Skip to main content
000000 000001 000002 000003 000004 000005 000006 000007 000008 000009 000010 000011 000012 000013 000014 000015 000016 000017 000018 000019 000020 000021 000022 000023 000024 000025 000026 000027 000028 000029 000030 000031 000032 000033 000034 000035 000036 000037 000038 000039 000040 000041 000042 000043 000044 000045 000046 000047 000048 000049 000050 000051 000052 000053 000054 000055 000056 000057 000058 000059 000060 000061 000062 000063 000064 000065 000066 000067 000068 000069 000070 000071 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 000883 1.slide1 2.slide2 3.slide3 4.slide4 5.slide5
English French German Italian Spanish

More on Model 50 Compression..........

Forums

Following much correspondence on the lack of compression on my newly assembled 1959 Model 50 - I never really got to the bottom of the problem. I completed the assembly with the rebore, new piston, gaskets, lapped valve seats etc. and got the engine running. Now, when cold and having not been run for a day or so the compression seems poor. However, once I've run the engine, just ticking over, for a few minutes a normal expected level of compression is evident. I stop the engine and then attempt to restart the warm engine - now I can stand on the kickstart ! Leave it again for a couple of days, limited compression, run & then re-check, full compression !

Is this just down to oil in the barrel sealing any air leaks past the rings ? Will things continue to improve as the rings bed in ?

 

Mike 

Permalink

A friend's 19S suffered occasional loss of compression very similar to what you have described ie plenty of compression when hot, sometimes none at all when cold. Eventually we found a worn exhaust valve guide, allowing enough movement of the valve to not always seat properly. Changing the guide sorted the problem. Many years ago a valve guide came loose in my 19S head (Alfin), giving similar symptoms. I know your engine has just undergone a top end overhaul so you probably checked the state of the guides at that time.

Ian McD

Permalink

Yes, Mike, as others have said the compression will improve with time, run in carefully, and if possible run with about a thou clearance on the tappers. My M50 has nowhere the compression as my Venom, but it doesn't seem to affect the performance, after all it is only a 350cc, with quite a low compression ratio...........Don't worry about it, just enjoy.

Regards John O

Yes, new guides fitted. Pretty sure they are not thge issue.

Mike

I relise this would, if I had the kit, identify a leak, but would it identify where that leak is from ?  Never tried this before.

Mike

 

Norton Owners Club Website by White-Hot Design

Privacy Policy