gaz73 Posted October 28, 2015 Share Posted October 28, 2015 I need new piston rings as I damaged one after removing it (no other damage to engine) and wanted to ask if I can just use a feeler gauge to measure the gap in the ring or if I need more measurements to make, when I look at the bikes manufacturer website they show rings that are 41mm/0.50mm and 42mm/0.75mm etc and im guessing the 41mm is the diameter of the cylinder and the 0.50mm is the gap you measure with a feeler gauge and thats all I need to know? Thanks guys. Quote Link to comment Share on other sites More sharing options...
oldie59 Posted October 29, 2015 Share Posted October 29, 2015 Take a look at this websitehttp://www.dansmc.com/pistons.htmI think the 41/0.50mm, 42/0.75mm etc sizes are for oversize pistons and rings that you use after a rebore. I take it your bike is still using the standard piston and ring sizes? In which case you need to determine the size of these before ordering any Quote Link to comment Share on other sites More sharing options...
gaz73 Posted October 29, 2015 Author Share Posted October 29, 2015 Take a look at this websitehttp://www.dansmc.com/pistons.htmI think the 41/0.50mm, 42/0.75mm etc sizes are for oversize pistons and rings that you use after a rebore. I take it your bike is still using the standard piston and ring sizes? In which case you need to determine the size of these before ordering any Thanks for that man, no the bike had a rebore 2 years ago and new piston and rings, I believe its still a 50cc not a 70cc because the piston has "50" on the top. I guess im knackered without the manual but there isnt one for this bike.BTW would you know what those numbers mean, is the 41mm the bore diameter and 0.50mm the ring gap? because i got some feeler gauges today and the ring gap I get is 0.05mm.I measured the bore diameter and its 41.44mm so I guess that means I need a 41mm ring? Quote Link to comment Share on other sites More sharing options...
gaz73 Posted October 30, 2015 Author Share Posted October 30, 2015 Ive took a risk and gone for the 41.5mm rings because my bore measures 41.50mm at its maximum or 41.44mm at its lowest. I hope thats right lol so I guess ive got to hope the ring end gap is around 0.03mm then and im ok, or hope that it needs filing. Quote Link to comment Share on other sites More sharing options...
Grumpy Old Git Posted October 30, 2015 Share Posted October 30, 2015 The second figure is the width (thickness) of the ring - If you have the correct diameter, then the gap will be correct.When fitting the rings, they should need to be expanded slightly to fit over the piston - be careful not to twist or over extend them - they are quite brittle.To fit the barrel back over the piston (and rings) you will need to compress the rings - This ally (such as a split open and cut coke can) can be very helpful at this stage. Smear some oil on the inside of the barrel and around the rings before assembly. Quote Link to comment Share on other sites More sharing options...
gaz73 Posted October 30, 2015 Author Share Posted October 30, 2015 The second figure is the width (thickness) of the ring - If you have the correct diameter, then the gap will be correct.When fitting the rings, they should need to be expanded slightly to fit over the piston - be careful not to twist or over extend them - they are quite brittle.To fit the barrel back over the piston (and rings) you will need to compress the rings - This ally (such as a split open and cut coke can) can be very helpful at this stage. Smear some oil on the inside of the barrel and around the rings before assembly. Thanks i was gonna make a compressor out of a can and some cable ties, ive heard some use a plastic bottle to prevent scratches. Quote Link to comment Share on other sites More sharing options...
gaz73 Posted November 1, 2015 Author Share Posted November 1, 2015 Just wanted to say a very big thanks to all that helped me here, bike is now running, its noisy compared to before and it doesnt stay at idle it stalls but I guess thats normal until run in.Cheers all Quote Link to comment Share on other sites More sharing options...
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