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67` Bomber running problems

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mo goldie:

Well with the Help of the guy`s on here I have finally got the bike out for its first run today, first went to petrol station to get fuel only about a 1/4 of a mile from me it went fine, filled her up pulled away and it was good for about a mile and it went on one cylinder made it back home and it was the right spark plug and they are both New ( Now got two more cumming ) so I hope that was it....... but the thing that got me is the Gears it`s ok going up to top but when you come down the box it seems to go from fourth to third ok then seems to jump second and go right down into first gear don`t do that all the time tho now and again......... I have Not touched the Engine well only to put a new clutch in but the bloke I got the bike off said it did Do that but I could not try it out at the time as it was Not running..... do anyone know what it could be ? don`t fancy taken the engine to bits after doing all what I have done to it ?



That's a bummer 'Mo. Always crap when a seller doesn't tell you the full story.

Worth somebody else chipping in here but you can check the shifter mechanism without separating the crank-cases (you  just have to take off clutch cover) See diagrams for things to check like the shifter shaft mechanism 1 and springs 2 &3 in top diagram attached.  ( and profiled shift plate and pins on the end of the shift drum plus the two spings 3 & 12  and associated roller mech 11. Also the spring loaded pin 9 that is mounted in the top crankcase and runs in the guides of the shifter drum. (possibly the 1st thing to check I guess before removing clutch cover etc) . Other than that you would have to check the shift forks and drum, which means removing the bottom crankcase. On the bomber the crank is totally different to most other Hondas of the period and later, in that the crank has pillar blocks mounted in the top case .... so splitting the cases (with top end undisturbed) is not too daunting ... albeit a pain in the ar*e seeing as you bought a supposedly restored bike. I feel you pain.

Perhaps someone else can chip in and confirm what I am saying ... Bryan/RoyHalliwell etc.

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McCabe-Thiele (Ted):
I've sent you a PM with a photo - I think diagnosing a gearbox fault is more difficult than distance diagnostics with electric niggles.

I'd agree with Ash in checking #9 item first to see if any problem there.

Seems to be a detent position hold (generally they are) to prevent the shift drum moving without command or instigated by lever.

Sounds like it's OK inside the main box, else you'd likely get conflicts between gear sets if there's variation within that part of operation.

Also as Ash notes, checking the drum etc with clutch cover removed to see if there's reasonably positive "stopping" of the drum itself ( shift exchange lever removed) would verify the positive operation of that #9 mech.

McCabe-Thiele (Ted):
On my 500 the bottom pawl type wheel on the shorter lever was badly worn - hole in the plate was oval - not visible until I took the plate off and cleaned it.
.gear shift levers etc by Macabe Thiele, on Flickr


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