Camshafts, 125 vs 250
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Hello!
I wonder if camshafts do interchange? ( physical / bearing size ++)
I know the timing-chain is different, (and all 4 cams are different on both engines… timing-gears can be swapped over..?).
Would be neat to try 250 intake cams on a 125!
Old and grumpy,(?), have fairly wide engine & tuning experience, "restoring/resto-mod" on cars & mc, worked as electronic tech. (retired).
GT125R - sold. New (used): 2012-GT250R-efi (sold)+ 2017-GV-125C (sold) - got my old 2018-GT-125R back... 🙂
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250 cams are heavier than 125cc and ofcourse they are thicker and have bigger egg lobes , so they may “press” down the cam buckets a bit further in to the cylinder so the valve could hit piston or just about “miss it” . Risky gamble but can try it.
Another problem = extra weight , more load on valve springs and slim cam chain. The 250 uses much fatter cam buckers and thicker chains ofcourse.
The sprockets of cam shaft may be removed , and use 125cc cam shaft sprockets to keep using the 125cc chain. However be warned on accelerated wear on valve parts, so frequent inspection may be advised.
250cc and 125cc vtwins have the same timings and same clearance, so i would not expect big performance gains. The most costly part in the engine is the crankshaft, so have to make sure crankshaft teeth of the 125 don’t get extra stress.
Just my thoughts 🙂
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Hoped buckets were the same, as they use same shims…?
Anyway: the difference:
Old and grumpy,(?), have fairly wide engine & tuning experience, "restoring/resto-mod" on cars & mc, worked as electronic tech. (retired).
GT125R - sold. New (used): 2012-GT250R-efi (sold)+ 2017-GV-125C (sold) - got my old 2018-GT-125R back... 🙂
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And mixed:
Old and grumpy,(?), have fairly wide engine & tuning experience, "restoring/resto-mod" on cars & mc, worked as electronic tech. (retired).
GT125R - sold. New (used): 2012-GT250R-efi (sold)+ 2017-GV-125C (sold) - got my old 2018-GT-125R back... 🙂
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Thinking the “advertized” 211 degrees of intake duration really restricts any power-increase… – witch makes 4 valves/cyl and dual carb a complete waste…
even my 1980 Honda CB125-Twin was rated 17,5Hp..! -from factory! (with slight variations, depending on marked, but has:2 valves/cyl, 2 x 22mm carbs)
Old and grumpy,(?), have fairly wide engine & tuning experience, "restoring/resto-mod" on cars & mc, worked as electronic tech. (retired).
GT125R - sold. New (used): 2012-GT250R-efi (sold)+ 2017-GV-125C (sold) - got my old 2018-GT-125R back... 🙂
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Yes, but have not found anybody that can do/and that I trust… (and afford)
Old and grumpy,(?), have fairly wide engine & tuning experience, "restoring/resto-mod" on cars & mc, worked as electronic tech. (retired).
GT125R - sold. New (used): 2012-GT250R-efi (sold)+ 2017-GV-125C (sold) - got my old 2018-GT-125R back... 🙂
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I have another question: If someone has a disassembled 125cc engine, please let me know the length of a con-rod, center-to-center (hole)
measurement in cm/mm preferred.
Old and grumpy,(?), have fairly wide engine & tuning experience, "restoring/resto-mod" on cars & mc, worked as electronic tech. (retired).
GT125R - sold. New (used): 2012-GT250R-efi (sold)+ 2017-GV-125C (sold) - got my old 2018-GT-125R back... 🙂
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I have another question: If someone has a disassembled 125cc engine, please let me know the length of a con-rod, center-to-center (hole) measurement in cm/mm preferred.
I have stripped engines to sell parts on my ebay shop , but i have not measured parts sizes inside because no one in UK asks me that questions , so its a long forgotten memory!
I will keep you in mind if i ever come across a wrecked engine again 🙂
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