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The V-Twin Project

the first steps

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So we had a Block and a lot of bits. The first thing that we had to get our head around was what the previous guy had been thinking for how every thing would go together.

There were some things that were obvious problems needing solutions and a few things that I didn't agree with that he had done in design. That happens, no one is every completely right. The main problems were getting the crank balanced, figuring out the oil flows and figuring out how to do the cam chains. Some of these problems are only now being fully solved 3 months later.

The Crank

Because we wanted to use the standard crank to make life cheaper and more straight forward (cough, cough yeah right) the crank needed to be rebalanced to fifty percent ( 90 degree v-twin standard) of the non rotating mass to accommodate the extra weight on the crank. This meant a lot more mass to the counter balance because
1 the single had a light crank shaft to start
2 it used a balance shaft which we weren't
3 we were adding a lot more metal to the engine (longer pin, piston, conrod and gudgen pin) .

This all meant adding very dense Mallory metal (twice as dense steel) to the counter weights. We shopped around as decided on Lynn Rodgers because he is amazing, has helped the team before and is very knowledgeable. This was the start of a long process that I will go into in another post

The Cam Chains

The second major problem, for the engine, was the cam chains. For simplicity we kept the chains on the same side to start with (we didn't want to have to run the cam backwards). This meant that one of the cam chains ran right into the main bearing because of the offset for the con rods. Oh. Shit. Bugger. This started the process of finding out if smaller bearings would do the job, how would we do the chain guides, and how am I going to make a cam chain sprocket that
1 needs to go on between two things of larger diameter,
2 is smaller size than any standard
3 is a chain profile that no gear cutter in Auckland has ever seen. (Yamaha proprietary information damn it)

The Oiling

The final major problem, (if the ones above weren’t enough) was to figure the oiling. there was scavenge points in the block but in bad positions, there were no points organised where I could mount a belt or chain set up and I had no idea how much oil was required for the engine. This was a big learning curve for me and I have learned a lot from it about oiling for engines and bearings.

I later posts I will talk about each of these and what we have done about them. Currently we are getting close to starting the engine on the dyno. (Fingers crossed.)

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