For the manner in which men live is so different from the way in which they ought to live, that he who leaves the common course for that which he ought to follow will find that it leads him to ruin rather than safety.

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Sunday, October 20, 2013

Engine building

I am by no means an expert engine builder. This is only the third one (actually, same one third time!). I'm not going to try and teach anyone how to build a Triumph T120R through this blog. There's very little that I can show that is not already common knowledge in the engine world.

When I first built this engine, it was a twin-carburetor, 650cc. It had a little bit of an over-bore, but nothing drastic. The cams were actually meant for flat track racing, and they were crap down low. However...when you got up into the RPM's a bit, all of a sudden the engine just took off. Not good for city riding, but a blast on the freeway.
Now, the engine has a single carburetor, and displacement has been bumped up to 750cc. The new cams add to the bottom and mid range, with only a slight bump to the top end. They are much better suited to bar hopping through the city.
Some people, mainly the ones who want to rip off the uneducated, will say that you can't build a durable hot rod Triumph engine for less than, say $4000. I call bullshit! My cost on this engine is below $3000. The head was built by a gentleman who holds records at Bonneville. The crank assembly is balanced. The cams are brand new (as opposed to rehashed) from Johnson Cams. The rods are from Crower. The cylinders and pistons are from Morgo (by the way, it is cheaper to buy them direct from England than from a US distributor). In other words, as long as you do a little research, you can keep costs down.
All the components in this engine are top-shelf. It will last a long time, and it will make some power.
On to the good stuff...
Morgo cylinders. It took some work to make those tubes fit, as they are from '71. The head and tappet blocks are from '66. The design changed in between. Nothing you can't do with a lathe and some patience.

Inner transmission.

Cylinders mounted. This engine was originally manufactured with Whitworth threads, an old British standard. The cylinder studs, along with other bits have been converted to imperial.

Always mark your parts so they line up correctly. With small variances in machining, you need to match everything together. The "E" on the pistons is for exhaust, meaning that that side of the piston faces the exhaust valve.

Seriously, this is probably the most obnoxious intake set up you could put on a Triumph. A 34mm Mikuni tied to a Cobb long runner intake. Totally impractical, but hey...this is choppers!

The head isn't actually tightened down at this point. I am doing some dry fitment work for those push rod tubes.

There will be more to come as I get everything wrapped up. Luckily there is very little work that needs to take place on the rest of the bike. The engine has been the slow down. As of the other day, it has been two years since I rode this bike. As I wrote about some time ago, there was some drama with a supplier, and then my accident this Spring. I'm looking forward to getting to spend some time with my baby again (a boy and his machine, sigh).

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