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1976 Motobecane Super Mirage

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1976 Motobecane Super Mirage

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Old 01-12-19, 10:29 AM
  #76  
Aubergine 
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Originally Posted by Cheseldine View Post
I should have the frame completely stripped down by Sunday - I'm planning to go over the paint with a little polish while removing any rust from the rock chip areas before touch up paint. Do you folks recommend spraying the frame (chrome taped of course) with an automotive clear coat to protect it once it is thoroughly degreased to protect it?
Motobécane paint is very tough, so I would not bother with a clear coat.
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Old 01-12-19, 10:36 AM
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Originally Posted by Cheseldine View Post
I just snapped this pic of the seat post that the 26mm long steel tube was in, but could not lower more than about half way. Anything you guys can gather?
Weird. It looks slightly pinched in spots but a bit open at the very top. Given that you can insert the long post so far, I would cut that post shorter and use it without worry. Three things to do: measure the “minimum insertion” length and make sure that you leave at least that length for insertion in the frame after cutting; chamfer the bottom edge of the cut post; use plenty of grease when you put it all back together.
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Old 01-12-19, 11:58 AM
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I don't know if this helps as Motobecane was evolving to ROW standards during the timeframe. Dimensions year to year can be different. My 1979 Mirage is made with 2040 straight gauge steel. My seat post is 25.4mm and the ST OD is 28.3mm which includes the paint. I doubt I could get a 26mm post into my frame.

Can you find a machinist who can measure the ID of the seat tube, a few cm below the seat tube top lug? That would "learn ya" some good data.

Get a good flashlight and inspect the ID of your seat tube. Ensure there is no ridge which is blocking the post from fully inserting. My winter project is a 73 Grand Record. It's stem wedge had rusted badly and left a ridge on the ID of the steerer. The stem would not insert past the min insertion point. I used a ball hone which did not help much. Quality time with a round file finally removed that ridge and the stem fully inserts now. Any obstruction in your ST?
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Old 01-12-19, 03:58 PM
  #79  
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Originally Posted by Aubergine View Post


Weird. It looks slightly pinched in spots but a bit open at the very top. Given that you can insert the long post so far, I would cut that post shorter and use it without worry. Three things to do: measure the “minimum insertion” length and make sure that you leave at least that length for insertion in the frame after cutting; chamfer the bottom edge of the cut post; use plenty of grease when you put it all back together.
The post is a really heavy poor quality steel one with some rust. I'd like to get something a bit lighter weight. The current one is also the clamp around the tube style, and definitely not original.

Originally Posted by Prowler View Post
I don't know if this helps as Motobecane was evolving to ROW standards during the timeframe. Dimensions year to year can be different. My 1979 Mirage is made with 2040 straight gauge steel. My seat post is 25.4mm and the ST OD is 28.3mm which includes the paint. I doubt I could get a 26mm post into my frame.

Can you find a machinist who can measure the ID of the seat tube, a few cm below the seat tube top lug? That would "learn ya" some good data.

Get a good flashlight and inspect the ID of your seat tube. Ensure there is no ridge which is blocking the post from fully inserting. My winter project is a 73 Grand Record. It's stem wedge had rusted badly and left a ridge on the ID of the steerer. The stem would not insert past the min insertion point. I used a ball hone which did not help much. Quality time with a round file finally removed that ridge and the stem fully inserts now. Any obstruction in your ST?
The OD of my seat post tube is 28.35 including paint, etc., so it must be different. That's interesting, I'll have to grab the tools from work or take my frame with me to grab the ID a few cm down from the top.

I'll also check for obstructions. Either way, I don't want to use the old seat post, but want to locate a new, correctly fitting one. It seems like a great and easy place to cut down the bike's current weight.

So far I've got in the following parts:

NOS 22mm Motobecane branded SR 22mm stem
Jagwire road pro cables and housing
New SRAM chain
Charge Spoon brown saddle

Still plenty left to get, but it's coming along. I spent a little time cleaning and degreasing the frame last night. With a little polishing compound some of the hazy look of the paint is clearing up nicely. I need to get some touch up paint and clean out all the small rusty rock chips next.

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Old 01-13-19, 11:33 AM
  #80  
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seat post size?- 1976 Motobecane Super Mirage


70s Motobecane w/ 25mm seatpost - which tubing?

Originally Posted by mparker326 View Post
The lugs look the ones on my 76 Super Mirage. My seatpost size is around 25.6 and the original seatpost was around 25 & had a shim. My SM, has 1020 tubing.
^From second thread. Hope this is helpful.

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Old 01-13-19, 11:55 AM
  #81  
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That is one nice project
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Old 01-14-19, 01:44 AM
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I just wanted to give a big thanks to Mountaindave. I met up with him this afternoon and he shared a small party of his knowledge with me. We dug a bit deeper into the bike and luckily the headset and bottom bearings look great, but all the old grease had turned to a waxy substance creating a gritty feel. Dave was kind enough to send me home with a set of 27" wheels, better brake levers, and some headset bearings. I'm not sure how to tag him in this reply, but all you folks have been great.
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Old 01-14-19, 01:53 AM
  #83  
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Originally Posted by Raleigh74 View Post
Interesting, we tried a 25.8mm seat post today and it was way to loose. I think mine is a 26.2mm.
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Old 01-14-19, 12:26 PM
  #84  
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There are older style SR 26.2 posts around. Part of the Custom group.
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Old 01-15-19, 08:42 AM
  #85  
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@Cheseldine;, it was a great pleasure getting to meet you and talk bikes, you are truly a kindred old soul - I wish I had your youth too! You’ve got a great project bike that can be completed largely with elbow grease (aside from consumables). Happy to share parts that will never get used - the beer was more than a fair trade . And, believe it or not, we retrogrouches are a bit of a rare breed so we love meeting fellow retrogrouches. I’m happy to help anytime!
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