Crank options for mild Lambretta tune

[victor]

Which crank solution would you recommend for a mild Lambretta tune?

The crank currently fitted is a Tv crank (so suppose li-taper and odd conrod length) that's been welded and balanced, but probably isn't up for the task (14-20 bhp) or will work with the cylinder/piston due to the length.

I suppose I'm looking at a middle segment and would like to avoid paying £250-300 for a crank (however will do so if that's the only solution to a reliable crank).

Let me know your comments, and please bear in mind I don't have the machinery to change conrod on an Indian crank nor the knowledge to get it balanced afterwards; would prefer something off the shelf.

Many thanks Vic

PS Will take the flywheel recommendation separately to not confuse the thread...

[a.j]

Lambretta Meceur road Race Crank

Had mine on two stage 4 tune scoots & they've been brilliant.

[bristolmod]

If you HAVE to change the crank then I'd go with AJ's recommendation.

If you can work round and the existing crank is good, why fix it?

Chris

[victor]

I've been told the Li taper isn't up for the load...

And I believe the Tv Conrod length is wrong for most kits, which would add packing plates, with the risk that the cylinder cowling wont work...?

[bristolmod]

FWIW I've been running a Mugello 186 on a TV crank for the past 5 years ( and on 6v points!!) with no issues whatsoever.

The only problem is finding a bigger piston (64mm etc) with a pin at the correct height for the TV rod, so it may well be the best solution to replace the crank to a "correct" length rod.

Chris

[victor]

I'd obviously prefer to keep the current crank if possible, it's new, will need to check with the kit provider if possible.

How many km have you run on your Mugello and what power output do you have? I'm aiming at about 16bhp, which is more I believe than a standard Mugello which could, or could not, mean that a threshold is passed?

I'm running on points as well and like that, no problems whatsoever and rock solid tickover. Worried though that they wont keep up with the increased revs from the kit, but 1 thing at the time: crank -> kit -> 12V (-> electronic ignition)

[bristolmod]

probably done about 4000 miles on the kit- power output is not known but it was a Muggy V1 straight out of the box, so around 14 BHP or so?

Really revs out very well with no indication of points bounce. A basic rev counter I had fitted showed c8k RPM at full revs.

Chris

[victor]

And your driving style is... moderate or rather full throttle trash it around as hard as you can...?

[corrado]

A few years ago I bought a complete engine with an Imola kit fitted. I'd just blown up my 175 kit and was wondering which kit to replace it with and the complete engine cost less than the cost of the kit plus other rebuild costs. I did about 6,000 miles on it, including Lands End to Jonny Groats, before I holed the piston in the middle lane of the M1. It wasn't until I stripped it down that I found it was built with a TV crank. It was a flyer and I usually thrashed it everywhere on it. I had it replated and bought a new piston to suit a TV crank but I did fit a new AF Rayspeed RB race crank with a TV rod. I thought that I'd pushed my luck long enough with the original crank, but it was still perfect and had nothing to do with holing the piston, that was carb related. The longer rod supposedly equates to less engine vibration so maybe it has an easier life than a 107 rod.
Maybe you'll be as lucky sticking with your TV crank.
My next engine build will be an Avanti and I plan on using a BGM 58 x 110 rod with 3mm packer. MB look like they've stopped supplying the Alpha crank and now supply the BGM as their crank of choice for their own engine builds which can only speak well of this crank.

[victor]

Many thanks for the info Corrado, really appreciate it.

I get the feeling that although a GP style crank supposedly is stronger than the Li crank, the Li crank is still strong enough for the kind of output we get from our engines?

That would be good info as it would save the hassle and expense of changing it alongside the stator plate although I think I should go for a slightly lighter flywheel...

Problem though is that I couldn't fit it straight in as it would mess up the port timings right? So it would be under barrel packing plates with the potential problems (cowling, exhaust) it could bring...

Anyone had any bad experiences with original or newly made (Mec) Li/Tv cranks?

Ciao V