Author Topic: bsa a10 650..the problem child !  (Read 13133 times)

Offline a10sausage

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Re: bsa a10 650..the problem child !
« Reply #15 on: 13.06. 2010 22:01 »
i will try a hotter set of plugs that may work,i still have this horrible feeling about the valves though!
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1959 bsa bantam d1
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Online chaterlea25

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Re: bsa a10 650..the problem child !
« Reply #16 on: 13.06. 2010 22:09 »
Hi Andy
A frustrating problem indeed????
When the bike cuts out, try gently kicking it over and see if the compression is good
Also check the oil feed to the cylinder head, the holes in the feed bolts are easily blocked!!
It would seem that the bike has not been used much since the work was done on it, have you contact with the previous owner? did he have the same problems
If the bike was lying idle did you clean out the oiltank and sump filter before running it??
if there was sludge it might have blocked the head oil feed, leading to sticky valves

Check also the battery voltage the electronics are sensitive to high or low voltage???

HTH
John O R
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Offline a10sausage

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Re: bsa a10 650..the problem child !
« Reply #17 on: 13.06. 2010 22:20 »
hi..i bought the bike from a friend and i knew its history..i bought it knowing about the fault..i just liked the bike so much and wanted to sort it out..i will remove the rocker oil feed bolts tomorow,i have another high oil delivery set somewhere in the garage with enlarged holes...i will fit these if i can find them and see how we get on..thanks for the help..ps the bike runs an external oil filter and i do know that the oil has been changed very regular 
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1959 bsa bantam d1
1956 ariel huntmaster
1922 triumph model h
1930 sunbeam model 8
1936 bsa q21 500 bluestar
1939 velocette mac
1975 honda cb750
2013 victory vegas

Offline wilko

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Re: bsa a10 650..the problem child !
« Reply #18 on: 14.06. 2010 02:43 »
Next time you test and it starts to cutout, immediately shut off fuel and remove the bowl cover Then see how much fuel is  in it. That way fuel can't leach into it in the time span it's taken to  remove it.You are checking the top banjo screen for filth aren't you?
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Offline wilko

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Re: bsa a10 650..the problem child !
« Reply #19 on: 14.06. 2010 02:45 »
By the way, can i have your knackered maggy!!
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Online RichardL

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Re: bsa a10 650..the problem child !
« Reply #20 on: 14.06. 2010 02:45 »
This sounds like a heat build-up problem. And after everything you have done its probably not going to be an easy to find one either....Is the petrol pipe routed too close to the the engine and its picking up heat?

I zoomed way in on your photo. Adding to what Lee said, it appears that your fuel line is running between the slide chamber of the carb and the cyclinder head. Is this correct? This is a hot location. Moreover, it appears that your fuel line is covered in stainless braid. The stainless will retain, transmit and spread heat much more efficiently than rubber. If rubber is near heat that doesn't actually melt it, it will not conduct or hold it well. Now, maybe a heated fuel line isn't the issue, but if it is a possibility, it seems that it would be encouraged by the apparent routing.

Richard L.
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Offline Rocket Racer

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Re: bsa a10 650..the problem child !
« Reply #21 on: 14.06. 2010 05:21 »
you mention running consistently above 40mph, does it actually rev out nicely in the lower gears or is the problem effectively limiting speed and revs even for a short sharp blast?

Going back to your fuel flow did you do a decent test of a litre or so. A blocked fuel cap breather can flow well initially then quietly pressurises the tank. When you stop this can then equalise back to normal and at lower revs the issue doesnt arise.



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A good rider periodically checks all nuts and bolts with a spanner to see that they are tight - Instruction Manual for BSA B series, p46, para 2.
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Online Brian

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Re: bsa a10 650..the problem child !
« Reply #22 on: 14.06. 2010 06:42 »
Afternoon Andy,

Firstly there is nothing wrong with magneto's or monobloc carbies.

Now to your problem, it is sounding like a sticky valve. You have tried two different ignitions, maggy and electronic and it made no difference. You have tried two different carbies and that made no difference.

I gather this bike has had this problem since it was asembled. If it was starving for fuel then you would expect it to just die, not backfire etc. The fact that it starts to miss and then backfires and stops makes me think it could well be a a valve, the only small doubt here is that I would expect it to let a pushrod jump out but yours does not seem to do that.

The next step is to take the head off, at least this doesnt cost much. If its a solid headgasket then re-anneal it and use it again so a couple of rocker box gaskets is all that is needed. So take the head off and drop the valves out and see how much clearance they have. As to the right clearance its hard with valves to quote any figure but lift the valves off their seats and they should move side to side about .020". If they are a nice slide fit with no sideways movement then they are too tight.

Once this is sorted you will have a very nice bike, it looks good.   PS. Do not fit oil feed bolts with larger holes, stick with the correct ones that only have the small hole in them. The ones with big holes are drain bolts from the B series BSA's.
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Offline a10sausage

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Re: bsa a10 650..the problem child !
« Reply #23 on: 14.06. 2010 11:53 »
thanks all for your help...heres just confirm...it has run two different carbs...two different fuel caps...two ignition systems...two sets of fuel lines...filter is clean on to monobloc..the bike runs great for first few miles..revs out in all gears...lovely and smooth..loads of power...then when it gets hot after you give a good load of throttle it misfires and sometimes backfires...and just cuts out, just like somebody had flicked a switch..as quick as that....i think brian might and a few more of the helpful forum with the valve problem..one thing i did not mention is that the bike was pinking when the previous owner bought it,we solved this by setting the timing correct.

i am just wondering...would a run through of slick 50 coat the valve stem and guides as this product sells it self on reducing heat.....see below.just to save removing the head

Slick 50® Advanced Formula Engine Treatment

Slick 50® Advanced Formula Engine Treatment combines Slick 50® Protection Chemistry with a fully formulated 10W-30 motor oil to provide protection against friction and heat. Slick 50® Advanced Formula Engine Treatment is compatible with all types of motor oil, safe for all automotive gasoline engines and will not void manufacturers' warranties.

Overall, Slick 50® Advanced Formula Engine Treatment:

Contains unique and proprietary Slick 50® Protection Chemistry
Protects against friction and heat
Will not cause corrosion of engine components
Comes with a 50,000 Mile Engine Limited Warranty
Available Size: 32 fl. oz. bottle

cheers andy

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1959 bsa bantam d1
1956 ariel huntmaster
1922 triumph model h
1930 sunbeam model 8
1936 bsa q21 500 bluestar
1939 velocette mac
1975 honda cb750
2013 victory vegas

Offline andy2565

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Re: bsa a10 650..the problem child !
« Reply #24 on: 14.06. 2010 12:09 »
i didnt mean to offend the monoblock users sorry !
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Offline MG

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Re: bsa a10 650..the problem child !
« Reply #25 on: 14.06. 2010 12:10 »
Andy,

Your description sounds very much like a sticking valve indeed.
If it turns out to be so, you should definitely take the head off and cure the cause, instead of treating the symptoms with some "miracle stuff".
A sticking valve could have caused damage to the pushrods or rockers, even the surface of the camshaft and/or follower COULD have suffered. I personally would even pull the barrels off and check the cams and followers.
A quite common cause for sticking valves can be a leaky valve seat, allowing the hot exhaust gas to heat the valve stem, which will finally lead to a burnt valve any way.
If the oil supply to the rockerbox has been cut off, the rocker arms and shafts should be inspected either.
In case the valve guides have been made too tight, giving them a little hone will cure the problem for ever, and nothing else will.

However, I'd rather invest one or two days of work and some gaskets now to sort it out and finally get it right than taking the risk of serious subsequent damage.

Just my 2p worth.

Cheers, Markus
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Offline mike667

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Re: bsa a10 650..the problem child !
« Reply #26 on: 14.06. 2010 12:15 »
i think the guy that invented that stuff is pretty "slick" how he can get $50 for his product that is of very questionable utility.

I like the idea of looking at the compression when the bike conks out -  if it is indeed a sticky valve  one would expect the compression to be off in the offending cylinder - have you check'd it out-

 markus idea of the heading coming off might tell you a lot for only a few hrs of work too

no doubt it its going to be a small matterv - once remedied you have a great bike
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Online RichardL

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Re: bsa a10 650..the problem child !
« Reply #27 on: 14.06. 2010 13:00 »
As to the right clearance its hard with valves to quote any figure but lift the valves off their seats and they should move side to side about .020". If they are a nice slide fit with no sideways movement then they are too tight.

First, let me say that I am trying to learn as much about this as Andy, or anybody else, is. It's an interesting and important topic.  

My question is, should the clearance test suggested by Brian be applied to either steel or bronze guides. I'm sure the bronze guides have a greated coefficient of expansion. Would that not make them looser as heat builds?

EDIT: Ah! but the valve stem probably gets a lot hotter than the guide. Correct?

Richard L.
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Online muskrat

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Re: bsa a10 650..the problem child !
« Reply #28 on: 14.06. 2010 13:21 »
G'day all.
               the problem sounds just like one I had when first got the cafe on the road. It too was pinging and getting very hot and would play up and cut out after 5-10 miles. Let it cool for a while and go again.
Turned out it got that hot that the valve clearances closed up enough to prop open the ex valves. Increased clearances to racing spec, solved. Richen mixture (a lot) and hotter plugs, pinging solved.
Andy try opening up the valve clearances a few thou and try that. If that helps then try to cool things down by richening up the carb and advancing the timing back to about 34 degrees.
Cheers
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Offline MG

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Re: bsa a10 650..the problem child !
« Reply #29 on: 14.06. 2010 14:15 »
Quote
Turned out it got that hot that the valve clearances closed up enough to prop open the ex valves. Increased clearances to racing spec.

That would explain why the push rod didn't jump out.
For a Flash in standard tune (I assume it is?) with the valve clearance set correctly this would mean that the carb setup must be on the extremely lean side (or ignition still is too far advanced).

Andy, can you tell us what your carb setup (main jet, needle jet, needle position) and ignition timing is?


Quote
My question is, should the clearance test suggested by Brian be applied to either steel or bronze guides. I'm sure the bronze guides have a greated coefficient of expansion. Would that not make them looser as heat builds?

First of all, valve guides are made from cast iron by centrifugal casting. Steel doesn't have the necessary emergency running properties (the carbon in the cast iron acts as a solid lubricant, especially important when used with valve stem seals)
You are right, the bronze guide will expand more than a cast iron one, so if fitted to an alloy head it might become looser, depending on head temp. But not if it is fitted to an iron head. The surrounding material of the head will constrict radial expansion, so due to the difference in thermal expansion the inner diameter might even decrease relatively with higher temperatures, leading to sticking valves.
That's why in iron heads only iron guides are used usually.
In today's modern engines even special cast iron alloys with the same (or very similar) thermal expansion coefficient as aluminium cast alloys are used, so that they can be fitted in alloy heads as well.
General consensus (although some engine experts disagree here) says that cast iron is the superior material for making valve guides due to the excellent fretting and wear properties, which is what I tend to belive, too.
I am also using custom made cast iron guides in the A7 SS alloy head without any problems. You just got to make sure they are a good shrink fit in the head.

Quote
EDIT: Ah! but the valve stem probably gets a lot hotter than the guide. Correct?

Yep. Part of the problem is the temperature gradient between valve stem, guide and head.

Cheers, Markus



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