoll »

Image

Yeah that doesn’t look right.

There’s no doubt Amal are capable of selling bad parts.
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Re: JAPton blog

Post by Rockburner »

So, I couldn't help myself and wandered back over to the workshop this afternoon. :D

My first intent was to sort out that banjo union.

I started by taking it apart and discovered that I'd done it up so tight that the washer under the bolt had disintegrated!
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But weirdly, I still don't believe that was leaking!

I started examining all the bits as closely as possible and started to get suspicious about the banjo union itself:
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I then dug through all the old odds and sods that I had from Dad's workshop...

And eventually I discovered that I had a nearly new Amal nylon filter!
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I think this was part of the upgrade parts I bought for the Monobloc - that's where I found it anyway, in the amongst the Monobloc stuff. It definitely does NOT have that lip.

So, I fitted it, and re-did the petrol pipe on the banjo union as well and ... er... it seems to have fixed it! :D :D

I also found I have a couple of competely useless twin feed banjo unions...
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So while I was waiting for fuel to seep through the filter, I had a mooch around the rest of the bike...

And found this:
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Buggeration!

So, I started stripping the rear mudguard off the bike:
First off - the catch-tank holder.
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That long screw is what holds both the mudguard on, and the catch tank!
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Removing the upper bolts
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All undone, and it pulls out actually surprisingly easily.
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You can see the "cut out" on the side clearly here, and this is the cause of th cracks.
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The larger crack is clear :
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Sorry - did I jump ahead of myself... yes there's 2 cracks
Lower end
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Upper end
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Cleaned off the inside and marked the end of the cracks with a white paint pen.
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The holes were drilled easily after judicious use of a centre punch
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3mm each should be enough. (They look a bit bigger because I cleaned then up a bit with a larger bit.)
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The mudguard went back in fairly easily too.
First getting that long set-screw in place
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I was sweating having to take the rear wheel out, but I didn't need to: the set-screws at the bottom end are allen-heads, and there's enough clearance to get the long set-screw out of the bracket, luckily.

Once I had the mudguard back into place.. I had a close look at the fitment.... and now I'm wondering why the hell the cut out is there!
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I then fitted the tank strap.

First I got the tank out of the way - there's just enough play in the fuel hose to allow this :
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More ultra-lightweight fitments...
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And I locked-wired the R-clip just to be safe.
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The other end of the strap is yet more in the ultra-lightweight theme
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Fitted the seat
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Fully bolted down
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A while ago I decided that I don't like the Unity Equipe screen that comes with the nose-piece, so I made up a lower, darker version.
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It needs a bit more work, the top corners need to be curved off and tidied, but that shouldn't take long with a dremel.
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I fired it up again in order to try to get the tick over improved (it either hunts and dies, or revs like crazy at the moment)
Didn't realise that strap was actually pushing against the downpipe... oops! :D
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Gassed myself, obvs!
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The last piece... Dad's home made primary chain cover.
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There's nothing left to fit.
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I pondered taking it out at that point..... but realised I'd run out of daylight! :lol: :lol: :lol:

I am interested to see how it runs ... I expect there'll be a fair bit of carb tuning to be done.

Hopefully soon! :D
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Re: JAPton blog

Post by Lutin »

Splendid. :clap:
Blundering about trying not to make too much of a hash of things.
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Re: JAPton blog

Post by Count Steer »

The delights of WFH. :D

Those sharp angles and cracks on that cut-out are text book stress-raiser illustrations. I'd have been tempted to round 'em off with a rat-tail file or summink.

Top work though. :thumbup:

Do you plan to tax/insure it and get out and about on it while the summer lasts? (Is it road legal?).
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Re: JAPton blog

Post by Rockburner »

Count Steer wrote: Sat Jul 25, 2026 8:18 am The delights of WFH. :D

Those sharp angles and cracks on that cut-out are text book stress-raiser illustrations. I'd have been tempted to round 'em off with a rat-tail file or summink.

Top work though. :thumbup:

Do you plan to tax/insure it and get out and about on it while the summer lasts? (Is it road legal?).
It's registered (tax is £0), and insured, and is old enough not to need an MOT....
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Re: JAPton blog

Post by Rockburner »

Today, after a bit of car booting, (found a large Elora spanner that will hopefully be useful, 1"W & 1.1/4"W) and wandering around town, I popped back into the shed to carry on prepping the bike.

First I drained the old oil, it turned out to be C40 from the last time the bike was run.
It's bloody hard to see into the oil tank...
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I've got a couple of litres of new Morris C40...
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And I also have these....
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The Morris is nigh on transparent when it's clean...
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One tin of Castrol is obviously used.... Euuuw
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Will have to get rid of that some how... Dad would have just chucked it on a bonfire! :D

The other tin was still sealed, and is nice and clean.
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It looks like the still plenty of room in the oil tank, so I'm going to get some more C40 and top it up to about 3.5 - 4 litres.
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In the meantime time I added a dribble of the R30... ;)Image

After that I messed around for a bit making sure the bike was ready, and prepping a toolkit to carry on the bike, before nipping inside and putting my gear on.

I also remembered to pour some more petrol in the tank! :D



The first ride was, to be honest, both exhilarating and a bit of a let down! :lol:

I did a couple of loops around the triangle of roads near the house, and it runs fine, handles fine (the something odd, tyre pressure, a bearing or something), however it's pretty gutless. I wasn't expecting a rocket ship by any means, but it still felt a touch underwhelming. It pulls ok up to about 60-65 then seems to completely run out of wind.

I was going to carry on a bit further afield, but looked down at the engine and realised that the cases were covered in oil, so, I returned home to check things over.

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That's after just a couple of minutes back on the work ramp
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This is main feed pipe to the pump, dripping wet
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This push rod tube is loose enough to be rattled, and is definitely one of the sources of the external oil.
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There was so much oil it was pouring over both sides of the cases, although sitting it on the side stand for a few moments would have caused that.
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This is somewhat concerning though, a pool of oil by the rear left head stud, seems an odd place for it to be, unless the base gasket has gone already..
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The exhaust "was" nice and shiny...
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The plug actually doesn't look too bad if you ask me.
It's not quite right, but I've definitely seen worse!
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I left it to cool off before I clean it up, then may look at reducing the amount of oil being pushed to the head, one of the books says it should be " a drip for every 2 pulses of the pump" (you can see the pump pulses through the window on the pump), but that's a rate for racing WFO, so I think I'll reduce the feed to a drip every 3 or 4 pulses, and try to do some mitigating of the leaks!

There's also lots of other little niggles, the gear lever is a bit high, the nose cone isn't straight, the left fork leg seal has gone, etc etc.... nothing insurmountable though. But some things are fine, the rear brake works perfectly, the front is okay etc. So I need to do a few more things before it's fully ready...

That said... It's the local classic club monthly show tomorrow, and that's only about a mile away from the house... :D
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