Hello Everyone, Ive read here several times that TDC when changing belts should be on the compression stroke. I cant fathom out why it would matter that the compression stroke is the TDC requirement, so for the sake of the simple things in life, can someone explain please as in my mind its simply belt off/belt on and as long as TDC is the reference, why does comp/exhaust stroke matter? and also referring to the excellent CA videos, TDC is shown with (horizontal) cams in alignment pre belt removal. Am i correct in thinking that by definition therefore the valves will all be closed and therefore that is compression stroke as shown in the vids? Thanks
The engine should be set to the timing position when changing the belts with all marks lined up. The horizontal cylinder is at TDC at the start of the firing stroke with all valves closed but the vertical cylinder is 90º after TDC, halfway down the inlet stroke. The belts should be tensioned with the respective cylinder at TDC with all valves closed.
As far as I know, the only reason why the timing marks have to be lined up is to make sure the timing doesn't go out by one or more teeth.........or in other words, so that the new belts go on to the pulley teeth in exactly the same relationship as the original...... ..........that's why I mark the old belts and the new belts in the same place by counting the teeth. But the distances / dimensions between the cam pulleys and the drive pulley doesn't change wherever the cam is rotated to............ .........if it does, then you have a rubber engine.........
cheers everyone, yeh I agree there is a 'factory way' to do these jobs but logically it seems that common sense and a methodical approach, ensuring for example TDC is correctly utilised on a belt change, will ensure the same end result.
Update on this for anyone who is considering changing belts but not sure... It really is a simple job if done in a methodical manner. As long as the pulleys are clearly marked and the belt rib that sits in each of the pulley indents is marked, the job takes less time than the removal of the tank/fairing etc. I didnt use a crank turning tool, just stick the bike in 6th before you start and rotate the rear wheel to line up TDC mark on the drive pulley. When the belts (CA exacts) have been put back on and the horizontal belt tightened to approx 99-101Hz, screw a 10mm bolt into the crank (remove cover) attach a spanner to the head and use to gauge a 90degree reverse rotation, again using the rear wheel. Tighten the Vertical as per Horizontal and you have just saved £££'s + the satisfaction of doing the job yourself. BTW I ordered a 16mm long reach socket for the plug removal, only to find a plug spanner in the supplied toolkit velcroed to the right side fairing... Also make sure you contact @Exige for belts..! Helpful links: CA Cycleworks 749 Belt change Microphone for Hz measurement 3.5mm Adjustable Free Standing Desktop Microphone PC Laptop SKYPE MSN Voip MIC | eBay Paint Pens - Much better than Tipex Hellfire Trading PERMANENT Car Tyre Tire Metal Outdoors Oil Based MARKER PEN | eBay
