Have a 1330cc running 4 speed 4 syncro box, with foot off the clutch can hear knocking noise, with foot on clutch noise disappears. Pretty sure is going to be idler gear or input gear at fault. Any ideas on best way to set end float of idler or input gear once the gearbox is removed from engine?

For the idler, refit the flywheel housing to the gearbox with a new gasket. You can stick a feeler gauge down in there to check endfloat. Or, you can stick a dial gauge thru the idler gear's bearing boss in the gearbox casing.

I don't think it is endfloat.. mine does it too, if I idle it too slow.... and I've got new idler bearings and correct endfloat on both it and the primary gear.

Actually, the `knocking noise' (aka primary gear rattle) is common on 1275 or bigger motors running lumpy cams or light flywheels. It's just backlash between the gear teeth, combined with rough running. Worse when hot because the oil is thinner.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Yep thats true Min does that noise as well but Like drmini said only when the oil is hot and thinner.

It use to do iton my old motor as well and it went like that for 7 years and no probs with the idler gear.

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I've Got One
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A Bloody Mini

1970 Mini K, 1380cc, 1.75 HIF SU, 30 70 Cam, 2" Zorts
1969 Mini K, Stock Standard and Orginal. (Slow as Hell)

Have you considered the clutch release bearing as being the source of your noise?

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Master of the obvious - Prophet of the past

Isn't clutch release bearing when your foot is on the clutch, not off?
When my idler gear went it sounded like I had straight cut gears for the day before it went bang. It physically had no bearings left, but it made no noise at idle, only a little bit in 3rd and a lot in 4th. It was so bad that the idler gear had eaten through the clutch housing and shed five teeth into the sump!

Checking idler gear end float is easy as Dr Mini points out, but make sure you get the primary gear correct as well, especially on helical drop gears. My primary gear was at about 20 thou!

Anto.

Thanks guys, I built the engine myself (1st time) and, know that the primary gear enlfloat is spot on, i replaced the bearing in the clutch housing that the idler shaft runs in, but missed out on checking clearances on the idler gear. Yes the idle is rough because it does have quite a lumpy cam in it, throwout bearing is new. Has only done 6000 miles and has been the same noise the entire time. Might as well just drive it till it stops!!!!

I now use Castrol Formula R, 25W/50. Same as the old GP50.... it's good stuff.
I used to use Penrite HPR30 (20W/60), but found it tends to sludge up the rocker gear etc, even though I changed it every 1500 miles.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Dr, I also fount that with my "controlled leak" (read: Turbo bearing..) it didnt control oil pressure as well as my Pennzoil GT
Just changed to Valvoline to try that though... Will let you know in about 1500 Miles !

Cheers
J

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Yeah will try that castrol stuff, I used to use GP50 years ago but havnt been able to find it anywhere. I am using penzoil streetmachine 25w/50 at the momment, its more suited to 6's and 8's but thought would give it a try, says good for engines with higher load so thought with the gearbox and diff running it might b alright. Next oil change will give that castrol formula r a shot.

Just watch you get the RIGHT Formula R.. there's 4 different ones... (marketing- ho hum)
Use the 25W/50- its blurb sez for Street Machines...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Cool, no worries will keep my eye out for that. See if it shuts any of this geartrain noise up?

Only idle rattle in mine at the moment is the radiator in its shroud... so I idle it at 1500...

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.