We used to have data for piston skirt clearance which was then measured with feeler gauges. Many pistons where not produced round on purpose but somewhat oval. The design principal being to allow the skirt to expand with heat to accommodate the fore and aft forces that are produced on the piston via the connecting rod on the gudgeon pin. (aka piston slap in worn engines) . Not sure if this relates so much to these smaller motors though. If when you place the ring without piston in the cylinder perfectly square and the gap is very small (necessary as they will expand with heat) then the rings you can assume are the right size so you then check the piston for size if the exhibit the same gap when installed on it.
Looks like you’ve got two top rings as the diagram you showed definitely has the rings different sizes. Your vernier measuring them both as 1.9 + a few points of a millimetre different seems to confirm it, even a not too accurate vernier like that would’ve shown one as 1.94 and the other as 1.7 say if they were different.
There a two schools of thought re reed valves. Some thing that as they should be flat they MUST be fat to the block. Others seem to think that if the gap is relatively small the back pressure in the engine should push them closed. If there is an issue its likely to manifest itself in poor starting or “spiting” back through the carb.
I'd turn the reed petals mate . Ditch the compression ring you don't it . I'd place a ring on its own in the barrel and measure the ring gap. Specs will be in the manual what it should be . Double check the piston size and barrel size with veneer Caliper 👍
There's a chap on eBay who has a wanted add with the picture of a blue FZ. Message him, that's who i got mine from. Top bloke, hope this helps bud. Best regards Ade
the piston and rings are to tight, good chance of it seizing up when the piston expands when it warms up, need to find out what the piston clearance gap is and then measure what you have to see if it is right or not, wondering if they have given you a + size piston and not a standard sized one, also worth checking the ring grooves to make sure there is nothing stopping the rings seating properly, the copper head gasket is the one to use but would anneal it first and use a smear of gasket paste with it
Thanks bud, it's in now, the piston seems fine so I'm going without the spring ring. Will see how it goes, got me thinking now about the piston and weather it's the right size
Pretty sure you said 6 - 8.5 Ib-ft and then proceeded to set the torque wrench to 7 Nm. If that is the case you've under-torqued those head nuts Eadsie. 6 - 8.5 Ib-ft equates to 8 - 11.5 Nm. Hardly a disaster - potentially bad news the other way round ie. over-torqued fasteners.
I'm sure you know this, but you have to have the rear brake pulled in. If you're doing that, check the adjustment of the actuating lever (a few inches ahead of the bear brake actuator).
We used to have data for piston skirt clearance which was then measured with feeler gauges. Many pistons where not produced round on purpose but somewhat oval. The design principal being to allow the skirt to expand with heat to accommodate the fore and aft forces that are produced on the piston via the connecting rod on the gudgeon pin. (aka piston slap in worn engines) . Not sure if this relates so much to these smaller motors though. If when you place the ring without piston in the cylinder perfectly square and the gap is very small (necessary as they will expand with heat) then the rings you can assume are the right size so you then check the piston for size if the exhibit the same gap when installed on it.
Looks like you’ve got two top rings as the diagram you showed definitely has the rings different sizes. Your vernier measuring them both as 1.9 + a few points of a millimetre different seems to confirm it, even a not too accurate vernier like that would’ve shown one as 1.94 and the other as 1.7 say if they were different.
I’ve had that problem with parts too. Crazy how they can still put them out there for oe parts
There a two schools of thought re reed valves. Some thing that as they should be flat they MUST be fat to the block. Others seem to think that if the gap is relatively small the back pressure in the engine should push them closed. If there is an issue its likely to manifest itself in poor starting or “spiting” back through the carb.
Thanks Andy 😀
Quick Question where did you buy the Barrel, Piston and Head from?
There's a chap on eBay, has a photo of a blue FZ and the add says WANTED......drop him a private message
I'd turn the reed petals mate . Ditch the compression ring you don't it . I'd place a ring on its own in the barrel and measure the ring gap. Specs will be in the manual what it should be . Double check the piston size and barrel size with veneer Caliper 👍
Thanks joe
Spot on
Where did you get the piston and barrel kit from? I'm in desperate need for mine :(
There's a chap on eBay who has a wanted add with the picture of a blue FZ. Message him, that's who i got mine from. Top bloke, hope this helps bud. Best regards Ade
the piston and rings are to tight, good chance of it seizing up when the piston expands when it warms up, need to find out what the piston clearance gap is and then measure what you have to see if it is right or not, wondering if they have given you a + size piston and not a standard sized one, also worth checking the ring grooves to make sure there is nothing stopping the rings seating properly, the copper head gasket is the one to use but would anneal it first and use a smear of gasket paste with it
Thanks bud, it's in now, the piston seems fine so I'm going without the spring ring. Will see how it goes, got me thinking now about the piston and weather it's the right size
Maybe you need a spring compressor mrE
No because i got the piston in but it won't move, Mmmmm
Pretty sure you said 6 - 8.5 Ib-ft and then proceeded to set the torque wrench to 7 Nm. If that is the case you've under-torqued those head nuts Eadsie. 6 - 8.5 Ib-ft equates to 8 - 11.5 Nm. Hardly a disaster - potentially bad news the other way round ie. over-torqued fasteners.
Thanks Mike, I will take a good look at some torque wrench tutorials.
@@eadsierestorations My wrench has Nm graduations one side and Ib-ft the other. Easy to use the wrong scale. Ask me how I know 🙄
Get your vernier out mate and start measuring
Hi can you help my fz50 won't kick over something's wrong with the kickstart
Hi Matthew, has it 'just' stopped working?
I'm sure you know this, but you have to have the rear brake pulled in. If you're doing that, check the adjustment of the actuating lever (a few inches ahead of the bear brake actuator).
Yep get the grinder out you can do it