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I'm doing a full engine rebuild on an Honda GB250 clubman, RFVC & DOHC four stroke. I would like to know how to set cam timing from scratch?

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  • RFVC? Does that equate to "Rear Facing Valve Cover" ... I just guessing. Aug 13 '18 at 1:41
  • Radial four valve combustion chamber
    – SkylerX
    Aug 13 '18 at 4:26
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Usually there are marks on the crankshaft and camshaft(s).

The crankshaft mark will match a specific point, mark or even have a hole with a pin to locate the timing point precisely on the front cover for example and the camshaft(s) will also have a hole for a pin so they will be correctly located.

Once all are located then driving belt/chain can be fitted and tensioned.

I tend, once the locating pins have been removed, to rotate the engine two or four revolutions by hand - checking for binding etc and get back to TDC on the crank to check the cams also land in the correct places.

Some engine require the use of dial gauges on the cams to locate the precise timing points...

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  • Hi Mike, thanks. Currently i have 2 camshaft with sprockets and one middle sprocket for the cam chain. I have signs on both side of each camshaft "In" and "Ex". How do I set those once the middle one is perpendicular to TDC?
    – SkylerX
    Aug 13 '18 at 18:51
  • So any holes in sprockets that line up with holes in the head ? A workshop manual will show diagrams - this is not something to guess - I knew what to look for on engines that I built often (5 V8 engines of the same and you know exactly what is where)
    – Solar Mike
    Aug 13 '18 at 18:59
  • Hi Mike, unfortunately there is no manual for Honda GB250 Clubman, however what i have done is to video record and take a picture of how does the 3 sprockets line up with each other till the last teeth. My only fear is that when i moved the middle cam chain tensioner it seems to have moved the middle cam chain sproket of few mm, but not sure how since the engine is not in gear. Maybe since i removed the tensioner with a looser chain it looked like moving, however the other cam chain sproket at the bottom of the engine did not move? I hope so!
    – SkylerX
    Aug 14 '18 at 19:39
  • Can you see any marks (like numbered arrows, for instance) on the cam sprockets? I recently replaced the cam chain on my Suzuki. The procedure was to get #1 at TDC using the mark on the end of the crank. On the exhaust sprocket there was an arrow marked "1" that had to line up with the gasket face of the head. , and another marked "2" that pointed straight up. I had to count the pins in the camchain between "2" and another arrow "3" on the inlet sprocket - there had to be 13 pins. Maybe Honda used a similar system? Aug 9 '19 at 22:01
  • @upsidedowncreature no I could not, but perhaps you should address the OP... and, btw, it is likely sorted by now. either running or scrapped...
    – Solar Mike
    Aug 9 '19 at 22:05

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