Benelli Dynamo Scrambler Restoration

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Re: Benelli Dynamo Scrambler Restoration

Post by wi11iam @ Wed Nov 14, 2018 3:37 pm

Might yet resort to grinding down one of the puller feet so it gets past the casing.

But the it’ll probably sulk and bind as not using the Special Tool.
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Re: Benelli Dynamo Scrambler Restoration

Post by Il Duce @ Thu Nov 15, 2018 9:47 am

Some parts of that remind me of the little red bastard. I feel for you.

Not sure if you know but I'll tell you anyway, the piston grooves should have 1 notch in each. This is where the ends of the piston rings should be (either side of the notch) when you slide the piston into the head. Mark the piston on top with a sharpie where each one is and it'll make it easier to line them up.
I only found this out by a chance comment from a friend talking about his kart build. He found out the hard way.
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Re: Benelli Dynamo Scrambler Restoration

Post by wi11iam @ Thu Nov 15, 2018 10:57 am

Thanks ID. Engine rebuild going to be a while away at this point but that’s still helpful and with it being here I hopefully won’t forget it.

In today’s news: lawnmower is officially dead. Something seized in the engine to make the start pull really notchy and so wouldn’t start so the lot has gone to the tip. Only 6 months after the wife told me to do exactly that before I started tinkering. I’m just not going to fess up as the piss taking will be merciless.
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Re: Benelli Dynamo Scrambler Restoration

Post by wi11iam @ Sat Dec 08, 2018 8:36 pm

Swing arm has been stripped and repainted - more of later - and has had plenty of time to harden and I got an hour or two to potter in the garage so the reassembly has begun.

Image

Generally easy but for one nut having gone AWOL and a brake shoe shedding the friction pad - all can be bought (I think) cheaply but it does limit the front end for now.

I don’t think the rattle can swing arm is as bright as the gun paint on the frame but I doubt anyone will be able to tellll in daylight - but input welcome as it’s ‘speak now or forever lump it’ time.

Anyway. That’s probably it for a few months as I’m away (not NNK style) but will pick up in the spring.
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Re: Benelli Dynamo Scrambler Restoration

Post by wi11iam @ Mon May 27, 2019 3:29 pm

Tinkering with the bike finally got some time.

Where did I get to?

IIRC Novemberish I rebuilt the rear hub and brakes and flushed with that success I attempted to do the same for the front. On picking up the brake shoes the liners promptly fell off. Bugger. I couldn't finish the hub and had no confidence in the ones I'd just put into the rear drum and that's where reassembly got left.

I ordered two sets of brake shoes, measuring the old ones for size, and they didn't fit. Top tip: Measure the drum not the shoe for size (or follow ID's patented advice of just do it properly the first time). Another slightly larger set of new shoes ordered and the wrong ones put on ebay (where only one fcuker bid and got them for 99p so a minor defray of cost FML).

Apart from the odd scratch on the paint work and a lost saddle fixing it went together pretty well*

Front forks on
Image

Headstock, handlebars and very expensively retrimmed saddle on
Image


And then spent an hour fitting the horn onto the front mudguard fixing bracket - reshape horn bracket, fiddle, reshape, faff, search for dropped nut/washer/bolt, repeat in a different order and fit.
Image

* Headstock nut has grown enough during rechroming to no longer fit a 30mm spanner but not enough for 32mm. My adjustable won't go that wide so another tool on order.

That pretty much leaves the engine as the next step. Barrel has been bored to accept an oversize (0.6mm extra) piston, new seals and bearings to be sourced and crank will need a refurb so a few things to chase.
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Re: Benelli Dynamo Scrambler Restoration

Post by tanglerat @ Mon May 27, 2019 3:47 pm

Where's yer welder?
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Re: Benelli Dynamo Scrambler Restoration

Post by Damien Thorn @ Mon May 27, 2019 4:03 pm

Good work!

But,
wi11iam wrote:Headstock nut has grown enough during rechroming to no longer fit a 30mm spanner but not enough for 32mm.


WTactualF?
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Re: Benelli Dynamo Scrambler Restoration

Post by Deuteronomy @ Tue May 28, 2019 8:30 am

Nice progress, well done
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Re: Benelli Dynamo Scrambler Restoration

Post by Paul H @ Tue May 28, 2019 9:39 am

Loving your work. But I'm sure I speak for a lot if us here when I ask,

Image
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Re: Benelli Dynamo Scrambler Restoration

Post by GingerNinja @ Tue May 28, 2019 11:00 am

Paul H wrote:Loving your work. But I'm sure I speak for a lot if us here when I ask,

Image


I’m glad you got in there with this important question, as that monstrosity is already haunting my dreams.
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Re: Benelli Dynamo Scrambler Restoration

Post by Careless Whisperer @ Tue May 28, 2019 11:22 am

Damien Thorn wrote:Good work!

But,
wi11iam wrote:Headstock nut has grown enough during rechroming to no longer fit a 30mm spanner but not enough for 32mm.


WTactualF?

In a situation like that, my Dad would just make a spanner to fit (assuming he didn't have an imperial one which happened to fit perfectly), whereas I would probably try to bodge it by squashing a rag between the nut and the 32mm spanner...
Last edited by Careless Whisperer on Tue May 28, 2019 11:23 am, edited 1 time in total.
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Re: Benelli Dynamo Scrambler Restoration

Post by S1K @ Tue May 28, 2019 11:34 am

That’s Humpty Dumpty, surely?
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Re: Benelli Dynamo Scrambler Restoration

Post by wi11iam @ Tue May 28, 2019 2:30 pm

It is indeed a Humpty Dumpty - left over from a Scarecrow Trail a couple of years ago that too much time and effort went into for him to be chucked out.

This year’s entrants are a Help for Heroes bear who has just been squeezed into trousers really too small for him and Burglar Bill as theme is Heroes and Villains.

As an aside who has heard of Burglar Bill? The wife hadn’t and I assumed everyone learnt to read with that book as I did.
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Re: Benelli Dynamo Scrambler Restoration

Post by S1K @ Tue May 28, 2019 5:05 pm

Burglar Bill (or Boglar Boll as I called him at the time) was one of my favourite childhood books, along with Dogger.
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Re: Benelli Dynamo Scrambler Restoration

Post by Careless Whisperer @ Tue May 28, 2019 6:22 pm

S1K wrote:...one of my favourite childhood books, along with Dogger.

Have Yewtree started looking at children's authors yet..?
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Re: Benelli Dynamo Scrambler Restoration

Post by Pigeon @ Tue May 28, 2019 8:56 pm

Who's Durgger?
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Re: Benelli Dynamo Scrambler Restoration

Post by wi11iam @ Sat Jun 27, 2020 12:00 pm

Time for a thread resurrection.

I'm begging time from a friend for help with the engine (as in 'you do it, I'll watch, make the tea, provide the parts and the doughnuts') but now furlough has given him three months of Sundays time isn't such an issue for him so I took a day off and the rebuild restarted.

Mostly it was reacquainting ourselves with how it all went together and what has to be done - it's probably two years since it was disassembled.

Two halves of the engine case before and after cleaning. Looks like the engine had managed to ingest a good gulp of muddy stream water along with a small stone judging from the crank housing.

Image

Image

Remaining bearings pressed out and replaced. One small funk up on my part. All the other bearings in the two cases were interference fit so heat and press out but not the one behind the gear 'Christmas tree'. This fcuker has circlips inside and out. In an attempt to leave all the gears in situ I didn't spot the internal circlip and pressed that out too. Bugger. However the retaining lip is very small so it evidently wasn't expecting much lateral load - may even have just been for spacing. Workaround is to replace the bearing and the circlip and attempt to peen what's left of the lip enough to hold the circlip.

Should have done the more difficult things and separated all the gears, spacers, etc so would have seen the circlip rather than trying to be clever/lazy and keep it all as one assembly. Still annoyed at myself.

Both halves are now clean with new bearings so more part washing as we go and it's reassembly. Other than the crank and piston that were ruined (and OEM replacements found, eventually) everything else is in good shape given age supporting the theory that it got ruined very early on it its life. It looks like I have most bits, oil seals and gaskets aside. Gasket paper should address the latter and the clever Italians had gone metric so there's a chance the oil seals will be readily available, the bearings were all off the shelf sizes so hopeful.

I'll try not to leave a 2 year gap before doing something else to it.
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Re: Benelli Dynamo Scrambler Restoration

Post by Careless Whisperer @ Sat Jun 27, 2020 12:18 pm

Good to have an update!
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Re: Benelli Dynamo Scrambler Restoration

Post by Il Duce @ Sat Jun 27, 2020 3:08 pm

It looks very similar to a Vespa engine.
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Re: Benelli Dynamo Scrambler Restoration

Post by wi11iam @ Sun Jul 26, 2020 4:25 pm

A few hours over two evenings in the last couple of weeks.

First job put the last bearing in and peen the remaining lip over to retain the circlip where some pillock didn't look for/notice it and drifted the old bearing out and the drove the circlip through the casing.

Image

Fortunately the aluminium casting is very soft and there isn't lateral load (I think) so it should be OK. If it isn't it will be terminal. Finger crossed.

Gear trees and kick start shaft in.
Image

And then the crank.
Image

Which of course required the bearings to be removed from the casing and then put onto the crank in order to make closing the engine halves less of a problem. Cue mild swearing, application of heat gun and tap them through.

Onto the gasket. How do you make a gasket when you can't put a piece of paper on the casing or the casing on the paper? Make a masking tape 'gasket' from small pieces and then transfer to gasket paper and cut out.
Image

Image

And then it was liberal smear of gasket goo on both hales. Line it all up, apply plenty of heat and gently tap together. Oven gloves would have been more use than rags to hold the hot casings but they were in doors so top tip for any re-doing.
Image

It doesn't look much for 4 hours work when written down but a crank now turns in the casing for (probably) the first time in close on 40 years.

Hopefully final bit (sidestand) bought of ebay and inbound so there will be more sand blasting and painting - plus petrol tank sealing when stuff arrives alongside building up the engine. Next job: piston, barrel and cylinder head.
Last edited by wi11iam on Sun Jul 26, 2020 4:28 pm, edited 1 time in total.
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Re: Benelli Dynamo Scrambler Restoration

Post by manfromdelmonte @ Sun Jul 26, 2020 5:25 pm

Nice, good progress.
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Re: Benelli Dynamo Scrambler Restoration

Post by Damien Thorn @ Sun Jul 26, 2020 5:53 pm

Cool, well done!
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Re: Benelli Dynamo Scrambler Restoration

Post by Il Duce @ Tue Jul 28, 2020 4:18 pm

I'd be tempted to run a small bead of jb weld around the outer edge of that circlip, and maybe even some underneath it. Just in case it decides to move. Can't hurt can it?

Pity the poor bastard who has to rebuild it in 20 years time though.
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Re: Benelli Dynamo Scrambler Restoration

Post by Deuteronomy @ Tue Jul 28, 2020 5:05 pm

Il Duce wrote:I'd be tempted to run a small bead of jb weld around the outer edge of that circlip, and maybe even some underneath it. Just in case it decides to move. Can't hurt can it?

Pity the poor bastard who has to rebuild it in 20 years time though.


Yeah, I was thinking along those lines too, there's so little of the material left that I can't see that circlip staying in place for long.
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