Crankshaft worn

[Puffs]

Following a moderator choice that is IMO biased and flawed (someone posting aggressive personal attacks is rewarded, while my technical posts are removed), I have withdrawn from this forum.

[Blurredman]

Okay,

First thing I did was check for light coming from bulb whilst very very slowly turning the wheel, I got nothing out of the ordinary.

I removed the cam washer and put the cam back on, still ran backwards. The cam is a little grooved, sure but we move on.

But decided to change points and back adjuster plate the time, still the same.

Then I put the washer back on with the cam and something changed- the timing was way off, the small recess which is a bit of bent down metal (presumably with a hammer and tiny chisel) that coincides with the key of the cam broke off- so... i take a different rotor from one I have spare...., time it all up, and it times up the same as before - everything is exactly the same! Still it runs backwards half the time.

I then put original back adjuster plate and points on but you guessed it- Backwards running.

I also put total gap as 0.4mm but same thing.

The only thing I did do for experimentation was have the points gap about 1mm- that seemed to stop it running backwards, but that isn't a solution.



Hmmm


At the minute, I think the only thing I can do is swap the electronic ignition from my 251 onto this ETZ250, and equally put the contact breaker system onto the 251. And see what the results will be- for example, a question in my mind is would the 251 run backwards?

[Puffs]

Following a moderator choice that is IMO biased and flawed (someone posting aggressive personal attacks is rewarded, while my technical posts are removed), I have withdrawn from this forum.

[Blurredman]

That's a good point concerning the EI on the 251. I never have done that test on the particular EI I have. And I can do it without touching anything but the spark plug.. This will tell me whether it's even worth attaching it to the Orange ETZ250.


You're also right to consider the point on the location of the gudeon pin and thus potentially influencing compression. But the bike never ran backwards with old piston when I had the compression @ about 12:1 for a brief period. But, I wasn't looking for it then- however, it was running nicely at idle. Typically the backwards running right now, and back in '17/'18 coincided with a lumpy idle when the engine was warm.

[Blurredman]

Okay,

So I have found something interesting. I have a maximum contact breaker gap size @ TDC exactly, and the points do not continue to open, or stay open for what is normally considered (on a single cylinder) roughly half the rotation of the crankshaft. Infact the contact breakers on the bike start to rise (as timed by me) at 2.5mm BTDC, and then as they just swipe past TDC they are already closing and are closed at about 2.5-3mm AFTER TDC. Therefore I think this is where the issue is. Total points opening is no potentially more than 50 degrees of rotation!


But: The way around it? I suppose the only thing I can think about if I want to retain points is to see whether I can open up the gap of the points considerably to see whether I can prolong the amount of time before they close.... But then whether the timing could be adjustable to compensate for that I really am not sure...

Another possible thought is that I could implement some sort of tapered ring or indeed a slight shim between the cam and the rotor opposite the highest lifting point of the cam in order to hopefully influence a longer opening time. If that is a possible workaround.

What are people's thoughts?

[Puffs]

Following a moderator choice that is IMO biased and flawed (someone posting aggressive personal attacks is rewarded, while my technical posts are removed), I have withdrawn from this forum.

[Puffs]

Following a moderator choice that is IMO biased and flawed (someone posting aggressive personal attacks is rewarded, while my technical posts are removed), I have withdrawn from this forum.

[Blurredman]

Here is video as requested.

As you can see, the points lift for about 90 degrees but spent the rest of that time closed.

If I adjust the gap much wider, then the cam seems to be doing it's work and the points are open for 3/5 to 3/4 of rotation. These cams are original to the bikes I do definitely believe, and seem correct as evidenced by the witness marks on them indicating that a good 3/4 of the cam's rotational surface has been in contact with the points actuating heel.

[Puffs]

Following a moderator choice that is IMO biased and flawed (someone posting aggressive personal attacks is rewarded, while my technical posts are removed), I have withdrawn from this forum.

[Blurredman]

Thank you Puffs for your extensive investigation, but It comes to me to realise finally that this is all self inflicted and the route cause of the problem is an out of true crankshaft. For anyone reading, I urge you not to use hammer force when inserting the crankshafts. I have been part lucky, and part unlucky in this process (lucky in the case of my Trophy for example) in the past, evidently, but ultimately doing so will cause the crankshaft to be unbalanced and out of round, and it doesn't take much of a wack to do that (after all, that is how you balance them in the first instance). In the short term, being unable to to use points effectively as I have found out, and if you use electronic ignition to get around it then in the long term the issue with main bearings may become apparent over the course of time and many thousands of miles.

My only real option is to disasemble the engine again, and get the crankshaft trued and balanced (I don't have the equipment to do it myself), and then reinstall THE PROPER WAY. Of course hindsight is wonderful but it took me a lot of hours, and pondering, and also failed attempts to simply plaster a solution to this- but ultimately, I am back to square one, and I will have to re-build the engine. My fault- and never again - lesson finally learnt. I'll update this thread with the result of getting the crankshaft trued (it doesn't need to be rebuilt), and will update with what the outcome is.

[Blurredman]

So I bought and have had delivered a new crankshaft. It looks good.

Came from Germany directly, so I wonder if I should stop by a machinist to double check the balancing is right. You never know how these packages have been treated in transit.

[Puffs]

That looks very nice & shiny!

They're not made of cheese, so if it was packaged properly and without damage to the packaging, you'll have to assume it'll be fine.
At any rate, if you cannot measure it properly yourself, or have a workshop nearby, assessing imbalance will be difficult. You can send it to a workshop, and they can measure it (and, if required, re-balance), and after you pay them, they send it back. And in that transit it can be damaged again. So still no certainty...

Sounds like the equivalent of Heisenberg's uncertainty principle for the modern age.