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Messages - gusmagicbus

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Singles / Re: Running in troubles - engine fade
« on: 18 April, 2018, 22:58:58 »

Thanks for all the new suggestions! I will pick this up again and feed back.  Dabbist - I think you're right, I have the chain case cover off currently so will sort the charging issue out. Derek - Yes raised the clip and weakened the mixture.

One thing which has just sprung to mind is I couldn't find any guidance on how to tighten the timing side nut at the end of the crankshaft. As per the photo below (hopefully it appears somewhere). So what I did was tighten the nut enough to take up as much lateral play as possible whilst ensuring the engine still turned (manually) without resistance. Is this how you would do it?

Singles / Re: Running in troubles - engine fade
« on: 08 April, 2018, 09:30:38 »
Thanks folks

Valve clearances - I've checked these and slackened them off a little, they were a little bit tight. Btw - The Rupert Ratio engine book recons that the valve clearances increase when the bike gets warm and advises reducing the valve clearance more. Anyway, it's certainly worth a try, as its is something changing when the engine gets warm. I did notice that my exhaust rocker is not very well aligned over the valve and there is some lateral play in the rocker so I can pull it towards the top of the valve to align it better, but it springs back to being off centre. I don't think this is particularly my problem but something to look at next time the rocker box is off?

Carburation - I think fuel flow is good, I have an inline clear filter which looks good and I can see fuel in their under running conditions and the one in the banjo is also good. It has a new hose. I have the standard wire mesh filter in the battery box. I have the correct carb (376/281) for the model and bought a refurb kit for it from Amal, so everything is new apart from the body. When I had the glowing exhaust incident I dropped the needle down, it is now on the second to lowest setting. I've also played around to get the idle ok (throttle stop and air screw). But that's it. I've looked in to the correct method to set it up, but because this starts with a wide open throttle test for the main jet, I thought i'd leave this until I have run the engine in for a few hundred miles. The thread at the top of the carb does have a piece missing, it still tightens up, and I have tape around it at the mo to stop any potential air leak. I have noticed that oil, which makes its way onto the spacer between the carb and the inlet flange tends to bubble a little (coz it's hot) but wondered if an air leak develops when its warm. I'm not sure the best way to check this though?

Ignition timing - Thanks for the service sheet, that solves one mistery. My model is one of the SS80s that has the 10 deg advance mechanism, and the correct 10 deg bits are in the distributor (I thought these were wrong until yesterday and it was on my list to get the 15 deg weights - but I won't bother now). I printed and made a timing disc last night, so i'll set it to 5 deg BTDC tonight. I think this is going to be much more retarded than it is at the mo. I will also check the valve opening and closing at the same time. I guess the deg points stated in the books for when the valve opens, is when is just starts to open, and when it closes is when the valve is fully closed? The spec I have for the SS80 states Inlet Open 51 BTDC, Close 68 ABDC, Exhaust Open 78 BBDC, Close 37 ATDC. Hopefully that does not change between years. I don't have a dial gauge, but can see when the valves open and close. Perhaps this is good enough to check the valve timing is on the right gear tooth?  Don't know how this effect things but I know for a fact that it doesn't have the correct high compression piston in for the SS80, it just has the std piston. I don't see how I can get 5 degs in retarded setting and 33 1/2 in fully advanced (because the difference is fixed based on the distributor mechanism), but I guess the service sheet you sent stated the retarded setting so i'll just set to this?

Barrel - Hopefully this rebore (+60 bought from ebay) is ok, I remember checking piston skirt clearances were as per the book when I put it together.  I think I had to file a smidgen off the edge of the rings to get the ring gap right though.

Singles / Running in troubles - engine fade
« on: 06 April, 2018, 20:45:22 »

I've just rebuilt a 1964 BSA SS80 (after 7 years and quite a bit of help from this forum!). Its had new big end, small end, piston, rings, re-bored barrel, valves, valve guides, bushes.....the works. After fiddling with carb settings and timing, it was running ok for the first test ride (around 12 miles). However, on a test run last weekend, after 20 miles the power delivery became jerky and then lost power, I could get some power back by shifting down a gear but soon lost power again. It still idled. It was a bit better after cooling down while I checked all the settings on the road side, but had the same symptoms soon after. I changed nothing and took for a ride this evening, and exactly the same thing happened after 4 miles this time. I have been keeping to about 1/4 throttle and speed between 30 and 40 mph to run things in. It feels like the loss of power could be the engine tightening somewhere but I'm not sure. My first move was going to be to take the head off and see if I can see anything unusual. But would appreciate any advice of what to look for first.

It has a few other things going on that I don't think are related, and aren't my priority until I sort this engine problem out (but just in case you think this is effecting it). The charging circuit isn't working at the moment, but the 12v battery has not dropped below around 12.4v  on the test runs as I have been keeping it on an optimate when its in the garage. Lots of oil leaks, but I don't think that's unusual. The first time I fired it up the exhaust glowed red hot, but since dropping the needle in the carburettor and changing the ignition timing to 1/16 BTDC (as per the BSA service sheets), rather than 5/32 BTDC (as per RR book) it;s run a lot better and the exhaust has not glowed. The spark plug seems a good shade of grey.


Singles / Re: C15 brake pedal return spring location
« on: 05 February, 2018, 22:28:39 »
Thanks all.  I've managed to sort it.  In the end I  slackened off the brake arm nut a little at the rear hub which allowed the brake shoe springs to assist the return spring in returning the pedal to the correct position.


Singles / Re: C15 brake pedal return spring location
« on: 29 January, 2018, 20:35:41 »
It's 1964

Singles / C15 brake pedal return spring location
« on: 28 January, 2018, 20:17:40 »
I'm rebuilding a C15 SS80 and just can't figure out how or where the brake pedal return spring fits. I have managed to fit it where I thought it might work but there's not enough spring pressure to return the pedal. Any advice or photos would be ace. Thanks.

Singles / The big day is nearly here..
« on: 27 December, 2017, 19:55:43 »
Hi Folks,

After seven years of hard labour, laughter, sweat and tears, it's nearly time to see if the BSA C15 SS80 runs again. It was my first rebuilt and not a single nut or bolt on the entire bike has been spared. New big end, cylinder rebore, new piston and rings etc. etc. I am looking for any advice on a sensible way to commission/run in?

Also i'm thinking of buying an oil filter protect all that hard work. What's the general opinion on aftermarket oil filters?

All advice gratefully recieved,


Singles / Re: C15 Ignition Switch
« on: 12 November, 2017, 11:22:28 »
Thank you for the clarification. Looks like I have bought and installed the wrong one! Looking at the two diagrams, it seems straight forward to convert from one to the other. I just need to move the purple wire from the rectifier to go to the ammeter instead of the ignition switch and then shuffle the wires around at the ignition switch so they match the connections for the 88SA switch?

Singles / C15 Ignition Switch
« on: 11 November, 2017, 21:22:12 »

I am replacing the wiring loom on a 1964 C15 SS80. The wiring loom which was on the bike had (what I believe) is a 88SA switch and it was wired like this

The wiring loom I bought from ebay is wired like this and I think this requires the 63SA ignition switch. Does anyone know what the correct wiring and ingnition switch is for the 1964 SS80?

Singles / Re: BSA C15 Carb
« on: 24 May, 2017, 20:26:26 »
Thank you.. very clear now.

Singles / BSA C15 Carb
« on: 23 May, 2017, 23:46:45 »
Hi Folks,

I have an BSA SS80 1964 with a 376/281 Monobloc carb, I have stripped the carb to recondition it and whilst looking at carb diagrams I have noticed that mine has no air valve or associated operating gear. Although there does appear to be a hole in the carb cap for an air valve control cable. Do you know if the air valves were fitted to all the carbs in this series? I am also not sure how the the air valve is operated, I think there is meant to be a valve leaver on the handle bar, but looking at poor quality photos on the internet of SS80's i'm not sure I can see one of these.

Can anyone shed any light on my missing air valve?


Singles / Distributor shaft lube system
« on: 10 May, 2017, 23:06:20 »

I have stripped the distributor on my C15 1964 SS80. I see that there is an oil groove and long recessed area along the drive shaft (the bit half way between the drive dog at the bottom and where the cam presses on at the top). I am meant to pack this shaft recess with grease when I reassemble?


Singles / Re: C15 Head Gasket Advice
« on: 09 February, 2017, 00:16:24 »
Hi TTJohn

Sounds like an excellent offer, thank you. How do we arrange that then!?

Singles / C15 Head Gasket Advice
« on: 05 February, 2017, 20:32:36 »

I'm rebuilding a C15 SS80 1964. I've measured the thickness of my cylinder head gasket (~.039 - .040") and bolted the head onto the barrell without the gasket and measure the thickness of the gap which is about ~.035 - 0.38 depending on which corner you stick the feeler guages in. Hence, compression on the gasket could be as low as .001" in one section.  I think the head has probably had one too many skims, and I am worried that the gasket will blow (or leak oil).

I guess a slightly thicker gasket would be good, does anyone know where I can get one off these or if there is another trick commonly used. Or even if 001" gasket compression is ok.


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