Smeared Big end on an AF Crank

[davidblythe]

Looking for opinions

Doing 75mph today on a TS1 and engine locks

push home and strip engine down, Nickasil and piston are fine

but the big end on an AF crank has smeared all the rollers and locked the conrod

any ideas was running 2% fully synthetic rock oil, no blueing around the crank

any ideas anyone

[Knowledge]

Sorry about the failure, and I'm glad to know you survived to write about it.

I would be more surprised if this had happened at a 3% mix. I would risk 2% in an engine where the fuel enters the crankcase directly (Vespa or DakTec Lambretta), but not where a proportion of the fuel is able to by-pass the big-end altogether like a TS1 or RB.

BTW was it a 58mm or 60mm crank?

[davidblythe]

58mm crank

[ralph95]

hi david warn out big end we use the same bearings in our group 4 race engine's and they get thrashed to death 10,000 rpm plus with no problem ,dont use recycled oil use pro 2 race

[J1MS]

hi david warn out big end we use the same bearings in our group 4 race engine's and they get thrashed to death 10,000 rpm plus with no problem ,dont use recycled oil use pro 2 race

Is that the Silkolene Pro 2 ???

[ralph95]

hi david warn out big end we use the same bearings in our group 4 race engine's and they get thrashed to death 10,000 rpm plus with no problem ,dont use recycled oil use pro 2 race

Is that the Silkolene Pro 2 ???

oh yes

[J1MS]

Pro 2 is a Top quality oil, as used by Taffspeed.... once you find somthing that works stick with it....I used to use bellray MC+. ...now that was very expensive but it worked well plus it had an octain booster in it, never ever had a seize till we tried somthing else.....If it aint broke dont fix it..... Dave Websters words of advice back in 86....

[scootRS.com]

>>any ideas anyone

Wait for Sticky to start a fierce recall campaign demanding they replace every single crankshaft for free because even 1 failure is dangerous, and then write a huge Scootering article about it?

Just kidding, just kidding.

Sorry to hear about your troubles, David.

>>no blueing around the crank

Would that necessarily indicate that the bearing itself wasn't too hot and simply failed?

Isn't 2% good synthetic sufficient and a match for 3-4% old-school oil? What percentage do racers run, Ralph?

[drunkmunkey6969]

This was an excellent thread ref oil: http://scooterotica.org/forum/viewtopic ... &hilit=oil

It certainly made me re-think my oil %, the article it links to ( http://edj.net/2stroke/jennings/oilpremix.pdf ) is also very good.....

I was running 3% and swore by it, and after various advice i was thinking of trying 2%....but since reading the article, i am now experimenting with 4% oil, and increased jetting to offset the leaning of mix that results.

ie - in Rossi's test (see linked thread)....more oil gave a higher running temp, this is because the increase in oil % decreased the petrol % (eg - 97% fuel + 3% oil vs 96% fuel + 4% oil) and petrol is a coolant in a two stroke. So if running a higher oil % then (presuming you were set up correctly at a lower %) uppjetting should occur to compensate and retain the correct fuel mix to aid cooling.

My opinion at this stage, would also be that 2% is not a good idea for a road going machine that doesnt draw fuel in over the crank, and that a higher % (with jetting adjusted to suit) is a better idea.