Author Topic: Changing cylinders - anyone done it?  (Read 697 times)

Thoppa

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SYM, my Speedy Young Motor
« Reply #15 on: May 05, 2021, 10:34:14 PM »
How fast does she go mister? was a question I sometimes got asked on my Yamaha YZF many years ago, but it is not a question I expect to get asked on the SYM. But, just in case someone does ask, I need to be prepared right? :-)

So, I took out for a spin, got her warned up and then gave her WOT from a standing start onto {edited} for 2 miles, with no wind. So, I can say 130kmh on the GPS, that's 140kmh indicated, with maybe a little more with a new belt etc. She still has the K&N air filter but is running the standard exhaust - when she was fully tuned with a straight through exhaust she did 148kmh indicated, 135 on GPS. The calculation anomaly for the maths is likely tire diameter.

I also noticed that the "knock" noise the engine used to make when cold has gone, and the engine feels smooth or at least smoother, at all engine speeds too. I can't tell if the 250 camshaft has made any difference.

The next stage is to run her for month and see if she has stopped using oil, measure the compression pressure, and calculate fuel economy. 
« Last Edit: May 05, 2021, 10:50:40 PM by Thoppa »
Ninja 650R
Citycom 300

Thoppa

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Re: Changing cylinders - anyone done it?
« Reply #16 on: June 04, 2021, 08:12:10 PM »
One month later... and still no leaks or problems of any kind. :-)

The ring replacement has restored engine power so the top speed is very similar to what it used to be as a low mileage machine. The engine is noticeably smoother and quieter. So far, she is not using much, if any, oil so I guess no top up will be needed between changes. The fuel economy is almost back to normal too - she was as low as 28km/l before the new rings, and now is a little over 30km/l so far, instead of the long-term average of 32km/l. I've been giving her more WOT than I used to - perhaps the camshaft has affected the bottom end power so I'm more inclined to give her lots of gas. Not sure.

Anyway, the ring replacement is a success - it's done a good job of renovating the worn engine. I wonder for how long...
Ninja 650R
Citycom 300

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