Half time pinion.


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JM's motor started to get noisy, so off with the timing cover.
With some good look noticed the 1/2 time pinion was moving on the
shaft. Found that the key was not a good fit in the 1/2 time pinion.
Made up stepped key. it only needed 5 thou step. now the slightly disconcerting bit. On tightening the E80 nut I have more thread proud of the nut, or more accurately I think I have. Also the 1/2 time pinion is slightly further back than the idler, again I feel it is. The E80 nut tightened up OK.
The timing side noise is back to it's usual not too bad self.
Some one tell me I am imagining things. John.

Len Matthews

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Half time pinion mystery

Hello John, I had dealings with a Comet engine where the H/T pinion was too far inboard. I had to part the crankcase to find out why. Initially, nothing seemed wrong until I pulled the bearings off the drive side mainshaft. The boss on the flywheel where the roller bearing abuts was so badly worn that the whole crank assembly was misaligned to the left. Trapped under the bearing was a heap of paper-thin shims;over a dozen of them-I counted! The answer was to make up a steel washer of the appropriate thickness to restore the situation. I hope you not faced with the problem. Len.

captain vincent

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Don,t worry about it John,senior Vincent moment,s occur more frequently at your age.Timing spindles fall out at the same time as your teeth!


Big Red Hunter


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Half time pinoin

Dear Len,
Thanks for that, the motor was built by myself, so I know there are no shims. The pinion nut was slack so it is possible that the boss is worn.
It is a little worrying but the motor is still quiet and it has just done 1200 miles to the Hever without missing a beat.
Flattered to see that your photo has me perched on the Steib mudguard.
I will ignore captain Vincent!


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Half time pinion

Hi John,Wish i had a half time pinoin,must be a new mod or something. :)
I´ve had the same problem on my twin,caused by not tightening E 80 up enough,noticed"the noise" after 500 miles or so.
You mention that it was necessary to make a 5 thou oversized E81.On mine,the key wore,and not the keyway/s(the key being much softer).I fitted a new key,and everything was tight on the mainshaft again.Maybe worth closer investigation methinks.
As you´ve correctly deduced yourself,the flywheel boss (timing side) is almost certainly worn,as nothing else in the line of gubbins on the timing side mainshaft is softer than the flywheel boss,and nothing else can account for the increased play/extra thread/s now showing past E80.
As long as the primary side(PD7) is still F.T,crankshaft alignment will not be an issue.
You´ve got two problems.
1)Swarf (relatively small particles,probably all in the UFM by now,so out of harms way:eek:)
2)A slightly misaligned half time pinion (ET94 & ET92 are still running within there rings/tracks,as the rollers are shorter than the rings are wide (OP31-uninteresting as long as it´s roughly in the middle of the plunger).
I shimmed mine back out flush with the large idler (but then i´m probably an anal retentive,and just wanted all me timing gears running flush).
Shim between ET49 & ET94, or ET94 &OP31 it doesn´t really matter(if you´re lucky,you can get OP31 through the ring from ET94 and so shim between OP31 & ET92).
I can´t quite recall where i shimmed,but there were issues with slot/s in the shim for key/s/way/s,and/or clearance issues with the oil pump plunger when using a large dia shim.
Haven´t had any problems (with this job at least,;))for over six years.
commonsense prevails.
Tip: When tightening ET80 OR PD7 (PD7/2 in my case)
1)Use loctite,fresh,or at least in-date(amazing how many people buy a big bottle of the stuff,don´t realize that its got a shelf life,and keep it in service for 20 odd years.)
2)I use a specially formed (corners rounded off to fit the teeth,and short enough not to touch the primary chain)piece of square aluminium bar,placed between the engine and clutch sprockets(copied from andy everett at the northwest german rally in 2001).
With steadily applied pressure(don´t bounce/jerk or hammer)tighten to F.T (or untill yer shoulders pop)(i use a 40cm long ratchet handle)(ask me for a conversion to inches,i dare ya).With this method,i´ve never stripped a thread,broken a tooth off a sprocket,or bent anything.
P.s If your shaped like Garth,and youré tightening up the halftime E80 with this method,try not to twist the flywheels :rolleyes:,theres a good chap.
Question,"Why did i have this problem in the first place??"
I couldn´t be bothered to remove the primary cover,clutch,other associated gubbins in order to use my "specially formed(corners rounded off to fit the teeth,and short enough so as not to touch the primary chain ,copied from andy everett at the 2001 west german rally) piece of square aluminium bar"!!!.
Lesson learned methinks.