Thanks for the replies.  I'll richen the idle mixture a little and see if that helps. As you say, it seems to start, idle and run ok so maybe there isn't too much wrong. Maybe it is a material issue, the header and silencer came from Armours so should really be ok. I wish now that I hadn't thrown away the original rusty header, I could then have refitted it to see if it suffered the same.

Having not touched the bike since last November, I'm now tackling the exhaust blueing again.

Would anyone know if a header pipe that had previously turned blue is more susceptible to it happening again later? Although I could see nothing wrong with either of the two carbs that I tried, I have fitted a brand new 928 carb along with a new tufnol spacer and flange gasket. The carb flange on the cylinder head appears to be as it should be and the valves and valve guides were replaced as part of the rebuild. The exhaust header has been sealed into the head with high temp silicone and the static ignition timing checked again. The header pipe was polished back to its correct appearance.

The bike starts and idles nicely but after about 10 minutes of running whilst setting up the slow running the header still turned blue.  Although the header and silencer did of course get quite hot, the gas leaving the silencer was barely warm. After letting it cool down, the blue on the header pipe polished off really easily in less than a minute with no real effort.  It almost felt as though I could just have wiped it off. Previously it took a bit of effort to polish away the colour. Hence the reason for asking if the header might now be more susceptible to changing colour?

Thanks for the replies.

The reason for enquiring is that if I try to adjust as per the manual the inlet rocker arm fouls the top valve collar.  The exhaust spindle can actually be just turned fractionally in the correct direction to achieve a clearance and the rocker doesn't foul the valve collar, although to my eye the rocker geometry looks better when the spindle is turned the other way.


According to the Draganfly website, there are different part numbers for the spindles and rockers for the later engines.

I'll get the rocker box off and investigate. Thanks again

Hello. Ref my early C25 engine No C25-317. I've owned the bike for nearly 50 years, but have only recently reactivated it.

The workshop manual and the excellent RR book show that adjustment of valve clearance is achieved by turning the eccentric rocker spindles outwards.  Later engines from engine No C25-2050 onwards had revised spindles and rockers and adjustment was achieved by rotation the spindles inwards.

However, on my bike the spindles have to be turned inwards to set the valve clearances when according to the above they should be turned outwards. The engine starts, runs and idles nicely.

A BSA Service sheet from July 1967 shows the modified rocker arrangements and states that the new arrangement is interchangeable as a complete rocker box assembly, but individual components are not.

Would anyone know if the later rocker spindles would in fact fit into my earlier rocker box. The rocker box does seem to be original as it includes the internal rib that the Service Sheet shows as being removed for the later arrangement. If so and a previous owner had done this it might explain why the valve setting procedure is apparently reversed.   

.

Quote from: scifi on 21 October, 2024, 10:26:17As a quick and dirty method of checking your valve timing, you can put the engine at tdc on the non compression stroke.  The valves should both be open by the same amount.

Some engines do however have asymetrical overlap of the cams, so this method may not be accurate in those cases.

Thanks for the suggestion, this is also shown in the Rupert Ratio book.  Having done this check it appears that the valve timing is correct.

I've removed the cylinder head to deal with a head gasket leak and its clear that there has been an exhaust leak between the head and the back of the finned collar on the exhaust header. Is it possible that this could have anything to do with exhaust blueing?

Quote from: DAVE BRADY on 09 October, 2024, 10:16:13Hi,

Unfortunately some pipes tend to 'blue' more than others regardless of timing etc. but perhaps related to the quality of the pipe.
Coating the inside of the pipe with VHT exhaust paint can help to prevent this to some extent. 

Dave.

Hi Dave

Thanks for that, I hadn't considered that it could be a material quality issue. I've got some VHT paint so I think I'll give that a go.

Andy

Thanks for the replies.

The header pipe is new but is not stainless steel. I did initially suspect ignition timing or a weak mixture as being the cause, I have now though checked the ignition timing several times.

Although it starts and idles nicely, maybe I could check the fuel mixture with an old "Colour Tune" that I might still have in the garage.

The reason for asking about valve timing is that I was wondering if the exhaust valve was opening too early maybe fuel would continue burning as it leaves the cylinder head.

Hello.  This is maybe a daft question, but does anyone know if incorrect valve timing could be responsible for the exhaust header changing colour?

I have only run my newly rebuilt C25 for a few minutes whilst trying to set up the carb. Initially the bike was reluctant to start or idle once started. I noticed the exhaust header becoming golden in appearance. Presuming that this was due to weak mixture I stripped the rebuilt carb again to ensure that all was as it should be. This carb was the original Concentric 928/1 with the pilot jet at the base of the carb body. I found nothing obviously wrong and also checked the carb flange and inlet manifold for leakage with nothing found.

I then double checked the ignition timing and found this to be about right at 35 degrees BTDC. After this work I found that nothing had changed and starting and idling was still poor and the exhaust header was changing colour.

Presuming this to be a carb issue I then fitted a 928/8 concentric as fitted to later B25's, this carb has the later idle bush pressed into the carb body opposite the pilot air screw. The engine now starts and idles as it should, but the exhaust is still changing colour!

As the carb seems to be set up correctly and I cant find an induction leak and the ignition timing seems to be ok, I'm now wondering if incorrect valve timing could cause the exhaust to change colour? If not, does anyone have any suggestions for other things for me to check?

             

Wishing to protect the rebuilt engine of my 1967 C25, I've bought a remote oil filter kit, this seems to be of the Norton Commando type with 3/8" hose spigots on the filter head.

Whilst mounting the bracket and filter onto the rear engine mounting stud is straightforward, I'm struggling to work out suitable hose routings.  One concern is that it looks like I will have to shorten the inlet pipe of the engine oil manifold 40-1035 to allow the hose to pass between the rear of the crankcase and the filter mounting bracket on its way up to the oil tank.  The other concern is that as well as having to force the supplied 5/16" return line hose onto the 3/8" hose spigots, the orientation of the filter head means that I have to bend the hose well beyond its intended minimum bend radius to get it onto both hose spigots.

I might well have missed the obvious.  Does anyone have any photos showing how they have installed such a kit or any advice?  Thanks in advance for any help.

I'm finally getting around to getting my 1967 C25 back on the road after 40 years. The original gearbox sprocket had 16 teeth, but the new one that I bought at a classic bike show has 17 teeth.  I was assured that this is the sprocket that most people now fit. Does anyone know if the standard 100 link chain can still be used with the bigger sprocket?  I need to buy a new chain so need to make sure that I get the correct chain length. Thanks for any advice.

I too would be interested to hear an answer to this enquiry.  My 1962 A50 has developed a slight cylinder head gasket weep despite having the cylinder head and barrel faces gently skimmed and despite having annealed the head gasket. I have retorqued the head to the original workshop manual figures. 

Hello again. I wonder if anyone would know the paint codes for my 1967 BSA Barracuda.  The fuel tank is orange and white/cream and the side panels are orange.  The frame is of course a gloss black, but I'm aware that there are different shades of black. I would be grateful if anyone could help with this information. 

Thanks for the replies, I'll carry on with the original bushes.

Hello.  I'm carrying out a total restoration of my C25 which has sat unused in our garage for 40 years.  The frame is completely dismantled ready to go to local paint strippers.  I Have not removed the swinging arm Silent Block bushes as they seem to be ok. I guess that this means that the swinging arm will have to be shot blasted rather than acid dipped to avoid damage to the bushes.

What do others think about me not replacing the original bushes? Are others still using original bushes which are now 48 years old?

I think I've got to the bottom of this.

I'm not sure how I missed this but page 268 of the excellent Rupert Ratio book shows that in 1969 BSA shortened the length of the studs of the clutch centre and compensated by lengthening the spring cups. It seems that I have the later clutch centre but the earlier spring cups!

This information is not reflected on the Draganfly website.