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twisted crank..how do i tell?

Technical help for Series one, two and three Lambrettas. Models include the Li, Li Special, TV, SX, GP, Serveta and API/SIL models

twisted crank..how do i tell?

Postby swissdean » Fri Jul 08, 2016 5:05 pm

fitted a new (RT) cylinder kit and thought to finish things off I'd check and adjust the timing. Struggled like hell to get the crappy varitronic flywheel holding spanner to cope with the brut force needed to undo the nut so reverted to the tow rope in plug hole trick..which worked a treat...adjusted stair and put back together. Then saw that it is 50lb torque figure to do back up so used a torque wrench..rope still in the plug hole...not realising these don't always work in reverse!

stopped after a while and tried to kick over and it seemed like I had clamped the flywheel so tight it was catching on the casing or stator itself..not really sure..only knew this as when i tried to kick over it wouldn't budge.

loosened off the flywheel nut and it made a minor difference.flywheel.would turn but very stiff,,,whipped off the flywheel and all looked ok underneath, tried kicking over again and it seems almost lumpy in action..

bit anxious about what to do next..I have had the head off and it turns over fine, so I am hoping/thinking crank is ok...just when head back on it seems lumpy..squish was set bang on pre timing set up issue, so not thinking too much has changed there..

this kit has yet to be run on the open road ..only fired up twice on the driveway pre the flywheel problems..

any thoughts/experience?
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Re: twisted crank..how do i tell?

Postby MK Monty » Fri Jul 08, 2016 9:04 pm

In the absence of an adult here I go.
I would go back to basics that entails barel off and check that crank. You can put a dial gauge on the ends of the crank in situe and see if it has any run out on the ends.better to remove it. The rope trick may be ok for removing an old set up but you have no idea what you have done to the crank or even twisted the rod. Sometimes new setups rub on the oil seal side and a tap on the gearbox side is all it needs to free everything off. I would want to go back to crank in, does it turn freely. Barrel and piston on, check squish is it still free? Etc, etc
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Re: twisted crank..how do i tell?

Postby Raveydavey » Fri Jul 08, 2016 10:02 pm

Sounds bearing related. Worn mag side maybe? Tightening the flywheel could be trŷing to pull the crank out of the drive side bearing and forcing the mag side crank web against the mag housing. Is there any lateral play on the crank in situ? Put a feeler gauge down both sides of the crank webs when all torqued up.
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Re: twisted crank..how do i tell?

Postby swissdean » Fri Jul 08, 2016 10:14 pm

thanks Gents, both very logical advice...back apart it is then..
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Re: twisted crank..how do i tell?

Postby coaster » Fri Jul 08, 2016 10:43 pm

I can't see the crank being twisted by using the rope method to lock the crank but over tightening the flywheel nut could have caused the taper on the flywheel to crack along the keyway and thus allowed the flywheel to pull onto the crank further and lock against the mag housing. look for a hairline crack, use a magnifying glass if necessary.
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