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#Post#: 14006--------------------------------------------------
Advice on valve springs please
By: Ade Colmar Date: October 21, 2025, 4:19 am
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I ordered a pair of '18lb' valve springs off eBay (from China)
and when they arrived they were the same size as the originals,
but massively stronger. From a bit of research it looks like
the standard GX200 springs are around 11lb so on a relative
basis I would guess the springs I bought are 35-40lb. If I
fitted them they would sap power and accelerate wear on the
valve train, so they are going in the bin!
So I am wondering where I can source springs with a more
reliable rating? I don't intend to build I high revving engine,
but I can hear the valves start to clatter at just beyond
5,000rpm.
#Post#: 14007--------------------------------------------------
Re: Advice on valve springs please
By: DavidandCarolynne Date: October 21, 2025, 7:24 am
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I got mine from GX Tuning Store:
HTML https://www.gxtuningstoreuk.com/inc/sdetail/126/156
#Post#: 14008--------------------------------------------------
Re: Advice on valve springs please
By: Jimr1999 Date: October 21, 2025, 7:42 am
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Id in doubt, don't fit Ade, anything over 20lbs could break the
pressed rockers
Jim R
#Post#: 14009--------------------------------------------------
Re: Advice on valve springs please
By: Jimr1999 Date: October 21, 2025, 7:46 am
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HTML https://cyclekartsgb.createaforum.com/where-to-get-stuff/18lb-up-rated-valve-springs-to-fit-lifan-212cc-engine/#msg13792
#Post#: 14010--------------------------------------------------
Re: Advice on valve springs please
By: Ade Colmar Date: October 21, 2025, 1:36 pm
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Thanks for the feedback and apologies for not spotting the
earlier similar query from Scotty. So, two more pairs of
springs arrived today from KKC and I now have four quite
different springs including the original from the engine (a
Maxspeedingrods GXR212). See the attached photos.
Original engine spring is 30mm free length, 1.8mm wire diameter
and five turns.
KKC Heavy duty Honda GX140/160/200 spring is 34mm free length,
1.9mm wire diameter and 7 turns
KKC aftermarket GX160 G4 spring is 26mm free length, 2.2mm wire
diameter and 5.7 turns
Chinese heavy duty GX200 is 27mm free length, 2.4mm wire
diameter and five turns
I'm surprised to find such variation in free length. I don't
know if this is by design or a nightmare of quality control! The
compressed length of any valve spring when installed in the
engine is 22mm. This leaves me concerned that the 26mm Gx160 G4
spring would have marginal pre-compression to ensure the collet
cannot come lose under the dynamic loads. By contrast, the HD
GX140/160/200 spring seems unnecessarily long at 34mm. Although
it is made of thicker wire than the original spring, the two
extra turn make it soft again. My best guess that it might be
around 20% stiffer than the original, which doesn't seem enough.
The GX160 G4 spring seems at least 50% stiffer, which is about
right. However, as mentioned earlier, it is worrying short.
On balance, the safest bet out of this bunch is probably the
long HD GX140/160/200 spring. I'll give it a try and see what
the engine sounds like. Any other suggestions welcome :)
#Post#: 14011--------------------------------------------------
Re: Advice on valve springs please
By: Jimr1999 Date: October 21, 2025, 9:29 pm
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It would be interesting to see the force necessary to compress
each spring from the installed length to say, installed length
minus 5mm. That would probably be in the ballpark of comparative
ratings. A percentage difference could then be calculated.
JimR
#Post#: 14012--------------------------------------------------
Re: Advice on valve springs please
By: Jimr1999 Date: October 21, 2025, 10:09 pm
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The factory cam valve lift on a Honda GX200 is around 5.5mm
JimR
#Post#: 14013--------------------------------------------------
Re: Advice on valve springs please
By: Ian F Date: October 22, 2025, 2:24 am
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Without writing down the formulae for spring stiffness, it
should be noted that the biggest influencing factor is the wire
diameter, which influences the stiffness by the fourth power!
There is a well trodden and proven path regarding valve springs
for our engines and that is the 18 lbs" ones from GX Tuning.
When I spoke to the bloke there he said they do go soft over
time, however Jane has now done 28 events and GNasher has done
24 events without issue.
HTML https://www.gxtuningstoreuk.com/valve_train
#Post#: 14016--------------------------------------------------
Re: Advice on valve springs please
By: Ade Colmar Date: October 22, 2025, 11:38 am
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Thanks Ian and Jim. GXtuning springs are £7.99 a pair, but £9
for the cheapest posting!
I did a bit of measurement today using my Heath Robinson test
equipment shown in the photos below and the better of the
springs I already had :)
The inlet valve is moved 5.25mm by the rocker arm. I guess in
principle, it should take around 12lb force to move the valve
that distance with the standard spring fitted and 18lb force
with the KKC Honda heavy duty (34mm) spring fitted. In practice
the measurements were greater. Rather than get distracted by
that I concentrated on the relative difference which was 25% and
so a little less than expected.
Once fitted I warmed up the engine and then slowly increased the
revs until I heard the clattering of the valves again. This now
happens at 5,400-5,500rpm. Previously with the standard valves
fitted the clattering started at just over 5,000rpm. So a
useful increase, but not good enough in the long term.
I guess I will have to try the GXtuning valve springs at some
point!
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