The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: alanp on 05.06. 2012 15:22

Title: Extracting the crankshaft pinion gear
Post by: alanp on 05.06. 2012 15:22
Just thought I'd mention that the small pinion gear on the crankshaft timing side can be a very tight fit (it's supposed to be) and a special extractor may be needed to get it off. Normal extractors can't get behind the gear to pull it off, especially those of us with the SRM crank end feed system which has a small tube in the crank end which prevents using an extractor's screw on the crank end without damaging the tube. However, if you warm the gear up carefully with say a small gas soldering flame you can lever the gear off using screwdrivers in the gears machined slots.
PS  Don't forget that the pump drive spiral gear on the end of the crank has a LH thread before you get to the crank pinion.

Alan
Title: Re: Extracting the crankshaft pinion gear
Post by: bsa-bill on 05.06. 2012 16:51
I have a strange shaped tool, it has a curved claw on one end and a wide (inch and half maybe) dished pry come scraper on the other, think it came from Halfords or maybe a make weight from screwfix.
Anyway the dished bit is shallow enough and thin enough to slip behind the pinion and  then you can apply "gentle force" to the rear of the pinion while giving the crank end a tap with a plastic hammer.
Sounds horrific but I've done it about three times without any problems
Title: Re: Extracting the crankshaft pinion gear
Post by: A10Boy on 06.06. 2012 10:28
Or, if you are splitting the crankcases, you dont need to remove it first. Just leave it on and knock the crankshaft through the pinion.
Title: Re: Extracting the crankshaft pinion gear
Post by: Topdad on 06.06. 2012 15:12






"Or, if you are splitting the crankcases, you dont need to remove it first. Just leave it on and knock the crankshaft trough the pinion."

but not with the SRM conversion ,BobH


Title: Re: Extracting the crankshaft pinion gear
Post by: A10Boy on 06.06. 2012 20:47
Yes, well obviously you don't hit the end feed quill if you have the SRM conversion. But you can still split the cases and pull the crank out.
Title: Re: Extracting the crankshaft pinion gear
Post by: muskrat on 07.06. 2012 11:17
 Tried that about 30 years ago. The pinion damaged the bush. Make a puller and get it off first.
Cheers
Title: Re: Extracting the crankshaft pinion gear
Post by: alanp on 07.06. 2012 11:47
Yes, well obviously you don't hit the end feed quill if you have the SRM conversion. But you can still split the cases and pull the crank out.

With the SRM conversion the gear must be removed before you can take the crank out of the cases since it wont pass through the SRM bearing.
Title: Re: Extracting the crankshaft pinion gear
Post by: A10Boy on 07.06. 2012 13:12
I was coming from the context of a full engine rebuild including a new bush and not specifically regarding the SRM conversion.

I've never stripped an engine with the SRM conversion but would have thought that the crank would pull through the bearing the same as with a bush, leaving the pinion behind. The bearing might be damaged but would be replaced anyway. I have stripped engines with the old bush many times, and if I'm doing a full rebuild, [and theres no other reason to split the cases], I dont care of the old bush is damaged as I am replacing it anyway, although I've never damaged one as I always fit hardwood wedges between the pinion and bush. I was merely offering that as a tip which saves dicking about for hours knocking your knuckles off with home made pullers and heath robinson levers.
Still what do I know?
Title: Re: Extracting the crankshaft pinion gear
Post by: bsa-bill on 07.06. 2012 14:41
Quote
Still what do I know?

I reckon you know quite a lot Andy, but my aesthetic designed pry bar come shoehorn was not designed by Heath Robinson I'll wager.
Nor have I ever lost any skin removing the crank pinion, I have only done about three and found each to be fairly easy to remove, perhaps they weren't on correct but there was never any sign to this effect on the crank.
Didn't take your mail to be offensive in any way, just throwing in the odd hap peth
Title: Re: Extracting the crankshaft pinion gear
Post by: metalflake11 on 07.05. 2018 20:26
I'm in the process of splitting my crank cases, S.R.M. Conversion. The crank pinion will not pass through the bearing, and it's not even a close thing.

 I'm doing it solely to replace the cam, so there are sometimes reasons to split them without a full rebuild of the bottom end.

I use a puller on the two flats. To protect the quill, I screw the oil pump drive back on, nut end first keeping the quill below flush with it. A flat piece of steel between that and the puller spike then protects it.

A good method if the pinion isn't absolutely welded to the crank.
Title: Re: Extracting the crankshaft pinion gear
Post by: chaterlea25 on 07.05. 2018 20:52
Hi All,
The ball bearing element that is part of the SRM combined bearing has a split inner race
The outer part of the race is held in place by a spacer and the timing gear, This must be dismantled to remove the crank
Metalflake, you can change the cam without removing the crank assembly
Are you up grading ? its bad news if a cam wears  *ex* its a sign of poor oil pressure,

This topic was covered in a thread some time ago where various owners posted pics of their versions of the puller

When I got my SR project the crank end was badly damaged by the dopey PO who tried to drive the crank through the bush, and wound up driving the bush out of the case  *eek*
Keep hammers away from cranks

John
Title: Re: Extracting the crankshaft pinion gear
Post by: metalflake11 on 07.05. 2018 21:09
The cam followers have score marks, but the cam may clean up. I doubt the oil pressure is low John, S.R.M. Pump and PRV, neither of which have covered more than 15-20,000 miles. A good sign is very clean magnets in the sump and oiltank. I think I may have run to long into winter with straight 40's, coupled with the rocker feed banjos only having the smaller holes in them. (I notice S.R.M no longer sell them, and only the larger holed variety.) The bike is high mileage now, so I'd expect some wear and tear.

I'll be checking oilways for blockages of some kind though. I'm having trouble splitting the cases though, and yes, I have taken the internal nut off!😃
Any suggestion on that please?
Title: Re: Extracting the crankshaft pinion gear
Post by: chaterlea25 on 08.05. 2018 00:20
Hi metalflake,
I would check the PRV, there have been reports on the plunger "galling" within the body and sticking (on Britbike)
I have not come across this problem myself though ?
What sealer was used on the cases? Some of the "yamabond" and the like make separation very difficult

What about making a "jacking jig" ?
Trace the primary case bolt holes onto a piece of steel plate make up some long studs, fix these into the case with locknuts and fit the plate over the studs with more nuts to push on the end of the drive side mainshaft / pull the drive side case ??

John
Title: aRe: Extracting the crankshaft pinion gear
Post by: metalflake11 on 08.05. 2018 00:58
Thanks John!.......No idea which sealant, S.R.M. Put them back together after the conversion over twenty years ago.
The PRV seems ok, but I'll double check now you mention that possibility.

Your 'puller' idea might yet be the only solution, and certainly far superior to bludgeoning things!

First things first though, I need to get to grips with the bearing. For some reason I've got two spacers behind the gear, one of which wont come off. When it does, does the ballrace come out John? This is the first time I've had to split it since the conversion.....Thanks for your time!
Title: Re: Extracting the crankshaft pinion gear
Post by: muskrat on 08.05. 2018 08:05
G'day mf11.
The SRM conversion is similar to mine. The inner race of the bearing is in two pieces. The outer race and rollers/balls are held in the case, the long part of the inner goes on the shaft before it's inserted into the case/bearing. Then the small part of the inner race is put on the shaft and is held in place by the pinion (srm version must have another spacer  *dunno*). So for the cases to split the pinion and the small inner race must be removed first.
I have split stubborn cases with a set up similar to the one John describes. Most two strokes need the cases split that way.
Cheers
Title: Re: Extracting the crankshaft pinion gear
Post by: BSA_54A10 on 08.05. 2018 10:20
We just did this job 4 times and found that a small bearing extractor could be clamped into the slots cut for the removal tool which of course
1) did not actually fit properly
2) broke the 2nd time we tried to use it.

With them on you can use a puller with a socket on the end of the shaft to protect the quill.
Came off so easy we were rather crnky about having wasted money on what was supposed to be a pinion puller.
Title: Re: Extracting the crankshaft pinion gear
Post by: metalflake11 on 08.05. 2018 13:43
Thanks for your help Muskie and John. ......The second 'spacer' was actually the outer ball race Muskie, so that sorted that one.

In the end I split the cases with a pair of spring compressors for car suspension. I unscrewed the claws and put them back on so they face outwards.  Using the outermost barrel studs to push against, and inside the sump, the two halves slid apart beautifully.