RT.  The box under the sidepanel is the battery.

The bike was bought under the pretence that it had been fully overhauled and restored by a motor industry professional.
It was being sold cheaper than the norm because of a couple of minor electrical issues he could not get to the bottom of and he needed the space to start another project.

He had done a conversion to 12v and I was of a mind to put it back to original as Yamaha built it, so no big deal.  I had no idea just what a big deal that electrical system was going to be.  I was ready to jump in my car and go kick him up and down the street before I completed it.

As for buying it, the bike was at the other end of the country, too far to view and too easy to obtain. It looked the business though, very nice in the pics.  All I needed to do was press the buy it now button and the bike magically appears on my doorstep a couple of days later.
At last, I would not need to get my hands dirty.  Someone else had done the work, all I needed was to ride it and enjoy it.

As easy as that.  Just like buying a pack of batteries from Amazon.

I broke my own rule by not viewing and paid the price.

I did a full thread on the problems I had with it before I joined this forum.  Unfortunately that forum no longer exists so I cannot link it.
It was the pics in that thread that convinced the seller that he would lose his shirt in a court battle and be handed over £500 as a "goodwill gesture".

If there is sufficient interest, I would be happy to do the thread with the pics again on here..  Let me know.

 

Blimey this just gets better. That 750 is a thing of beauty.
Thanks for the answer above.

Just put about 20 miles on it. Ran OK for the first 15 miles or so, then developed a very rough misfire above half throttle. Smooth below half throttle.
I have gapped a new B8ES at 20 thou and stuck that in to see if it makes a difference.

Old plug is a milk chocolate colour and dry, not oil fouled.

Since the fuel line has a wix 7 micron inline filter in it, cant see it being a partially blocked main that suddenly developed, but then again with the curse...

My money is on the coil and its 40 odd year old insulation breaking down when it gets warm.

Will it ever end?????

Come to think of it, I seem to remember it developing a slight misfire last season, a bit higher in the rev range though.

I see you did a 12volt conversion.
Is it an aftermarket like Vape with no locatng key.
Any likelyhood of it slipping?.
Sorry,-- had to ask.

It came with a cobbled together and totally insane 12v conversion. Cut, twisted wires all in the wrong sizes and colours, and insulating tape everywhere. I put it back together as Yamaha designed it.

I checked the timing when I changed the left crank seal for the IT175 one and was very careful to double check that the key was located correctly in the rotor keyway before fitting the washer and nut.

This is what confronted me after unwrapping the insulation tape from the stator harness, a depressing theme continued from headlamp to rear light.

Ok, yes i did read it had a 12volt bit of mess come to think.
But thought maybe you'd gone the whole hogg & updated to a new 12 aftermarket system.
I should catch up--too slow to catch a cold--but covid caught 'me' lol.

Did you strobe the timing? If the source coil insulation is a problem, what usually happens is the bike stops running when it gets hot, and will start again when it's cooled down.

Have you rebuilt the motor completely, or just the top end? I had a bike whose motor had been rebuilt by a shop, and had cost a fair amount of money to do.

Had issues with poor running, when it got hot, the owner had fitted a new ignition and a new carb, but still the same.

It turned out to be a cracked crankcase, that had been caused by the idiots in the shop tightening up a crankcase bolt, while the threads were clogged with debris. This cracked the case, and the crack opened when the motor got hot.

Welded the crack up, and re-cut the thread, which cured the fault completely.

Always something new to catch us out--& here's another one above thanks.
But in hindsight it reminds me of a Husky motor at work that had oil in a threaded hole, might've been the mag cover or a non oil holding cover & just the pressure of screwing in to an oil filled hole caused a crack.
Probably engine oil not beez wee penetrating thin oil so thick-ish to squeez out past the screw going in. So--things ya never forget--from 50 years ago.
Never make the same mistake twice but there a hell of a lot of mistakes to make first time lol.

When dealing with a poorly done "restoration", depending on how bad it is, there is sometimes a need to do everything again. If this were my bike, I think stripping and rebuilding the motor properly, would be high on the to-do list.

I just read this whole thread. Excellent!

The original coils are quite robust, my experience they are rarely the cause of an issue like this. Not never, just rarely.

I would be more interested in seeing if the issue was not there after the bike cooled down and ridden again. If it's OK but after time developed the misfire again, I'd get back to the shop, leave it running, and want to test battery voltage at high revs. Based on your description sounds like there's a battery voltage issue, CDI needs proper juice to do its job. I guess if OK I'd head to the check the keyway and make sure it's intact and stout, I know you said you were just there but "last thing touched" is my rule. Then, check the CDI trigger gap, then chase debris in the carb bowl. If those simple things are all OK, maybe you do indeed have a coil breaking down, source or ignition.

Just me. Bike is beautiful, very nice work!