St4s Camshaft Wear | Engine Rebuild

Yes, that's where all of mine are currently - Newman Cams has a backlog of them to do.
If I could borrow a spare, that would be great - I'd return it after I'm finished with it of course. Will PM if that's OK?

 

So, slow progress on this recently, as I didn't manage to get the opening rockers back in time to measure which shims I needed before all the dealers shut for Christmas - and also our Son was born on 11/12! Much less time for mucking around with bikes now!

So, as an aside, I tried to answer the question "what do you get the petrolhead who has everything" for my Dad for Christmas.

Using the old parts removed from the engine, some rough measurements, Fusion 360 and 3D printing, I came up with the below:-


A functional display model of the desmoquattro valve gear. I laughed when I needed to check and adjust the valve clearances to make everything turn smoothly, and found myself wishing that the actual desmoquattro heads had such good access to the different components! I also found that the cambelts can be shortened and super-glued, but wouldn't recommend it for longevity!

 

Little update, all opening valve clearances measured and shims ordered.
A question for the collective hive mind - I'm using ExactFit belts and I know from previous discussions that the "new" tension for installation is 99Hz, but what do people use when checking cam timing cold? I've seen 200Hz in other threads. I'll use an old belt (low mileage, removed from the engine before strip down) to check cam timing.

 

General setting to "(not) good enough" factory specs is done by the dots on standard non-adjustable pulleys. That gets us a place to start.

What I am talking about, though, is measuring and setting the exact opening and closing timing vs crank rotation for each cam and adjusting it to exactly where I want it. According to information available on the 'net, the standard settings are +/- half-a-housebrick versus the intended spec due to manufacturing tolerances (position of cam and pulley key ways vs cam lobe and pulley teeth machining, tensioner roller exact diameter, exact position of cam bores in the head, etc). There were offset keys that were available to adjust the timing of each cam to the nearest degree - I'm not sure that these are still available, though.

However, I am using adjustable pulleys from a later engine to get the timing of each cam exactly dialed in. So to do that, I need to replicate the conditions found when the engine is hot. Due to thermal expansion the heads will effectively get further away from the crankcases, raising the belt tension.

These adjustable pulleys weren't really intended for doing this, rather for ensuring the belt tension on later engines was set accurately. Nevertheless, in effect they're a vernier pulley which is adjustable throughout a wide range, so more infinitely adjustable without having to resort to offset woodruff keys.

Paul, you're right in saying that the setting tension on a brand - new cold belt is 99Hz. What I'd like to know is, does anyone know what the "engine hot" belt tension is.

Hope that makes sense?

 

So, little tiny update on this, hopefully with a view to getting this finished at some point during the year......

I had decided I didn't like the way the inlet manifolds were partially machined from the factory, leaving a sharp edge and a rough sand-cast inner surface up near the throttle bodies.

So a quick tickle with a sanding drum on a low-cost Dremel alternative soon had that looking a bit better.

Probably won't make naff-all difference, but looks better to me!

Today I've been looking at the cam timing, and have definitely fallen into a trap due to my mixing and matching of parts, but more on that later.

 

Does anyone have a torque value for the 3 x M5 bolts that hold the cam pulleys together? obviously there's nothing in my service manual, as my bike didn't come with these pulleys. I managed to find an ST3 service manual online, but it doesn't specifically list the torque for these. Do they come under "unspecified fasteners"? 5Nm?

 

Hadn't actually thought about the throttle-body end of things. Will check that out.
The inlet stub-to-head matching was surprisingly good, I was impressed.

 

To cam timing, then. First off, I fitted the crank turning tool and degree wheel to the crank, and using a piston-stopper that I made from an old Honda caliper bolt, found TDC.

Deciding to start with the vertical cylinder, I put the old belt back on and carefully turned the engine over by hand. Which then stopped as the inlet valves hit the piston. Balls. After checking all of the marks were aligned and getting the same result, I promptly got fed up and gave in for the night.

Got back out there today and worked out the issue. Anyone paying attention earlier in the thread may well have predicted the cause - I'm using a combination of cams and pulleys - a mix of early (1L inlet, A1 exhaust) and late (3K inlet, 3H exhaust) cams, with the later factory adjustable pulleys.

What I hadn't noticed (or thought to look) was that on the vertical cylinder the timing marks are in a different position on the cam bearing carriers, due to the need to be able to put the timing locking pins in, to keep the timing in place whilst loosening the pulley screws to set belt tension.

I'd used the old cam bearing carriers, which carry the timing marks at ~12 o'clock, as seen here:-


But luckily I had kept the ones I got with the pulleys, as can be seen below, the marks are in a completely different place (~8 o'clock exhaust and ~2o'clock inlet):-


So, by working out which combination of bits I'd used, I sorted out my error and worked out where everything was supposed to be. Made a note inside the cam belt cover for future reference!


From there I was able to dial in the cam timing for the rear cylinder to the specs suggested by Brad Black - 113° ATDC inlet centreline, and 110° BTDC for the exhaust, using a home-made end for the DTI.


Rear cambelt is now on and tensioned.

Finally, I checked the actual vee angle of the engine, using the TDC stopper in the horizontal head, and the degree wheel which was still set to TDC of the vertical cylinder. TDC of the horizontal cylinder should be at 90° ATDC relative to the vertical in an ideal case.

There's some parallax (sp) error in the photos, but you can see we hit the stopper at ~122°ATDC(Vert) one way and 55°ATDC(Vert) the other. Half difference between the two is 88.5°, but there's absolutely nothing I can do about it. This means that the horizontal cylinder is 1.5° "late" or retarded vs the vertical, or conversely the vertical is 1.5° advanced versus the horizontal.

Not the worst I've ever seen - I once saw a Ford Kent crossflow crank that was 4° different between cylinders 1/4 and 2/3 for TDC.

I'll try to do the horizontal head during the week. Oddly enough, the marks for the front cams are identical between new and old.

I'd like to know if the IAW59M ECU can make a timing offset between the cylinders, to compensate - anyone know?

 

Does anyone know the correct location of the spacers for the horn bracket? I've got the engine back in the bike, and have 2 spacers (a thick one and a thin one) that I had cable tied to the horn bracket. The problem is the thinner one seems too thin to take up the recess in the cam bearing support. I can't find them in the parts list, either.
Any ideas?

 

Finally an update! Short version, it lives!!!! For the longer, slightly boring version, read on....

Last weekend I got the engine re-installed, wiring re-attached and oil system plumbed back in. Couldn't complete the water cooling circuit as although the parts manual suggests that all the worm drive hose clips are identical - they aren't. 16-27mms work for everywhere except the inlet to the thermostat and the inlet to the water pump, which need a size up (20-32mm). Got those ordered, and they arrived during the week. Put a label inside the rear belt cover in case I forget where the timing needs to be:-


So yesterday I fitted the remaining hoses and filled the cooling system, with only one small leak at the vertical cylinder inlet, fixed by changing the position of the clip slightly.


With the sump full of oil, (I also back-filled the oil cooler through the port for the cylinder head feed line), I turned the engine over on the starter until the oil light went out. I checked for oil at the heads by slackening the banjo bolts - all good.

So with no excuses left, the tank and fuel pipes were refitted and eagerly thumbed the starter button.

Plenty of cranking, but no life. Then the occasional cough and at one point even a half-a-second of running on both. Gave up for the day at that point, as I didn't want to turn the engine over on the starter enough to risk wearing things out. At least I gave plenty of chance for the oil to get round it....

Today I started again from the basics. Used JPDiag to check I had spark and fuel, which I did, and even tried swapping the fuel pump/ignition and fan relays in case they were dodgy. No dice, same behaviour.

Then it dawned on me that I hadn't checked the gap on the crank sensor, so the shim was whipped out and we tried again - more life than before, but only on the vertical cylinder. Knowing I've had issues with ECUs in the past, I swapped to a spare but no change.

Last step was to reset the TPS as per Brad Black's site - 150mV fully closed using a multimeter, 2.6° at the idle stop using JPDiag. I then set the throttle bodies to approximately equal opening using a piece of thin paper as a feeler gauge.

The engine started easily once again, but still on the vertical only. I could hear the horizontal trying, so had a quick twiddle on the air bleeds, and hey presto - happy on both cylinders, with no obvious signs of any fluids peeing out or horrible noises. Not even any oil smoke from the exhausts.

TLDR; it works. Next step put it back together and book an MOT!

 

Bringing this one to a close, got the bike back together this morning, having made a couple of spacers for the horn bracket from a couple of stainless steel cap head bolt heads.


Then off for an MOT which it passed. Was a bit nervous taking the newly rebuilt bike back out on the road, but the short distance covered to the MOT centre shows the engine, gearbox and clutch being much smoother than before, although the idle mixture is now all over the place. Haven't used the throttle much in anger yet, and was keeping the revs reasonably low, but it certainly seems willing.

Now looking forward to getting some more miles on the ol' girl and getting the engine run in properly!

 

Bringing this one back, got out to the garage this morning and found a small puddle under the bike, that was clearly antifreeze.

Got the fairings off, and found the lower radiator connection leaking. The hose clamp was tight, but looked like it was too tight, causing the spigot to be D-shaped instead of round.


So I drained the coolant and removed the radiator to have a better look. It's not in great condition, with some odd-looking bends in it and the inlet & outlet spigots looking to have had trauma in the past.

Is this shape along the front lower edge (for mudguard clearance?) supposed to be there?


Bend at the top edge near the mounting brackets.


Top hose connection too close to fan bracket, end tank deformed.


Bottom hose connection D-shaped - I probably over-tightened the hose clip when I put it back together.


The core doesn't seem toooo bad, with no missing fins but some of them folded over, so I decided a bit of gentle reshaping of the inlet/outlet around a suitable former (impact socket) using a clamp.

It's not a brutal as it sounds, and the clamp is used gradually around the spigot to persuade it back to somewhere close to round. The aluminium is soft so I had to take care.

Put it back in the bike and refilled it, so far it seems to be keeping the water on the inside, which is novel.
We'll see how it goes.....