KAWASAKI Z1-R TC TURBO
Top resto man and journo Will Barber was asked to restore a super-rare Kawasaki. He shared part one of his story with us.
Will Barber does the business on this loveable rarity!
What we have here is Chris Kitchen’s 1979 Kawasaki Z1-R TC, imported into the UK from Australia in March 2017, and it was my job to get her sorted. So here we go!
First of all, what is the Z1-R TC? Well, she’s less well-known than the 1980s raft of turbo bikes. By 1977-78 the Z1-R was looking a little long in the tooth compared to the opposition and the reasoning (well, in Canada and the USA) was that to boost (ahem) the bike’s flagging sales they should add lots of extra power by slapping a turbo on it. Alan Masek was the man behind the plan. A former Kawasaki USA general manager, he’d formed the Turbo Cycle Corporation in California to offer bolt-on turbo kits to customers. He secured a number of Z1-RS from Kawasaki and did a deal where he’d bolt-on the kits and sell the bike without a warranty. So, it wasn’t strictly an official bike – more a dealer special – and the resultant machine was over-powered and under-engineered: no special suspension or internal mods were made. The turbo itself (a Rajay 370 F40 unit, normally seen on light aircraft) running at 10lb of boost would give the Z1-R an extra 40bhp to deal with – but all power claims vary as to what the TC was actually pumping out. Period road tests of the time reported that the bike would behave like a run-of-the-mill Z1-R until 4500-5000rpm before around 6-10lb of boost kicked in and the thing took off… The price was $5000 compared to the Z1-R at $3695. Changes in underwear also proved pricey. The result was a wayward beast that could melt pistons and tackle the quarter mile in the high 10 second bracket at over 120mph terminal velocity… Crazy bike, crazy times. The original bikes were sold in Stardust Silver and were a moderate sales success along with updated TC1 models. More was to come with the definitive TC2 – complete with black paint job and multicoloured ‘Molley Design’ neon stripes and some improvements. By 1980, laws had changed in California so no exhaust modifications could be made to production machines. It wasn’t until the early 1980s that official ‘Turbo’ bikes from the manufacturers, such as Honda’s CX500 Turbo would hit the market. It was a short, sweet and exhilarating ride. Christopher Kitchen bought this TCII and – via the splendid Kawasaki Z1 Owners Club (Z1OC) UK – got hold of me to help with the restoration. So what of me? Well, I am a fully qualified automotive engineer and work as senior technical author for Bentley Motors Limited at the main factory in Crewe, Cheshire. I have been working on classic bikes since starting out at the tender age of 14, learning a great deal from my late father who was also an engineer. I also specialise in inline four-cylinder models and forced induction is also where my heart lies, having recommissioned a number of TCS over the years and thanks to my own past bikes, including an S+S Performance Silver Saxon, which uses the same turbo system as the TC. Christopher’s bike (if standard, as suggested) should only be reliable to a maximum of 5psi state of boost, giving around 120bhp, and even then it should have a number of mods, including a 40lb
waste-gate conversion, an anti-surge gate in the standard sump and other changes. If he wanted more power, then you’d want bigger changes, including a welded crank, forged pistons, a deeper sump, etc. On inspection the crank was standard but with forged pistons (displacement unknown) with standard studs, head nuts etc. It also had a build-up of sludge in the sump and some damage to the cylinder fins. With the turbo there was some play in the rotor, the ‘Spyder’ exhaust was corroded and had a dent in it and the boost gauge was broken and loose in its bracket. The Mikuni HSR42 carbs needed a good clean and sorting too. Under the skin many of the electrical connections were corroded, an indicator lens was damaged, the front brakes needed an overhaul, bodywork was tired and bar grips needed changing to standard again. Setting to work, I did a ‘cold’ compression test and number three cylinder seemed a bit low, at just 75psi, but later found that the valve clearances on that pot were out. I also knew that I would be shimming the valves to factory spec and doing a ‘hot’ compression test later. The camshafts themselves were standard (as was the cam-chain tensioner) and the camshaft cap restraining screws weren’t over-tightened! During strip-down I could see an area of repair I’d need to look at on the cam-cover, but once sorted I knew a fresh coat of tough satin black paint would get it looking like new. At the bottom end of the engine the oil filter was binned and – despite being told the motor had been drained before shipping – three litres of oil was dumped on my clean bike lift! The sludge and carbon deposits in the sump looked awful. After a thorough clean and removal of all the old paint, work could begin on the anti-surge flap for improved oil control. Basically this involves drilling the sump in a predetermined position, tapping it to 4mm then inserting a screw from beneath and sealing with industrial strength two-pack epoxy adhesive to ensure there’ll be no leaks! From the inside of the sump, a thin 4mm shim is then adhered in place over the screw followed by a hand-formed aluminium flap that swivels to determine the flow of oil. This is then held in position with a 4mm locknut. With the anti-surge oil flap fitted and in the open position, under braking and normal riding conditions, this will allow the oil to flow freely towards the oil pump pick-up. Under boosted acceleration however, the weight of the oil forces the flap shut, ensuring that the oil pump pick-up has a constant supply of oil by not allowing the oil to slosh towards the back of the sump. If this modification isn’t done then chances are the oil pressure light will come on as the oil pump sucks air instead of oil! The oil pump is also removed at this point and checked to ensure it is within the service limit and as a precaution the seals are also replaced with new genuine Kawasaki items. I also checked the oil pump, which felt fine with no nasty bits in
the strainer. New O-rings were fitted and it was then reattached. The crankcase breather on the TC also isn’t up to the job, so I wanted to do what I’ve done before, which is to remove the original breather pipe stub in the centre, and then fitting two new outlet stubs either side of the original. One of the new larger bore breather hoses will go to atmosphere, and the other hose will go through a V8 Range Rover flame trap and then to atmosphere. The crankcase breather will then be secured to the top crankcase via a long sealed bolt complete with O-ring. When it came to the turbo, having had experience of these bikes I knew what could go wrong. After some issues the turbo came apart and the sealing between carb and turbo was a mess. Then I found someone had made an adaptor plate (with hacked manifold rubber) which was well-made but then badly fitted to the turbo. The holes (bar two) would be sealed with industrial strength epoxy. With all this sorted, I fitted a nice new inlet manifold rubber from Allens Performance. I also decided to rewire the right-hand switchgear to give the turbo bearing an easier time on initial fire-up. So, with the kill-switch in the OFF position, the engine can now be cranked until the oil pressure light goes out before flicking over into the RUN position. This ensures that the oil reaches the turbo bearing as fast as possible. Fingers crossed the ceramic seal is okay, as they are not available at all. With the waste-gate, I was worried that the screw was wound in a fair way, giving a lot of boost. On stripping it, all looked well so they were cleaned and painted once more in Simoniz Tough Black satin paint. A 40lb spring was fitted instead of the standard 80lb spring. With polished parts and the screw now set to a blow-off of 8psi, it was sorted. The exhaust headers were (on my suggestion) nickel, not chrome plated, meaning Solvol will be able to attack any ‘blueing’ of the exhausts. A copy of the original boost gauge was sourced to replace the damaged original along with replacement hoses. The fuel system is sorted by fitting a larger-bore fuel valve (4.8mm up from 2.3mm) and ultrasonically cleaning the Mikuni carb. Handy this is fitted as it costs around £300 and is better than the Bendix original. The following components have now been changed: main jet – from 220 to 240. Jet needle – from 85 to 97. Primary jet – from 30 to 25. The float height has also been set at 19mm and the carburettor now rebuilt ready for fitment. I also fitted a new choke cable. I use one from a Honda NSR125R – like the one I fitted to my Silver Saxon and mounted on the left-hand side of the engine. I also used my Venhill cable kit to add a pull cable to the throttle set-up. The control of opening and closing the slide MUST include a pull cable. If this is not adhered to, there is a chance that under boost conditions the slide will stay open, causing full throttle operation even when the throttle is closed! I now turned my attention to the air-filter set-up. The original and extremely rare triangulated air filter was only ever fitted to the TCII (Molley) model. Unfortunately, this had been replaced with a K&N air filter from a car! The air filter fitted to the TC1 (Stardust Silver) model was of the conventional round type and only the TCII had this gorgeously shaped filter fitted. I was not going to be able to replicate the triangulated version due to the complex curves so I suggested making an exact replica of the round TC1 air filter like I did for the S+S Silver Saxon. While not only replicating the looks of the round TC1 filter assembly, by using two Triumph Spitfire 1500 chrome air filters I was able to increase the depth over a standard TC filter by 20mm giving a good 40% increase in breathability: another thing that the original TC suffered from! I started by disassembling both Triumph air filter assemblies and discarding the rear covers. One of the front covers would be utilised to make a new rear cover. The new rear cover was firstly and securely
screwed to a block of wood to make a more secure hold while I was working on it. After drawing a circle (slightly off centre) I then chain drilled along the line and cut the piece out with tin snips. After that I used a burr in my drill stand and finished the 65mm hole nice and smooth until the section of 65mm plastic drain spout would just slide in nicely. The inner diameter of the 65mm drain spouting slides perfectly over the inlet throat of the Mikuni HSR carburettor and was ideal for the job. Next I cut the drain spouting to give a total length of 30mm, then slid it in the 75mm hole until it butted up on the inside face of the cover. I then fixed the drain spouting in position with industrial strength two-pack epoxy adhesive. That concluded the work on the covers. After that, I cut two lengths of stainless steel matrix mesh 50mm wide. One length was to suit the outer circumference of the cover, and the other to suit the smaller circumference slightly bigger than the inlet throat of the Mikuni HSR carburettor. I also spun up two 50mm aluminium spacers (with 6mm ID holes) and these would sit between the inner faces of the two covers to stop them compressing together. The filter foam from the Triumph filters also then got installed and then all got bolted together. Then it got fixed to the Mikuni HSR carburettor. Eight small cuts were then made to the drain spouting where it goes over the throat of the carburettor (to allow some flexibility) and finally a Jubilee clip clamped the spouting on the carburettor. Job done and a vast improvement over the original TC1 air filter! Now it was on with the fuel tap. The original fuel tap was way past its serviceable limitations, seizing no matter how much stripping and lubricating was carried out. A ‘high flow’ Pingel tap from the USA is a minimum of £150 + shipping, and I simply can’t justify that kind of money: Zed Power here in the UK does a great replica Z1R fuel tap for the paltry cost of just £42. Sorted! Join me next month!