Author Topic: Learning old school the hard way 74 TX500  (Read 8047 times)

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Offline kickstarter

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Re: Learning old school the hard way 74 TX500
« Reply #15 on: February 01, 2016, 03:22:21 PM »
I'm back, been a long time I know. I had to put all my projects on the waaaay back burner for awhile but I've started working on the ole Yammy again.

First, Dean about the pipes, you can see in the pictures where the pipes end and a new section is welded in. That second section has baffles inside of it but I don't know what you would call it or where it even came from.


Secondly, Guy, I did lap the valves when I swapped the head. I was lucky enough to be able to do some stuff at my college and they had some lapping compound and one of my instructors walked me through the process. He also told me about his race buddies who lap valves on their race engines with a drill. They just stick the valve in the chuck and have at it.

So now I'm thinking about where I want to go from here. The carbs that were on it were junk, the pilot screw orifice is so wasted and scored up it makes wonder if an old pilot screw tip broke off in there and some one went to town with a pick trying to get it out. I still have the carbs that came on the bike and I'm re-building them now. But should I re-jet the carbs or put the intake and exhaust back to stock? I'm having a hard time finding parts for this thing so I'm leaning towards re-jetting the carbs but I can't find jets specifically for these carbs. And I'm not sure what the stock flow rate is. 145? 150? I don't know but I do love this bike and I will get it running right and I will post pictures of the final project (it might take me another year though).

 Crap it's been so long I forgot how to post pictures in the post.
« Last Edit: February 01, 2016, 03:33:28 PM by kickstarter »

Offline kickstarter

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Re: Learning old school the hard way 74 TX500
« Reply #16 on: February 01, 2016, 03:44:24 PM »
Hey Garn, how'd that copper head gasket work out for you?

Offline Jewbacca

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Re: Learning old school the hard way 74 TX500
« Reply #17 on: March 06, 2016, 11:01:49 PM »
Looking good so far! Some things I've noticed on my own 74 build:

The stock carbs suck. Like metaphorically, not actually, haha! The stock Keihins are horrible carbs for anything but absolutely stock setup, and even then, they're mediocre at best. Save your money and get a set of Mikuni carbs. They're easy peasy to work on, and have mechanical slides, which standardizes your throttle openings. Also, they're much easier to find jets and parts for (literally hundreds of different machines use Mikuni stock)

That exhaust has, what looks like, a generic welded in flow through baffle. Again, with the stock Keihins, anyone here who has chopped their exhaust will tell you, they don't like shortened, modified exhaust. Switching to Mikuni's will save you a ton of headache when it comes to your exhaust. You could leave it like it is, or you could eventually swap out the shorty pipe for longer pipes with a broad, spread out baffle, which would tone down the sound a bit as well.

DON'T USE A DRILL TO LAP YOUR VALVES! Whatever you do, DO NOT do this. You'll end up burning out the lap compound and gouging the valves or the seats. Your race buddies may know how to do this without destroying the valves and seats, but unless you have tons of experience doing it, you'll just end up ruining the head. Best thing to do is buy a 5-10$ lapping stick with a suction cup on it. Start with medium grit compound and work your way to extra fine. Finally, do a bluing check after you think your done to make sure you're getting 100% contact between your seat and valve with no pressure other than gravity. (I worked as a machinist in an industrial valve shop for 6 years, and this is the exact same process we used to make sure valves could hold down 2500# of steam off of power station boilers, it's not hard, but it will work).

Keep us updated. I'm looking forward to getting mine on the road at some point this year.
1974 TX500A
I'm unique, just like everyone else.