Two-stroke timing gauge toolVenhill Engineering | Two stroke motorcycles | VT22 | Product review
You can use a drinking straw if you prefer. Or, if you've got the equipment, you can machine an old spark plug and replace the central electrode with a sliding bolt or similar. Or you can muck around with a degree disc. Or you can buy a dial test indicator. Or use some kind of depth gauge. Or you can simply guess. But if you're riding a classic (or, for that matter, a modern) two-stroke motorcycle, you might be interested in this handy gadget.
Venhill Enginerring Ltd, noted leaders in motorcycle hydraulic hoses and control cables, is currently marketing this tool. It's aimed at "men of straw" (to misappropriate a legal term) who, like us, have long been doing things the sloppy way and need to sharpen their pencils.
How it works is perfectly simple. Find a two-stroke motorcycle with one or more 14mm spark plugs. Remove the plug/s. Screw this gauge into the appropriate plug hole (check your manual for details). Loosen the knurled screw on the side of the gauge to free-up the central pin/probe/whatever. Gently raise the motorcycle piston via the kickstarter or by turning the back wheel with the engine in top gear (taking care to monitor and exclude backlash where possible, etc).
Tip: don't use the electric starter.
When you've raised the piston as high as it will go, tighten the screw on the side of this gauge. That locks the central sliding pin/probe/pointer/whatever. Then you can (gently) move the piston clear (probably by rewinding the rear wheel). And then you can turn the large knurled adjuster on the gauge. One full revolution will raise or lower the pin/probe/pointer by 1mm. When you've wound it down 2mm, 3mm, 4mm, 5mm (according to your timing specifications), you can gently bring the piston back up to the central pointer/probe/thingy.
Now you've established the correct amount of advance, and you can set the points or adjust whatever electronic ignition system your bike is fitted with. Sounds simple enough, but note that our account of how it all hangs together and works might not be entirely correct for your particular motorcycle. We're painting this thing with a very broad brush.
When we agreed to a review of this gauge, we were hoping that it would also serve as a useful tool for one or more of our current stable of four-strokes and sidevalves. But alas, it won't work.
Our sidevalves are both BSAs, and as such the spark plug holes in each instance are over the inlet valve rather than over the piston. Therefore, this gauge can't reach the piston let alone measure the travel.
As for our four strokes (currently a handful of 750cc Triumphs, a 250cc Triumph, a BSA A10 and a recently acquired Royal Enfield Bullet), this device won't work obliquely. In other words, it needs a plug hole directly above the piston, two-stroke style. A plug hole angled to one side is a non-starter, measurement-wise.
Moreover, the central pointer/probe/thingy has a travel of around 8mm, max. Our T140 demands around 10.5mm, our BSA sidevalves demand 11.5mm, our BSA A10 needs around 9.5mm, and we didn't get around to the Bullet (currently in a friend's garage about 20 miles away). But we're pretty sure we'll have the same problem.
But if you're working on certain Villiers-engined bikes, maybe one or two Greeves-engined, and any number of European or Jap two-strokes, 2mm to 4mm of adjustment is all you need to dial in the correct piston position BTDC.
As for the gauge itself, it's a nice little device that does exactly what it claims to do. The gauge didn't arrive in a case or a box, and that's a pity because it's a precision tool that warrants looking after. And there were no instructions with it which, unlike a hammer or a screwdriver, would benefit from a little basic guidance if only to make buyers feel more confident about the correct procedure. But Venhill has at least produced a small video which you can watch via YouTube (you can access that video via the Venhill website).
And here's a thought, if you remove the central pointer/probe/whatever, you could replace it with a length of stainless steel rod marked appropriately and capped with a nut or something to stop it falling into the cylinder. That would double-up as a crude gauge for your four-strokes, if only to carefully measure the highest point of piston travel. But once again, unless the piston is directly beneath the spark plug, it won't work in the way the manufacturer intended, if at all.
Venhill is asking £27.54 for this gauge, and that's a fair price. Shipping is by Royal Mail, first class service. Allow 3 -5 days for delivery. Ask for the VT22.
Conclusion?
It's a decent little tool that will well serve the needs of many owners of two-stroke machines, be they motorcycles, go-karts, or what have you. Buy it once and use it for a lifetime. There's really nothing to go wrong here, and setting accurate ignition timing is one of those basic things that's fudged at your peril.
Telephone: 01306 885111
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