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Ossa MAR ..restoration advice please!


ScottyA
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Hi there,

 

First time using the forum and I’m looking for a bit of help with my Ossa.

My dad and I acquired it many years ago and it was our intention to get it back to working order and maybe use it for the odd trial. My dad passed away before we got round to it so now I’m going to have a go myself. My dad was an engineer and knew the history of the bike. I’m ok with routine maintainance and minor repairs having owned modern MX bikes but have never done a restoration on a classic so it’s a bit beyond my experience/ skills. The bike is currently dismantled in boxes etc and has been like this for years

im probably going to get the engine rebuilt professionally and then I will know it’s all sorted. 

What im looking for here is confirmation that it actually is a 250 MAR and if so what colours it should be (as I’ve seen a few variations. ) Also any general tips and good sources for parts / manuals etc

The tank ( alloy) is completely green and the frame is black ( with surface rust). So from what I can see it’s either been painted or isn’t an MAR ( only had a silver frame ? ) Mudguards are white plastic. Im going to try and attach a few pics of some of the bits. Can send more if it helps. 

 

Ultimately im not going to try and make a show bike as I’m going to use it but I would like to make it more original and presentable 

 

Thanks in advance!

 

Scott

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It is a MAR.  The MAR ran from '71 right through to '79 and changed little. The MK1 ran from '71 - '73. In '74 it became the MK2 MAR with a longer swingarm, bigger crank assembly and the inlet was changed for a push on not bolt on carb. Hubs changed (although externally looking the same apart from black, not polished) to take slightly bigger brake shoes. Green tank stripe changed from broad stripe from side to side to thinner stripe running lengthways. Biggest change came in '76 with the MK3 when it received angled shocks, longer forks and a longer front pipe. In '77 they changed it from silver frame with white tank and sidepanels to black frame with green tank and sidepanels and changed the rear silencer for an abortionate looking thing stuffed with wire wool. On the green bike the barrel got different porting (maybe) and in '79 the frame and mudguards also went green.

It was referred to as the MAR throughout this time but I guess in reality the only true MAR was the MKI1 which ran from '71 - '73 as Mick Andrews had leftt for Yamaha by then.

You have a MK1 or MK2 frame (they're the same) which would have been silver. If it has a frame number on the headstock which begins 340--- then it's a MK1. If there is no number it's probably still a MK1 as they usually had a sticker with the chassis number rather than it being stamped.

The engine looks MK1 due to the split outer fin on the head and the inlet manifold with studs to take a bolt on carb - these could obviously have been changed in 40 odd years but again, the engine number will tell you as it will also begin 340--- if MK1.  You need to know for an engine rebuild as the MK1 had a smaller crank than the following models and the crank pin is stepped. The later pin won't fit. The head is on back to front but it doesn't actually make a difference to the way it will run.

The tank is from the last green model, it's not the original. The original would have been fibreglass and a different shape. From MK2 onwards the UK bikes had an alloy replacement, different from the original fibregloass shape, which was the same whether for the white and the green bikes, apart from the last all green bike where it had the extended front part like yours. Side panels also look as though they are from the green bike but there's not enough showing in the picture

Bike below is a MK1 with a longer MK2 arm and MK2 barrel. The bottom picture is a MK2 but with the original fibreglass tank

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Edited by woody
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14 hours ago, woody said:

You have a MK1 or MK2 frame (they're the same)

The mk1 and mk2 frames were slightly different in one area that I'm aware of and that was the length of the rear mudguard mounting bracket, it was about 25mm longer on the mk2 to compensate for the longer swing arm I assume. I can't see the bracket on ScottyA's black frame, looks like it has broken off. The location of the top shock mounts would suggest mk1 or mk2 frame. Also the right side engine case is not mk1 or mk2 due to the shape and oblong hole but hey, this could have been replaced with a different models case or modified at any time over all these years. Below is a pick of my mk2's bracket which is cracked and ready to fall off but is longer than that of the mk1. You might have a "bitza" ScottyA.

004_(2).jpg

Edited by fourex
modified.
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The Twinshock Shop (bikes) has an Ossa very much like your bike that is in bits. There could be some useful pointers in the pictures as to what your Ossa should resemble. Your carb looks to be an Amal 600 series and parts for that are easily obtainable, or you can buy a new item from Amal as the company still trade on-line. Thats for originality but you may want to change to a more modern alternative. 

Before spending your money have a look at the many suppliers of parts and accessories on line to give you an idea of the budget needed for your rebuild. When correctly set up the Ossa MAR handles very well, with further small mods such as footrest location and type and a bit of suspension magic they will perform very well in most types of going.??

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11 hours ago, fourex said:

Here's a pic of an original mk2 right side engine case.

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This is the same casing as Scotty's bike as all the MAR models had the same casing it's just that the one in your picture is in original condition. Many UK bikes had their casings modified with the slot cut in and the back end cut off to relieve mud build up and also to help hook the chain back on using the slot should it have come off the engine sprocket. See the casing in the picture on my bike. The back end of the case can also get smashed off by a chain derail and it's not uncommon for the bottom rear screw mount to be missing altogether.

You're right about the mudguard brackets which is a good ID point but it looked as though it is missing in the picture. I was just meaning the basic frame is the same - on all MAR models in fact apart from the top shock mounts on MK3 and green bikes. I think the Verde also has the short swingarm and mudguard bracket

I think Scotty's bike is a MK1 with replacement tank and panels rather than a bitsa, in which case the forks and wheels should be MK1 also

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That’s Brilliant, thanks guys.

I’m away with work at the moment but when I get home I will check the bits over again armed with your info. Seems everyone is convinced it’s a MK 1/2 frame so should be silver. It needs painted anyway so I may as well try to get the correct colour.  Does anyone know a good match for the silver that would be readily available in the UK? Same for the green paint but as I’ve got the tank and side panels ive got something for comparison so it should be easier to sort. 

I’m considering having a go at the painting myself or the fun / learning exercise. I figure that if I’m not happy with the result I can get it done by a pro after and I haven’t lost out on much. Any tips would be appreciated! 

 

Thanks again !

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Ford silver fox used around 1970 is a good match but not sure where you can get that now unless a local paint shop can mix you an aerosol for it. I don't know the RAL code. 

NOTE - If you use Halfords paint it will dissolve at the merest touch of petrol, it will need a coating of petrol proof lacquer otherwise you'll be really peed off with the outcome.  And whereas Halfords paint does spray very nicely and evenly out of the can and leaves a really nice finish, their petrol proof lacquer doesn't, it splutters out so you need to be very careful when applying it

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Best to do a dry build prior to painting to see if any brackets need attention, fitting the motor is a bit like doing a Rubik Cube but once you find which way not too bad. I would lower the footrests in the way Woody has done on his bike, the originals are far to high. Shock mount bolts are M7 fine a size not always easy to find, I got them for my bike from Barfast Engineering Newcastle under Lyme (find them on google) also check everything around the rear wheel spindle to see if it is bent. A better made replacement in high tensile stainless is available as well as a carrier for modern Beta type spockets which has a third bearing and completely cures the problem. If you can make Telford show in Feb Steve Sell is usually there he is definitely the best person to speak to for everything OSSA.

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The shock bolts are normal M6 on the earlier bikes, MK1  2 and 3,  they went to M7 on the green bikes

Strangely, the fork yoke bolts are M7 on the earlier bikes and changed to M6 on the later bikes...

Fitting the engine, I've never been able to fit one with the barrel in place, or remove it. I take the barrel off before removing and fit it after the engine is back in the frame  -  I could never do a rubik cube either...

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26 minutes ago, woody said:

The shock bolts are normal M6 on the earlier bikes, MK1  2 and 3,  they went to M7 on the green bikes

Strangely, the fork yoke bolts are M7 on the earlier bikes and changed to M6 on the later bikes...

Fitting the engine, I've never been able to fit one with the barrel in place, or remove it. I take the barrel off before removing and fit it after the engine is back in the frame  -  I could never do a rubik cube either...

Nor me with the Rubik cube. When I fitted the engine into my TR77 the motor with top end on was placed on a workmate bench then the frame somehow lowered over it and sort of rolled in position I do know when it was finally built the downtubes were covered with bubble wrap to protect the finish. Never having owned an earlier model I was unaware that the shock bolt size was changed. 

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  • 1 month later...

Hi Scott

I am restoring a 1976 OSSA MAR mk3. It to had been painted black and I rubbed it down ( not to bare metal) and sprayed it with this from EBay, using the primer suggested from the same supplier: FORD 3 SILVER FOX Aerosol Spray Paint 400ML Direct Shine Gloss https://ebay.us/iZJdtU

3 coats primer with 20 minutes between coats and 3 top coats with 20 minutes between coats. I didn't rub down between coats unless I got any runs. The attached picture shows the finished frame. Like you I want to do everything myself, so lots of reading on the internet etc.

Gordy

 

image.jpeg

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On 2/1/2019 at 9:51 AM, gogs56 said:

Hi Scott

I am restoring a 1976 OSSA MAR mk3. It to had been painted black and I rubbed it down ( not to bare metal) and sprayed it with this from EBay, using the primer suggested from the same supplier: FORD 3 SILVER FOX Aerosol Spray Paint 400ML Direct Shine Gloss https://ebay.us/iZJdtU

3 coats primer with 20 minutes between coats and 3 top coats with 20 minutes between coats. I didn't rub down between coats unless I got any runs. The attached picture shows the finished frame. Like you I want to do everything myself, so lots of reading on the internet etc.

Gordy

 

image.jpeg

Appears you painted the fork lower tubes.  Pretty certain if you are restoring, I thought all the MARs had polished aluminum lower fork legs.

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The MK3 generally had black legs but some early versions with the normal up and over chrome front pipe may have had plain alloy (not a criticism of what you've done, I'm no purist or originality obsessive when it comes to paint jobs)

The MK3 changed a bit during it's short run, early bikes had the normal MAR exhaust, then they fitted the longer front pipe and some later versions had the TR77 style rear silencer

That's a good shine on that paint for silver fox  -  I might try some of that on a Cotton tank I have to paint

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