Differences between NC24 F and R geartrains/gearcases?

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Differences between NC24 F and R geartrains/gearcases?

Post by julianharty » Sat Aug 03, 2019 6:38 pm

Could anyone advise me on how we can recognise the Front and Rear geartrain or gearcase? These drive the camshaft from the centre of the crankshaft and the ones for the front and rear have different part numbers on CMSNL.com and a noticeable difference in the lead/lag of the secondary sprocket that is driven by the crankshaft. According to the NC21 manual (page 9-18) the text to the left of the middle photo says "ギヤケースほはFまたはRの識別マークがあり、Fはフロントシリンダ、Rはリヤシリンダに取付けること" which Google Translates as "The gear case has an identification mark of F or R, F is for the front cylinder and R is for the rear cylinder."

However, neither the image, nor my actual geartrains have any clear marking of which is front or rear. They do have shorter codes stamped on both sides of the frame/cage e.g. CD17256 and CL18339 but not the full part numbers listed on cmsnl.com e.g. 14410-ML-0721 (front) and 14420-ML-0721 (rear).

I would appreciate any insights on how to recognise the front and rear geartrains.

Background: I've got several NC24 engines, including one in my bike. On my bike, I've noticed the timing mark on the RH of the crankshaft does not seem to align exactly with those on the RH end of the camshafts. They appear to be a few degrees out, and whatever I've tried in terms of removing the cam and refitting it 1 tooth either way I've not seem them line up exactly. I also borrowed a camshaft from one of the spare engines to try that. I am checking the timings with everything correctly torqued down (to minimise the chances of play, etc. being a cause of the mismatch in alignment). I have also checked I've the correct camshafts fitted in the front and rear heads, etc.

When I align the markings on the RH of the camshafts to the line in their housing (at the top and parallel with the sparkplug hole) then the line between the respective T1, T2, T3, T4 is a few millimetres either before or after the V pointer at roughly 11 o'clock inside the timing inspection hole in the clutch-side casing. (For better visuals see viewtopic.php?t=1943 )

I wondered whether the bike had the geartrain for the F and R swapped over, or whether I'm confused, or whether I'm misunderstanding the instructions on this forum and/or in the NC21 manual...

As all the engines have probably been rebuilt by others over the years I don't have a trustworthy engine to use as a reference :(

Thank you


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