Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: ebmbiker on May 26, 2022, 11:44:04 AM
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Hello again folks,
I've got my crankcases assembled, no top end on. When I rotate the input shaft by hand and use the gear shift lever, it won't shift through the gears. The selector drum only rotates a small amount. The shafts rotate easily and the output shaft is engaged and rotating.
Any ideas?
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Did you assemble in the top case or bottom case?
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Did you assemble in the top case or bottom case?
I assembled in the top case. I'm using the Haynes manual.
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Is your engine on the bench or in your bike?
If it's on the bike is the lever unimpeded?
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Is your engine on the bench or in your bike?
If it's on the bike is the lever unimpeded?
Engine is on the bench Ted.
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These are the limits of movement of the selector drum
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Second position
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Sorry I do not think I can help you as it's outside my limited knowledge.
Only question I would ask is was the gear selector drum/selector forks in the neutral position when you assembled the gearbox internals ?
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Sorry I do not think I can help you as it's outside my limited knowledge.
Only question I would ask is was the gear selector drum/selector forks in the neutral position when you assembled the gearbox internals ?
I can't be sure if it was in neutral. The shift drum guide screw [the part that screws in from the top of the crankcase] that I have is the later version without the ball and spring. So there's nothing to fit into the detent on the drum.
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I’m no expert and the photo is upside down. But that drum appears to be 180deg out of position. In the neutral position the wheel should be nestled in the neutral drum recess. So you might be correct Ted. The gearbox my not have been assembled in the neutral position.
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Makes sense. I'll start dismantling it! Everyday is a school day!
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Like this
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Is the cam plate correctly assembled. It’s difficult to get wrong as only one locating pin is ‘raised’ relative to the others. If not the drum is in the wrong orientation, which is equally difficult to get wrong! Good luck.
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I'd say you are right Phil, the top roller goes into the indent in the pin plate when it's in neutral, it's so you get a positive selection of neutral when you need it.
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Cheers guys for the continued advice and wisdom. I need to get an M12 X 1.25 metric fine bolt so I can draw the primary shaft off. My car mechanic mate might have an actual slide hammer.
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Long engine mounting bolt is the correct thread. It's an ill wind that doesn't blow a bit of luck!
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Use the rear engine bolt and footrest as a make shift slide hammer. It really shouldn’t be tight. Worked for me.
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Crossed in the ether…
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Sorry I do not think I can help you as it's outside my limited knowledge.
Only question I would ask is was the gear selector drum/selector forks in the neutral position when you assembled the gearbox internals ?
I can't be sure if it was in neutral. The shift drum guide screw [the part that screws in from the top of the crankcase] that I have is the later version without the ball and spring. So there's nothing to fit into the detent on the drum.
If I remember correctly I fitted the neutral switch so it was obvious when the switch was in the neutral position but mine is a 400.
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To isolate the problem - ie, whether its the selector mechanism or the internal drum/forks/gears is the problem area, can you not remove the external selector mechanism and try to turn the drum with a a large adjustable pair of plyers (with suitable cloth protection on the drum) - you may need to turn the output shaft to help gear selection (mimiking the gearbox moving). If this works, you will know its the assembly of the external mechanism.
It may save you needlessly splitting the cases.
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Don't rush into splitting the crankcase take your time & try suggestion on here. I was going to taking my cam cover off as I was sure I had made a mistake when setting the valve timing - as it turned out and thanks to advice here I could check valve timing it was okay. Weeks later I found a photo on my project site showing all was OK.
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To isolate the problem - ie, whether its the selector mechanism or the internal drum/forks/gears is the problem area, can you not remove the external selector mechanism and try to turn the drum/plates/pins assembly with a large adjustable pair of plyers (with suitable cloth protection on the drum selector mechanism plates) - you may need to turn the output shaft to help gear selection (mimiking the gearbox moving). If this works, you will know its the assembly of the external mechanism.
It may save you needlessly splitting the cases.
Sent from my moto g(50) using Tapatalk
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The drum is in the wrong position, it’s almost certainly got one of the dowel pins locating the forks stuck down a slot in the drum instead of inside the track where it supposed to run. As you can’t see or get to these pins without splitting the cases you’re going to have to do that.
Learn the lesson, always check for gear selection before you seal the cases. You made a mistake but luckily you spotted it before you put the engine back in the frame, it could have been a bitter lesson to learn but it wasn’t that bad in the end.
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Good afternoon guys, found the problem. The 4th gear on the layshaft was on the wrong way round!
Because the engine was disassembled when I bought it, I just put the layshaft assembly in as I found it in the box. At some point in the past, the previous owner must have taken off the 4th gear and put it back on the wrong way. Anyway, I can now put the crankcase halves back together.
This leads me on to another question. Do you apply gasket sealant to the big end-bearing joint faces? The ones that house 2, 3 and 4 main bearings? I didn't the first time I assembled it but was thinking it might need it?
Cheers,
JB
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Do you apply gasket sealant to the big end-bearing joint faces? The ones that house 2, 3 and 4 main bearings?
No they should be dry and clean, that's all. My CB750 crank was completely ruined by a previous owner painting the cases all over, including behind the shells. The tolerances are very fine, after painting they were zero or less, ruining the crank and shells.
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Is that correct? My original and unmolested 550 F2 had cement that I removed with acetone. Just the merest suggestion of goo, just like on the crank case surfaces, but it was there all the same!
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Do you apply gasket sealant to the big end-bearing joint faces? The ones that house 2, 3 and 4 main bearings?
No they should be dry and clean, that's all. My CB750 crank was completely ruined by a previous owner painting the cases all over, including behind the shells. The tolerances are very fine, after painting they were zero or less, ruining the crank and shells.
I think you are referring to the outcome of something else Dave. He was asking if he should put Hondabond on all the machined mating surfaces of the crank cases, not just around the main edges of the crank cases.
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Is that correct? My original and unmolested 550 F2 had cement that I removed with acetone. Just the merest suggestion of goo, just like on the crank case surfaces, but it was there all the same!
Yes, you are correct.
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So Hondabond on all mating surfaces?
Cheers, JB
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Before you put the case together have you checked you can select all the gears? And does the cutout in the drum now mate up with the roller on the positive selection mechanism when it's in neutral? It should do or there's something else wrong somewhere.
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So Hondabond on all mating surfaces?
Cheers, JB
Yes, all mating surfaces. I believe Honda originally put the sealent on with a roller, or the cases went through a machine that rolled the goo on very, very sparingly. That's what you need to replicate.
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Before you put the case together have you checked you can select all the gears? And does the cutout in the drum now mate up with the roller on the positive selection mechanism when it's in neutral? It should do or there's something else wrong somewhere.
I've checked and all good now thanks Oddjob. Won't have time to reassemble the cases as I've got a bloke off on holiday leave so I've got to do some actual work on the shopfloor!