The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: WozzA on 30.09. 2014 12:33

Title: Kaboooooom..
Post by: WozzA on 30.09. 2014 12:33
With Spring in the air a couple of weeks ago I decided I needed something or another
& would take advantage of the sunshine to ride the Beeza. 
About 10 minutes into the ride I was cruzzzzing along at a very respectable 70-80Kms   *whistle*
when out of the blue .. BOOOOM...  she back fires & splutters to a hault.   *doh*

I quickly check plug leads are on...
Fuel is on...
try to restart...  nope...  just a back fire again..  ahhh   haaaa.... TIMING says me...
so I push her into a drive way & ask can I leave her there while I go home to get my recovery vehicle.. ( Rescue One )    ::hh::

A couple of days later after checking for spark @ the plugs, points & maggy, fuel, I did a compression test...
Ohhhhh   Nooooo..... ZILCH, NADA, NOTHING on the Left Hand pot...    *dunno*

I removed the L/H exhaust header to discover the exhaust valve was stuck open..

After confering with Musky & Brian ( THANKS lads ), it became obvious that the valve had nipped up in the guide...
Due to heat expantion of the valve stem... & not enough play in the guide.

Simple fix says me...   hahahaa.... nothing's simple...   it appears that the valve must have just kissed the piston & is bent.
( possibly during one of the 3,428 times when I tried kicking it over )    *angry*

Luckly a new valve was obtainable from Modak...

I took the head back to the company which did the valve seat grinds, & reamed the guides last time, to show them the damage,
they were very understanding & agreed that there was not enough clearance in the guides, so would re-ream ALL guides again for free.

Now for the rebuild .... again...

Soooo... moral of this story is...sometimes a little loose is better than too tight...  Size DOES matter...   *lol*
Title: Re: Kaboooooom..
Post by: Greybeard on 30.09. 2014 12:43
 *sad2*
Title: Re: Kaboooooom..
Post by: a10gf on 30.09. 2014 15:10
 *conf* small detail (a few thou's) making big problem. Thanks for the report.
With a little luck it'll 'only' be a matter of a new valve (and the (uninvited) work).
Title: Re: Kaboooooom..
Post by: morris on 30.09. 2014 17:21
Bugger Wozza...
Don't suit me neither. I'm rebuilding the plunger with new valves... scares me a bit now...
Title: Re: Kaboooooom..
Post by: Topdad on 30.09. 2014 17:55
That's a real pian Wozza, while you 've got it stripped check therocker oil feed , I did for an ex valve 5 miles into my first ride, ,turned out to be the feed full of crap that I'd missed. a new valve and a proper clean out sorted it, best of luck mate ,bob
Title: Re: Kaboooooom..
Post by: WozzA on 01.10. 2014 07:25
She LIVES...    *smile*   
I spent a couple of hours in the shed today & fired her up after a couple of kicks..
Now to find out why the primary clicks when the clutch is out while she's up on the lift..
*bright idea* My guess is a DODGY joining link..   
Title: Re: Kaboooooom..
Post by: WozzA on 07.10. 2014 10:16
Bad news...  after the rebuild I replaced the 1/2 joining link on the primary chain that was clicking.
& took her for a shake down run. I got as far as the bottom of the hill near my place when she
started running rough & spluttered to a stop...   *doh*
You Ba$#@%*...  I had to push her all the way up the hill to her home again..
I've just spent 2 days going over the timing, maggy, points, & carb,
I've had the timing side cover off so many times I can do it blind folded..  *whistle*

Now for the good news..  After spitting the dummy & leaving her in the shed for a couple of days
while I unscramble my brains & thinking of selling this piece of Pommy $h#@ cheap...
I remembered I took out the NEW spark plugs I had just put in,
& replaced them with a couple of old plugs I was having trouble with while I was working on the head..   *problem*

I just replaced the old plugs with new ones & now she's a runner again...   *wink2*

I should have known that this piece of fine British craftsmanship wouldn't let me down..
( till next time )   *red*
Title: Re: Kaboooooom..
Post by: Topdad on 07.10. 2014 10:40
naughty,naughty Wozza, she'll get her own back on you at some stage !! ;) ,why does there always have to be a hill that you have to push her up , my first trip out some 10 yrs ago she died in Seaforth and I lived in Waterloo about 5 miles boy was I knackered when I got her home and I feel that more than a few curses and threats were issued including a 4lb hammer etc soon got over it particularly when I had to admit it was my stupidity that caused the problem !! Glad you've got her sorted regards Bob.
Title: Re: Kaboooooom..
Post by: muskrat on 07.10. 2014 11:23
Bugga, I was hoping of picking her up cheap.
It's always something stupid.
Cheers