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Bridgestone Racer

2396 Views 6 Replies 6 Participants Last post by  jalsteve
Does anyone know what we're looking at here? A friend picked it up.

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Does anyone know what we're looking at here? A friend picked it up.

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I really don't know much about them. It's pretty cool. It has aftermarket heads and what looks like Amal GP's (feeding the rotary valves) with the remote floats hanging off that god awful bracket on the heads. Hard to tell, but it looks like a lump of lead or something on the bracket to dampen out the vibration so the the fuel doesn't foam/aerate and make the pistons squeak. Someone put some time and money into it back in the day.

I'll take the carbs if he wants to simplify his life.
going off the tank alone I'd say it is a Bridgestone Mach II 200RS chassis. I can't remember the years they made them but it was somewhere in the middle 1960's up until the early 70's. Since it doesn't have the chrome tank I am going to say it's probably a 70's model. AD used to have one when I worked at Vespa. The Amal GP carbs are a big deal - those things are expensive.

The heads are Tabloc and if they are unmodified they have the same compression as stock but have a different squish chamber that gives a little more power. Chances are they are modified. Tabloc was eventually bought out by DG and the radial head design is what you see on radial head RD's from them. As Cyorg mentioned someone poured buckets of cash into this engine.

here is a good site with some specs:
Bridgestone RS200 Roadracer

There have been quite a few 175-200cc b-stone racers throughout the years, they are solid bikes and pretty quick for what they are. Certainly would shame a cb175 just about everywhere. I am a little surprised at the rest of the stock chassis considering the amount of work in that engine. It's too bad he doesn't have the custom chambers that would have been made to support that race engine, I have to imagine they were specific to this engine's output and would be hard to duplicate without trial and error through racing.

The long bracket from the headstock is for a full or 3/4 fairing that the bike must have run at some point. It has rearsets so that's good. The absence of safety wire on the front end and the different tread pattern tire leads me to believe that it wasn't the racing setup - it probably ran something period like 32mm ceriani forks. rear shocks look aftermarket too...if they are as period as the rest of it they could be girlings, konis, SWs, or mulhollands. My guess is koni based on the gold decal on the shock base.
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looks like it needs a proper front end. Those carbs need a fairing to keep everything tidy and free of grit.
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Not sure if the carbs are TT or GP but those are "Matchbox" float chambers and probably means the carbs are GP which were smooth bore before they invented the term and had the needle outside the main bore IIRC. Had one on a 350 Goldie years ago.

I don't think it's a production racer but a modified street bike Dual Twin 175 or maybe a 200. Looks like a Dual Twin frame and tank but I am no expert on them. An A1R fairing would probably fit or maybe a TD2 which was wide over the engine side cases and narrow above. What engine size is cast into the barrels?
I had just assumed they were GP, but now that you mention TT...

Have a look on the base of carb body next to the air valve and see if it is stamped 10TT9 or something similar.

Either way, if it were mine, although it's got the cool factor I'd use Mikuni round slides with UFO's and put the Amal's on something more deserving... and have them tucked in out of harms way.
Given that dampening weight (assuming that's what it is) it looks like they had some fun getting it to run right if they ever did.
A trip into the rhubarb would be expensive. If he doesn't have a good home for them, he could sell them to finance the proper front end etc.
Does anyone know what we're looking at here? A friend picked it up.

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The frame I think is definitely Bridgestone, the tank too. The engine looks like Bridgestone bottom end, that big alloy lump behind the cylinder for the generator gives it away. BUT the heads are not the Bridgestone 175 or 200. Front hub looks too big for 175 or 200 Bridgestone but might be just the angle of the photo, the front end looks like 350 GTR and not 175/200. Interestingly there's a proper modern Dunlop race tyre on the rear and a lousy TT100 up front.

Currently building a 1968 Bridgestone 175cc for a client to original spec, they are pretty little bikes and can be very quick.

I had a 175 sleeved down to 125 with Mahle race pistons, race prepped crank in a Lyster frame, alloy tank, Ceriani forks and Suzuki Titan front brake with race linings and much lightened everywhere. It was a nice thing. Final version of the bike was 207cc using Suzuki pistons and X7 rods and chucked out 33HP at the rear wheel all thanks to disc valves and delorto carbs, tight squish and proper pipes but always thought the was another 4 or 5 HP in there somewhere. It weighed nothing. Interestingly we created air boxes on the inside of the fairing on each side. I found long bell mouths were a waist of time and so used very short stacks - disc valve engines have a longer intake cycle than piston ported engines.

The main thing to remember with these bikes is keep them light, putting big forks and brakes on will just add weight and if hustle them you'll wrap yourself around a tree. Its all about corner and exit speed; a bit like driving an old diesel van. And if sorted there's very little out there from the late 60's with similar CC that will stay with one of these little gems.

Photos below of 175cc engine c1968, note standard head photo'd to those in the feature photo, cases with the big casting behind the cylinders and another of correct cylinder.

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