The BSA A7-A10 Forum

Technical => A7 & A10 Engine => Topic started by: tlmark on 12.03. 2017 14:03

Title: Top end strip
Post by: tlmark on 12.03. 2017 14:03
My plan had always been to try to fix some of the oil leaks and track down why the left cylinder would smoke, over the winter.
best laid plans and all that busy at work and a bad dose of the Flu which over 4 weeks later is still not gone.

Anyway so this weekend I started the top end strip and it looks like the exhaust valve is the culprit what do you guys think? 
Title: Re: Top end strip
Post by: edboy on 12.03. 2017 18:52
it looks like oil is blowing across from the pushrod tunnel to me.
Title: Re: Top end strip
Post by: Klaus on 12.03. 2017 20:56
Have a check at the valve guid, or a pistonring is brocken.
Your headgasket is one I would throw it to scap. It dont fit the bore realy good.
 I made my own gaskets of 0.8mm copper special for any singel barrel.
Title: Re: Top end strip
Post by: BSA_54A10 on 13.03. 2017 10:03
Inlets suck and exhausts blow so no the oil is not coming in the exhaust it is blowing out the exhaust & burning on the red hot valve.
Title: Re: Top end strip
Post by: Greybeard on 13.03. 2017 11:12
When I last looked inside my A10s head it looked rather like that. I put it down to too much use of lead additive/octane improver and too many short runs. I now do not use additive and I try to get the old girl hot, (also the motorcycle!)
Title: Re: Top end strip
Post by: tlmark on 14.03. 2017 11:19
Thank for the ideas Guys.

Some progress I've removed the suspect exhaust valve only to find the edge is damaged?
there is no evidence of it hitting anything on the head. I'll have to clean the piston crowns and check those but the damage is at an odd place?

Anyway so it's gonna need a new valve at least.
check the pix and see what you think?
Title: Re: Top end strip
Post by: muskrat on 14.03. 2017 11:44
G'day tl.
She's started to burn. The most common cause is the valve not seating properly. This can be caused by the tappet clearance being too tight or riding, lean fuel/air mix, retarded ignition. This all creates excess heat which wears the valve and seat till it leaks, then erodes the valve.
Might be time for a head job  *shh*
Cheers
Title: Re: Top end strip
Post by: tlmark on 14.03. 2017 12:51
Ha Ha yeah I'm thinking the same I have found some corresponding damage on the valve seat  *sad2*
Title: Re: Top end strip
Post by: coater87 on 14.03. 2017 19:31
 I always look at this kind of thing as opportunity.

 Done right, the head will be better than new and last a long time.

 Done "good enough for today" just means doing it again tomorrow. *sad2*

Lee
Title: Re: Top end strip
Post by: tlmark on 16.03. 2017 20:28
I have packed the head and shipped it of to SRM for look and Recommissioning.
I decided as newbe with classic bikes I should start with a clean slate
Title: Re: Top end strip
Post by: tlmark on 26.04. 2017 12:26
My head is back from SRM.  *wink2*

hopefully get to work on it this weekend
Title: Re: Top end strip
Post by: ralph on 26.04. 2017 23:28
My head is back from SRM.  *wink2*

hopefully get to work on it this weekend

gosh that looks tasty work. I think I'd be tempted to go another step and treat the engine to new rings. But you know their history...........
Title: Re: Top end strip
Post by: coater87 on 27.04. 2017 00:52
My head is back from SRM.  *wink2*

hopefully get to work on it this weekend

gosh that looks tasty work. I think I'd be tempted to go another step and treat the engine to new rings. But you know their history...........

 I second that. I would at least pull the cylinders and check the condition of the rings if you have any doubts at all. At this point it only costs a little time and a base gaskets..
Title: Re: Top end strip
Post by: tlmark on 28.04. 2017 11:43
I had the barrels off while I was waiting for the head to be finished and it all looks fine (fingers crossed)  ;)

Title: Re: Top end strip
Post by: TT John on 30.04. 2017 13:47
Don't forget to fit a new set of Solid copper rocker box gaskets when you re assemble the top end, still available from me at ?16 Plus p+p. Make it easy on yourself, I think I could write a song about that. *smile* *smile*

TTJohn
Title: Re: Top end strip
Post by: ralph on 01.05. 2017 09:50
Hi Mark, Sounds like you've got the job sorted.

Just had another look at your valve pics, and I have to say it does look like a rough edge, and a bit burred, as if a bit broke off?? It could of course be my eyes and its a bit of soot. *eek*
Title: Re: Top end strip
Post by: tlmark on 01.05. 2017 12:19
when I spoke to the guys at SRM we came to the conclusion that it may have had a blow up on the left pot.
if you look at the pistons the left one looks brand new, even more after I cleaned them up.
And we think maybe the previous owner either hadn't noticed the damaged valve or couldn't be bothered? As he was going to sell it on?

 
Title: Re: Top end strip
Post by: tlmark on 01.05. 2017 12:57
Sorry John I've already started reassembly.
Title: Re: Top end strip
Post by: TT John on 02.05. 2017 14:28
Looks nice *smile*
Title: Re: Top end strip
Post by: Coppernut on 03.05. 2017 01:15
If its not too impudent could you give me an idea of how much it cost to get it done I would like some idea as I too have a similar problem .
Title: Re: Top end strip
Post by: tlmark on 03.05. 2017 12:01
Hi Copper nut  no problem SRM charged me ?480.00 and that is a full rebuild everything new and unleaded proof. If I had wanted the head bead blasted it would have been another ?50.00, but I didn't want to lose the finish mine has.
Title: Re: Top end strip
Post by: Coppernut on 03.05. 2017 20:05
Thanks for the info great to be able to get a figure in order to cost out my rebuild.
 *smile*
Title: Re: Top end strip
Post by: tlmark on 06.05. 2017 12:24
Happy face here she started second kick and it sounded so much better than before few little bits to finish up then a test ride  *smile*
Title: Re: Top end strip
Post by: a10gf on 07.05. 2017 20:37
Hoping it'll be 100%.
& good topic \ pictures \ followup \ information. +1 good karma :O)