1946 bitsa project

[SEDoan]

Thought I'd take Vincent's advice and post an update instead of just spannering away.

Before Christmas I'd decided to use a cylinder head with a badly recessed intake valve seat. I had hoped to get a local shop to replace the valve seat but two said "no" and the third said only in the distant future. I'd worked around the edges of an automotive machine shop as teenager so had an idea of how to do it. The biggest hurdle was the cost of the valve seat counterbore cutter. So I decided it was time to spend some money and learn something. I bought the cutter and seat and made the rest.

Heated the head in the bbq and drove out old valve guides to drive in new. Why are there so many cast iron heads with bronze guides??? Also check out the depth of the intake seat.

Turned a pilot to center the valve seat cutter on the valve guide.

Then made a fixture to drive the cutter and platform to hold the head at 37.5 degrees approximately.

Wood it work? Seeing as I was only ever going to do a few cast iron Ariel heads I figured why spend the $$$ on a fancy tilting fixture? It did ok, but it chattered under power. Adding the spring did not help matters so I just turned the spindle with a wrench.
(also considered tilting the head the required angle but was concerned that the weight of the tooling would tend to force the cutter off center.) Don't know why the picture is sideways.

[SEDoan]

There is a messier part of the story in that I originally bought a cutter for a 1 13/16" valve seat. This would have been fine for any normal Ariel valve seat, but this one had been ground so deep that the new seat would still be recessed. I ended up buying a second cutter of 1 7/8" so failed my attempt at doing it on the cheap. Wiser folks than me would have learned that it is cheaper to leave it to the experts - but not me!

One concern was the extreme interference fit. The valve seat was made oversize and the cutter cut undersized so there was about 0.007" interference fit. Looking up the expansion rate of iron and steel it turns out that the valve seat bore will expand about 0.001"/100*F. I could heat the head to a generous 300*F and liquid nitrogen is about -300*F. But only dry ice was available to me at -100*F. I chilled the seat and driver, heated the head, and the seat went in without problems though it did cause some anxiety.

I had carefully aligned the mill to the guide pilot in preparation for cutting the counterbore - lapping the valve showed that it was time well spent.

You may remember from a previous post that I had rebuilt a prewar gearbox for my '39 bitsa so that I could swap its postwar gearbox into this bike. But I'd put the gearbox together 15 years ago and it whined in 3rd gear. Sometimes it's best to leave well alone (or if it ain't broke don't fix it) but that whine and uncertainty was nagging at me. So I made a big mess. Yuck! It wasn't worth it! The gearbox is in really nice shape. I reduced shaft endplay by about 0.010", made a new nut for the KS end of the mainshaft and installed a kickstart stop cushion. And then reversed the layshaft clutch putting it together so had to pull the cover back off...

Getting the gearbox ready to put in the frame meant making an adjuster draw bolt and nut, and a clutch plunger and adjuster. "Fortunately" my Moto Guzzi had been rear ended so I had a bent Italian steel axle shaft with which to make parts.

[KenS]

Been busy working long hours as well I see. Excellent work on the valve job!

[John O]

Great work well done

[SEDoan]

Thanks for the compliments. It's a learning experience

So the last 2 posts were the big lead up to putting the engine in the frame. I'd already fit an empty crankcase and the gearbox, but I'd not been fussy about the fasteners and all that.
One of the goals of this project was to use up some of the extra parts I had lying around while still building a solid bike for a friend. Some of those parts are an eclectic array of cycle thread fasteners. I ended up making the bolts with the D-shaped shoulders for the rear engine plates and the lower gearbox pivot bolt. Some of the studs I had lying around needed to be shortened - more threads cut, then cutting the stud to the correct length. Next task was to find a matching set of nuts and washers of appropriate thickness and diameters. You know how it is... Most ended up as blackened steel with a coat of linseed oil that also serves as a thread locker. Everything is in tight and it shouldn't have to come out.

This allowed me to check chain alignment and start installing the primary. Alignment looks great - surprize! New chains are on order.

And today we had the warmest day of the year so far so was able to paint the cylinder head in the sunshine.

[Vincent.vanGinneke]

very nice work ! thanks for sharing!

[KenS]

Looking good!

[SEDoan]

Primary and clutch update:
Installed the chains. I tried to get away without using a 1/2 link in the primary, but the 23 tooth engine sprocket requires it...
I've always made my own primary gaskets, but this time I'd ordered one from Drag's and it was so easy!

Next was the clutch - I had the parts but they were in rough shape. It had been in an HS that was beat to death then left to rust. The clutch basket spot welds had to be drill out and basket slots filed.

For some reason the pushrod hole in the pressure plate button was off-center. Not sure how it happened but probably involved an arc-welder and sloppy drilling. So new button made.

The clutch center was in terrible shape. Apparently the studs had been stripped or ? so someone had welded all-thread into the clutch center with a arc-welder. Gobs of slag. (Wish I'd taken a picture of it) It had good splines though. After drilling and grinding out the all-thread, the stud holes had to be repaired with a rethreading kit. It now required studs with 20tpi on one end and 26tpi on the other so I made them and mushroomed the ends so they would not pull out. Also filed the slots and turned off the bottom flange so that a 4th friction plate could be added to the bottom of the basket. Clutch plates were cleaned up and installed.

I had two pushrods, one too short and the other too long. After excessive trial and error the long one was worried into submission and the end hardened. The clutch lever, an old AMAL, was missing the threaded adjuster so made one on the lathe and practiced knurling for the first time. A clutch cable was made which revealed the clutch lever flexing under pressure because of a gap between the bar and the pivot anchor. The old Amal lever has a step in the clamp casting that allows it to flex when pulling the lever. The matching Amal brake lever has a similar, but much smaller gap. I made a small aluminum channel to tuck between the pivot and the bar to backup the pivot anchor. Then I did the same for the brake lever.

The clutch pull is stiff but the pressure plate lifts amazingly evenly.

[Vincent.vanGinneke]

I use a clutch cable with a teflon liner, it does make a difference.
And I have elongated that hole in the engine plate where the cable passes to get the route better.

[SEDoan]

Thank you for the ideas Vincent.