The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: tlmark on 12.03. 2017 14:03
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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?
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it looks like oil is blowing across from the pushrod tunnel to me.
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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.
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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.
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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!)
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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?
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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
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Ha Ha yeah I'm thinking the same I have found some corresponding damage on the valve seat *sad2*
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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
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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
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My head is back from SRM. *wink2*
hopefully get to work on it this weekend
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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...........
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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..
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I had the barrels off while I was waiting for the head to be finished and it all looks fine (fingers crossed) ;)
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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
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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*
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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?
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Sorry John I've already started reassembly.
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Looks nice *smile*
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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 .
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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.
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Thanks for the info great to be able to get a figure in order to cost out my rebuild.
*smile*
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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*
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Hoping it'll be 100%.
& good topic \ pictures \ followup \ information. +1 good karma :O)