new crank advice

[lam1962brettagg]

Hi all
looking to get a new crank for my standard li 150 s3 (6v points system). whats the best make and where from? anyone tried the casa new original spec ones?
thanks in advance for any suggestions.
john

[Knowledge]

A couple of questions.

Why do you want (or need) to change the crank?

Are you thinking of changinging from points ignition?

Your engine is not very powerful. Are you thinking of upgrading the barrel in the near future?

[lam1962brettagg]

Hi crank is well past its sell by date. ie seal surfaces worn. flywheel side pitted and worn. im looking to keep it standard. aint bothered about speed and have always found points 6v system reliable. so looking for the best original spec standard crank.
cheers

[Fast n Furious]

Cant say from personal experience but suspect the Casa one will suit your requirements.

[clyde]

Just removed one from my s3 lis150 if your interested.

[lam1962brettagg]

Hi Clyde
have sent you a PM
cheers

[Warkton Tornado No.1]

Hi crank is well past its sell by date. ie seal surfaces worn. flywheel side pitted and worn. im looking to keep it standard. aint bothered about speed and have always found points 6v system reliable. so looking for the best original spec standard crank.
cheers

Just to add my twopennyworth.....

The surfaces on which seals run should be neither too smooth or too rough. In fact, manufacturer's of rotary lip seals tend to recommend that the surface be obtained by plunge grinding & that the finish be between 0.2 & 0.6 micro m. In layman's terms, the surface is better if it has a dullish surface by treating with an abrasive pad (Scotchbrite etc) so that oil is retained on the surface to stop the lip burning out.

In addition, in the case of the Lambretta crankshaft oil seal journals, the tolerance on the diameter should be h11. For the mag side seal, that equates to 33.00 to 32.87 mm.

For the record, the first two crankshafts I came across in my garage were a nearly new one & another dating from the sixties. Both were comfortably above the lower limit so equally useable.

So, in many cases, the oil seal journals will 'clean up' to allow the continued use of an old crankshaft. I know where I would sooner spend my money.....

However, whilst on the subject of seals, I will say this:

Unfortunately, there are many that would argue that Viton is a necessity due to the chemical composition of modern fuels. If you research that (on sites that aren't out to sell Viton seals & the premium that they command), you will find that we are some way yet off the stage where conventional Nitrile seals cannot cope.

(I have lifted part of the technical information that an ISO accredited company, Humphreys of Kalamazoo, have to say in the comparison of Viton & Nitrile (Buna) seals)

Buna is much less universally resistant than its Viton counterpart suffering degradation from weather and ozone exposure. For most circumstances, however, this is not an issue, and Buna seals also offer the benefit of superior abrasion and tear resistance making them more suitable for more heavy duty industrial applications.

The last sentence sums up my own experience.

Like many others, I suspect, I have tried Viton seals in performance engines, considering that they would offer the advantage of 'Peace of mind'

That was not the case & the Viton seals suffered significantly more wear than I would have anticipated had their Nitrile counterparts been fitted.

[lam1962brettagg]

hi Warkton.
your twopennyworth is much appreciated
and probably a bit beyond me to be honest. i am no expert or engineer but suspect my original crank surfaces are beyond useable and i think the big end has gone anyway. i'm just really wondering if anyone has bought and used a good quality new original spec crank. i would rather fit a new one to save messing about.
input very much appreciated though
cheers

[NorthernJordan]

I would suggest it's a much of muchness tbh from any of the main makes of cranks for your spec of engine. I would go for AF, Mec, mazz or casa depending on price.

Personally, if I was spending 130 quid plus I would be looking at getting a GP race crank to future proof engine against any potential upgrades. However, if you are certain you're happy with current engine then I would pick any of the above brands.