Engine build prep (2014)

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I remember , Ken or Jim saying that those torque plate are compulsory for alloy barrel or 920 (iron), but for std 750/850 I don't know ?
however I never seen any in all the machine shops I had visited with my jugs ! and to make one (a pair) you need a milling machine , may be there is a niche market for , at least for a club as hopefully we do not need to bore our barrels so often , but...........?
 
Thanks to those who responded by PM, but didn’t want to post because they “don’t want to get caught up in all the BS of the forum” ... that in its self is an interesting turn of events...

Meanwhile back in the shop...

Ign timing and mixture are already ruled out as possible causes.

Oil choice was also mentioned by some. I was running Redline 20w60 fully synthetic motorcycle oil. I know this didn’t fair well in Comnoz’ test and I won’t be using it in future, but I have used it for many years in many engines without issue. And, as both pistons share the same oil, I really can’t see it being the cause here.

The bores checked out good, cyclindrical, perpendicular to the base flange and parallel to each other. So we can rule out the cockeyed bore this time.

The clearence is .006” on the good piston, .0065” (as good as can be ascertained) on the bad piston. They were bored to .0055” so there is half a thou of wear and / or allowance for the fact the pistons had been in my car all night in the cold. Either way, we can rule out lack of clearance.

Torque plates: my machinist was adamant that they have no benefit on iron Norton barrels, so I doubt they’re relevant here. But he did advise using them on alloy barrels. This is different to when I spoke to him about them a year or so ago when he honed my Maney 920 barrels, so I assume he’s learnt this recently himself.

Two people I conversed with by email, and my machinist, sited petrol wash as a possible cause. I have FCR carbs with accelerator pumps; maybe they need adjusting? Maybe someone was twisting the throttle whilst it was parked up? Maybe I’m just to heavy handed with the throttle? I always give the throttle two twists before starting as they have no chokes, maybe this is too much? All in all, petrol wash definitely looks like it is, at the very least, a contributing factor.

Then there is my own theory that the anodising was somehow part of the issue. This is a very uneducated guess I know nothing about the technicalities of anodising, can it be applied incorrectly? Is there scope for operator error in the process? If anyone knows anything about this, please do let me know.

So, petrol wash and / or anodising are the current #1 and #2 suspects.

As to countermeasures:
1. I’ll stick to one twist instead of two before starting.
2. I’ll Reduce the quantity of fuel supplied by the accelerator pumps.
3. I’ll try and leave my helmet on the twist grip, or something similar, to dissuade absent minded throttle twisters when parked up somewhere.
4. I shall avoid anodising of such things in future.
5. Not sure how to be less heavy handed on the throttle, old dogs and news tricks etc!

So there y’all go, I think that’s about as conclusive as I’m gonna get on this one.
 
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Hi Eddie

Petrol wash is interesting. Honda CBX locked up (hydraulic lock) Petrol leaking into the engine.
My Rickman triple did mark up the pistons when I sat on the slope at Cadwell waiting to race. Was worried that I would not be able to bump it. Turns out my float height was to high & togeather with the slope fuel ran into the engine. I had fuel in my oil when I drained it.
Chris
 
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