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Re: AAC 16 AAC250 Drag Bike

PostPosted:Sat Mar 30, 2019 8:52 pm
by shasta
The original bike first appeared with Amal carbs and as the bike was improved it finally ran with Hilbourn fuel injection running on Nitro. Experience and finances meant I would be using carburettors running on petrol ,but using Kawasaki carbs were out of the question due to their cost; anything related to Z1s or Z1000s commands high prices these days.
The obvious choice were the carbs fitted to the Suzuki GSF1200 Bandit model as these have been around for years so there is a good supply of them on the market. Having obtained two sets and offering them up to the Kawasaki cylinder head showed up a potential problem. The air inlet spacing of the Bandit cylinder head is different to that of the Kawasaki Z900 head and the Suzuki rubber inlet stubs have a different bolt spacing so can't be used either. Trying to fit the Suzuki carbs to the Kawasaki inlet rubbers didn't work either as the diameter of the Suzuki carbs is too big to fit.
The difference in spacing is about 5 mm and by luck it was found that the inlet rubbers used on the Kawasaki GPz600R have an offset of 5mm and are the same size as the Suzuki rubbers although are a push-on design and not bolted on, so all that was needed were some inlet stubs and I'd be in business.
The photos below show the stages in the production of the stubs ending with the carbs fitting the Kawasaki engines perfectly.

Re: AAC 16 AAC250 Drag Bike

PostPosted:Mon Apr 15, 2019 12:08 pm
by oily bike bloke
Interesting thread indeed, thanks for posting.

Re: AAC 16 AAC250 Drag Bike

PostPosted:Tue Apr 23, 2019 10:57 am
by shasta
The rear brake fitted to the bike was originally a cast iron dished car item which was really heavy, and used a Kawasaki rear twin piston opposed type caliper from a 1970s motorcycle. Due to the design of the car wheel used, a dished disc had to be used to avoid hitting the rim and if this was to be replaced by a modern flat, two piece floating type disc from a modern bike then it would have to be spaced out from the hub.
A disc from a Kawasaki ZR 1200 was chosen and a spacer made to move the disc out enough to provide clearance for a Honda VFR750 four opposed piston caliper to be used. The spacer was lightened and a new mounting bracket and lighter brake torque arm were also made, the total weight saving over all the old components was over 10 lbs!
There was no sign on the frame as to how the rear brake was operated, no mounting points or pivots, so a thumb operated lever has been fitted to the left-hand side of the handlebars using a BMW rear master cylinder.
The photos show 1.Finished brake assembly, 2. The old brake arrangement, 3. Aluminium bar before machining, 4. Finished spacer, 5. New disc fitted, mounting bracket for caliper under construction

Re: AAC 16 AAC250 Drag Bike

PostPosted:Mon Apr 29, 2019 9:22 pm
by shasta
One of the last tasks has been to work out how to start the bike! Using rollers turned out to be a non-starter as the gearbox has a one-way sprag clutch fitted so it does not allow the rear wheel to drive the engines. The obvious choice was to make a plug-in starter to pick-up on one of the engine drive pulleys. However there was always the thought that if the engines started, then the starter drive may become jammed into the pulley preventing the operator to pull it free. The design has made the drive 'fingers' to be angled on the reverse side, so that when (if!!) the engines start then the pulley will drive the starter fingers and force them out of the pulley. It should be tried out in the coming week or so once the few remaining tasks have been completed, including making up a battery carrier and wiring it in, it should be start time. I hope to video that moment, so that could be the next post.
The photos show the stages of making the drive to engage with the pulley.

Re: AAC 16 AAC250 Drag Bike

PostPosted:Thu May 02, 2019 8:49 pm
by shasta
After putting oil in the engines, plugs out, ignition off, it was time to spin the motors over to circulate the oil. All connected, push the starter button ....and the starter barely moved the engines. Doh! The scene in Jaws came to mind when Sgt. Brodie says 'We're going to need a bigger boat'. Off to the breakers to see what the largest 12 volt starter motor is available...

Re: AAC 16 AAC250 Drag Bike

PostPosted:Fri May 03, 2019 1:23 pm
by NitroWars
Some nice engineering going on there, good luck with the starter motor

Re: AAC 16 AAC250 Drag Bike

PostPosted:Thu Jun 27, 2019 11:24 pm
by shasta
This motorcycle will be on display at Santa Pod Dragstalgia meeting on the Saturday and Sunday along with former Competition Bike BC245 which held the ACU No.2 plate in 1990 and 1992, they will be in the Historic vehicle marquee. Do come along and say Hi, hope the weather holds out.