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Old 04-08-2015, 06:17 AM   #1
MayerMR OP
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Carb issue on Honda thumper

Hi fellas!

I recently completed the top end rebuild on my little 1972 Honda SL100 and she will start on the first kick every time. But I am struggling with a couple of small complications;
  • The bike runs great when cold, but by the time I've ridden a mile or so it starts to act like its starved for fuel and I'll have to rev it to keep it from dying. When/if it does die, it starts right back up first kick every time. I'm pretty sure it's a float level issue, but would love to hear some others' opinions.
  • Though I replaced the gas cap gasket, the damn thing leaks like crazy - it's not a vented cap. I don't know how else to seal it and I'm at a loss...
  • Lastly, my buddy has a 73 CL100, more miles, no top end rebuild, and I'm the one that got it going for him recently. I'll be damned if his bike doesn't have more power. It'll lift the front end and has a higher top speed as well. I'm baffled by this. I have a larger rear sprocket as well so I expected the lower top speed, but I'm pretty confused as to the lower end *grunt* that his bike seems to have over mine. Could I have a timing issue or are the tranny ratios considerably different between the CL/SL/CB models?

Appreciate your opinions guys!

-Matt
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1972 Honda CB450 (Rebuilding)
1971 Ducati 450 R/T (utter disrepair)
1971 Honda SL100
1967 Honda CM91 -> CT90 conversion
1986 BMW K75 - Storage until I figure out a way to tell the wife
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Old 04-08-2015, 06:26 AM   #2
Rizingson
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The gas tank needs to be vented. Look for the small pin hole just outside of the gasket, you may need glasses.
Go back and check valve clearances, points and timing just to be sure they are correct. If that doesn't help raise the float level a little at a time.
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http://advrider.com/forums/showthread.php?t=924068
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Old 04-08-2015, 01:31 PM   #3
MayerMR OP
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Quote:
Originally Posted by Rizingson View Post
The gas tank needs to be vented. Look for the small pin hole just outside of the gasket, you may need glasses.
Go back and check valve clearances, points and timing just to be sure they are correct. If that doesn't help raise the float level a little at a time.
I kind of figured it needed to be vented in some way shape or form; I'll look to see if there was a plugged hole or something preventing it.

So I literally just buttoned up the top end and checked the valves after a brief run in period, the valves are spot on. I will check out the timing once more to ensure it's on - the advance was in good shape so it should be opening up fine as well.

I'm pretty sure it's the float level (I forgot to mention, it's a new float and I didn't adjust it out of the box)...all signs point to a maladjusted float...I shall report back!

-Matt
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1972 Honda CB450 (Rebuilding)
1971 Ducati 450 R/T (utter disrepair)
1971 Honda SL100
1967 Honda CM91 -> CT90 conversion
1986 BMW K75 - Storage until I figure out a way to tell the wife
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