AUS TX500 Resto

After getting stranded about 100 klms from home I decided to go to electronic ignition. I did like the concept of staying as original as possible however the benefits are a convincing argument. Ever since I have had this running one of the points sparked significantly more than the other. New condenser and contact points did not solve this.
Newtronic make a kit for the tx but they seem to only make them in batches. Fortunately they were in stock when i enquired.
The instillation did not go to plan.
I followed the instructions to the letter and it fired up straight away. When I checked the timing it was way advanced on both cylinders. No problem ill just retard the plate.
That is when things went bad. To cut a long story short it tuns out each optic sensor was firing both cylinders and the engine had spun backwards at some stage from such an advanced timing, jumped two teeth on the timing chain and locked up the engine.
after splitting the cam chain and resetting the timing I contacted the vendor and told them what the system was doing.
To cut another chapter short they tested the kit after I mailed it back and stated that nothing was wrong with the kit.


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As shown in the above photo there is only a small cut out of 15 degrees or so. When this window is clear and the optic receiver "sees" the transmitter the coil discharges and emits the spark. while blocked the coil is charging which is the dwell time.

The problem I had was, clearing one beam would produce a spark on both cylinders, this was still evident after the vendor returned the tested unit. After many long distance phone calls (Aus to England), they concluded it was a wiring fault on my behalf, but to their credit offered a refund if I returned the unit.

After playing around with the unit more, I found with both optics clear I could get one cylinder to fire by interrupting one at a time. The problem here is the chopper disk is about 340 degrees and the optics are only 90 degrees apart. This was never going to work as the above pic shows only one optic is clear at any given time.

After getting coil values I calculated the dwell time would be ok up to about 8000 rpm with 80 degrees of dwell. So what the hell, I cut the chopper disk down to about 85 degrees.

This proved to be a victory. With the exception of a loose cable in one of the supplied loom plugs she has run great ever since. Revs harder, idles more consistently and starts easier too.

As shown in the above pics also is a new vs old sprocket. Both sprockets were changed with chain but the back was hardly worn so no vs pics necessary.
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Hey Guys-
I've got a xs650 tracker and love it but I just bought a pretty nice x500
and I don't know squat about it other than I like the looks of it.
Can anyone tell me the pro's and con's of these bikes?
I'm trying to decide whether to keep or sell.
Only two owners and everything looks pretty original


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I owned one and loved it. It had a head oil leak problem that Yamaha took care of with a new head. Very powerful for a 500 cc motorcycle.
Looks like a great original example. As mentioned they are prone to oil leaks and cracks in the head.
However with good preparation if rebuilding, such as head skimming and quality gaskets, and a re-torque after 500-1000 klms they can be oil tight.
They will need more time to check valve lash because its pretty busy in there. There was a factory amendment to the lash settings which they are very sensitive to.
A ignition upgrade to electronic is worth the money but you will need to upgrade the coils.

All this info and more is available on
I think every bike is worth keeping but its up to you to work out if it is worthy of the room in your stable and your time.
MVLUV- nice effort on your bike. pretty serious setback you had with that aftermarket ignition requiring cam chain splitting and motor out/in...

sonnysboy2- keep it! turn it into a cafe or tracker- they are very quick with carbs and exhaust work. seat-of-the-pants dyno says more top end than a 650 but less torque.

tossed in one pic of my latest TX500. the TX is my favorite motor in the 500cc range, even though they always seep oil all over the head. i just check it often and top off as necessary. with 4 valves/cyl and the counterbalancer they spin up fast and smooth, and the 5 speed tranny has the best ratios for hilly twisties of any i've ridden. when i rebuilt my clutch with kevlar discs i also shimmed the springs a bit to get all that power to the road. frame, suspension, wheel, and brake mods, 34MM VM's, light exhaust porting, custom exhaust... lotta fun.


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Fortunately you can split the cam chain and reset cam timing with engine in frame.
Touch wood mine has been oil tight for 4000klms.
good to know re the cam chain- fortunately i've not had to deal with that. motors have been pulled anyway for the two i've built and since they were both only in the 4K miles range i did not tear them down, just did all necessary adjustments and then did chassis and tuning work. they do have a large casting bump in each exhaust port that i like to smooth out with the Dremel...

you'd think you could re-torque the sandwich head to prevent some oil seep but they just seem want to spin a stud or two. risky proposition. so i resign myself to the oil film... you may have the only 500 that doesn't leak! runs great anyway, although a bit hard starting from stone cold. as you point out, a coil upgrade would likely help.

in terms of the ignition, mine did strand me once when the advancer unit nut came off, but was an easy fix once i trailered it home for diagnosis. other than that the points setup works well on mine.
With regard to the head, if I ever take the engine out again I would heliciol all the threads on the bottom half of the head for a little more tension. Your's looks great by the way
I have read some road tests done on release and they stated it was good for the ton.
I have had mine to an indicated 130 kph.
I have changed the gearing to a taller ratio and have some high performance PVL coils waiting to go in when I have the time so I think a top speed run is on the cards..... Stay tuned.
Have had a set back with the old girl. We are doing a major reno on our house at the moment so we have rented a place a couple of klms away. I trailered the bikes to the rental and as I rode the TX up the driveway it stalled and stopped with a loud clunk.
This clunk I have heard before.....
It was the same noise it made when the engine kicked backwards and jumped a couple of teeth on the exhaust cam.
Gently turning the motor over confirmed my suspicions as it locked up.
This is very frustrating as I don't have the room to do the repair at the moment.

I'm reasonably confident the ignition system was the culprit again as I had some intermittent miss on one cylinder on the last ride I went on. I didn't have any time to look into it as I was waist deep in moving preparation.

I am tempted to convert back to points as the electronic system has a habit of firing on the upwards compression stroke. It is also a pain in the arse job to split the chain and rejoin, mainly as chain links are about $90 each.

I have plenty of time to formulate an action plan as I don't have my workshop back until September.
Bit of an update on the old girl.
Once the house was done we moved back in and I couldn't wait to tear into the engine.
While waiting I purchased a NOS later model cam chain tensioner and new exhaust valves.
While the head was off I helicoiled the threads in the lower head.
Touch wood she has been running great since January.
In parallel I have had another project going that is near completion.


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I just read your entire thread. Quite the tale MV and a beautiful bike too!

That’s a very odd problem you’re having with the ignition system.

I also just read your entire thread. Really terrific resto you did. I’ve always had a soft spot for the 500’s and yours is a beautiful example. You’ve persevered through some difficult challenges and in the end you’ve brought a nice bike back. Well done!
I just read your entire thread. Quite the tale MV and a beautiful bike too!

That’s a very odd problem you’re having with the ignition system.

I think I have changed my primary suspect to the cam chain tensioner. With the original tensioner I would have an intermittent advanced spark as indicated by the timing light. Now with the new tensioner it is consistently bang on the mark.