Kick start shifting into gear

I have been getting a lot of backfires trying to start my '74 850 rebuilt basket case (I had the Boyer timing set wrong for a while.) The Emgo kick starter arm looks like it's bending and twisting in, making it hit the muffler on the way down and catch on the way up (especially on back fires). I bent the kick arm out again, but after another backfire it stuck on the muffler. It is also shifting into gear when I am kicking it over. I assume something in the gearbox is stuffed?

I cleaned and rebuilt gearbox, with new layshaft bearing. But I have had shifting problems before (figured out it was an upside down spring, thanks to this forum.) I am going to try bump starting tomorrow

noco, what is this backfiring you speak of?

can you elaborate, when, details, etc

we might be able to help sort that and maybe related

When I kick it over, sometimes it makes a loud bang, and the arm kicks back hard. I have been topping up the gel battery, and have a good spark when I lay the plugs on the head and press the kill switch. It is hard to turn over (.50 oversize pistons), but turns free when I pull the plugs. The first 20 kicks, I had the Boyer set 90 degrees off, so I assume the kick backs were due to miss-timing. It was at this time that the kick arm started to hit the muffler. I re-set the Boyer correctly, bent the kick start to clear the muffler. topped off the battery, jumped up and down on it, it backfired twice (in 20 tries) and the arm started hitting the pipe again, catching on the under side when it back fired. It is during the second time trying to start it that I noticed it was slipping into gear. I was wondering if this meant there was something obviously wrong in the gearbox? Maybe something is miss-aligned, and the kick start is deflecting because of it? Not sure how to be more specific? Sorry if it's a dumb question, just wanted to ask before I bend out the kick arm and try again tomorrow

After reading "triplex chain tension vs gear shifting?" post think I have the triplex chain too tight. I am probably dealing with multiple issues at once (incorrectly set timing, chain tensions, clutch...)

I once on 1st time rebuild got the triplex too tight, which then also bent the tranny shafts, unknown after replacing the obvious damage by too tight chain, but bushes didn't last long, in when in again to find the real reason, so hope yours is not as mean a lesion as mine. Not bad Id to check chain at full heat. Back fire kick offs imply a bit over advanced ignition setting. i just back off till no backfire then put light on to mark or record objectively. I ain't been at this that long myself but long enough to know to order spare pawl spring, 1st gear bush and kick ratchet but have run out d/t giving those items to my buddy so now must order again as about to go in again on another AMC let down show stopper hobby desire tester.

It sounds as though you have both the Boyer timing and the primary chain tension set wrong. When all else fails, read the instructions. (Please don't tell my wife that I said this).

Emgo stuff is really crap junk. Get a later kickstarter and you will have pretty of room to avoid fouling the muffler and it won't bend either.

When adjusting the primary chain follow the procedure in the manual. Be sure to recheck after a trip around the block because they can tighten up on you. On the loose side is better as long as it isn't hitting the chaincase. A too tight primary chain can bend the transmission mainshaft as hobot says.

Thanks for all the help. Finally had some time to work on the bike (and heal up, had to take some time off because I was limping around for 4 days, after the kick starter jammed my leg up into my hip socket) The primary chain was indeed way too tight. I am still a little unsure about the static timing of the Boyer. The instructions say to use the mark for TDC on 72/73 models. I have a 74, there does not seem to be a mark for TDC, just increments of 20-40 degrees, so I set it to 31. When I pull the plug, and put a screw driver in the cylinder, and move it back and forth until it is TDC, the marker is on 20 degrees or less (beyond the marks). Should I just find TDC manually with a screwdriver in the cylinder, and then set the Boyer magnets to be horizontal with the Norton logo? It has been suggested that the timing is still too advanced, so I want to adjust it. (yes, I have a timing light standing by in case I get it started)

noco said:

The instructions say to use the mark for TDC on 72/73 models. I have a 74, there does not seem to be a mark for TDC, just increments of 20-40 degrees, so I set it to 31.

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There isn't a "TDC" mark on any Commando. The correct alternator rotor timing mark should be set to 31 degrees (with the pistons near the top of their stroke).

There are usually two timing marks on the alternator rotor (180 degrees apart) however, neither of them line up with any "TDC" mark. The Boyer instructions attempt to point out that only one of the two rotor marks (the mark that shows in the timing aperture when the pistons are approaching TDC) is the correct one to use.

http://www.boyerbransden.com/pdf/KIT000 ... 00017_.pdf

5. Set engine at 31 B.T.D.C. on the alternator mark (ensure correct mark is used - there are two marks on
the alternator on 1972/3 models, use the mark indicating T.D.C. with the pistons in top position).

Click to expand...

noco said:

When I pull the plug, and put a screw driver in the cylinder, and move it back and forth until it is TDC, the marker is on 20 degrees or less (beyond the marks).

Click to expand...

If the crank is at TDC, then the timing mark would be aligned with 0 degrees if the timing is correct, however "0 degrees" or TDC is off the timing scale.

noco said:

Should I just find TDC manually with a screwdriver in the cylinder, and then set the Boyer magnets to be horizontal with the Norton logo?

Click to expand...

With the Boyer rotor magnets in that position, the alternator rotor timing mark should be at 31 degrees (BTDC) on the timing scale, not TDC.

Gotcha, thanks. Nice to know I had it set correctly, I think I will retard the timing a little (by rotating the outer plate on the Boyer.) I am also going to refresh the fuel and clean the float bowl, as there was some sediment in the lines. Looking forward to know if it runs