Okay I give up. My bike keeps stopping as it climbs a long slow hill to my house. It will immediately start up but the "tapping" (which I believe is normal), turns into a knocking. If I don't let the bike cool down the knocking becomes more concisitent and the bike keeps shutting down.

I am pretty sure it is over heating but I don't know why. It has a brand new AMAL carb with a 170 main and 106 needle jet. I have timed it and it starts and runs great until that hill. Spark plug is a light grey/brown.

Th only thing I can think of is that I didn't have a spacer between the carb and head. But I don't think that would cause it..but i am installing anyways. Thanks again for the help.

Video of the bike running .....

http://www.youtube.com/watch?v=qIciM6-HIwc

email (option): jeff@infinitymedspa.com

hi jeff,you definitely need a spacer between the carb and the cylinder it'l make a difference you are boiling your petrol cheers rick

email (option): richardholt@rocketmail.com

Would that create the knocking from missfiring? Also I was told I could create a spacer from MDF if I couldn't find anything else. Wouldn't that catch fire?

rick

hi jeff,you definitely need a spacer between the carb and the cylinder it'l make a difference you are boiling your petrol cheers rick

email (option): jeff@infinitymedspa.com

Stupid question Jeff. I assume your are changing down through the gears to keep the engine revving? Not slogging it up that hill in top gear Ron

email (option): ronpier@talk21.com

Assuming you are going the right way through the box as Ron pointed out it sounds to me like you need to check the ignition timing. Knocking under load could be pre ignition (pinking.) I would fit the tufnol spacer first which you must use on an M20 to avoid fuel evaporation. Symtoms of that are difficult starting, and banging and misfiring when you start up with a hot engine..once underway the symtoms disappear as the carb cools down.
Next check your ignition timing..7/16" BTDC on the compression stroke with the adv/rtd lever set in the fully advanced position. Make sure you have correctly identified whether you have a 'slack' or 'tight' wire advance magneto fitted. If the mag cable enters the magneto to the right of the points housing it is a tight wire system, to the left a slack wire system.
I suggest you check out the technical section of the website...there is a very complete description of the whole procedure there if you are unsure...Overheating will be caused by one of two things..incorrecrtly set ignition timing or a weakness of the fuel/air mixture....this can be caused by incorrect carburettor settings , a blockage in the supply of fuel either to the carb or within the carb, or an air leak.....Ian

email (option): ian@wright52.plus.com

when engine getting overheated the petrol can ignite early even in the inlet manifold causing knocking noises look up surrey cycles an amal specialist they do tufnol spacers in different thicknesses i made a metal spacer that has a larger outside diameter looks like a fin between 2 tufnol spacers works a treat before i did this i would have to put a wet cloth on it when it stopped

Yep I am downshifting when appropriate. I recently timed it and it runs beautifully until it gets hot I will put the spacer on next to see if that helps. It feels like it is almost running out of gas. No air leaks and good compression. ( I am putting the spacer on today and I will see what happens)

Ian Wright

Assuming you are going the right way through the box as Ron pointed out it sounds to me like you need to check the ignition timing. Knocking under load could be pre ignition (pinking.) I would fit the tufnol spacer first which you must use on an M20 to avoid fuel evaporation. Symtoms of that are difficult starting, and banging and misfiring when you start up with a hot engine..once underway the symtoms disappear as the carb cools down.
Next check your ignition timing..7/16" BTDC on the compression stroke with the adv/rtd lever set in the fully advanced position. Make sure you have correctly identified whether you have a 'slack' or 'tight' wire advance magneto fitted. If the mag cable enters the magneto to the right of the points housing it is a tight wire system, to the left a slack wire system.
I suggest you check out the technical section of the website...there is a very complete description of the whole procedure there if you are unsure...Overheating will be caused by one of two things..incorrecrtly set ignition timing or a weakness of the fuel/air mixture....this can be caused by incorrect carburettor settings , a blockage in the supply of fuel either to the carb or within the carb, or an air leak.....Ian

email (option): Jeff@infinitymedspa.com

Thank you for the lead on the tufnol spacer. What did they use during the war?

email (option): Jeff@infinitymedspa.com

I don't think they needed a spacer during the war, not even in the sahara desert, but you definitely need one these days

email (option): robmiller11@yahoo.co.uk

Is your piston new?, if it is, is it a genuine BSA or Hepolite, or is it a spurious one? The reason I ask, is it seizing up on the top end?

email (option): davmax@ntlworld.com

Rob Miller

I don't think they needed a spacer during the war, not even in the sahara desert, but you definitely need one these days

email (option): ian@wright52.plus.com

"Shirley" 66-127 is just the paper gasket, and "Halite" (NaC1) is Sodium Chloride or salt which I presume was added to the paper to make it heatproof?

email (option): robmiller11@yahoo.co.uk

Pass....Hallite is a trade name for gasket material which comes in various thicknesses. I have no idea what it is manufactured from. I guess the thicker the material the better its insulating properties...Ian

email (option): ian@wright52.plus.com

Since I am in the U.S. and hard to get parts, would it be okay to use a 1/8 thick or more cork gasket that i could cut to fit?

Ian Wright

Pass....Hallite is a trade name for gasket material which comes in various thicknesses. I have no idea what it is manufactured from. I guess the thicker the material the better its insulating properties...Ian

email (option): jeff@infinitymedspa.com

Hi Jeff..Cork may not stand the heat...plus it compresses a lot. You can make the spacer from any material that has reasonable insulating properties...I have seen them made from a piece of hardwood with a standard paper gasket on either side working just fine. Nylon sheet also works ok.
Always fit a paper gasket either side to take up any surface irregularities and ideally go for a thickness of about 1/4"...Ian

email (option): ian@wright52.plus.com

I think I still have a 6" (I think they were 6") square 3/16" tufnol sheet that you can have for £2 plus the postage if you need it

email (option): davmax@ntlworld.com

That would be great, how do I get it to you?

email (option): Jeff@infinitymedspa.com

Can you paypal me the money as a "gift" in GBP to the email at the bottom of the posting, I guess the postage would be no more than £2. I just looked and I couldn't find a full sheet, I've got one where I cut just one spacer out for myself, so I think you'd certainly get another 7-8 or so out of the sheet. A hole saw is the best to cut the hole in it and a very fine tooth saw (maybe a hacksaw blade) to cut the shape out, it sands pretty well so you can get the curves of the edges on a grinder. If you want it can you put your address on the payment
Dave

email (option): davmax@ntlworld.com

I just sent it. Thanks again

email (option): jeff@infinitymedspa.com