- Thread starter TheBrick
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AND a wet test immediately afterwards , using a tea spoon of clean engine oil .. it would not be unusual to see an increase of 10 PSI if it is worn due to the oil giving a temporary seal to the leakage .
Sometimes you can take the air filter off open the throttle and using a tiny LED torch look into the cylinder . It should look shiny on the cylinder walls not dull grey and the postin a very light grey with no bright streaks running top to bottom on the piston which would indicate metal pick up No scratches or scores on the cylinder skirt . . If you can easily get the exhaust off without wrecking the gasket or breaking studs you'll get an even better picture of the state of things.
normally you can get a look in the cylinder well enough to judge from the exhaust port
I've now got a small borescope that runs off my phone .up to 20 x magnification and with an LED illuminator adjacent to the magic eye. Not yet used it in a cylinder but for the £ 8 or so it cost me it's handy to have as I used it elsewhere . Was puling my hair out at first as the offered link would not work for me and my phone .
Fizzy gave it a try on his phone and at first it was the same, but then he downloaded a generic camera app and it worked.
at that price it would nearly be rude not to have one
ok just ran a compression test but missed the comment about doing a wet test.
Dry it was about 98psi so on the low side but not awful...
I will try to grab a wet and dry test later and take a look in the exhaust port.
Thanks for everyone's tips learning loads.
Dry it was about 98psi so on the low side but not awful...
I will try to grab a wet and dry test later and take a look in the exhaust port.
Thanks for everyone's tips learning loads.
Those light score marks on the cylinder wall sound as that is what is causing a bit of crank case compression aka. blow back in the carb at high off load speed when the engine warbles and sluggish re- accelerations off load .
jo1010
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Ok.....tbh "light score marks" could be significant....only way of telling is to take head off and see what's going on. 1). Once piston is out you can also check rings for sticking in the piston (jubilee clip to compress them again).....being jammed can be instant compression loss. 2) if you can feel scores on piston or cylinder with your fingernail its a problem that needs fixing though (new piston / cylinder).
Once fixed use new headgasket and honda seal or similar to seal up again...
....btw hs80 is a hedge trimmer not a strimmer ?
Once fixed use new headgasket and honda seal or similar to seal up again...
....btw hs80 is a hedge trimmer not a strimmer ?
Ok will remove head thanks.
Crank case compression sound right as every so often the pop results in feeling pressure at air intake.
Yes it is a hedge cutter. I don't know why I wrote strimmer :/ So head gasket and the honda seal. Is that because you are expecting the head to be out of true more than the gasket can take up / correct?
jo1010
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I think I can see a lot of pitting in the Cylinder walls around 2mins on the video (or is it the camera / lighting?). If so that could mean the cylinder has worn away at those points - and will lose some compression. (If you've not got internal gauges for bore measurement take it to someone who has for a second opinion). But if there is oval wear will it explain your popping? Not necessarily - your compression readings aren't terrible...
Could pull crank seals with a hole drilled into the seal and a self tapper inserted - pulled out with vice grips or whatever...
The idea with the three bond sealant is the slightest trace to seal any imperfections in an old engine - yes you can use emery paper (180 thru 400) on a glass plate as well for the head, but the crankcase is harder to polish flat ....some argue it shouldn't be needed though.
There appears to be a lot of vertical scoring in the top end of the cylinder where the piston reached 10 mm before top end almost at the end of your video .
Try using a less bright light and set the camera on a stable device like a tripod so you get some still pictures at differing angles .
I noticed that there also appears to be a long score to the bottom of the cylinder wall and microscopic burring around the bottom thrust edges of the ports Clean the piston off so there is no oil on it AT ALL , dull grey patches will indicate well worn areas. The same applies to the cylinder.
Try using a less bright light and set the camera on a stable device like a tripod so you get some still pictures at differing angles .
I noticed that there also appears to be a long score to the bottom of the cylinder wall and microscopic burring around the bottom thrust edges of the ports Clean the piston off so there is no oil on it AT ALL , dull grey patches will indicate well worn areas. The same applies to the cylinder.
dobbslc
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I also noticed the pitting on the lower part of the cylinder wall, has this tool been stored in a damp shed for a long time?
It could be a Nikasil bore that's worn away and now the rings are running on the aluminium cylinder casting.
The con rod bearing looks like it has a lot of movement if you can tilt the rod that far left and right, side to side on the crankshaft is ok but they don't normally tilt like that. Try pulling it directly up and down, you should have no movement at all.
It could be a Nikasil bore that's worn away and now the rings are running on the aluminium cylinder casting.
The con rod bearing looks like it has a lot of movement if you can tilt the rod that far left and right, side to side on the crankshaft is ok but they don't normally tilt like that. Try pulling it directly up and down, you should have no movement at all.
I took it round to a neighbour and he mentions what he thought were some either heat mark or scoring. Yes arounds the top.
Re camera lighting, I am never sure how to light with a camera it either ends up dull or if I use a torch too much reflection. Not an art to which I am versed!
It stored in a shed but a prefab concrete one with a good dry floor and off the floor on a shelf 4' up. Its used even during the winter every couple of months max to trim back bits when needed to work here and their.
I guess Nikasil is some sort of anodising or hardened coating?
Conrod I can tilt left and right and lit left and right but up down and it's pretty solid from memory as I did check that thinking that would be more important but I will double check as I have miss remembered before!
Some rdg bore gauges on order to do some measurements. Out of interest as much as anything as I am pretty sure I need a new cylinder now but I am over analysing to death to get a feel for what is wrong. Thanks all again. Will update when gauges arrive.
