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shovel engine miss @ high rpm

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krc3517

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Sunday ride went bad, At higher rpm's engine misses, backfires. Idles and runs good at lower rpm's. Thought it was a fuel issue, but after removing and inspecting the S&S super B, found no dirt or debris in the fuel system. The ignition was changed to a magneto when built last june. Had been working great till now. Has anyone ran across these symptons before? Not sure if timing advance or fuel problem was over looked???? HELP
 
do not know about mags but if not a lot of trouble switch back to points. i had good luck w points in my 73 & 75 fl. except w/ they got wet.
 
Has the bike been sitting awhile? I would try a fresh tank of gas and a new set of plugs first, and check the point gap & clean them like Jack sugguested. How do the plugs look?
 
I've ran three tanks of fuel this year, the gas is fresh. the plugs have a dry black powder, carbon residue but no build up or heavy deposits. The points had a white residue covering 1/2 of the contacts. will check the gap, was told to set at 0.018, is that correct??? I'm trying to get some specs on the mag. only name I can find on the front cover of the mag is TCME. I'm going to try running until it misses and pull the enricher valve out to determin if its fuel issue or spark, after i change the plugs. Thanks for the input.

Great news guys, Todays ride was the best yet!!! Thank you. The problem was with the breaker in the mag. Removed and filed and set the gap @ .014. Doing this eliminated the backfiring, missing, and los of power. I think its the best its ran yet. Thanks to all
 
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krc3517 said:
I've ran three tanks of fuel this year, the gas is fresh. the plugs have a dry black powder, carbon residue but no build up or heavy deposits. The points had a white residue covering 1/2 of the contacts. will check the gap, was told to set at 0.018, is that correct??? I'm trying to get some specs on the mag. only name I can find on the front cover of the mag is TCME. I'm going to try running until it misses and pull the enricher valve out to determin if its fuel issue or spark, after i change the plugs. Thanks for the input.

Great news guys, Todays ride was the best yet!!! Thank you. The problem was with the breaker in the mag. Removed and filed and set the gap @ .014. Doing this eliminated the backfiring, missing, and los of power. I think its the best its ran yet. Thanks to all
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Ah, the magic of points and the DIYer friendly technology...sometimes the good ol' days ain't so bad eh? :newsmile075: WhaHOOO?
 
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