Skip to main content
000000 000003 000006 000009 000012 000015 000018 000021 000024 000027 000030 000033 000036 000039 000042 000045 000048 000051 000054 000057 000060 000063 000066 000069 000072 000075 000078 000081 000084 000087 000090 000093 000096 000099 000102 000105 000108 000111 000114 000117 000120 000123 000126 000129 000132 000135 000138 000141 000144 000147 000150 000153 000156 000159 000162 000165 000168 000171 000174 000177 000180 000183 000186 000189 000192 000195 000198 000201 000204 000207 000210 000213 000216 000219 000222 000225 000228 000231 000234 000237 000240 000243 000246 000249 000252 000255 000258 000261 000264 000267 000270 000273 000276 000279 000282 000285 000288 000291 000294 000297 000300 000303 000306 000309 000312 000318 000321 000324 000327 000330 000333 000336 000339 000342 000345 000348 000351 000354 000357 000360 000363 000366 000369 000372 000375 000378 000381 000384 000387 000390 000393 000396 000399 000402 000405 000408 000411 000414 000417 000420 000423 000426 000429 000432 000435 000438 000441 000444 000447 000450 000453 000456 000459 000462 000465 000468 000471 000474 000477 000480 000483 000486 000489 000492 000495 000498 000501 000504 000507 000510 000513 000516 000519 000522 000525 000528 000531 000534 000537 000540 000543 000546 000549 000552 000555 000558 000561 000564 000567 000570 000573 000576 000579 000582 000585 000588 000591 000594 000597 000600 000603 000606 000609 000612 000615 000618 000621 000624 000627 000630 000633 000636 000639 000642 000645 000648 000651 000654 000657 000660 000663 000666 000669 000672 000675 000678 000681 000684 000687 000690 000693 000696 000699 000702 000705 000708 000711 000714 000717 000720 000723 000726 000729 000732 000735 000738 000741 000744 000747 000750 000753 000756 000759 000762 000765 000768 000771 000774 000777 000780 000783 000786 000789 000792 000795 000798 000801 000804 000807 000810 000813 000816 000819 000822 000825 000828 000831 000834 000837 000840 000843 000846 000849 000852 000855 000858 000861 000864 000867 000870 000873 000876 000879 000882
English French German Italian Spanish

Norton 16h backfire.

Forums

Hello I have a 54 Norton 16h, a while ago it started backfiring through the exhaust when the throttle is rolled off, it’s very annoying and even more annoying to pedestrians, I tried resealing the header pipe and it was no different, the timing is correct and the bike runs perfect and starts perfect, the spark plug looks a good brownish color. Any advice is more than welcome. Thank you 

Permalink

Hi Kelvin,  In my experience, an air leak on the inlet side is usually the culprit, eg. between carb and barrel in your case. 

Try spraying the joint with WD40 or similar with the engine idling and if the revs drop there is a leak there. 

Otherwise, worn throttle slides can also be a cause of overrun backfiring. 

Hope that this helps,

George. 

Permalink

Have you tried opening up the valve clearences by about .002 or so to see if the backfiring goes away?

Mike

Permalink

Hi thank you for the replies I will give them jobs a go, the throttle slide was new less than 4000 miles ago as the carb was bored out to suit, so hopefully it’s not that. 

 

Cheers Kelvin. 

Permalink

I had a mystery issue with loss of valve clearance last year. It turned out to a valve guide coming unscrewed from the case. I had to modify a spanner to get in there to avoid stripping the top off the engine.

Permalink

Engine timing is out, valve open slightly or my guess us its running too lean. Either sucking in air or carb mixture screw has moved. Check for air leaks etc then run down hill in 3rd gear throttle shut. If mixture weak it will backfire cough and fart. Adjust mixture till it comes down the hill without the backfire. Used to set Morris Minor carbs down hill works a treat.

Permalink

In my youth, my first motorcycle was an old (1930) Harley-Davidson. Right hand throttle, left hand ignition timing. It made lovely backfiring when rolling back both handles at the same time. So it could be ignition timing as well as the more probable air leaks.

P.S After three years I saw the light and bought my first Norton.

 

Norton Owners Club Website by White-Hot Design

Privacy Policy