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Ftwelder

Getting a MAR ready for first event in two weeks.

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I found a barn fresh MAR with mostly original equipment and under 1250k fresh motor. It's worthy of a full restoration but I was looking for a cheap rider so I am bagging/boxing all the nice original bits and going to ride a season or two before doing the restoration. It's got spark, compression and carb is clean. It had no brakes or fuel tank so I hasn't been started.

50230315133_b19492d54b_h.jpgRare find in these parts by barnstormerbikes, on Flickr

50230315158_70807445ec_h.jpgRare find in these parts by barnstormerbikes, on Flickr

The bike had been stored with ethanol fuel and the tank was mush. I am using Caswell epoxy liner/ shell to remediate but not sure if it will work, assuming it will. I have already replaces the brake linings and have a new brake cable, I have installed IRC trials tires (rear is tube/comp, front is tube type but low end model)

The original sprockets are great so Ill replace the stretched original chain and keep it wet and adjusted. 

I removed and stashed the alloy fenders with the seat and replaced with plastic. Ill do the same with the shocks and do the fork seals, the center bolt has severe leak. I got a side pull throttle and will build a skid this week.  I should make a list.

The kicker was a mess also.

50406461567_f64b9fa684_h.jpgUntitled by barnstormerbikes, on Flickr

50405605138_00684e39eb_h.jpgUntitled by barnstormerbikes, on Flickr

50406313536_03f7d35cfe_h.jpgUntitled by barnstormerbikes, on Flickr

Made a comp seat (yet to be reduced)

50414034072_03dea13df5_h.jpgUntitled by barnstormerbikes, on Flickr

I have all the intake and fuel delivery parts ready to go also. I should be able to pull it off. ?

 

 

 

 

 

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Sounds like a tight time challenge. Good luck. Those mudguards look great. There's a few things that MK 1 MARs benefit from that you didn't mention.

The standard ignition wiring comes out the bottom of the casing and typically gets squashed between the bashplate and the motor. There's an easy fix by rerouting it out the front of the engine casing. Only a problem if the bashplate touches things.

The fibreglass bashplate will fall apart real fast if it touches things.

That carby may annoy you enough to replace it with something different. If the bike is leaned over, it will flood.

The rear axle bends very easily. A common fix is to extend the hub to the right with an extra bearing closer to the RH end of the axle. Kits for this were very common back in the day.

The axle holes in the brake backing plates are not all on the same centre as the brake linings. Common fix is to enlarge the axle holes.

To get it geared low enough for modern sections using a small enough front sprocket you will probably need to machine the sprocket nut to provide chain clearance.

If you fit 360mm shocks with that set of sprockets, the chain will need careful attention to its adjustment to avoid sawing into the cross tube under the lower chain run.

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 Feetupfun is right on the money moving the wiring. This is the first thing you should do before you ride it!

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Had a MAR back in the day & bought one recently for old times sake. Brakes defy comment !!!. Rear brake especially bad. Motoplat ignition may give you problems. Amal carb very old school. Steers OK, pegs a tad high. Dished rear sprocket very rare, Most folks have gone for flat one / spacer. Later pre Gripper models had a longer more modern style front pipe & bigger silencer, which seemed to make motor a bit smoother.

Ethanol (E5) fuel is a major headache, but quite easy to remove. (see You Tube). You don't need any fancy equipment.  GRP tanks go to mush, & old rubber O rings swell terribly when contacted with ethanol. If you are successful in reclaiming tank, empty out fuel after very ride & let vapours flash off with cap removed. You should be OK. (Works for me) . Ethanol additives now commonplace, & we (UK) reportedly going up to E10 (10% instead of 5%).         

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Thanks for all the great info!  This is helping develop a strategy.

I should have mentioned my last time on a trials motorcycle was 25 years ago... I have ridden plenty of off-road, bicycle trials over the years but riding the easy line all the way as a senior these days.

Here is my list for the immediate future.

1) Add small front sprocket and extra nut/washer to shopping list. I would have missed this for sure.

2) make alu bash plate, add delrin chain guide block. This is actually an area of great interest. I don't care for spring loaded chain management devices.

3)(pjw123)  I will have to use the original rear sprocket one more time. I would like to find a worn original and machine an interface for replaceable chain rings and retire mine. 

4 I have seen the wire re-routing) fixes and am going to look for a work -around to avoid altering the original pieces by drilling holes. I may change my mind. 

3) Check rear brake concentricity and resolve any issues. Thanks feetupfun.

4) Change fork seals/washers.

pjw123, I have no trouble getting any fuel I want.Low population density in my area. I think the carb is IRZ.  Thankfully I have a nice hot spark!

 

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For info, dished sprockets are available new as 44T, works ok with 11T front. Original gearing was 12/46 on MK1 MAR (yours ) and 11/42 on MK2 onwards.  You'd really only want a 10T front with a 42 rear.  There is a specific nut you can buy for the 10T sprocket which has a shoulder on the inside to space the nut and prevent the chain catching it

The wiring is old and brittle, if you leave it at the original angle where it exits the case it may well crack open the insulation and short out. Many bikes have been altered to run the wires out by the front engine mount, you're not devaluing it by doing that

Brakes can work quite well if you have modern linings fitted to the shoes in oversize and then machine them down to fit the bub for maximum contact. EBC and Newfren are that thin on their linings that you barely get an inch of contact when the brake is operated

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On 10/4/2020 at 7:52 PM, woody said:

For info, dished sprockets are available new as 44T, works ok with 11T front. Original gearing was 12/46 on MK1 MAR (yours ) and 11/42 on MK2 onwards.  You'd really only want a 10T front with a 42 rear.  There is a specific nut you can buy for the 10T sprocket which has a shoulder on the inside to space the nut and prevent the chain catching it

The wiring is old and brittle, if you leave it at the original angle where it exits the case it may well crack open the insulation and short out. Many bikes have been altered to run the wires out by the front engine mount, you're not devaluing it by doing that

Brakes can work quite well if you have modern linings fitted to the shoes in oversize and then machine them down to fit the bub for maximum contact. EBC and Newfren are that thin on their linings that you barely get an inch of contact when the brake is operated

I ll try to locate a 10T and have it in time.

After seeing the wire routing, I can see your concern. Ill change that up. Ill take another look at the motoplat and see about changing the wires out. I hate taking those case screws out!

I have installed Newfren brake components and hope they work for a few rides though my expectations just dropped considerably. . I reduced the width to make them fit but I guess I need to blueprint the parts and do it right over the winter.

I figured out a strategy for the skid plate and ordered some 5mm 6061.

Thanks for advice and support.

 

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It sounds as though you've bought MK2 brake shoes if you've had to reduce the width to make them fit as the MK2 and later bikes use wider shoes than the MK1

Use the old shoes and have them relined with modern linings, oversize and then have them machined down to achieve full contact with the hub

This is the nut for the 10T but you only want 10T if you like really low gearing, unless you have 42 rear, the 10/42 is not too bad

https://www.inmotiontrials.com/product/mar-tr80-gripper-front-sprocket-tab-nut/

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On 10/10/2020 at 8:09 PM, woody said:

It sounds as though you've bought MK2 brake shoes if you've had to reduce the width to make them fit as the MK2 and later bikes use wider shoes than the MK1

Use the old shoes and have them relined with modern linings, oversize and then have them machined down to achieve full contact with the hub

This is the nut for the 10T but you only want 10T if you like really low gearing, unless you have 42 rear, the 10/42 is not too bad

https://www.inmotiontrials.com/product/mar-tr80-gripper-front-sprocket-tab-nut/

Exactly right on the brake shoes I bought,. Feetupfun mentioned drilling the axle hole larger and allowing the brake plate to self center. I have some machines so Ill bore a hole in piece of plate that matches the drum size, drop the backing plate in with shoes, and locate the hole center in the backing plate. If the shoes fit the bore diameter I should be able to locate center and solve the problem. Perhaps.

I can get a smaller front gear from my local dealers stock on short order, haven't heard if it's 10 or 11T. I remember my Montesa was geared to ride in 2/3 most of the time and first seemed crazy low. That suites me fine and may be a winter upgrade to go 10/44.

I went to remove the drain plug and although it was snug it didn't retract when unscrewed. I applied a side load while turning the wrench and the drain plug came out with some bits of aluminum and the last remains of a couple threads. If the motor was apart or coming apart soon I would weld up the hole but just going to tap to next size up at this point in time.

50463753763_b9797c96c6_h.jpgUntitled by barnstormerbikes, on Flickr

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On 10/11/2020 at 12:02 AM, larry s. k. said:

Nice score very collectable  bike  , cheers

Thanks, Ill take care of it.

 

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On 10/13/2020 at 10:08 AM, Ftwelder said:

Exactly right on the brake shoes I bought,. Feetupfun mentioned drilling the axle hole larger and allowing the brake plate to self center. I have some machines so Ill bore a hole in piece of plate that matches the drum size, drop the backing plate in with shoes, and locate the hole center in the backing plate. If the shoes fit the bore diameter I should be able to locate center and solve the problem. Perhaps.

I can get a smaller front gear from my local dealers stock on short order, haven't heard if it's 10 or 11T. I remember my Montesa was geared to ride in 2/3 most of the time and first seemed crazy low. That suites me fine and may be a winter upgrade to go 10/44.

I went to remove the drain plug and although it was snug it didn't retract when unscrewed. I applied a side load while turning the wrench and the drain plug came out with some bits of aluminum and the last remains of a couple threads. If the motor was apart or coming apart soon I would weld up the hole but just going to tap to next size up at this point in time.

50463753763_b9797c96c6_h.jpgUntitled by barnstormerbikes, on Flickr

Rather than tap up to the next size, wouldn't a helicoil of the the same size and thread pitch be a better option. I also like the look of the mudguards, where did you get them from ?

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16 hours ago, fourex said:

Rather than tap up to the next size, wouldn't a helicoil of the the same size and thread pitch be a better option. I also like the look of the mudguards, where did you get them from ?

Helicoil is a great idea. I’ll give that a whirl. I got the fenders from Ron Bors in upstate NY. They are Acerbis items. 

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My parts arrived today (Friday) . I pulled the flywheel to move the wires and noticed some residue showing a crank seal leak. Not a good sign with the ride on Sunday but we will see. I rerouted the wires with the heat gun and it worked really well. Ill probably make a washer type device to hold the wires away from the flywheel.

The heli-coil went really well!

50521121063_03fe1eb200_h.jpgUntitled by barnstormerbikes, on Flickr

I bent up a skid plate I like that fits pretty good. The first one wasn't so good but the drilling went well so Ill use it for a template.

50521121093_61b13da525_h.jpgUntitled by barnstormerbikes, on Flickr

Quite a few things to do but hope to be wrapped up tomorrow afternoon in time to fire it up if it works out that way.. 

 

 

 

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