Catastrophic Engine Failure - What Are my options?

[twenty eight]

sorry to hear about this mate had the same thing happen to me last year conrod snapped same place almost identical damage conrod not up to job,ts1 tuned barrel had this repaired and plated at langcorts,chiselspeed rebuilt crank with rb conrod new racetour pistion and v force reedblock had engine case welded up
not cheap but no tuned lami is hope you get sorted

[Lamaddict]

Tameni is a guy who I think has always made the MEC cranks and also those for a few other scooter firms besides. He'll build to a price and TBH I always thought the Black MEC ones were pretty good - used them in TS1s for years but only recently seen my first rod failure with these.

As for the standard MEC ones - standard rods were never up to the job of anything tuned in original form, never mind pattern versions. Sadly Jordan you've learned by your mistakes.

As for Storkfoot's idea of upgrading to a Jap rod at Grampian. I think this is a simple enough conversion on Indian webs or and 'race crank' with a 22mm pin, but standard type cranks use a 22.9mm pin and to convert these requires an expensive stepped pin. Maybe someone can find you a blown race or late SIL crank to convert to an RD rod. The only other issue is that with a 110mm rod you will need a 3mm cylinder packer.

I have a SIL GP crank wich i was looking at getting built with a Jap rod, but i decided it wasnt "economical" as i had already got a "good" crank. Overall condition is fairly decent, but has some rust type marks on the webs. I've got this as an option.

This was my first proper project and i was possibly a bit naive with what components i used. I've learned a hell of alot since running this machine, and now I've learned some more (shame about the circumstances). I was feeling low yesterday. but today I'm feeling more positive and i am detirminded to get it sorted properly! I now have a fair few options, and hopefully its looking like it could potentially cost me less than i initially thought to get it sorted again. So onwards and upwards!

The Yam 110 rod conversion into a SIL crank is pretty economical in the long run. 30- 40 for the rod, same cost to fit it and a fiver or so for the 3mm packing plate. You are then looking a great crank as said earlier in the thread. Good luck with whatever you do Sorry about the damage

[dsc scotty]

Re: Catastrophic Engine Failure - What Are my options?

Hi there!
Sorry to read/hear about your bad luck. Seen this several times over the years, the last one was Phil Stewart (Newcastle) who snapped a vespa ape rod on his suzuki converted rapido 225 on route to Scotland.
The rod cut right through the piston, barrel and casing just as yours had.
On closer inspection it appeared that the break was so clean we came to the conclusion it was a fault in the maunfacturing process.
Having used ape rods in many different set ups this one was the first we had fail, I was a little reluctant to use ape rods again after this but to date I hav'nt had another one go.
There may be several reasons as to why this has happened as stated in previous posts, however it it could just be a manufacturing fault combined with bad luck.
I hope this doesn't put you off modifying, tuning and riding your Lambretta? Many of us can certainly quote many a disaster from our scootering past (and present).
If you need any parts, crank etc just give us a shout!

Good Luck

Scotty

[servetakid]

Cheers for the kind words, i am starting to get a plan together!

[Toddy]

Cheers for the kind words, i am starting to get a plan together!

Keep us updated Jordan

[Rich_T]

Sideways displacement? By that do you mean that the barrel has say been fitted and moved a mm or two to either the left or right on the space say between the studs and holes? And thus putting the crank out of line?

No, although there is a production tolerance involved.

What I mean is that the position of the crank is dependant on the depth and position of the drive side bearing counter bore. If the counter bore is deep or shallower than it should be then the crank will be off centre from the CL of the bore. To accommodate this positional tolerance it is ESSENTIAL that there is sufficient float in the big and small ends. If both are shimmed it isn't a good idea.

What can happen is that there is machining position tolerance in the case mouth and crankcase bore depth. Combine the top end of these tolerances (including crank web width) and you might have more misalignment than the big end float can cope with. At this point, if you elected to shim the small end, you are in trouble as the big end of the rod will be held off the cylinder CL by the misalignment yet the small end of the rod will be forced onto the cylinder CL by the piston and shims...not a good place to be.

Your SE bearing looks tightly shimmed and your crank webs do not look central to my eye. Measure them with a digital caliper to be sure. I also see that the later pictures of a similar broken rod show a forged piston with very little small end float too.

[Yanker]

Re: Catastrophic Engine Failure - What Are my options?

H the last one was Phil Stewart (Newcastle) who snapped a vespa ape rod on his suzuki converted rapido 225 on route to Scotland.
Scotty

Blinkin-eck shared a couple of miles to-and-fro with Phil: he was riding a certain 225cc 'APE' rodded conversion to Borculo in 2004 when I pointed out an oil leak all down his cases at a petrol stop. 'F=me' he said "someone didn't not put the clutch shaft 'o' ring in properly" Gear oil was boiling - literally- and pumping out of the gear and clutch shaft holes in the case tops. Got back to Wallsend I believe no prob though.

If 'that' rod gave-up within living memory it was no dud, and dare I say perhaps lived a charmed life?

SK: SIL webs + Yam rod

[Yanker]

Sideways displacement? By that do you mean that the barrel has say been fitted and moved a mm or two to either the left or right on the space say between the studs and holes? And thus putting the crank out of line?

No, although there is a production tolerance involved.

What I mean is that the position of the crank is dependant on the depth and position of the drive side bearing counter bore. If the counter bore is deep or shallower than it should be then the crank will be off centre from the CL of the bore. To accommodate this positional tolerance it is ESSENTIAL that there is sufficient float in the big and small ends. If both are shimmed it isn't a good idea.

What can happen is that there is machining position tolerance in the case mouth and crankcase bore depth. Combine the top end of these tolerances (including crank web width) and you might have more misalignment than the big end float can cope with. At this point, if you elected to shim the small end, you are in trouble as the big end of the rod will be held off the cylinder CL by the misalignment yet the small end of the rod will be forced onto the cylinder CL by the piston and shims...not a good place to be.

Your SE bearing looks tightly shimmed and your crank webs do not look central to my eye. Measure them with a digital caliper to be sure. I also see that the later pictures of a similar broken rod show a forged piston with very little small end float too.

Or in VERY simple terms The big-end is not in ligne with the small-end and you have then shimmed-out any compensation allowing the con-rod to float. Not that out of line bearings are acceptable - they would wear and fail relativley quickly: just not that quickley