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Anglia4's Bucket Bike


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I've been meaning to start a build thread for this for ages. 

When we were living in Nelson I decided to get into Bucket Bike Racing.

@Duke Blackwood was parting out a CBR250RR, and @Bellicose (I think) was selling a TF125, which seemed like it might be a good combination.

So some deals were struck, Blackwood picked up the TF and stripped it down and put the lot on a pallet destined for Nelson. According to the timestamp on my photos it arrived on the 14th of September 2017.

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It didn't take me long to start mocking things up and get the motor mounted, it was a very easy fit in place of the 4 cylinder donk!

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A bit more shed time had a racey light weight tail frame made and Ali-expresses finest pit bike tank mounted.

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I then started shaping some foam to make a tank cover as the Duke had other plans for the original CBR tank and it was on the northern island.

This bike has been treated to only the finest of chinese components. Fork seals, levers, brake pads etc. The brake pads are actually bloody brilliant!

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Next up was to get onto some fibreglassing.

As I had moved back to New Plymouth and was much closer to Blackwood manor and hence the original MC19 tank, I stuck the glued foam abomination on the top shelf in my workshop and took a mold off the original tank.

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Not having done any fibreglassing before, I massively over did it, its about 10mm thick in places where the sheets folded over themselves and weighs nearly as much as a steel one :doubt:

I scored a TZR250 race tail section off the buy and sell but it was massively wide, so I cut about 125mm strip out of the middle and glassed it back together. This left it with a cool pointy tail thing going on. 

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About this stage we got the racing off the ground. Our first real event we invited the bucket racing guys from wellington and had an awesome field of about 15 bikes, this was awesome as it really got some hype going for us and we built numbers very quickly. We have a solid 9 or so bikes turning up most club days now and only a year in.

We had a roll of red duct tape that was nearly a perfect match for the existing red paint on the tail and front mudguard, so for most of its racing so far the bike has been liveried with tape. Great from afar but far from great.

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Some bits of development have happened along the way.

Firstly the pegs were a little low, we have to have nylon under them so we don't damage the track when we bin it. My nylon was a little thick and the pegs a bit low and they would drag on the track through our sweeper... One race I cut a bit close to the inside of the corner and the peg dropped off the rumble strip and promptly vanished from existence.

So I hand made some new ones which are all nylon over an aluminium center. With skateboard grip tape on them they have better grip than any other pegs I've used and they're great for the track protection.

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Pipe wise, initially i made the most bastardized hack and weld job of the original TF125 pipe just to get it going.

I've read a bit on 2-stroke tuning in recent time and knowing what I know now, what I did to that pipe would genuinely have been quite an improvement over standard i think.

Unfortunately though the bike has always been horrendously down on power compared to all the other F4 bucket bikes so I started playing.

First up was a spare chamber that we had floating around in a box of parts. Completely unknown origin, looks home made. I made it fit, again using the bastardize technique.

Its got a massive mid section diameter and was horrendously long with a looooong header. So it had wicked pull off the corners to about 4000rpm and then wouldn't rev past about 6000rpm... not exactly race winning stuff going on here...

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So I took some length out of the header and shortened it up by quite some margin. This made the bike rev to around 7000rpm, with little to no improvement otherwise, and I couldn't for the life of me get the carburetion to work.

From the book I've read and some software that the internet gave me, I've applied some technology and started on building a pipe that is actually designed for this engine and application.

 

 

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The last piece of the puzzle to date has been the engine itself.

My search for that elusive horsepower led me down the rabbit hole of port timing.

I raised the barrel 1.5mm
Raised the exhaust port roof 6.6mm (+ the 1.5mm)
Lowered the floor of the inlet port 10mm
Cut the inlet side of the piston skirt 10mm

This theoretically results in port timings of 195°Ex/128°Tr/185°In, however I haven't checked it with a degree wheel yet.
Originals were 155.5°Ex/118°Tr (didn't bother to measure inlet because of the reeds).

As well as taking the 1.5mm back from the top of the barrel, I machined the head about 1.1mm and used a thinner gasket to get from 17.5cc to 13.7cc (8:1CR to 10:1CR - Uncorrected)
This gave me a squish band of about 1.8mm, which is about 0.8mm higher than I would like it to be.

These engines have a bizarre piston port/reed inlet system that suzuki trialled in the 70's. Basically it just ends up being shit at both. So I've blocked up the reed port and massively adjusted the piston port to make it a piston port engine only.

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Comparison of before and after inlet port sizing:

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Have you ever seen someone precision machining their piston with an angle grinder?

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You have now!

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  • 2 weeks later...
  • 4 months later...

Soooo... Something has happened that I really didn't want to happen... but now that it has, I'm quite happy about it...

I left the bike with Bucket Barry over the lockdown with some loose instructions on what I wanted. He had plenty of lock-down time and I had to work through.

When I picked it up after lockdown, it had some sweet new camshafts.

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Dad had a spare FXR150 in the shed that didn't owe him much money, so I brought the engine from it.

The further I got down the rabbit hole with the TF, the more I could see that it was going to take huge amounts of development time to get it remotely competitive. I was sick of getting my arse kicked / not finishing races / spending all my shed time on this thing when I've got other projects.

Theoretically now it should start every time I push it out of the shed, not rattle itself to pieces and be very competitive.

I've done a test day on it and am absolutely stoked. I also changed it to a race shift setup (1-up, 5-down) which will take a bit of getting used to.

First race is on Sunday, hopefully it goes well.

It might need a name change now, "The penetrator" doesn't seem appropriate given the extra strokes. Maybe it should be "The Wank".

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  • 4 weeks later...

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