Ossa MAR '74

Need help finding information or parts for that old machine in your shed? Someone in here will know!

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David Lahey
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Re: Ossa MAR '74

Postby David Lahey » Sat Jun 28, 2014 8:09 pm

Montesa13 wrote:
David Lahey wrote:here's what I'm bringing to Conondale in November, haven't decided which "look" yet



Wow what beautiful looking machines David!!

Thanks Montesa13, but I only have one of them! Those are one and the same bike with different tank and sidecovers


relax, nothing is under control

Rod
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Re: Ossa MAR '74

Postby Rod » Sat Jun 28, 2014 8:50 pm

I agree, Ossa's are beautiful looking bikes, ahead of their time in many ways with their geometry and compactness, and no under engine frame rails. However, fibreglass bashplates, dished rear sprockets, footpegs with no springs and cucumber mufflers held on with a single spring makes me wonder if there was 2 x engineering teams working on this bike. One team were smokers and the other were not ?

David, your motor has a much longer outer head fin then mine from that pic (mine is 90mm long at the head), also no breather tube top left crankcase on mine. What year is yours ?



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Re: Ossa MAR '74

Postby David Lahey » Sat Jun 28, 2014 9:37 pm

Sorry I don't know for sure what the bike is, but here is what I think the important bits are from:
Explorer motor (Explorers were sold in 74/75 and from what I can tell share a motor with the Mk2 MAR)
Explorer frame
Mk1 MAR swingarm
Explorer wheels and forks and from what I can tell these are the same as the Mk 2 MAR


relax, nothing is under control

Rod
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Re: Ossa MAR '74

Postby Rod » Sat Jun 28, 2014 10:57 pm

There is one mod I intend to do on my MAR that will piss off the purists, '"Fat Bars". I just can't do 7/8" apehangars ,they don't look safe. I've already fitted some s3 adjustable bar clamps to the top triple clamps, 6" jitsie fat bars are next as they are the tallest fat bar I can find.

If anyone has the Renthal "Trials 110" (829-01) bar for sale in new condition, please let me know.



Montesa13
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Re: Ossa MAR '74

Postby Montesa13 » Sun Jun 29, 2014 10:22 am

David Lahey wrote:
Montesa13 wrote:
David Lahey wrote:here's what I'm bringing to Conondale in November, haven't decided which "look" yet



Wow what beautiful looking machines David!!

Thanks Montesa13, but I only have one of them! Those are one and the same bike with different tank and sidecovers


AH! Got me (that wouldn't be hard) I'm really enjoying these forum posts if some of the info is retained I'll actually learn something :) Cheers David



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Re: Ossa MAR '74

Postby Montesa13 » Sun Jun 29, 2014 10:28 am

Rod wrote:Very nice, the MAR look for me. That's the stripe setup I think mine should have.


Now I'm up to speed ... I'm with you re: MAR look too Rod



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Re: Ossa MAR '74

Postby Rod » Mon Jun 30, 2014 8:14 pm

Hi David, how did you achieve that look with the MAR, is it just the sticker kit applied on top of the gel coated white fibreglass and that's it ? It looks good from those pics.



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Re: Ossa MAR '74

Postby David Lahey » Mon Jun 30, 2014 8:26 pm

Line inside of tank with epoxy, paint with white auto paint, add stickers then paint with clear auto paint. Same for side covers. Stickers from Anglia Vinyl Art. I think the stickers might have been made for the pommy aluminium version of the MAR tank, because they took lots of careful trimming to get them to look OK on the fibreglass tank.


relax, nothing is under control

Rod
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Re: Ossa MAR '74

Postby Rod » Mon Jun 30, 2014 9:41 pm

Awesome, tell me more about the epoxy for inside the tank please. I have an Italjet T350 (all green) that I intend to resurrect some day, its plastic tank was hopeless for keeping the stickers attached. I still have the original stickers albeit in very poor state. Would this epoxy be suitable for sealing the inside of the Italjet plastic tank?



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Re: Ossa MAR '74

Postby David Lahey » Tue Jul 01, 2014 9:50 am

Sorry Rod I've never lined any plastic tanks, and would think that it would not be successful with epoxy, because the HDPE used for plastic motorbike fuel tanks has very low stiffness, so any impact would load up and crack a stiff lining like epoxy
The epoxy I use is low viscosity (made for brushing) so it can be spread inside fibreglass tanks by moving the tank around and letting gravity move the wet resin. The inside has to be completely degreased so the epoxy sticks to the polyester resin and any exposed glass. I wash the tanks out with hot water with dishwashing liquid, then rinse with hot clean water, then dry the tank fully, then do a rinse with acetone, then mask the places I don't want the resin to go using plasticine. You need to mix up excess epoxy, coat the inside, then let the excess drain out before it starts to thicken. I experimented with the resin and hardener mix to get the right ratio to provide at least 30 minutes before it started to set. I've used two different brands of brushing epoxy, both bought from a local boat shop. I think the first was Epiglass and the others have been West Systems. From memory It costs about $50 in resin to treat a tank.
It's not just for protection of the original polyester resin that I line them, but most of the 1970s Spanish tanks I have looked inside there is a lot of exposed glass strands and I want to make sure the tank won't leak and ruin the fancy paint job that goes on later.
Back on plastic tanks, some people claim to have had success keeping stickers on them using some sort of external sealer coating before adding the stickers


relax, nothing is under control


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