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| Measuring Ports http://www.kawi2strokes.com/forum/viewtopic.php?f=14&t=14476 |
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| Author: | Never2Old [ Tue May 25, 2021 9:35 pm ] |
| Post subject: | Measuring Ports |
I'm building what will be my second H2. I never had to do any engine work on the first one so some of this is new to me. I bought a motor that I was told had been ported, to some degree. I wanted to compare the dimensions against the Kawasaki Maintenance manual to see what might have been done. In trying to make some measurements I found that my caliper was too wide to fit in the bore making some ports hard to measure. I was able to use a mic and measure from the top of cylinder to the top of one port but this only works on some ports. I do have some t-bore gauges but I don't think these will help. So a couple of questions; 1, Are port edges supposed to have a sharp edge which would make it easy to measure or do they have a rounded edge so it's hard to determine the true dimension? This can change the measurement by a several thousandths, maybe tens of thousandths. 2, Do I need a narrower caliper to measure port dimensions, one that will fit in the bore, or is there a different method to measure ports? From the measurements I did make it does look like the ports have been enlarged, but I really need good measurements first. Also, I did a couple of quick measurements on the cylinder bores and they were coming out about 71.9mm, so it looks like this motor has had some work on it. Opinions and advice welcome, Dave |
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| Author: | Jim [ Tue May 25, 2021 10:05 pm ] |
| Post subject: | Re: Measuring Ports |
Never2Old wrote: 1, Are port edges supposed to have a sharp edge which would make it easy to measure or do they have a rounded edge so it's hard to determine the true dimension? This can change the measurement by a several thousandths, maybe tens of thousandths. They should have radiused edges, especially where the rings need to slip past them without snagging. The radii do increase the duration to some extent. Some judgement is needed. Quote: 2, Do I need a narrower caliper to measure port dimensions, one that will fit in the bore, or is there a different method to measure ports? A caliper that will fit would be nice. A machinist's scale and some good glasses and a bright light will get you pretty close. I don't lose sleep over getting the dimensions to the nearest thousandth of an inch. I've held a scale along the bore and stuck a straight edge through the port so it hits the scale and read the intersecting point. A little mismatching of the three cylinders just widens the powerband slightly. Unless you're drag racing and trying to shave off another couple hundreths of a second, a wider powerband isn't a bad thing. |
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