Nice Martin,

I agree with your thoughts, I was at a trial a few years ago and an Ariel rider said "those 1980s Bultacos are the best bikes in the trial". I thought it slightly ironic and considered pointing out the they were older than most of the pre65 bikes. Anyway, it's just a bit of fun.

Can I ask about your yolks? Are the fork legs not parallel to the steering stem?

Cheers

Hi

The yokes are parrallel to the stem.

I made a jig, located the two yokes on 35mm pins one above the other split the difference on the front to back original bores and bored out to 34mm.

Whilst on the jig skimmed the faces to 90 deg to the bores, then mounted them on an expanding mandrel and turned a recess 3mm deep to stop the new stepped bushes/inserts from moving.

Then just reassemble.

In my opinion it works fine and turns tight without washing out. Counter to this it can be lively over rocks but note unduley so, just like a modern bike.

The mudguard does not hit the frame or exhaust due to the Magical spring never bottoming out. Even if they did there is still clearance.

Hope this helps.

Martin

Edited April 20, 201412 yr by triple_x

Hi, man am I glad I found this thread. I have a 73 ish Model 92 parts bike fitted with a Model 49 250 motor, about mid way in the serial number range. Its got Sammie Miller rear shocks, some front springs we found laying around in the shop that work great, OKO 26 mm carb and electronic ign. I've got it geared 11/52 as we have alot of technical rock sections here. I alternate a 11/48. It also has a late model Alpina front hub which greatly improved front braking. 

I am keen to implement some of these mods. My initial interest was to move to a ported 280 but as I see the Motak 280 I spy what looks like swingarm mods. Can anyone point me to information about how I might go about this? I'd prefer to use local talent but buy the parts as much as possible. Is the gas gas 74 mm piston easily obtainable and is that all you need (piston kit)? What does that swingarm mod do?

I think the swing arm is from a 199b model Bultaco not modified in any way.

2 hours ago, rootsman2 said:

Hi, man am I glad I found this thread. I have a 73 ish Model 92 parts bike fitted with a Model 49 250 motor, about mid way in the serial number range. Its got Sammie Miller rear shocks, some front springs we found laying around in the shop that work great, OKO 26 mm carb and electronic ign. I've got it geared 11/52 as we have alot of technical rock sections here. I alternate a 11/48. It also has a late model Alpina front hub which greatly improved front braking. 

I am keen to implement some of these mods. My initial interest was to move to a ported 280 but as I see the Motak 280 I spy what looks like swingarm mods. Can anyone point me to information about how I might go about this? I'd prefer to use local talent but buy the parts as much as possible. Is the gas gas 74 mm piston easily obtainable and is that all you need (piston kit)? What does that swingarm mod do?

The frame and swingarm are standard 198b, there is no swingarm mod so not sure what you've seen

No idea on availability of GasGas 280 pistons but I believe the 270 is easier to find. I have an M49 with 26mm OKO and electronic ignition (set on full advance to overcome the curve that isn't really needed and makes them too lazy on advised setting) and to be honest I don't see that it needs anything else. These had the Matador barrel/porting, they aren't lacking in power and rev like hell. They're just a bit woolly at the bottom due to the porting but going bigger on the piston won't change that - my 49 is on 73.50 using a Wossner TSS piston -  they go to 74mm so you don't need the GasGas piston. The inlet skirt just needs trimming to match the trials piston. If you use the GasGas piston you may also have to cut the inlet skirt to match the Bultaco piston

Hi, I realize I am several  years late to the party, but is  Motak Racing Sherpa 280  still in existence? I can't find them! Thanks

1 hour ago, rootsman2 said:

Hi, I realize I am several  years late to the party, but is  Motak Racing Sherpa 280  still in existence? I can't find them! Thanks

It is a nicely built one off from a 198a in need of renovation.