Progress on the 74 TX.


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I've slowed right down now, I can only manage an hour or so in the workshop before the elbow complains. But, I haven't been totallymidel: I stripped the clear coat off the forks and gave them another polish. Pulled the front wheel apart, polished the rim and hub and re laced it. I stuck the caliper together, hoping the pistons would seal, no such luck, so I'll have to,order some new pistons. Still haven't re painted the seat and covered it yet or bought tyres.

Most of my interest is making stuff, and mostly machining, but being as the bike is all but finished I didn't have anything more to make. So, I thought real hard about it and decided on some air cleaners, pods just don't do it for me. I turned up an aluminium base and a couple of knurled nuts, then beat up a rear plate and polished them. I was going to use the black, stainless mesh to hold the foam in place, but changed my mind, just don't like the look of it, so I'll look around for some perforated sheet and use that.

I was going to use a catch can for the engine breather, but being as I'll have pancake air filters I'll plumb the breather hose into the filters via a T joining piece.

I finally decided on a shrink fit for the base of the filter, so did a little experimenting with heating and freezing.: The carb bell mouth is tapered slightly by around .05mm,, so I chucked the carb body and trued up the bell so it measures 57.38mm, then stuck it in the freezer for a couple of days to see how much it would shrink - virtually nothing, .01 mm. Next I bored out the centre of the air cleaner base to 57mm and stuck it in the over at 250C, it expanded by .18mm. So, I chucked the base again and turned the hole to 57.20mm. So if I heat the base to 240c it'll expand to 57.38. That of course won't fit over the bell mouth, because it's not a clearance fit, so a little light pushing in the vice will be required. That should give a good tight fit and just to make sure it won't come off, I've tapped the side of the air cleaner base for a 5mm grub screw.

So, you'd probably think freezing the carb body is a waste of time as it doesn't shrink enough to make a difference, but there is a good reason to freeze the carb: Bringing the air cleaner base and carb together to press fit them can't be done quickly, so heat transfer will take place and the carb will heat up slowly, if I'm quick enough it should reach normal temperature sometime during the press fit and hopefully the air cleaner base won't cool down too quickly.

Tomorrow, I'll find out if my plan works, if so, all I have to do then is is make another air cleaner for the left carb.

Well, it's not quite that simple: A while back I made a fuel distributor block that bolts under the front lip of the battery carrier to neaten up the hoses joining carbs and taps, and also to get a level fuel flow in both carbs. Unfortunately, the distributor block hangs too low, so the filters interfere with the fuel lines, I've made the filters as small a diameter as I can, so another 'narower' fuel distributor block will route the fuel hoses around the filter.

There is a method to my madness, I've now got more stuff to machine up, Oh happy days!


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Keep up the fine work on your 74TX toglhot.I look forward to seeing an XS/TX 650 Yamaha on the 2024 calendar with more than an XS650 motor and a couple hubs.


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