How to build a 30hp motor – by Last Triumph, age 34 ½ …..
Part 1
With days off now a distant dream for the time being due to my work, I’m restricted to evenings to get anything done, so here are the results of the last few nights when I’ve scrounged a hour here and there.
So, with the left had side of the case in the stand, clean and ready, the first job is to clean, grease then mount the distributor shaft, thrust washer and spring.

When installed with the distributor and spring in place, (mine came had just one thrust washer, others may have two) there should be clearance of 2.54mm (0.100”) which measured spot on for me. The distributor shaft and gear was given a coat of grease upon installation.

At this point, it is best to set the distributor timing position – theoretically, this can be done later, but if you want the distributor to be in the correct position so the vacuum line meets up etc, it’s best to do it now before installing the crank.
Before I did this, I completed the one thing I neglected to do when I rebuilt the distributor which was to set up the correct rod length for the vacuum advance. It should measure 43.4mm from the tip of the rod to the base of the housing. This is done by means of adjusting the threaded rod and lock nuts. Also, to prevent the unit ‘over advancing’ the clearance between the housing body and the bottom of the lock nut should be 3.5mm. Obviously, I spent half the night getting this absolutely perfect…. I just can’t help myself sometimes.



With the distributor installed on the shaft, the next job is to install the cam follower guides which on early motors are attached to the ends of the pushrods, which themselves needed a thorough cleaning, inside and out. They were soaked over night in a tray of thinners, then when fully drained, I squirted brake cleaner down each one until it came out the other end crystal clear. I’d already made a note of which one went where previously. A final blow out with the air line ensured they were absolutely spotless.
This pic was before I started to clean them. For any youngsters out there – cleaning pushrods is not a great ‘first date’.

The pushrod tubes are soaking as I type – uurrgghh!

So – back to the followers. They all had the usual thinners bath, tooth brushing, wipe down, then brake cleaner followed by an air line to remove anything the cloth might have left behind. Boring and laborious it may be, but my Dad really read me the riot act about cleanliness during assembly.

They bolt inside the case with the nuts held tight with little locking tabs bent to the flat of the nut – not tightened in this pic.

You will notice that there is a machined flat surface on them which aligned the cam follower on the end of the pushrod which is a very close tolerance fit indeed. With the pushrods and guides oiled, the pushrods should fall out of the case under their own weight without catching or binding which can take a few goes to get the guides in just the right place, and keeping them there as you tighten the nut. It’s best to spend a while doing this as the last thing you want when the case is together is not to be able to get a pushrod through the guide…

Whilst were’ talking cleanliness – make sure all your tools are clean before starting any assembly – you don’t want bits of crud falling in your gleaming motor that have been stuck in a socket or ring spanner etc.

Now things started to get a little more serious. I needed to complete final assembly of the crank, so after checking the torque of all the rod bolts was 36ft/lbs for what must have been the 10th time, I fitted the 1 and 4 bearings and the oil thrower ring – after a thorough cleaning in the usual manner of course. Note that the oil thrower ring has the concave side facing away from the crank. Double and triple check all the journals are immaculately clean, and then coat journals and bearings with oil.



Remember these little critters that were blasted across the garden with the air line? – These are the bearing locator dowels and now is the time to install them into the bearing saddles.


The split number two bearing also had a bath. One half goes into the case at this point, ready for the crank.


And here it is, ready to go home….

Just before installing the crank, now is the time to make sure the distributor is in the right rotational position and that the rotor arm is facing towards the little notch in the top rim edge of the distributor body. This is the position that the number 1 cylinder will fire.

This is because we will install the crank by holding rods 1 and 2, with rod one being all the way up in the top dead centre position, thus when installed on the distributor shaft, the timing will be correct, or very close and the distributor will be in the correct position.
So, by holding the rods, gently lower the flywheel end of the crank and bearing into it’s saddle – you will probably need to rotate the bearing a little and then you’ll feel the dowel enter the location hole on the bearing and it’ll drop in place nicely. Then move forwards and repeat on the number 3 bearing and finally the number 4 by the crank pulley. Once this one is in place, the crank seems to click into place with a very satisfying a precision ‘thunk’ and will feel rock solid. Gentle tap the crank along it’s length with a soft mallet, but be sure not to hit the bearings. This will help seat everything when we want to close the case later one.
Here it is - safe and sound! Interesting to see the oil thrower ring – nice design.


Next up is the cam, which needed a thorough cleaning also. Here it is after a very deep bath and scrub, followed by the brake cleaner, air line routine…


With the gears and bearing areas (30hp motors don’t actually have bearing, the cam just runs in the case) oiled, and the cam lobes covered in assembly lube, it is now time to fit the cam. The cam needs to be timed with the crank by means of lining up the dot stamped on the cam gear between the two dots on the crank gear. You can just about make this out in the picture.

With the crank rotated so the cam gear can be engaged in the crank gear without being near the case, slowly roll the came down into the case making sure the gears stay meshed.
One installed, rotate the crank using the roods several times in both directions. If all rotates freely and the cam doesn’t try to climb out of the case, all is well. I did a backlash test but there wasn;t any on mine – it was a perfect fit as it is the original cam and gear etc.
Here is the cam installed and timed. Note how close the cam thrust faces are to the case.


At that point I called it a WIN and packed up. Next I’ll be doing a little assembly on the other case half then closing them up!!!
Tune in next time for more LT action!
“Taxi.....”
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