Hitchcocks Forum

Just dropped the bomb on a 612 kit from our hosts. Scary, now spent more than the cost of a brand new UCE bullet on this project! But anyway. I've just split the donor engine. A 2004 500 bullet. A few questions and observations for interest.



First off, I was wondering if there's anything I should be doing while I'm in here? It's getting new bearings throughout and the crankcase will need to be relieved to fit the new exhaust cam in but anything else?



Secondly, It looks like two of the pairs of stud holes have been machined to take dowels. None are shown on the schematics and this is definately the first time this engine has been split so it's like that from the factory. I'd intended to ask my local machinist to fit dowels when he's fitting the bearings etc. but it looks like I should be able the throw some in there anyway. Is there a reason there aren't any?







Third thing. I'm intending to re-instate the "original" breather system. This engine still has the castings from the original crankcase breather on the upper left side just below the barrel present but not drilled. I've ordered a Redditch style bolt-on breather stub and I'll run it past my machining guy to see if there's enough alloy to face-off the crankcase casting and bolt that on. Failing that, it'll be a case of drilling the cast stub and tidying it up enough to fit a hose to it (maybe cut a thread on it and fit a hose-tail). Also lets me look at the breather hole between the crankcase and oil tank. It's tiny! No bigger than 5mm. I'm going to solder this closed.



















On the last one I had apart, the return hole between the crankcase and the timing chest also seemed awfully small for the volume of oil the pumps can chuck out to passively return through. I was considering enlarging the hole (maybe slotting it to maintain the oil level in the timing chest) Someone at the factory must have thought so too, this one has the small hole then another, bigger one above it.




Hope I got my HTML tags right!

My last paragraph should read "the return hole between the OIL TANK and the timing chest."

All the best for your project. Another option for re-instating the breather is to drill and tap a hole 1/4" BSP just behind the existing stub and fit a hose-tail to take a 3/8" or 1/2" hose.



A.

Hi Stinkie, I done my 612 a few years ago. A couple of points: 1. you may have to file a little bit off the lip that forms the sump chamber at the bottom of the crankcase – the flywheels are slightly larger diameter and can rub there. 2. Don’t be tempted to run with just the 3mm compression plate! I made that mistake at first and suffered terrible pinking as a result. So use both plates supplied (2mm + 3mm) and I suggest a minimum of 3 base gaskets. I also smoothed off all the sharp edges (including the valve pockets) from the Accralite piston, which I felt would reduce the likelihood of any hot-spots, and would further reduce the compression a little in the process (just my preference). 3. When grinding clearance for the exhaust cam sweep, you will find improved access if you remove the cam spindle. I have a cam spindle that I made slightly undersize (sloppy fit), so that it can be dropped in and out in order to accurately check the clearance of the cam as you grind (thus avoiding removing more material than absolutely necessary). When done, you can then fix the proper spindle back in. 4. My engine breathes via the elbow at the base of the barrel (which was already in use) with the pipe running high over the mudguard and into a plastic bottle in the right toolbox (with a duckbill on the end). Mine breathes into the bottle approximately 100ml of oil per 100 miles (proper miles, not Km’s), which I’m fine with. 5. From memory, I’m pretty sure there were no dowels locating the crankcase halves – I think at least two of the studs are suitably machined to act as such (others may confirm this?). If you want, I will be happy to post you the dummy cam spindle, as long as you return it when you’re done! (Let me know on that). Good luck with the build – I think you’ll enjoy the result! Regards, Barry.

Thanks for that. Plenty to be going on with.



I've actually already ordered a cheap cam spindle from India for that exact purpose but thank's for the kind offer.



I'm quite excited about the whole process. I'm looking forwards to doing some bits of "proper" engineering like measuring cam end-float. I'm also going to borrow a burette from work and physically measure the compression ratio.



I'm not sure if I'll be able to bring myself to modify that piston.

The upper hole was originally there to equalise pressure between the timing chest and the oil tank not as an additional return route for oil exiting the timing chest. The oil level sits a lot lower than the bottom of the smaller hole. If you could (temporarily) fit an old style filler cap with a built in dipstick into the threaded crankcase orifice you'd be able to see where the upper and lower oil levels sit in relation to the lower hole.

Reinstalling the old breather system and blocking the airway between the crank and oil tank will result in a dramatic reduction of air movement (and oil loss) from the spigot hole currently used for all engine breathing. Probably wouldn't do any harm to retain this rather than revert back to the original breathable filler cap required to relieve air pressure in the timing chest built up from scavenged air from the sump.

kudos for doing this


i mounted my 612 kit long before there was speak of the efi's.



today i wouldend bother to pour this amount of money the old type of engine.

its not only about putting the kit in, because in time you'll find you'll have to upgrade everthing around it.



these days i would get a second hand conti, put a high bar on it and have a way beter bike for in the end less money.

"The oil level sits a lot lower than the bottom of the smaller hole. If you could (temporarily) fit an old style filler cap with a built in dipstick into the threaded crankcase orifice you'd be able to see where the upper and lower oil levels sit in relation to the lower hole. "



It actually has the threaded type filler cap with dipstick. I was going to do this anyway tonight to see where the oil normally sits, I'll post a picture.



"Probably wouldn't do any harm to retain this rather than revert back to the original breathable filler cap required to relieve air pressure in the timing chest built up from scavenged air from the sump. "



Good one. I've done this on my 350 on the basis that it probably doesn't want a vacuum in the oil tank to fight the feed pump. I fitted a small filter element designed for a car crankcase to the oil tank spigot.

Some more thoughts on the 612 build! With the 5mm stack of compression plates (if retaining the original cylinder studs) you will of course lose 5mm of thread length to engage with the cylinder head nuts. To go some way to counter this, I trimmed off the tapered “lead-in” of the thread at the end of the nuts to maximise the thread available (using a lathe to ensure squareness and removing just enough from the length, and no more). It may have not been necessary - the gain being not much more than 1mm - but I felt happier doing it! Another thing you will find, is that because the engine will be 5mm taller, fitting and removing the rear rocker cover is almost, if not impossible (because the frame tube is in the way) without removing one of the studs. I use an ordinary nut, with a saw cut through one of the flats, used with molegrips, to whip the stud in and out whenever I need to remove/refit the rocker cover. B.

Good tips.


I'm planning on making some new studs anyway. The cylinder head studs on my engine are bent from it being stored with no top end on and having stuff stacked on top of it. The plan is to make a set of new ones slightly longer than standard and with a square on the top (inspired by our hosts ones I have fitted to my 350) to allow for their removal with the head in-situ. Makes stuck cylinder heads a thing of the past because they can be twisted off.



Good tip on the rocker cover studs. Thinking about it, the simplest way may be to file a flat on the stud just abover the bottom thread. Then the cover can be lifted up slightly and a spanner inserted in the gap to loosen the stud. I'll have a look at that nearer the time.



I also think this would be a good time to make some marginally longer gearbox studs, again with a flat/square filed on the end, so the gearbox can be fitted or removed with the engine in the frame.