Troubleshooting a JAP Special

[Rockburner]

Report from the weekend.

I snuck into the workshop late Saturday evening and did some more checking and tinkering.

I decided to try RTV-ing the rocker cover:


I also realised that the fuel line was very very close to the spark-plug cap, and then remembered that I'd seen a 90 degree fuel union somewhere... so dug it out and this is a lot neater (if needing a bit of a clean up)


I'd decided to forego the Ardningly bike-jumble in favour of actually getting the JAPton out and visiting the local classic meet.

So, Sunday morning I checked the oil:


4.6cm as a baseline.


Oh - and I added the finishing touch..




Made it to the meet alright (even though I went to the wrong location first..... D'oh!)


Got a fair bit of interest from everyone, mainly because it's 10x louder than everything else, so your arrival is noted....





On the way home I nearly had a KSI, I was coming up for the turning into my driveway, a right hand turn, so I stuck my arm out for at least 5 seconds (I learnt how to make VERY OBVIOUS hand signals a long time ago riding Dad's old bike collection), brought my hand back to make the turn, and the ABSOLUTE $%^ in the Merc CLK tailgating me OVERTOOK ME.

IF he'd been a microsecond less impatient,  he would have had me over his bonnet.

I was so enraged I chased him down with the horn blaring and gave him a piece of my mind (the only bit working, sadly).  Didn't really resolve anything, but I think I did get an apology out of him... (eventually, after I had to apologise for using bad words at him, wtf?? He was at least 30, has he not lived in the real world? :wtf: ).



Post-mortem of the ride:  The RTV on the rocker cover seems to have worked, but oil is still pouring out of the engine somewhere.  The most obvious  location would be the base of the push rods, and it's got me thinking: I reckon it needs a crankcase breather.

The engine, as designed, has a crankcase that is (essentially) open to atmosphere, so the down-stroke pressure wave has somewhere to go.  Now that my engine has the return pump blocking that exit route, and there is no longer a cable-operated decompression lever, there's no crank-case breather.  The De-comp system in the timing chest was cable-operated, so there WAS a route to atmosphere through that cable (not great, but there).

I'm going to talk to one or two people about it, but I'm pretty sure I need to put a breather tube into the crankcase/timing chest, luckily, there's a very obvious and handly location for one.

I also reduced the amount of oil flowing to the head, siply to reduce losses but if the fitment of the breather works well, I'll wind it up again to make sure the head gets enough (it doesn't want too much otherwise the oil overwhlems the valve-stem requirements and gets into the head).  I reduced it down to about 1 drop every 7 -10 seconds (it's difficult to get an accurate measure with the random tickover...)

[Rex]

Looking good though.
Where was the meet?

[Rockburner]

Looking good though.
Where was the meet?

Thanks! With the short-track tank it's a bit of a looker, it's different to most Featherbed specials (Tritons, Norvins) because they almost always use the big Manx tank (or something like it, Lyta etc) for the extra capacity (and almost all of them are silver or bare metal these days).

Down in Selsey, West Sussex, I think it was a bit quiet tbh, propbably because there was a lot of other meets going on along the South Coast (including the bike jumble at Ardingly which is popular)

[Rex]

Yep, there was the Old Fossils Run at Waterlooville, and another classic meet near Guildford on the same day.

[Rockburner]

Have been in and out so trying to keep up to date with everything....

Yesterday I spent an inordinate amount of time looking for anything that was 7/16" in diameter in order to make up a new breather insert for the timing case, then eventually I found the remains of the stud I used to make the grub screws for the holes in the cases. I thought I'd thrown it away, which is not like me, but eventually it turned up in the Imperial taps & dies toolbox!

I also found the remnants of the tubing I'd used for the push rods, which is 7/16s as well.

I first tried making fitting from the old push rod tube


But the die got away from me somewhat....

So I tried to make something up from the stud.
But I only got so far...


Unfortunately when I tried to drill the hole down the axis of the stud... The bloody drill bit snapped.


So that was plan B down the shitter.

I had another, more successful go at Plan A, with the other bit of tube from the new push rods


But to get to that stage... I had to get the grub screw out first.

Which was a struggle.

I used an impact driver, heat, a dugga dugga, more heat, the impact driver again, more heat, hammering one end of the slot with a screwdriver, more heat, more dugga dugga...

And EVENTUALLY the !"£%^% came loose!

I mildly mullered the thing, so today I started by cleaning up the grub screw in case I need it again, and cutting the slot a lot deeper!


Some more parts also arrived today.

These are extended adjuster screws for the Concentric.


Compare to the old ones


And fitted to the carb


The main benefit, as far as I'm concerned, is that I can tweak the screws without a screwdriver....

I then rummaged through the filthy bag of filthy hoses again and found something vaguely appropriate for the breather and fitted it.


It vents directly into the catch tank


Hopefully that will reduce the amount of oil being blown out of the push rod tubes, and if so, I'll have a go at sealing them with RTV, but I'm hoping to have time for a quick test ride tomorrow....

Maybe.

Because the other thing I did tonight was whip the Pilgrim pump off the timing case. Still not sure why I did that... But hopefully it was worth it.

Well, in wanted to see if the continued oil weeps that end up dripping off the bottom of the pump were actually coming from the pump.


This is a "spare" I have, which I got out to peruse and ruminate on, because I wasn't sure exactly which bolts were holding the pump on.


This is the driven side.


The pump is only held on by 2 bolts.

So I undid and drained all the hoses, and removed the fitted pump
The gasket came off easily with a sharp knife, it was shagged.


This is where the pump fits:
Top to bottom: fastening hole, drive aperture, fastening hole, oil feed oil.


(No wonder they leak...)

I was actually pressed for time, so I hurriedly made up a new paper gasket using the original as a pattern


Then got the 3bond out again and applied it "sparingly"


Placed the gasket


More 3bond on the outer face of the gasket, then refitted the pump, remembering, thankfully, to replace the drive thimble first!


The primary and secondary pumps are both held on by the 2 bolts... But nothing is holding them together. Well, I think there's some silicon sealant or something, but no visible bolts/screws or anything! I also have a nasty feeling that silicon bond might be compromised....


I did the bolts up "finger-tight" to let the silicon 3bond go off with a little bit of expansion, then I'll do them up properly tight tomorrow, and pray that the grey goop didn't get into the feed hole!

[Rockburner]

More Thursday afternoon Shenanigans!

Frist I tightened up the pumps, we'll see if that makes any difference whatsoever (I doubt it)


I checked the level in the oil, it was showing exactly 4cm (which is a bit odd because I could have sworn it was a 4.2cm when I returned from the  ride on Sunday, maybe the oil shrank in volume as it cooled? Either that or there's actually a leak somewhere.... which I doubt...)
I then added another 500ml... and the depth went up to 6cm.
So... 500ml is APPROXIMATELY (the tank isn't a uniform cubic shape...) 2cm...  Interesting.  6cm is roughly half-full.



I was then just going around the bike checking things and realised the bloody tank strap was coming apart.
So I pulled the thing off (easier said than done, natch...), punched a couple of new holes a bit futher in, and refitted the end piece


I moved the attachment point to the forward of the two holes and redid the pretty wire...


To be honest, I really don't like that tank fitting.... I am going to think about improving it somehow.  (more on the tank later....)

Tacho don't work.


(but the rest I think is reasonably accurate)

I pulled the plug which I hadn't done after the last ride on Sunday.


Black and sooty.... to be honest, I'm completely unsurprised.  The ride home was at snails pace and the engine was not happy at low throttle settings.


I gave the plug a quick Millyarding




And chucked it back in...
Note to self.. FIND A BETTER PLUG-SPANNER  I hate this cheap piece of tat.


I checked the engine was still running ok, fired it up and it was fine, so I tweaked the oil slightly, and the idle speed (REALLY easy to do that with the extended adjuster screws! )
Even just idling in the shed there was some oil coming out of the push-rod tubes, but the crank case breather was working well, and was surprisingly dry.


So, I took it out for a spin.
Selsey Beach.  I actually had an ulterior motive... I need to talk to the local JAP expert in Selsey about the engine so went down to see if he was around, he wasn't, so I took the opportunity to get a photo or two at Selsey Head.



I then fancied an ice-cream so wended my way slowly over to Bracklesham (the next village west along the coast).
Even taking the back roads I was baulked by traffic virtually everywhere...


I did assuage the frustration by overtaking a few cars and trucks though - maybe not much to brag about, but it felt good given the bike I was on.

The engine breather, I think, has actually helped the engine run a tiny tad better, it seemed a touch more eager today.

One thing it DEFINITELY does NOT like is pootling along.... it's quite positively happier at 3/4 to full throttle and when it's pulling.  It does NOT like trundling along at 30-40 on a constant throttle... I had to adopt a sort of "hyper-miling" technique of dropping back at idle, or with the clutch pulled, then letting the engine pull up to the car in front before dropping back again.  I'll have to look at the tuning guides and see which part of the carb is effective in that range - I "think" it's needle height, so that may need some fiddling with.

I then took a slightly longer route home (to avoid having to turn right into the driveway... :roll: ) and got a run through the local tight bends - the bike suspension may be somewhat hard and jarring, but it handles beautifully, holds a line and tracks very nicely, I can't wait to get it out on some open sweepers.

Oh yeah - I also tweaked the side-stand round a bit on the frame tube, and the bike sits up a bit straighter now, which I much prefer.

There's still a way to go yet though: things that need a good looking at:
- carb tuning
- oil leaking (hopefully some RTV on the push-rod tubes will contain most of it).  I have a nasty feeling there's a couple more areas though. The oil return feed line leaks where it goes into the tank, which confuses the hell out of me because there's absolutely no reason for it to do so - I even trimmed a cm off the end because it was looking a bit tired and it's made no difference. Hmm....
- the tank, yeah... it's rubbing against the steering head (well, the rhs downtube actually) and it doesn't sit centrally on the frame pads.  So - I need to make up a boss or something to hold it centrally... hmmm... I just remembered I have something that might do the trick... <makes mental note>
- LHS fork needs a new seal, and I may as well rebuild it (I hate rebuilding forks...),  On Sunday the seal seemed fine, but it was weeping today, it needs doing.
- Tacho - I suspect the speedo is just some old thing Dad bought at Kempton, so that may be a winter project to see why the Tacho isn't working.


It ain't over folks!