Monday, 31 March 2014

9 - More Twists

 Today I spent a couple of hours outside with the frames. I ground and sanded away the old welding from around the sumpguard. It looked tidy but it revealed another crack. That's two cracks now. I also cut the head off the bolt that was holding the brake pedal on. It will be replaced with a proper pin.

 I'll grind out the area of the cracks and weld them but the more I look, the more bends and twists I see in both frames. Either they both have had extremely hard lives, or these wee frames are more easily damaged than you would imagine.

 It will take a little more looking at, a bit more work and a bit of head scratching before I decide just which one of the frames is going back into the bike.

 I also sat with a mug of tea looking at the swing arm until I had convinced myself to move the bolt and make it right. So that's another job added to the list.


Sunday, 30 March 2014

8 - The Swing Arm

 I took the swing arm into work with me today and had a look at it on the surface table. With just a couple of measurements it seemed things were even more complicated.
 Although there was a 4.5mm difference in the heights of the shock mounting bolts, there was only a difference of 2mm across the height of the axle. 

 So the swing arm did have a twist but it didn't amount to the difference noticed at the mounting bolts. The only explanation could be that these bolts must have been welded into the lugs of the swing arm at different heights. It seems a bit odd because you would expect them all to be built in a jig. 

 After a lot of debating in the workshop about the best way to correct the problem we had to leave aside our "engineering heads" and think to ourselves "we're not going racing on this wee bike, in fact we'll probably not be doing any more trials on it, so if we could correct the 2mm across the axle we would leave it at that.

 It wasn't hard to do, I just clamped the pivoting end in a vice, placed a long bar between the two legs of the swing arm and gave it a push. Now the axle's level and the height difference of the shock mounts is approx 2.5mm. As someone remarked, the only time I'll ever notice it is when I'm taking the shocks on or off, and that won't be often.

 Still I'd like to know from anyone if they have come across a similar issue with their bike. 

Friday, 28 March 2014

7 - More stripping

 I've got the old sump guard removed from the new frame, it just needs cleaned up with a disc before re-welding it.


 Meantime I tore down the rest of the bike, there wasn't really much of it left.

 I've noticed a problem with the fit of the shock absorbers. With one side attached, the other doesn't fit. I measured the length of the shocks, they're identical, so it's not them. I tried the swing arm into both frames and the same problem occurs. There's a 5mm difference between the distance of the shock attachment points on both sides of the swing arm. 

 So it looks to me like the swing arm has got a twist. I think I might be able to move it with a crowbar but first I want to take it into work and inspect it properly on a surface table, then I'll work out the best way to do it.

Thursday, 27 March 2014

6 - Forks

After finishing the wheel I pulled out the forks and stripped them down. There wasn't a lot of oil left in them, and what little there was, was a muddy brown colour.

 I took all the bits into work and washed them with a high pressure washer then gave the lowers a polish on the buff. There's a huge amount of deep scoring on the outside of the forks. Marty reckoned most of it was done by the bike rubbing against the side of a trailer, he's probably right. There was not a lot I could do about it.

 The stanchions however were perfect, I remember buying a new set years ago so the chrome was good.

 The rebuild wasn't hard. New oil seals (35-47-7) o-rings on the bottom of the dampers and a couple of new cir-clips finished it off. The only thing I'm noticing is that the left fork tube is just starting to bind in the lower at about the last inch of its travel before it bottoms out. I might come back to this on the refit but for now I'm going to carry on stripping.

Wednesday, 26 March 2014

5 - Hmm...where to start ?

 This was the question I was asking myself as I sat looking at her one night. Front or back ? I decided to tackle the front end first. 

 I pulled the front wheel out and took it apart. Tyre off, spokes out and the hub bearings removed. The next few days were spent polishing the rim and painting the centre of the hub. 

 The rebuild was straight forward with new bearings and oil seals in the hub. The spokes were in fine condition but it was difficult to polish the nipples. I was going to buy a new set but couldn't find any aluminium ones, only chrome plated brass. So the old ones went back in.

 When I took the wheel apart I was pleased to see stainless steel distance pieces on the axle. I remembered making them last time round, and they had survived 20 odd years in perfect condition. 

 I finished off with a new tyre, Pirelli MT43.

Before and After

Monday, 24 March 2014

4 - The Frame

 I mentioned the frame had got a thump. It flattened the bottom tube a bit, and pushed it up against the engine. It was still ok and wasn't doing any harm, but it didn't please me. 

I was thinking about having it straightened out but didn't know who to go to. I even thought about ways of doing it myself when up popped a frame on ebay. I watched it all week and jumped in at the last minute with a bid (the only one as it turned out) and got it for £60.

Once I'd managed to get it out of all the packaging (thanks Steve) it looked good. I run my eye over it and could see a couple of things that would need further work - nothing serious. Someone has tried to fit a new sumpguard but the welding's terrible, I'll cut it off and redo it. The side stand pivot reeds repaired as does the brake pedal. So now I've two frames and more options.

Sunday, 23 March 2014

3 - Some Inspiration

Here's some of the bikes on display at the Moto Museum Barcelona

This bike once belonged to the King of Spain

 Bultaco even built bikes for the Red Cross

2 - The First Restoration

 About 20 years ago I had a go at tidying up the Bultaco. I stripped it down and painted the frame and tank, rebuilt the engine and wheels. It was looking better than it ever had in it's life, and running pretty good. At least it was easy to start. I decided to take it out and do a few trials. 

 Well that was a bad thing to do. In a short space of time it was as battered looking as ever. I rode it for a number of years then noticed I'd put a hole in the clutch cover. I'd also banged the sump awful hard against something and pushed the bottom frame rail up against the engine. I decided not to ride it any more.

 Two years ago while on holiday in Barcelona I visited a bike museum. There was a lovely collection of Spanish trials bikes, beautifully restored. When I looked at them I said to myself "that's what mine should look like". Since then I've been thinking just what to do with it.

 I removed the clutch cover to weld the hole and discovered bits of the primary chain tensioner lying inside. It had broken up and a piece of it had got trapped against the clutch and punched out through the cover from the inside. A friend in work done the welding for me so that was the first bit sorted, but how was I going to straighten this bent frame rail ?

 Some scans of old photos of the bike as she was after the first restoration.

Saturday, 22 March 2014

1 - Welcome

Well you join me part way through the restoration of a 1971 Bultaco Sherpa 250cc. I hope you enjoy following along for the next few months.