KAWASAKI HYBRID
Or is it hybrid hell? Our own Scoop returns with tales of this 500/400/250 mish-mash! Will he survive such mental anguish?
Steve Cooper gets the motor in the frame.
Thankfully, we now have the engine in the frame! If you recall the previous instalment, Ian Bird (only vaguely assisted by muggings here) had found there was a fitment issue. And on the assumption that engine cases rarely, if ever, expand, the only logical conclusion was that the frame must have shrunk.
The truth was not quite as literal as that, but hopefully you get my drift here. With the rebuilt motor heaved out of the chassis (they really aren’t lightweight, trust me on this one), a set OF bare and empty H1 cases were offered up by way of a sanity check. As expected there was a slight discrepancy of just under a single millimetre between the gap available between the rear mounts and alloy castings. It’s amazing how much the steel brackets had contracted immediately after welding. The initial plan was to use a length of studding, some washers and nuts ,and then oh so gently wind the nuts out and spread the frame just a tad.
Unfortunately we only achieved two things…nothing and bugger all, so an alternative, yet practical solution was sought, which led to some judicious dressing of both rear mounts with a decent quality engineer’s file. As if pre-ordained the empty engine dropped into place and less than half a millimetre of the substantial mounts removed from each side. Satisfied all was well the rebuilt motor was once again carefully wiggled back into its home, bolts and nuts fitted, tightened and everything triple checked – sorted, finished, completed, done, etc.
Ian has been sorting carburettors for the project from his pile of triple parts. Some hadn’t seen the light of day for a long while and were coated in layers of old fuel, dust and heaven knows what else. Now, bearing in mind that a lot of Ian’s stock has come from wrecks, barn finds, abandoned projects, autojumbles, etc., it’s not too surprising it took a good old rummage to find a trio that were in reasonable condition. As the project’s ethos has always operated via utilising good used stuff and not squandering new old stock, we’ve picked the best on hand and then gone in deeper.
After ultrasonic cleaning and a second go over with some elbow grease and bike cleaner, three carbs scrubbed up well enough. However, one was found to have severely blocked internal passageways so that’s now sitting in the ‘naughty tank’ of cleaner while another, better, unit has been pressed into service.
As we’ve said before, this project is not about producing a show winner, it’s all about what can be achieved with as many used parts as possible.
In a similar vein a used, but perfectly viable inlet rubber has been unearthed, cleaned and installed. There’s a set of pattern hose clips to try out later and if they fit properly then they’re going on regardless of whether an H1 should run bright zinc or passivated black fittings! Even on a stock Kawasaki triple there’s not a lot of room between some of the steelwork and the inlet rubber, but here when you’ve massaged a 500 into a 250/400 frame, space is even tighter but, fortuitously, the inlet rubber fits… just!
If you look closely at the opening shot you can just see that we’ve managed to persuade a genuine H1 air-box to fit between the seat tubes and inside the rear frame rails that link the top tubes of the chassis to the swingarm pivot. Some might suggest that, by using a rare H1 air-box, we’ve committed some heinous and heretical act against the Gods of Restoration. Yes, we could have gone for the more obvious and faster route of using pod filters, but many a triple’s good(ish) manners have been ruined by such fitments. Ultimately it should be possible to get any engine to run acceptably well on pods, but it can be a tortuous process, fraught with angst and hassle, so why cause ourselves more trouble than we need? A laminar airflow is always kinder to engines so that’s why we’ve gone stock all the way through on the inlet system up to
the reed valves discussed in the previous instalment. And for those who reckoned they wouldn’t fit, can you see any evidence of them? No, because they fit perfectly into the 500’s inlet tracks!
The final task on the induction system has been the installation of a K&N air-filter. They’re not cheap, but they do a good job of keeping the crud out of the carburettors, which is precisely what we’re after. Crucially, the filter selected is the correct one. Ok, that’s sounds stupid I know, but there have been a number of incidences where H1s have suffered from woeful carburation, which has been traced back to a K&N filter that effectively fills the entire volume of the air-box and essentially seals itself off from anything but the tiniest gasp of air.
As originally planned, the bike now has the one-piece Higgspeed expansion chambers fitted and I have to say they look the business, especially on the right at the rear where the two pipes run parallel to each other. The front ends fit to tailormade stubs that are bolted to the exhaust ports complete with crushable gaskets. Sealing relies upon a precisely engineered annular fit between the outer surface of stub and the inner surface of the down pipe; a long spring is then attached to the exhaust flange and secured on the pipe. The fit between the two tubes has to be sorted before anything else so what might look initially like a gap or poor fit is swiftly rectified with careful and controlled taps to the front pipe with a hide headed mallet – job done!
There appears to be two routes to producing these 250/400 framed, 500 engined hybrids and it all centres around exactly where the engine is located in the frame. With our version the engine sits back a little in the chassis, giving clearance to the heads and cylinders. The other option brings everything forward and generally requires fins to be trimmed and chamfered. This was not something Ian Bird had done on own his hybrid and he wasn’t keen on doing to this build either. Therefore, we’ll need to re-engineer the rear exhaust mounts with extension pieces on both sides. Ultimately this won’t stick out too much like the proverbial sore thumb as we have some period, pattern, pillion pegs that will take the eye away from the subtle bracketry.
One small challenge that’s popped up on the radar is the need to revise the linkage system between the gear pedal on the frame and its operating lever on the shaft. With both in position (yes, we know the bolt’s not in place), the pair are out of correct alignment by some 2-3mm. Rather than machine existing parts to fit, we’ll be looking at installing a rose-jointed linkage to ensure glitch-free changes.
This and so much more are what you sign up to when you commit to building a special, special!