Forum

[Simon Cornell]

Hi to all on here, I am new to the forum, and fairly new to motorbikes generally - I have been learning as I go fixing up a 2001 350 Bullet, and having great fun (for the most part!). It was my dad's and sat rusting in a lock-up for 15 years odd. I have since had it all the way to central France (from Luton) and back so I know it will run, however I just fitting a new Amal Concentric 600 and am having trouble starting it.

I have very thoroughly set the timing 0.8mm BTDC but get severe kick-back and smoke from the intake filter, which I interpret as the timing being too advanced. The only time I have managed to get it started has been with the breaker plate fully retarded, which is a long way off from a centrally placed position when sparking at .8mm BTDC. Then only by keeping the throttle open from the twist grip, before screwing the throttle screw fully in, which then gave some erratic up and down before dying. I am confident the join to the engine head is tight but not overly tight.

I have noticed a spot of black oil seeping from between the carb barrel and its cap, just beneath the cable adjusters, which is a bit disconcerting! There was also plenty of oil on the piston head judging from the tip of the measuring gauge when finding TDC. Is this a clue possibly, but I can't see what?

Perhaps someone can suggest anything? I know starting can be a many headed monster and have gone through as many threads/starting routines as I can digest but still no joy. Trying to avoid taking it to a shop!

Many thanks in advance. Simon

[stinkwheel]

My suggestion. Put the mikcarb back on to convince yourself it is definately a carb issue. Set the points back to a point where they give you a steady idle and good starting then lock those down and leave them alone. You probably won't even need to fit the throttle twist grip if it was idling well before, just bolt it on and attach the fuel line.

Now try the new carb back on. Any major problems you are now having are due to that. My 350 started best on an amal Mk1 concentric with the choke fully off (fully retracted into the throttle body), tickled once then the barest crack of the throttle on kicking over.

It had a little more top-end with the Amal but I could never get it to start or idle as well as it did on the mikcarb. Then it wore out the slide and body so I put the mikcarb back on.

Where did you get your carb from?

[Adrian]

As for re-setting the timing, I would set it at fully advanced 32° before top dead centre on the firing stroke, i.e. with the auto-advance unit behind the points fully wound out. Also check the auto-advance can move freely, nothing jamming or rubbing anywhere on the back of the contact breaker plate.

Our hosts also have a timing guide here.

https://accessories.hitchcocksmotorcycl ... 6&_xt=.pdf

A.

[Simon Cornell]

Thank you for these pointers, really helpful and encouraging to see them.

The Amal carb is new from our hosts, whose timing guide is excellent.
I will do as you suggest and go back to where I left off with the Mikcarb with 32degs btdc and see where I get to there. Will report ba k forthwith!

[Wheaters]

Check that the inlet valve clearance isn’t set too tight.

[Cranky]

No engine will start at 32 degBTDC.

[Wheaters]

I don't think that's what Adrian meant - but I had to read it more than once!

He means set the maximum advance to 32 degrees, not the idle advance. If the advance mechanism bobweights are physically pulled out against their springs then the timing set to 32 degrees, the springs will pull them back in when you let go, and the timing will retard itself for the idle.

I spent a few years building my own car distributor for my Liege sports/trials car, which used to be powered by a very high compression Reliant 850, and modifying the advance curves to suit other modifications to get the best output.

I ended up locking up the advance mechanism altogether and fitting an Aldon Amethyst, which is a simple electronic "ECU" to set the curve using a laptop. Far easier than modifying the advance curve mechanically. Could be done with a single cylinder bike, too - but I don't think I'd bother.

http://www.aldonamethyst.co.uk/

[Adrian]

Yep, the clue was in the words "at fully advanced", Cranky, you possibly forget how the mechanical advance and retard works.

No engine will start at 32 degBTDC.

John Hutchings of Tollgate Classics (builder of tuned and over-size Bullet engines) told me the story of how he once put one together with a Lucas SR1 magneto running fixed (full) advance for road use. I asked him how he coped with starting it, he said it was fine for him, he just kept the throttle closed. Other people would want to have a go on this bike, as it performed rather well, but they would forget or ignore his starting advice, and open the throttle when kicking over with predictable results. After a spate of ankle injuries locally, he felt obliged to replace the plain magneto pinion with an auto-advance and retard version, though the bike never performed as well afterwards.

A.

[PeteF]

The engine spends most of it's time fully advanced so it seems sense to set the timing in that state.
Mr H sells an advance lock washer so you don't need to hold it advanced while you set the timing.

[Wheaters]

My old BSA A7SS (magneto ignition) had a manual and advance/retard lever, which TBH was a novelty to me as a young man after the automatic advance setup on my BSA C15. TBH, I liked it because I could sense how it affected engine performance and it stood me in very good stead when I began tuning my own engines.