Kickback with Tri-spark installed

998cc

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Yes, it has happened to me three times so far. The first two times were not too bad. Last Monday, I was starting the bike, and the resultant kickback really hammered my leg.

The Tri-spark is touted for its property of purposely retarding the spark to allow easier starting. Most of the time, it works very well; however, there is a starting sequence where kickback occurs. Each time the kickback occurred, the engine was cold and initially started for a few revolutions then died—then immediate kickback. On installation, I timed the engine with a xenon timing light.

Unless this sequence only occurs on my Commando, I assume others have experienced this kickback? I assume there is no fix for this other than immediately stepping of the K/S lever at each kick.

Hoping to shed the knee brace soon!
 

maylar

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This is a valid thread for the Classic Commando forum, would be better there than the Pub.

Of the very few times I've had kickback with my Tri Spark in over 10 years it was always due to not getting a full kick. A cold motor, after tickle, should not die once running. Assuming timing is correct of course.
 

Tornado

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Have you confirmed the timing marks on the primary cover scale are in fact showing reality? Many reports of some being off a couple of degrees. Maybe you are just a bit too advanced so trispark cannot compensate enough?

Also do we know how this anti kb function works? Is it only operating for a few seconds after first kick then goes away until something resets itself?
Could be it is not operating on your restart immediately after engine stalls. Maybe it needs a ign off/on cycle?
 

998cc

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This is a valid thread for the Classic Commando forum, would be better there than the Pub.
Agreed. It was an error. I was going to post some 20 year-old photos of some 880's in the pub. Wound up writing the kickback and posted in the Pub unintentionally.
 

998cc

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Have you confirmed the timing marks on the primary cover scale are in fact showing reality? Many reports of some being off a couple of degrees. Maybe you are just a bit too advanced so trispark cannot compensate enough?

Also do we know how this anti kb function works? Is it only operating for a few seconds after first kick then goes away until something resets itself?
Could be it is not operating on your restart immediately after engine stalls. Maybe it needs a ign off/on cycle?
The marks could be off; however, I have no way to check without somehow attaching my degree plate to the crank.

How the T/S anti kb works is a good question.
 

998cc

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Of the very few times I've had kickback with my Tri Spark in over 10 years it was always due to not getting a full kick. A cold motor, after tickle, should not die once running. Assuming timing is correct of course.
Mine stalls after initial cold startup fairly often. It idles with throttle shut but dies after a few seconds or when cracking it open. No problems when warm. I also just installed a new ham can air filter. (Replacing the double K&N) That could affect the last carb adjustment.
 
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Fast Eddie

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I think you need to degree it. The only time I’ve ever had that is when I cocked up the timing and timed it like a Triumph, ie forgot about the Norton cam going ‘backwards’. That retarded the timing.
 

998cc

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I think you need to degree it. The only time I’ve ever had that is when I cocked up the timing and timed it like a Triumph, ie forgot about the Norton cam going ‘backwards’. That retarded the timing.
A good thought at that. I assume I can find something on the net that shows how to attach a degree plate/wheel to the crank? I have a few good piston stops as well. In any case, I may just retard it a few degrees to get through the summer and check the crank this winter when new isolastics are planned.
 

marshg246

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A good thought at that. I assume I can find something on the net that shows how to attach a degree plate/wheel to the crank? I have a few good piston stops as well. In any case, I may just retard it a few degrees to get through the summer and check the crank this winter when new isolastics are planned.
I use an old Dunstall plastic degree wheel. I remove the rotor nut - the hole in the degree wheel matches. So the rotor nut holds the degree wheel. This would would fine with a printed paper degree wheel as well - probably need a washer on both sides to stiffen it. Set the crank to 30 degree before TDC, remove the degree wheel without letting the crank move, install the cover, and check the mark.

Alternatively, if I don't want to take the primary cover off, I use an old Triumph degree wheel attached to the auto-advance or Tri-Spark magnet by the pull threads with spacers. Just have to remember to double the readings since the cam runs at 1/2 speed and don't bump hard so they don't come loose. Just check the mark.

Not positive it matters, but once I have found TDC, I turn the engine forward to the 30 degrees before TDC, not backwards.

Note, I'm not timing to 30 degrees, just checking the marks.
 

maylar

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Mine stalls after initial cold startup fairly often. It idles with throttle shut but dies after a few seconds or when cracking it open. No problems when warm. I also just installed a new ham can air filter. (Replacing the double K&N) That could affect the last carb adjustment.
Do you have a choke?
 

998cc

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Do you have a choke?
Yes. Still getting to know my engine and the Amal Premiers. I have used the choke; however, it flooded the engine requiring more kicking to clear it out. Just a tickling the carbs has been the best starting method. My old '71 was a two-kick start most of the time. It required tickle, full choke, one kick then choke off, ignition on and start right up. Looks like I need to experiment a bit more with the 850.
 

marshg246

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Easy enough to do.
Then no choke, tickle, don't touch the throttle. If it doesn't start and idle by the second kick, fix it :) If is dies when you ease the throttle open, fix it :) Once a little warm, blip the throttle, if stumbles, it usually means that it's still too lean :).

Low fuel height can cause havoc when cold starting or idling. It's a long path from the bowl to the throat of the carb and the only thing that fills that path is tickling and the only thing to maintain that path full of gas is suction from the engine. Opening the throttle when kicking leans it out - don't touch! Everyone who has tried to prove to me that they needed choke to start was opening the throttle.

I recently had a guy who bought his 73 850 in the late 70s. He insisted that it would not start without the choke and that it was always hard to start. When he came to pick it up, we made a bet. I got to kick it once and then he got to kick it once. Started for me. Not for him. So, I kicked again and it started - he was very confused. I told him that it was due to the front brake and that the had to hold the front brake tight for it to start (of course, a lie). He said it wouldn't work because he couldn't twist the throttle while holding the brake. Told him to try it anyway and it started. He was very confused what the brake had to do with starting so I told him to put his right hand on the tank and try to start it - started no trouble - that's where WTF was loudly spoken. All those years and he finally knew how to start his bike!
 

998cc

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Then no choke, tickle, don't touch the throttle. If it doesn't start and idle by the second kick, fix it :) If is dies when you ease the throttle open, fix it :) Once a little warm, blip the throttle, if stumbles, it usually means that it's still too lean :).

Low fuel height can cause havoc when cold starting or idling. It's a long path from the bowl to the throat of the carb and the only thing that fills that path is tickling and the only thing to maintain that path full of gas is suction from the engine. Opening the throttle when kicking leans it out - don't touch! Everyone who has tried to prove to me that they needed choke to start was opening the throttle.

I recently had a guy who bought his 73 850 in the late 70s. He insisted that it would not start without the choke and that it was always hard to start. When he came to pick it up, we made a bet. I got to kick it once and then he got to kick it once. Started for me. Not for him. So, I kicked again and it started - he was very confused. I told him that it was due to the front brake and that the had to hold the front brake tight for it to start (of course, a lie). He said it wouldn't work because he couldn't twist the throttle while holding the brake. Told him to try it anyway and it started. He was very confused what the brake had to do with starting so I told him to put his right hand on the tank and try to start it - started no trouble - that's where WTF was loudly spoken. All those years and he finally knew how to start his bike!
Good stuff, Greg. :)

Thanks.

When initially setting up the Premiers, I did drop the floats about 3/32" to compensate for the tilt of the carbs. Adjustment of the pilot air was the standard procedure--at least as I understand it. 1-1/2 turns out to start. Adjust pilot air screw for best idle then tighten about 1/8 to 1/4 turn to eliminate the dead spot when "coming off the pilot" and accelerating. Perhaps it needs another 1/8 turn.
Good stuff, Greg. Thanks.

When setting up the Premiers, I did drop the floats about 3/32" to compensate for the tilt of the carbs. Adjustment of the pilot air was the standard procedure--at least as I know it. 1-1/2 turns out to start. Adjust pilot air for best idle then tighten about 1/8 to 1/4 turn to eliminate the dead spot when "coming off the pilot" and accelerating. Perhaps it needs another 1/8 turn....

All of my years riding brit iron, best starting with Amals was with 1/8 throttle or slightly less. As you stated above, the 850 likes the throttle shut to start.


Yes, I'll fix it! :) Just have to wait until the leg is better. The brace is off, but the knee is still not quite up to par. :confused:

Best regards,
Russ
 

marshg246

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Good stuff, Greg. :)

Thanks.

When initially setting up the Premiers, I did drop the floats about 3/32" to compensate for the tilt of the carbs. Adjustment of the pilot air was the standard procedure--at least as I understand it. 1-1/2 turns out to start. Adjust pilot air screw for best idle then tighten about 1/8 to 1/4 turn to eliminate the dead spot when "coming off the pilot" and accelerating. Perhaps it needs another 1/8 turn.
Good stuff, Greg. Thanks.

When setting up the Premiers, I did drop the floats about 3/32" to compensate for the tilt of the carbs. Adjustment of the pilot air was the standard procedure--at least as I know it. 1-1/2 turns out to start. Adjust pilot air for best idle then tighten about 1/8 to 1/4 turn to eliminate the dead spot when "coming off the pilot" and accelerating. Perhaps it needs another 1/8 turn....

All of my years riding brit iron, best starting with Amals was with 1/8 throttle or slightly less. As you stated above, the 850 likes the throttle shut to start.


Yes, I'll fix it! :) Just have to wait until the leg is better. The brace is off, but the knee is still not quite up to par. :confused:

Best regards,
Russ
IMHO do this: http://amalcarb.co.uk/optimising-mark-1-concentric-fuel-levels with the carb level. The pickup is at the back of the carb. Also IMHO your air screw method is correct. I've removed the clutch choke on every British bike I've owned and I never touch the throttle until running.
 
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