Dating JAP 600 Sidevalve

[john.k]

Burman CP with clutch is easily found,cheap too,and cheap spares............the catch with all the industrial JAPs is the driveside mainshaft is too short for a 4 speed box.............as mentioned ,a Sturmey LS is ok ,but ,pricewise ..........not complaining ,cause I sold a Sturmey LS ,two stud mount,w/clutch,but had a busted tooth on second,.....to a tosser makin a fake BS or Zenith, for $1000........thats right,1k Ozzie pesos........but still.....its kinda a lot to someone used to buy complete vintage bikes for $10

[ColinF]

Right, a bit more research required. Just looking around the Autojumble last Sunday there were a few boxes about for around the £100-150 mark. Couldn't identify all of them, there was a BSA one but the vendor didn't know how many gears it had! I did see quite an elegant looking Ariel one that was cast onto the bottom end of a twin but didn't look unit ( if that makes any sense ) could have been cut off neatly where the casting joined if it was up to it ( Arrow or leader ? ). Haven't measured everything up yet, just thinking out loud.

[33d6]

Now is the time to start thinking. As you have to get both the primary chain and the rear chain in alignment plus provide means for adjusting both it's easier to buy a frame with gearbox still in it. This presents no alignment issues as does a frame from this, a gearbox from that and an engine from something else.

So, do your homework first and look for a frame and gearbox together.

If you don't go down the frame/gearbox combo track probably the cheapest gearbox option is a heavyweight Albion. In general Albion are unloved but with little effort can really come up to scratch. I recommend looking through the Hitchcock site and reading Don Morley's rebuilding instructions. Albion were used in many industrial applications so late ones are often found with hand change. Very vintage in character. Nor is it uncommon to find a three speed and reverse heavyweight. Useless in 99% of motorcycles but have their place in specials. Laugh at anyone wanting real money for an Albion.

Much research and thinking is required before jumping in further. All hours and hours of fun, fun, fun.


 

[john.k]

You used to be able to buy a complete new Indian Enfield box and clutch for about 250 quid.....but I think all the cheap Enfield stuff has been cleared........The last project i built with a JAP engine was using a AJS ,mid 30s ,complete ish,but with no motor..............anything project with girder forks wheels and guards wont be cheap tho......Tanks are generally cheap for AMC bikes and BSA s,if you arent too fussy...........Any kind of panel tank will be dear tho,especially Ariel or Triumph......................expanding on the JAP mainshaft length........most bikes went over to 4 speed boxes around 1932/33,and at the same time fitted an extra ball bearing on the mainshaft to support the extra length needed to line up with the wider box...........another thing with industrial JAP sv s ,is a long straight intake wont clear a magdyno,and even with a plain BTH mag,you need either a long intake ,or mount the carby on its side......as was done with some bikes.......but Amal 76 on its side is problematic,as anyone with a Triumph single will tell you............incidentally your JAP would have had a Amal 225/3 carby,which is where the long arm floatbowls come from ,often puzzled over at swapmeets.

[ColinF]

Thanks for all the input so far...this is brilliant!  I wasn't sure a classic bike forum would be that keen on a special with an industrial motor. I have to say the idea of building a special from scratch is very refreshing.I have restored modern "classics" to stock, am about halfway through restoring a Bultaco Sherpa with a few subtle mods and building an HRC VF400RK TT F3 replica ( from genuine HRC manuals ) .The Bultaco is quite straight forward and i have a list of known parts it needs, the Honda is a bit more involved because it uses different forks and wheels and most of the special HRC race kit parts it needs will have to come from Japan ( which isn't easy or cheap ). So although i want a simple looking bike it might actually exercise the old grey matter a bit and require some engineering solutions along the way.I've seen similar projects on the web where the builder has made the frame, it would be nice to have it exactly how i want it but don't really know how hard it is to get one through the SVA test. I'm led to believe the bike test is quite a bit simpler than the car one...............more research

[john.k]

If you arent fixated on rigid frames......a donor Ive used is the Kawasaki KZ400 twin....this frame has sufficient room for a separate motor and gearbox,and Ive bought nice ,roadwrthy bikes for a couple hundred dollars........Otherwise ,if you want rigid,an Ariel single frame easily fits one of these motors............but nowdays is a bit costly.........girders will be a lot more.................now,Im not dissing you,but IMHO,the motor you have is incomplete,and youd be a lot better off with another motor thats complete...............If you keep your eyes open at swaps,you might pick up JAP OHV heads to suit.....all the ally bits are available as newmade and the motors convert easily to an OHV,which looks a lot better...........i once went into a mower shop,and was buying chainsaw parts ,and mentioned JAP stuff,and the guy had a lot of new spares for the Howard Junior JAP motor,..I bought the lot.

[ColinF]

Funny you should mention the mower shop, i was just talking to my neighbour about an old chap he got to sharpen a cylinder mower blade for him.I remembered him saying at the time that he'd been there for years and you couldn't walk around his shed for all the old engines laying about so i'll try and pay him a visit soon to see if there's any old rotovator motors. Another possibility is one of my best friends work for an agricultural engineers selling chainsaws/mowers/ride-ons etc and he's always out and about around farms and estates where he comes across the odd older bit of kit "waiting" in a shed. I have to speak to him anyway because my sister has just killed another ride-on!