Valve clearances closed up?
Discussion
Helped a mate out a couple weeks ago after he snapped a spark plug on the front cylinder of a 2002 Suzuki SV650. Timed it all up, removed the cams, head bolts and popped it out ... took to engineering shop to have the spark plug drilled out and new insert put in... threw it all back together with new head gasket and torqued down correctly.
Fired up on the button and sounded good.
He then spent a few days doing jobs on it in preparation for the MOT, Went to take it for MOT and rode a mile down the road when it cut out and wouldn't start. He rolled it home and sulked...
Eventually he got it started and it was mis-firing. I talked him through checking plugs, leads, etc and clearly there was an issue with compression or valve clearances. Compression test showed a healthy 12.5 bar so suspected valve clearances....
Last night the valve clearances were checked... one inlet was fine, the other three are all closed up and cannot fit a 0.05 feeler gauge ... at least we have an answer now.
But I'm baffled as to WHY the clearances have changed given the valves / shims have not been touched.
Any ideas?
Fired up on the button and sounded good.
He then spent a few days doing jobs on it in preparation for the MOT, Went to take it for MOT and rode a mile down the road when it cut out and wouldn't start. He rolled it home and sulked...
Eventually he got it started and it was mis-firing. I talked him through checking plugs, leads, etc and clearly there was an issue with compression or valve clearances. Compression test showed a healthy 12.5 bar so suspected valve clearances....
Last night the valve clearances were checked... one inlet was fine, the other three are all closed up and cannot fit a 0.05 feeler gauge ... at least we have an answer now.
But I'm baffled as to WHY the clearances have changed given the valves / shims have not been touched.
Any ideas?
Valves by their nature tend to 'neck', i.e., the stem lengthens with use, especially on the exhaust side, which obviously has a lot of heat to deal with (helping it become more elastic/plastic) along with huge number of stress cycles as per the inlet valves. I guess it's been a while since it was last checked & re-shimmed?
StuB said:
Valves by their nature tend to 'neck', i.e., the stem lengthens with use, especially on the exhaust side, which obviously has a lot of heat to deal with (helping it become more elastic/plastic) along with huge number of stress cycles as per the inlet valves. I guess it's been a while since it was last checked & re-shimmed?
It's never been checked / and / or re-shimmed mate. But then the bike has done 9k miles from new ... and it ran fine until the head was removed for the spark plug removal issue.ktm rfs engines close up on the exhaust side, luckily they made the adjustment by a screw and not shims + made it really easy to get to.
Used to do mine every 3-6 months and the difference was incremental but still worth checking - if it had never been checked for say a year or so then it would have been closed right up and would not have been performing well.
Used to do mine every 3-6 months and the difference was incremental but still worth checking - if it had never been checked for say a year or so then it would have been closed right up and would not have been performing well.
Mr OCD said:
But I'm baffled as to WHY the clearances have changed given the valves / shims have not been touched.
Any ideas?
If it's only one cylinder I'm baffled as to why it completely cut out and wouldn't start. My dads' 2002 SV started and ran on one cylinder when a coil went on it. It was rough and obviously hugely down on power, but it ran.Any ideas?
It also odd why it showed good compression if the valve clearances were so tight that they were leaking.
Was the head supplied to the engineering shop with the followers still in it? If so then it's entirely possible they fell out and were replaced in random positions.
Edited by Mr2Mike on Thursday 2nd July 13:31
Mr2Mike said:
If it's only one cylinder I'm baffled as to why it completely cut out and wouldn't start. My dads' 2002 SV started and ran on one cylinder when a coil went on it. It was rough and obviously hugely down on power, but it ran.
It also odd why it showed good compression if the valve clearances were so tight that they were leaking.
Was the head supplied to the engineering shop with the followers still in it? If so then it's entirely possible they fell out and were replaced in random positions.
It might have been the owner ... he isn't mechanically inclined... but it ran eventually but sounded rough. It has good compression but the reading went down quickly (valves leaking) ... It also odd why it showed good compression if the valve clearances were so tight that they were leaking.
Was the head supplied to the engineering shop with the followers still in it? If so then it's entirely possible they fell out and were replaced in random positions.
Edited by Mr2Mike on Thursday 2nd July 13:31
The head was supplied with cams and followers in ... I don't think they were removed, but I will check.
Mr OCD said:
Hooli said:
I think valves are normally removed to skim a head, which is what I assume you've had done?
Head was not skimmed.I suspect they might have taken the valves out to ensure no swarf had got amongst the spring etc.
Or could it be a bit of swarf has got amongst it all & is stuck between the stem & shim?
Hooli said:
Sorry, I misread the OP.
I suspect they might have taken the valves out to ensure no swarf had got amongst the spring etc.
Or could it be a bit of swarf has got amongst it all & is stuck between the stem & shim?
But for all three valves? ... looks like I won't need to sort it now anyway as the owner has thrown it at a garage whilst he is away I suspect they might have taken the valves out to ensure no swarf had got amongst the spring etc.
Or could it be a bit of swarf has got amongst it all & is stuck between the stem & shim?
Sounds a little odd - had the clearances tighten on an EXUP years ago at sub 10k miles, adjusted & good til I sold it 20k later.
Compared to your mates issue, the bike was hard to start (due to no/low compression) when it was cold, once warm started OK. Always assumed the clearances when warm were greater due to the alloy head expanding more than steel valves/cams?
Just seems odd that the SV is proving problematic when warm, could the new plug insert be leaking?
Compared to your mates issue, the bike was hard to start (due to no/low compression) when it was cold, once warm started OK. Always assumed the clearances when warm were greater due to the alloy head expanding more than steel valves/cams?
Just seems odd that the SV is proving problematic when warm, could the new plug insert be leaking?
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