Guest Richzx6r Posted November 20, 2020 Share Posted November 20, 2020 I would actually say yes it could be the reason for the compression issues as the upper limit is there to limit the gap between rings and bores, if the bore is bigger than the upper limit with a hot engine this could be enough to drop some compression Quote Link to comment Share on other sites More sharing options...
Mickly Posted November 20, 2020 Author Share Posted November 20, 2020 Dunno yet, but the reduced compression was across all cylinders Quote Link to comment Share on other sites More sharing options...
fastbob Posted November 20, 2020 Share Posted November 20, 2020 3 hours ago, Mickly said: That’s the conundrum - is 0.05mm above the tolerance enough to make the difference? I would be tending towards new rings but I dread to think what they will cost for a Triumph , and a light hone to allow them to bed in . By the way , were all the rings completely free to expand when freed from the bores ? Quote Link to comment Share on other sites More sharing options...
fastbob Posted November 20, 2020 Share Posted November 20, 2020 1 hour ago, Mickly said: Dunno yet, but the reduced compression was across all cylinders Here's some essential reading . http://blog.wiseco.com/everything-you-need-to-know-about-ring-gap 1 Quote Link to comment Share on other sites More sharing options...
TimR Posted November 20, 2020 Share Posted November 20, 2020 .005mm is roughly 2thousands of an inch ...may not seem a lot but in engine engineering that is a lot And remember that the rings are there to create a seal and if they can't expand and maintain that seal ... Not doing their job Plus consider the extra wear placed on the liners caused by the slop in the pistons travel where the rings are not cushioning so to speak will mean that tolerance is even more critical . 1 Quote Link to comment Share on other sites More sharing options...
Mr Fro Posted November 21, 2020 Share Posted November 21, 2020 10 hours ago, TimR said: .005mm is roughly 2thousands of an inch ...may not seem a lot but in engine engineering that is a lot And remember that the rings are there to create a seal and if they can't expand and maintain that seal ... Not doing their job Plus consider the extra wear placed on the liners caused by the slop in the pistons travel where the rings are not cushioning so to speak will mean that tolerance is even more critical . He's talking end gap, not side gap. @Mickly - how square were the rings when you measured the gap? A little bit on the wonk and you'll get a false reading. Also, you should take a number of readings down the bore to give you an idea of whether it's the rings or bore that's worn. 1 Quote Link to comment Share on other sites More sharing options...
Mickly Posted November 21, 2020 Author Share Posted November 21, 2020 15 hours ago, fastbob said: I would be tending towards new rings but I dread to think what they will cost for a Triumph , and a light hone to allow them to bed in . By the way , were all the rings completely free to expand when freed from the bores ? New rings are £45 per piston !! yeah, all the rings were free when the liners came off. Quote Link to comment Share on other sites More sharing options...
Mickly Posted November 21, 2020 Author Share Posted November 21, 2020 4 hours ago, Mr Fro said: He's talking end gap, not side gap. @Mickly - how square were the rings when you measured the gap? A little bit on the wonk and you'll get a false reading. Also, you should take a number of readings down the bore to give you an idea of whether it's the rings or bore that's worn. Good point, I did try to ensure they were square, I’ll measure the distance from the end of the bore to make sure it’s square. Quote Link to comment Share on other sites More sharing options...
Mr Fro Posted November 21, 2020 Share Posted November 21, 2020 44 minutes ago, Mickly said: Good point, I did try to ensure they were square, I’ll measure the distance from the end of the bore to make sure it’s square. Get the ring in and poke the piston up after it - presto, nice and square. 1 Quote Link to comment Share on other sites More sharing options...
fastbob Posted November 21, 2020 Share Posted November 21, 2020 Beyond the upper tolerance . Well it's set for a reason I suppose . I couldn't actually tell you whether that is enough to cause a drop in compression or not . Generally , by the time an engine gets to me it's usually obvious what's wrong with it from the smoke or the telltale stink of petrol in the oil . 1 hour ago, Mickly said: New rings are £45 per piston !! yeah, all the rings were free when the liners came off. While we're on the subject of pistons , remember my ER5 ones ? Now look at them . There's still some bad scoring on on side of both the skirts but what I thought to be severe scoring around the rings has all scrubbed off with a Scotch Pad . So what was going on here ? I think all the carbon in the combustion chambers came loose when I initially fired it up and revved it . The lower portion of the bores is also quite badly scored so I would have replaced them anyway . Coming as it did from a training school , I wonder whether this scoring is a result of the bike lying on the ground while still revving it's tits off ? Quote Link to comment Share on other sites More sharing options...
Mickly Posted November 21, 2020 Author Share Posted November 21, 2020 1 hour ago, fastbob said: Beyond the upper tolerance . Well it's set for a reason I suppose . I couldn't actually tell you whether that is enough to cause a drop in compression or not . Generally , by the time an engine gets to me it's usually obvious what's wrong with it from the smoke or the telltale stink of petrol in the oil . While we're on the subject of pistons , remember my ER5 ones ? Now look at them . There's still some bad scoring on on side of both the skirts but what I thought to be severe scoring around the rings has all scrubbed off with a Scotch Pad . So what was going on here ? I think all the carbon in the combustion chambers came loose when I initially fired it up and revved it . The lower portion of the bores is also quite badly scored so I would have replaced them anyway . Coming as it did from a training school , I wonder whether this scoring is a result of the bike lying on the ground while still revving it's tits off ? My pistons don’t look anything as bad as that. The bikes only done 30k so I’m scratching my head about how the compression has dropped, these engines are renowned as being robust, the early Hinckley Triumphs were over engineered to break the link to the bad reputation that the Meridan bikes had developed. Quote Link to comment Share on other sites More sharing options...
Mickly Posted November 24, 2020 Author Share Posted November 24, 2020 On 21/11/2020 at 15:10, Mr Fro said: Get the ring in and poke the piston up after it - presto, nice and square. Right, taking @Mr Fro ‘advice I’ve measured all the gaps - I checked that the top ring gap was the same, top middle & bottom down each liner, which they were although they differed across the liners. so it seems that all gaps are within tolerance although towards the top end .... The head scratching continues !! Quote Link to comment Share on other sites More sharing options...
Mr Fro Posted November 24, 2020 Share Posted November 24, 2020 1 minute ago, Mickly said: Right, taking @Mr Fro ‘advice I’ve measured all the gaps - I checked that the top ring gap was the same, top middle & bottom down each liner, which they were although they differed across the liners. so it seems that all gaps are within tolerance although towards the top end .... The head scratching continues !! Looks alright. Did you check the ring gap at a few points down the bores? Quote Link to comment Share on other sites More sharing options...
Mickly Posted November 24, 2020 Author Share Posted November 24, 2020 3 minutes ago, Mr Fro said: Looks alright. Did you check the ring gap at a few points down the bores? Yep Quote Link to comment Share on other sites More sharing options...
Mickly Posted November 27, 2020 Author Share Posted November 27, 2020 (edited) Right, I’ve found a place that will skim the head, hone the barrels (& properly clock them) & reseat the valves. I decided to remove the valves myself to have a look at the condition of the seats. obtained a cheap valve spring compressor & oh bugger, because it’s a shim & bucket arrangement it can’t act on the spring coz it’s hidden. So a bit of head scratching & with the help of a modified old spark plug socket .. all 16 out - it got easier as I got the knack, still took 3 hours !! All out, Tagged & bagged. The inlet valve seats look ok, the exhaust seats look a bit crusty, but passed the diesel test? exhaust valve. Edited November 29, 2020 by Mickly Quote Link to comment Share on other sites More sharing options...
linuxrob Posted December 1, 2020 Share Posted December 1, 2020 Even though my Z500 valves passed the liquid leak test they looked like yours. I filled the port up with water and blasted my airline around the valve seat in the combustion chamber and saw bubbles at certain points. a light grind in sorted it. worth a try just keep them press in with the spring compressor no need to refit the collets to test, see photos Regards Rob 1 Quote Link to comment Share on other sites More sharing options...
TimR Posted December 1, 2020 Share Posted December 1, 2020 You have to remember how crude diesel is and its viscosity can alter with varying temperature so can effectively seal any minor leak . In minor leaka It only tends to visibly leak under pressure and seeps otherwise but very slowly Petrol or paraffin is a good leak down 1 Quote Link to comment Share on other sites More sharing options...
Bender Posted December 1, 2020 Share Posted December 1, 2020 Those need re lapped, nice to start seeing something that would cause low pressure. 1 1 Quote Link to comment Share on other sites More sharing options...
Mickly Posted December 11, 2020 Author Share Posted December 11, 2020 Head back from the machine shop. 4 thou skim, valve seats re-cut, valves ground in & reassembled. Crushed dowel removed .. There seems to be some kind of black factory finish on the valves & combustion chamber - it’s not carbon build up, don’t know what it’s purpose is? Also the top of the valve stems where ground down to compensate so same shims can be used ( I will be checking them ) There’s a bit of corrosion on the face, apparently this is not unusual & won’t cause any issues. Now needs masking up & painting ( again !! ) Quote Link to comment Share on other sites More sharing options...
Mickly Posted December 11, 2020 Author Share Posted December 11, 2020 Liner bores honed, they are within tolerance but they check the ring gaps & as I thought they are near the top end of the tolerances so new ones will be fitted - probably after Xmas as they will cost £45 per piston !! 1 Quote Link to comment Share on other sites More sharing options...
Mickly Posted March 12, 2021 Author Share Posted March 12, 2021 Right I’m sick of waiting for the temperature to raise enough to continue painting Trophy engine parts, and having investigated a few methods I’ve knocked up a table that goes over an oil filled radiator just using stuff I’d got hanging around - it seems to be doing the job 1 Quote Link to comment Share on other sites More sharing options...
linuxrob Posted March 12, 2021 Share Posted March 12, 2021 Careful with that setup. the warm air could possibly move dust etc from the floor through that grill and stick to the still wet paint. when i did the Z barrel i heated it up on the rad tehn painted over my workmate then after about 20 mins put it back on the rad to finish curing. here it is with the first guide coat after primer in the rad Quote Link to comment Share on other sites More sharing options...
Mickly Posted March 12, 2021 Author Share Posted March 12, 2021 11 minutes ago, linuxrob said: Careful with that setup. the warm air could possibly move dust etc from the floor through that grill and stick to the still wet paint. when i did the Z barrel i heated it up on the rad tehn painted over my workmate then after about 20 mins put it back on the rad to finish curing. here it is with the first guide coat after primer in the rad Thanks for the tip, reckon I’ll do the same. Also, as the rad has been ‘borrowed’ from domestic management I might throw a cloth over it to prevent any paint getting on it. Quote Link to comment Share on other sites More sharing options...
fastbob Posted March 12, 2021 Share Posted March 12, 2021 2 minutes ago, Mickly said: Thanks for the tip, reckon I’ll do the same. Also, as the rad has been ‘borrowed’ from domestic management I might throw a cloth over it to prevent any paint getting on it. Looks like it's too late to me . Quote Link to comment Share on other sites More sharing options...
Mickly Posted March 12, 2021 Author Share Posted March 12, 2021 5 minutes ago, fastbob said: Looks like it's too late to me . Haha, too late for @linuxrob The one I’m using is still unsullied by paint, it was looking at the pic of his that gave me the idea. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.