ColinPybus

Please see previous posts on rear brake mod. There's plenty of room for the rod, however I'm removing this and replacing with 8mm thick walled tubing for better strength. Rear brake arm lever still needs a bit more tinkering . Still struggling to attach photos, they always seem to be too big to attach. Can't remember how I've done it before.

One year later and I've just fitted my rear brake rod ( 5mm diameter) to the rose joint off the brake pedal and to a new rear drum brake arm I've made. All ok but rod flexes ( bends) when in use , not ideal. To this end I've ordered some 8mm diameter thick wall tubing which I hope will do the job. Hopefully I'll put some pics on the site once I'm done. P.S. I found out too late you cannot fit the brake pedal once the engines in. I had to grind of the left hand side to get it to fit and then fitted a longer oilite bush and sleeve to make up the lack of length.

Thanks Woody, I'll keep looking.

Hello everybody, Does anybody know where I can buy a Kickstarter for my 75 250 MAR in the UK? TIA Colin

Thanks Woody.

Hello all, Do I need a chain tensioner if I'm just green laning my 250MAR? TIA

With reference to an earlier post on here about a broken threaded boss on the right side engine casing on a 250 Mar, I have the same problem on mine. Upon further inspection I noticed the hole for the thread was a further 10mm deeper from where it was broken off. Using an M6 machine tap I managed to tap the hole to the bottom giving more than enough length and strength for an M6 countersink bolt. The only problem I'll have now is sourcing a bolt long enough! Site won't let me send pic as over 2mb big. Can this be changed or is there something I need to do? I've sent pics before no bother.

Thanks IDC good price as well.

Thanks for that, I'll size the seal at the sprocket end and go from there.

Ok cheers for that, I didn't realise there was a ball between the rods. I can't remember seeing one when I stripped it. I'll have a closer look at the drawing I have. Rods are about 112mm long and a non standard English or metric size. I think they were 0.225" in diameter. I was thinking of using through hardened 6mm diameter pins (0.236") that will fit easily and now I know, a 6mn ball bearing. Thanks again.

Hello there, Can anybody tell me the correct diameter and length of these rods and why does it have to be in two pieces?

Just made this today out of a couple of bits of ally bar and an old bike stand I had around for when I finally get round to rebuilding engine.

The saga continues, the bracket I'm using on the brake pedal shaft wouldn't drill as it was too hard, as I was going to bolt rose joint to it, so back to the spark eroder and I tubed a hole through and then fixed with a bolt and nyloc nut. I drilled and tapped the threaded end of the rose joint M5 and and fitted a threaded end 5mm diameter rod to it with an lock nut. In hindsight I should have used a female rose joint, it would have looked better. Alloy brake arm to make now and cut rod to correct length!

Hello again, First stage of rear brake rod mod was to file , fit and machine this old part I had laid around. I will then fit a rod end bearing to the upstanding diameter . I will drill and tap the upstand and secure rod end bearing with a cap screw and washer.I have mocked up a cardboard brake arm with a scrap brake rod I have to give you some idea . If brake arm is long enough it will clear the existing cable stay. I will copy an existing rod operated brake set up to secure rod to brake arm. Again I will use brake cam spindle to spark erode splines in aluminium plate I will use to make brake arm. I hope this helps.

Hello there, I will post some pics later on about my plans for a rear brake rod. Today however I managed to spark erode the splines on a generic gear lever using the gear change lever as an electrode. It went a lot better than I thought it might . Unfortunately I can't get video of spark erosion to work on this site.

This bush needs to be removed to get the crankshaft and flywheel from the engine casing. As it's pressed on at the factory you can get/make special tools to draw it off. As it's a shrink fit on the shaft a bit of heat on the splined bush helps it expand and then my turned aluminium dolly is placed at the end of the crank and then hit " gently" with a hammer. Upon reassembly I will place crank in the freezer overnight ( in a plastic bag of course ,this will help fitting of the bearings as well) to shrink diameter and then again use plumbers blow torch to heat up bush to make it expand. It should slip easily over and then once cooled it should be a tight fit again.I will take photos tomorrow of it all loosely assembled. Hope this helps. I am finding the refurb of this bike horrendously expensive!! To this end I am making it my bike and not straight out of the factory. I've cylindrically ground the swing arm shaft and turned new bushes to suit . I've turned new brake lever bushes as well. I intend to try and spark erode a generic gear lever with the gear lever shaft as an electrode. I am also going to make a new rear brake arm that will be rod operated as opposed to a cable. I know all these bits can be purchased new but I could spend £5k on a bike that's worth £2.5k . Hope Mick Andrews doesn't mind!!

This bush needs to be removed to get the crankshaft and flywheel from the engine casing. As it's pressed on at the factory you can get/make special tools to draw it off. As it's a shrink fit on the shaft a bit of heat on the splined bush helps it expand and then my turned aluminium dolly is placed at the end of the crank and then hit " gently" with a hammer. Upon reassembly I will place crank in the freezer overnight ( in a plastic bag of course ,this will help fitting of the bearings as well) to shrink diameter and then again use plumbers blow torch to heat up bush to make it expand. It should slip easily over and then once cooled it should be a tight fit again.I will take photos tomorrow of it all loosely assembled. Hope this helps. I am finding the refurb of this bike horrendously expensive!! To this end I am making it my bike and not straight out of the factory. I've cylindrically ground the swing arm shaft and turned new bushes to suit . I've turned new brake lever bushes as well. I intend to try and spark erode a generic gear lever with the gear lever shaft as an electrode. I am also going to make a new rear brake arm that will be rod operated as opposed to a cable. I know all these bits can be purchased new but I could spend £5k on a bike that's worth £2.5k . Hope Mick Andrews doesn't mind!!

Hello all, Please excuse my "butchery" but I managed to simply remove the splined bush off the crankshaft by turning an aluminium dolly to fit inside and then gently heating up the bush with a plumbers blowtorch and then hitting dolly to remove. Looked online and there's all sorts of special tools but this work a treat.

Thanks for that I'll check that out. I think they'll be the same.

Good evening IDC, I have done the same on my mar. However when I measured the swing arm spindle it was all sorts of sizes . I ended up cylindrically grinding the spindle between centres and then turning some new plastic bushes to suit on the lathe. You may want to check the size of your spindle before fitting new bushes as you may have excess clearance on the fit.

Hello everybody, could someone please tell me lengths of spokes I need front and back for a 1975 250 MAR? I know I can buy them off the shelf from in motion but don't want the expense of stainless steel . Best regards, Colin.

Thanks to everyone for their input. Who'd have thought refurbishing a two stroke single would be so difficult! Learning a lot from this forum, it's a great help .

I think they had points originally, I've got nothing on the ignition side of the crank so refitting an electronic ignition would make more sense. Thanks for the info.

Thanks Gezzer will do .

The problem I have is that there's no ignition system at all with the bike!