Hi, at this time I'm very happy to ride my track bike with the engine Honda CB 125 twin (1978 as the pilot).
But on the other hand against large engines I lose ground
, my regulation allows me use an engine up to 250cc.why not a 185cc. Following my research I find the work of Michael A. Moore from Eurospares.com about this Honda 160 tuning. (a very great site )
So why not a 185cc phased to 180°.
The 185cc engine exists at Honda >> CM185 Twinstar (cd185/cb185) Bore x Stroke, 53.0 x 41.0 mm (2.1 x 1.6 inches), these are cousins of the cm250, cmx250, ca250, cm200, rebel 250 engine, etc
The CMT185 s'stroke is the same as cbt 125
After 6 months of research and a few purchases, i have a new Honda cb 125 twin engine in my garage, plus the main components of a honda cmt 185 engine: a crankcase, a cylinder block and a crankshaft.
What I keep from the CBT 125, its the gearbox, the cylinder head and the camshaft. Everything will be put in the 185cc crankcase with the 185cc cylinder block. Remains the question of the crankshaft and the pistons.
My first approach is to find a 53mm diameter piston for a 13mm piston pin and with the dimensions of the original piston (squish, etc). with this idea i use the CBT 125 crankshaft in 185cc crankcase.
My second intention, is to re-phase the crankshaft, from 360° to 180° to keep the CMT 185 crankshaft, connecting rod, piston pin and piston, but the path is complicated.
See below is a cross-sectional image of a CBT 125 wedged at 180°.
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And finally the last idea, make a reduction on the piston pin. The idea have be found on youtube.
Keep the CBT 125 crankshaft in a CMT185 crankcase with a 185cc cylinder block, with original pistons (ϕ53mm) and adapt the piston pin with a reduction. Here 2 possibilities, CMX250 pistons (ϕ53mm) with a 15mm pin bore or CMT185 pistons (ϕ53mm) with a 14mm pin bore .
The reduction will be made in 100c6 steel (AISI 52100).
The piston pin of 13x38.5 is the maximum axis that I could find on the web, it is not the standard axis of the twin 125cc (34.5mm).
See below For that I made you a little drawing.
![Slope Rectangle Font Parallel Pattern]()
What do you think about this project? have you a other ideas?
Best regards
But on the other hand against large engines I lose ground
, my regulation allows me use an engine up to 250cc.why not a 185cc. Following my research I find the work of Michael A. Moore from Eurospares.com about this Honda 160 tuning. (a very great site )So why not a 185cc phased to 180°.
The 185cc engine exists at Honda >> CM185 Twinstar (cd185/cb185) Bore x Stroke, 53.0 x 41.0 mm (2.1 x 1.6 inches), these are cousins of the cm250, cmx250, ca250, cm200, rebel 250 engine, etc
The CMT185 s'stroke is the same as cbt 125
After 6 months of research and a few purchases, i have a new Honda cb 125 twin engine in my garage, plus the main components of a honda cmt 185 engine: a crankcase, a cylinder block and a crankshaft.
What I keep from the CBT 125, its the gearbox, the cylinder head and the camshaft. Everything will be put in the 185cc crankcase with the 185cc cylinder block. Remains the question of the crankshaft and the pistons.
My first approach is to find a 53mm diameter piston for a 13mm piston pin and with the dimensions of the original piston (squish, etc). with this idea i use the CBT 125 crankshaft in 185cc crankcase.
My second intention, is to re-phase the crankshaft, from 360° to 180° to keep the CMT 185 crankshaft, connecting rod, piston pin and piston, but the path is complicated.
See below is a cross-sectional image of a CBT 125 wedged at 180°.
And finally the last idea, make a reduction on the piston pin. The idea have be found on youtube.
Keep the CBT 125 crankshaft in a CMT185 crankcase with a 185cc cylinder block, with original pistons (ϕ53mm) and adapt the piston pin with a reduction. Here 2 possibilities, CMX250 pistons (ϕ53mm) with a 15mm pin bore or CMT185 pistons (ϕ53mm) with a 14mm pin bore .
The reduction will be made in 100c6 steel (AISI 52100).
The piston pin of 13x38.5 is the maximum axis that I could find on the web, it is not the standard axis of the twin 125cc (34.5mm).
See below For that I made you a little drawing.
What do you think about this project? have you a other ideas?
Best regards
