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I have just started my SuperBravo racer as you may have seen in the personal section.
I have taken off the kick starter to use a reed valve intake and two options for start remains, with
a drill machine or to run with it.The high compression makes the running difficult, the rear tyre will only slip and slide on the ground so I have mostly used the drill machine to spin the engine directly on the variator nut.
My engine is quite small, 63 cc´s but I have a high compression head and with the drill it turns a bit rough before it starts.
During assembly I found that the threads outside the variator was quite short, about 6 millimeters, but there was some additional threads in the variator bushing, like this:
To use the most of the threads and to save the crankshaft I fabricated this nut, to the right on the picture:
This way I put burden on most of the threads but still I´m worried about the start by drill.
Have you seen or heard of anyone stripping the threads off the crank or, even worse, that the crank snapped right off?The best would be to strip the threads in the nut but It may not be my choice…
By the way, the crankshaft is a Mazzucchelli, it´s not a stock unit.This type of nut is the best solution, even if you don’t start with a drill.
I’ve also been using this type for a few years now.The extra advantage is that it also helps centering the variator.
I came, I saw, and I forgot what I was doing...Yes I think it´s good but I´m still concerened about the crank tap.
Have you heard of any destroyed tap while starting the engine with a drill?
The crankshaft of my simo2007 engine survived starting with a drill. However my variator got damaged when the nut got loose after multiple starts. But the compression a simo2007 engine is way higher than a 43mm vespa cylinder so I think you should be fine.
However I think you should be able to start the bike by pushing. There are an awful lot of people on this forum with 43+mm cylinders with high compression heads and variomatic who are able to start the bike by pushing. Lean on the seat while you are doing it, that stops the rear wheel from slipping.
AW50-4t | 13.13 | Gianelli Citypower | 3.2Nm@6000rpm | 3.0pk@6700rpm
Home made engine dynoArvidW :
The crankshaft of my simo2007 engine survived starting with a drill. However my variator got damaged when the nut got loose after multiple starts. But the compression a simo2007 engine is way higher than a 43mm vespa cylinder so I think you should be fine.However I think you should be able to start the bike by pushing. There are an awful lot of people on this forum with 43+mm cylinders with high compression heads and variomatic who are able to start the bike by pushing. Lean on the seat while you are doing it, that stops the rear wheel from slipping.
I too found out that the nut came lose as the engine started up so I bonded it with some Loctite 603.
Now I will adapt a one way clutch from a lawn mower and use a weak 8.8 M8 bolt to secure the weakest point outside the crank.About the push start, I may need to refine the technique, I found the wheel to lock up easy and stay like that, rubbing the tyre to the ground.
I may need my son to do like this:
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