New to the forum

[DaveS1968]

Hi all, I've just picked up a near complete bike in bits, 1979 CB750f, I am new to these bikes and wondered if someone can tell me what this is as it looks broken to me

 

[Dave]

That's where the tachometer cable hooks to the engine and yeah, it looks broken. It should look like this.

 

[amc49]

X2...............if head cover is bolted down as it appears to be then yes probably broken. Could get complicated as that drive is machined into a cam holder cap. If cap itself broken then they are matched to heads in one assembly. No separate part available although depending on owner skills there may be a workaround.

More if needed.

 

[DaveS1968]

X2...............if head cover is bolted down as it appears to be then yes probably broken. Could get complicated as that drive is machined into a cam holder cap. If cap itself broken then they are matched to heads in one assembly. No separate part available although depending on owner skills there may be a workaround.

More if needed.

Oh no! That's sounds painful, what's the workaround ?

 

[amc49]

Pull it first to see the damage. If broken one finds another off junkyard engine, then you have to measure and plastigauge your way to making the new one fit without tearing cam up. The cam cap set is machined all at one time bolted down to the head which makes head and caps a custom fitted one-off part. Other assemblies will be close but not exact. While one might luck out to have one fit with no work, highly unlikely and you're basing the life of the engine on it.

Need to yank cover anyway, you may be missing half of what goes underneath it. Graverobbers and all that.

 

[DaveS1968]

Pull it first to see the damage. If broken one finds another off junkyard engine, then you have to measure and plastigauge your way to making the new one fit without tearing cam up. The cam cap set is machined all at one time bolted down to the head which makes head and caps a custom fitted one-off part. Other assemblies will be close but not exact. While one might luck out to have one fit with no work, highly unlikely and you're basing the life of the engine on it.

Need to yank cover anyway, you may be missing half of what goes underneath it. Graverobbers and all that.

Ok please bear with me as I am struggling to understand the implications of this. Do I need the thing to work other not having a speedo/ tachometer? Will I have another options for a speedo like an app or digital readout? Does it effect the running of the engine if I take it off altogether?

 

[DaveS1968]

Looks broke on the inside as I can see a rough metal edge on the left side

 

[DaveS1968]

This is what it's like with the cover off

 

[amc49]

Run it like that if you can accept having no tach. Need to plug the hole. Plenty filthy in there, engine may not last long anyway, I see what looks like scoring on cam lobe.