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Old 12-16-2012, 07:53 AM   #653
sakurama OP
on an endless build
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Joined: Oct 2004
Location: NYC & PDX
Oddometer: 1,491
I think he means it's a bit like stumbling over a 10' (3m) pile of old magazines.

So, back in NYC and I've asked Chris to wait on drilling the carbs until I can be there and document the process. It's a bit scary to start drilling into a $1200 set of carbs so if it all goes pear shaped it will be nice to be present. Also, there's going to be time to finally put the bike with it's set of 41's on the dyno and we can finally answer that age old question and knock on the door of popular wisdom - will the 39's make better torque at the expense of top end? Place your bets now folks because later on today you'll have your answer.

But that's not what we're here for right now - today is choke day! Yes today is the day reserved for choking that someone special in your life... er, no. No, today is the day we finally crack the last problem of the FCR's. We hope.

Chris has been working out the idea of how to machine on the 4th axis of the CNC but before you can do that you need to simply test the idea and that's what the Bridgeport is all about. Turns out the passages aren't square which makes it more complicated so the carb has to be shimmed. Here Chris is checking the alignment with an extra long center drill. There's very little meat on the boss so any misalignment and your carb becomes scrap.

Chris measured and ordered several different o-rings and we found one that likes it's new home. Here's the first center drill into the longest passage.

And then it's time to cross your fingers. Actually only I crossed my fingers, Chris had no doubts.

This one blew my mind. Chris brought out the dental mirror to align this passage.

The final passage where the choke will reside.

Then it's time to tap it with a bottoming tap. Done in the Bridgeport to maintain alignment.

And there you have it. The worlds first choked FCR carburetor. All you have to do is remove your seat and reach up inside and pull two small levers and... okay, it will have a cable. We needed to test the function with the choke from the MX carb. It works and all the passages function as they're supposed to. We still need to do some work on the mid plate but this was the lion's share of the work.

Chris will need to make up a dedicated cable to use the handlebar mounted lever and he also needs to make a body housing for the choke plunger. Here's the MX choke and in the background Chris is designing the new choke plunger housing to use with the cables. To test it we'll reuse my old carbs choke cables but they'll need to be cut and resoldered.

So, there's the choke. Chris is an animal. Many have tried but he did it. Hopefully we can finish it this afternoon and put it on the bike to test. Before we do anything though the bike will get strapped down and flogged while wearing the 41s. My guess is about 90% of the folks here with FCR's have gone the 39 route because of the popular wisdom - I know I did. Today we find out if popular wisdom is worth what you pay for it.

Place your bets folks!


sakurama screwed with this post 12-16-2012 at 07:58 AM
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