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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Valve Timing
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<blockquote data-quote="timetraveller" data-source="post: 118576" data-attributes="member: 456"><p>I am going to try to post a graph of MkII cam lifts so that you can compare them with your own. The maximum lifts on both your cams are not as high as MkIIs so you should not be running into clearance problems. If you only have, say, ten thou clearance then you do have a problem somewhere. The max lift on these MkII cams is .358 Ex and .368 In. Other cams might differ. On MkIIIs I have measured the equivalent figures are .35 Ex and .352 In so you can see that your values are not excessive. </p><p>If you copy and enlarge the graph then you can put your values for opening and closing times on there and then see what you think. 90 deg ATDC for the closing of the inlet does not look right and you might want to check your measurements.</p><p> For years I have tried to persuade people with unknown cams to produce lift curves like those here. It is tedious and time consuming. You only have to do it once but without this information you will struggle. If you look at this graph you will see that before the start of the inlet lift and after the end of the exhaust closing there was a fault. I have measured many cams with this sort of fault which is caused by the cam ramps not being correctly blended into the base circles. If you want to do this properly them please measure the lift every ten degrees of engine rotation and then plot an equivalent graph. Any spread sheet program will do. Once you have that detail then you might find, what I suspect, that there is a fault at the end of the lift on one, or both, of your cams and that is causing the strange values.</p><p></p><p>Incidentally you cannot just nitride any steel. It needs to be specified to be one which will respond correctly to nitriding e.g EN40b.</p><p>[ATTACH=full]33091[/ATTACH]</p></blockquote><p></p>
[QUOTE="timetraveller, post: 118576, member: 456"] I am going to try to post a graph of MkII cam lifts so that you can compare them with your own. The maximum lifts on both your cams are not as high as MkIIs so you should not be running into clearance problems. If you only have, say, ten thou clearance then you do have a problem somewhere. The max lift on these MkII cams is .358 Ex and .368 In. Other cams might differ. On MkIIIs I have measured the equivalent figures are .35 Ex and .352 In so you can see that your values are not excessive. If you copy and enlarge the graph then you can put your values for opening and closing times on there and then see what you think. 90 deg ATDC for the closing of the inlet does not look right and you might want to check your measurements. For years I have tried to persuade people with unknown cams to produce lift curves like those here. It is tedious and time consuming. You only have to do it once but without this information you will struggle. If you look at this graph you will see that before the start of the inlet lift and after the end of the exhaust closing there was a fault. I have measured many cams with this sort of fault which is caused by the cam ramps not being correctly blended into the base circles. If you want to do this properly them please measure the lift every ten degrees of engine rotation and then plot an equivalent graph. Any spread sheet program will do. Once you have that detail then you might find, what I suspect, that there is a fault at the end of the lift on one, or both, of your cams and that is causing the strange values. Incidentally you cannot just nitride any steel. It needs to be specified to be one which will respond correctly to nitriding e.g EN40b. [ATTACH type="full"]33091[/ATTACH] [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Valve Timing
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