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750 or 850? Dave Rayner gives his views
Dear Sir,
I believe you mentioned to Terry that there are a number of people in the
UK that wish to increase the performance of their 650s, but are reluctant
to use one of Halco's 840cc kits because it involves a complete stripdown.
I assume you know the difference between the 256, 447, and 533 motors. The UK and Europe got the 533s and we got the 256s up to 1973, then the 447s from 1974 onwards. A few years ago, I heard about Halco's 840 kits and called to find out about them. They use the piston from a Suzuki SP-370, because it has the same gudgeon-pin and same pin-height as the 533 version of the 650, which is most common in the UK. But of course, you'd know that. I also found that the cases must be bored right out to the studs and the cylinder-block almost out to the fins. I'm not keen on doing that.
However, people here are just as power-hungry as they are anywhere else and some would love an 840cc XS, regardless of what's required. A friend of mine bought an 840 kit from Halco, and a set of 533 flywheels. He then had to buy a set of 533 rods and bearings when his own 447s were quite OK. The 840 kit's cost is a given, but the cost of the flywheels, then sending four lumps of heavy metal from England to Australia, then paying tax on that, then rods and bearings, amounted to a small fortune. His bike is running now and would be just like any 840 you've seen.
Because the whole exercise was so expensive for him (our dollar equates to only 35p), I wondered if there could be another way. I explored having custom rods made with the big-end of a 447 and the length of a 533. It was entirely possible so I ordered 12, and let it be known that these would enable one to install a Halco 840 kit into a 447 or 256 motor. I sold ten rods to five people who then bought 840 kits from Halco. The cost of the rods was much less than buying a set of flywheels and having them sent over here, and a set of 533 rods and bearings as my friend did. Everyone was happy.
I kept two rods for myself but had no intention of installing an 840 kit as I have to question the reliability and longevity of it. Tony Hall tells me that there are hundreds of 840s running around the UK and Europe without a problem, and that may well be. However, I have reservations about a motor that's had so much metal removed from a critical area. Of course, Tony intended them for racing where that's not so much of a concern, but on the street.........................
In Australia, 750cc is the common thing to do and kits that accomplish that are readily available. However, they are made for the 256 and 447 motors only, as that's all we have here. Because the bore is only increased to 80mm instead of the 85mm of an 840, installing a 750 kit involves only the boring of the cylinder-block for larger sleeves. The cases are not modified in any way and need not come apart. You don't need to go beyond the base-gasket. The pistons are drop-forged, not cast like the Suzuki piston, and are designed for this application, not adapted from some other bike. The compression ratio is 10:1. Because there are a number of 650s being imported into the UK from the USA, these kits may be of interest to owners of those bikes which would have 256 or 447 motors.
But what if you have a 533, want to increase the capacity, but don't wish to bore or even split the cases? Either because you don't want to remove metal from that area or just because the bottom-end is in good shape and need not come apart. Why did I keep two of those rods for myself when I wasn't going to use an 840 kit? Because longer rods are better than shorter ones. For a road-bike, a good length is twice the stroke - 148mm for an XS. The 533s (and my rods) are 140mm and that is the longest that will fit into a 650. Not quite 148, but as close as we can get. The longer the rod, the more piston-dwell and the less angularity there'll be.
Of course I'd like all the cubes I could get and, in that regard, 840 is better than 750. But 750 is the limit without modifying (weakening) the cases. However, no 80mm pistons were available to suit a 533-type rod so I had six pistons specially made. These pistons would suit anyone who wants to increase the capacity of a 533 without boring the cases. I can easily have more made although the company that makes them has a minimum order of four. To look at, they are an absolute work of art - nothing like a cast Suzuki piston with half it's crown machined away. As for their quality, they'd be quite at home in a nitromethane engine. I'm serious. Terry's seen one, ask him for his opinion if you like.
I've supplied 750 kits which include forged pistons (with rings, pins and clips), sleeves, and a head-gasket for 447 engines to many, many people in Australia for A$890. By my reckoning, that's about £311. Then, there'd be postage from here to there. I've no idea what that would cost but these items are not that heavy.
For a 533 engine, the sleeves and gasket are the same, but a different company makes the pistons. This kit would cost A$1,020 - around £356. The latest Halco catalogue I have is 1997, and it lists an 840 kit at £425. I suppose they'd be more than that now.
What if someone has a 447 import but wants 840cc. They can fit a 533 crank like my friend did (much easier and cheaper if they live in the UK) but if they can't find one, I can have pistons for a 447 made with an 85mm dia. They can get the rest from Halco. These pistons cost the same as the 533, 750cc items - A$600 pr (approx. £210 + postage).
To sum up;
· 447 or 256 engine to 750cc - approx. £311 + postage. Available
at any time and in any quantity. Requires resleeving of cylinders only.
· 533 engine to 750cc - approx £356 + postage. Pistons must be
specially
made in quantity of four or more. Allow a few weeks. Requires resleeving of
cylinders only.
· 447 or 256 engine to 840cc - pistons only cost approx. £210
+postage + 840 kit minus pistons from Halco. Requires resleeving of cylinders,
cases must be split and bored.
When choosing between 750 and 840, you need to consider; Do you want to split
the cases? Does it need to be done anyway, for other reasons? If so, do you
mind boring the cases? If so, go for 750cc. If not, it becomes a matter of
cost - £ spent for horsepower gained. You'll have to weigh it up. Do
you prefer cast or forged
pistons? The 840s are cast, the 750s are forged.
Be advised that 256 rods are no longer available. I only mention the 256 because I can have pistons made for it. If someone has one that's crank is in very good shape, then OK. If it needs a rebuild, they'd be wise to buy pistons for a 447 because those are the rods they'll get.
As for VAT (called GST here, and it's 10%), Australian customs does not bother with amounts under $50. Therefore, one can import up to A$499 of goods and not pay any tax. Does the UK government have a threshold like that? In any case, I'd put whatever value you like on the customs declaration sticker, as long as it's half-way believable, to reduce or even avoid VAT.
To place an order,
or just to find out more, write to;
David Rayner
19 Thornbill Cr
Glenmore Park
NSW 2745
AUSTRALIA
