The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Thrang on 22.04. 2016 17:23
-
Afternoon all,
After getting a mate who's into his vintage cars take a look at the Mag on my SS and had it declared as 'shagged out' I made the awful mistake of following the Hayens manual... Yes I know, I should have known better.
Anyway the manual said remove the timing cover so I assumed they meant the inner as well, since the Manual said nothing about the removing the crank driving gear for the dynamo I just displaced the dyno slipped off the chain and removed the cover taking with it the crank gear, which of course means the crank timing will be screwed up, not a problem as I can set TDC and reassemble, if I can remove the dynamo gear, so does it just pull from the shaft or is their any thing odd about it that I should know? I've looked in the book and its says nothing, and I don't want to drop another bollock. Anyway on the bight side the Mag is out and will off the repair man in the morning for a full refurb. I'm not that bothered about the gear coming free as I intended to do the valve timing at the same time as fitting an SRM oil pump, sump filter screen and oil valve. (I'll keep the original parts in case I sell the bike in the future.)
My other question is there are a few stress fracture marks on a 3 of the fastener fixings in the crank cases which have probably been caused by over tightening over the outer covers in the past, any suggestions for a repair? I was thinking locktite run into the cracks as a temporary fix until I strip the motor down and get a more permanent repair done, probably a weld up re-drill holes and fit some helecoils.
Cheers
Tony
Cheers Tony
-
Looks like a nasty crack below the cam and mag gear, but not beyond repair I guess.
Is the thread in the hole still ok? It looks to me as someone tried to force a bigger bolt in?
Some advise though, when you have it welded up and need to re-drill the hole, use the inner cover holes as a guide to stay perfectly square to the case. The bolts are fairly long and the cover holes are tight. Drill the hole a little skew and the bolt won't go in.
-
Hi thrang, as the timing case gears are have alignment marks you only have to do the timing if you remove the gear from the mag, which you had to do anyway, you will have remove the Dynamo gear to line up the marks. The dreaded Haynes manual shows these marks.
If you do not line up the marks your cam timing will be wrong.
I completely stripped my motor down once without removing the mag so I could avoid re doing the timing as it is a real pain with my BTH electronic mag to get it right (long story, it should be easy but isn't).
Personally I would try to avoid welding the crank cases if at possible, maybe just put it back together and don't tighten the affected screws too much, maybe use a small torque wrench to ensure you achieve a low and even tightness *dunno*
It is possible to "split" bolt holes in cases by not cleaning out oil that has got down inside the hole which can cause an extremely high hydraulic pressure to occur when the screw is done up, it's more of a problem on japanese bikes but I guess could happen on Brits. The other mistake is use screws that are too long (can happen if the cover has various length screws and they get mixed up) it's worth checking you do not make either of those mistakes by test fitting each screw before fitting the cover.
-
I go with KiwiGF on cleaning the bolt holes. Just finished checking the timing side and found no dynamo chain lubrication. So now the chain is running in graphite grease. I decided to check all the threaded holes and found all of them had a build up of sludge from over the years, a quick clean out with a tap an all is now well. Can't beat a bit of inspection now and then.
-
Thanks for the advice folks!
I was going to clean everything out before I put it back together as I've had that hydraulic cracking happen on Japanese stuff. Although I could get away with light torquing, a couple of the cracks are so bad that I'd be worried about vibration splitting them off when in motion and then getting taken into the gear train, so I'm going to have to do something with them.
When I removed the cover/s I punched the hole pattern in an cardboard box, and inserted the fasteners into the same place as the bike on the box so I can't muddle up what went where.
I removed the dynamo drive with a puller and got it out undamaged but its pretty clear someone in the past had removed it with a hammer and a leaver.
Although the bike cosmetically is almost perfect, it's pretty clear that who ever worked on the motor was a bit ham fisted, rounded fasteners, buckled screw tops everywhere I have looked. They also appear to have been somewhat lazy when it comes wiring detail, (twist and tape) to the point that it makes my first attempt at building a loom as a teen on my FS1E look professional.
-
bitter experience tells me that putting it back like it came apart sometimes is not enough....you could perpetuate the previous owners mistakes...
Anyway, I'd be very interested to know how you fix the damaged holes so please let us know how you did it.
-
I was thinking about cleaning and degreasing the two badly damaged ones and then running a bead of super-glue into the crack as a temporary fix. A a small blob of medium strength locktite on the bolts and a careful torque on reassembly, should hold everything in place for the summer so I can at least do the Lakes run on her. Then next winter I'll strip the motor and get the damaged fixtures TIG welded and re-bored so I can fit helicoils.
As a bodge I know this superglue 'bandage' will work as I've done the same on an 80GS Beemer rocker box cover stud holes and it held together from the site of my prang near Tata in southern Morocco all the way back to Sunderland, more than 250 miles of which was done off road or on rough tracks.
-
As you removed the timing cover with the alternator sprocket still attached the timing gear marks on the pinion are not visible.
Once you remove the sprocket and pull the sprocket off (can be a pain in the proverbial as has a good taper - so typically heat sprocket) you'll see the pinion timing gears and be able to set the cam timing easily. The pinion goes on before the inner timing cover.
Looks remarkably clean in there! I've seen worse, cracks yes but havent broken off!
I'd echo the run a tap up all the threads to clean out any gunk
and if the threads hold, then simply assemble without excess tightening.
Not over tightening is a good recommendation anyway. People often do more harm than good trying to get things tight.
-
(sound of a robot) WARNING, WARNING WILL ROBINSON. Do not turn the crank or cam pinion without that pinion in place. You may bend a valve. Hopefully you haven't so remove the sprocket and replace the pinion. Sometimes the cam can move due to the valve spring pressure but not far (1-3 teeth). You will need to do a tooth count to get the marks lined up without rotating the crank.
Cheers
-
WARNING, WARNING WILL ROBINSON.
Nice one, I remember them well.
and if by chance someone had a micro moment of forgetfulnesses and was not sure, what is the best way to check a valve for straight, I OOPS someone may have just changed the valves to be sure ;)
-
If a different cover can't be had, and your not comfortable attempting a tig weld...
You could always try the capillary lock tite after you build up around the cracks with as much JB weld as you can pack in without interference.
I know of quite a few cases that are half alloy, half JB by weight. Sometimes the stuff works miracles.
-
Thanks for the warning Muskrat. I got a full gasket kit this morning from TMS, and I marked the crankcases with permanent marker before I removed the mag, so I know where the cam drive is meant to be. Since I have not moved the crank hopefully when I put the gear back in (tomorrow evening weather permitting) everything should line up. If not I'll just pull the head and set everything back to TDC.
I'm not bothered by TIG welding Coater and am pretty confident I can do the repair myself, but if once I have the cases split and can take a closer look at it, I'd rather not risk it, I know a bloke who welds Submarines at the Barrow yard who can do it for me. I'm gusessing JB weld, is plastic metal bodging goo.
-
. I'm gusessing JB weld, is plastic metal bodging goo.
You would be guessing wrong.
JB weld is nothing more than an epoxy that dries nearly to the color of aluminum and does a great job of sealing oil leaks like the kind that comes from cracked cases.
But I think that being an easy to source case, the best bet would be a replacement.
If it was numbered case from a war years civilian knucklehead, it would be worth the time and effort to try and save it.