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Author Topic: Motorcycle Carburetor Theory 101  (Read 41629 times)

Offline sxecafe

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Re: Motorcycle Carburetor Theory 101
« Reply #30 on: Mar 06, 2013, 15:10:03 »
Hell of an explanation... and your "Grumpy retired oldtimer... 'eat a Snickers bar'" made me chuckle too.

Lots of info to take in there. I'll do my best to process but the moral of the story is that pods are less then optimal.

Offline Kamn

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Re: Motorcycle Carburetor Theory 101
« Reply #31 on: Mar 06, 2013, 16:03:42 »
Best jetting post I have read.

However, my bike is giving me problems, and I can't figure out where my problem fits in all of this.

When I bought the bike it had sponge-like unifliter pods on each carb of my 82 CB650.
I installed K&N pods instead.

The bike runs pretty good, i have never ridden a bike of this size so I can't be sure. It idles fine, and seems to have good power. I have gotten it up to the ton no problem with more rpms to spare.

HOWEVER, today I finally put insurance on it, and plated it, and got ready to go on a road trip this weekend and I took it out for a ride. It was moderately windy (more wind than this bike has seen in the short time i've had it). It ran great going with the wind. No problem. When I turned around to go against the wind the bike ran like crap. Whenever a gust of wind hit me the bike bogged down so bad I almost had to pull over. I tried running with the choke half way and it seemed to fix the issue and it ran pretty decent.

So what is my issue? I suppose the bike is running lean since the choke helped.
Why does the bike run fine with lots of power as long as there is no wind?
I want to fix this problem fast for the weekend. I might try to tape up the air filter pods to limit some air and see if that helps.
Which jets would I be looking at changing in this case?

I think I'll post this under it's own subject too.

Thanks!



It can also be the pods blocking off atmospheric ports, finding a pod that has no internal lip can help ...........had this problem with my CX and pods then switched to MikesXS oval pods (no internal lip to block the atmospheric ports)  and problem went away


'82 Kawi GPZ550

'73 CB750 K3 (needs restoration)

Offline Kamn

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Re: Motorcycle Carburetor Theory 101
« Reply #32 on: Mar 06, 2013, 16:10:18 »
like this......

'82 Kawi GPZ550

'73 CB750 K3 (needs restoration)

Offline GoshenCafe

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Re: Motorcycle Carburetor Theory 101
« Reply #33 on: Mar 06, 2013, 18:31:57 »
If he's still running K&n's then I don't think those filters have the inside lip, whereas the cheap emgo pod filters do.

Offline teazer

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Re: Motorcycle Carburetor Theory 101
« Reply #34 on: Mar 07, 2013, 00:12:18 »
I had it rev'd fairly high for about 20 sec and then hit the kill switch. I just pulled 1-4 because they were easiest to get to. What would be wrong with the points coils? I have new Dyna ign and coils.
  I thought we were seeing 1-4 because they were worse than 2-3.  My bad.

Holding throttle open doesn't count as a plug chop.  The motor needs to be pulling hard at high revs and WOT to get a main jet reading.

It's possible that the pods are obscuring the air jet inlets.  I would check that first and if that's not the issue, try dropping the needles one clip position and see if that helps.  I love stock OEM Honda 4 airboxes.  Inside they contain perfect velocity stacks.  We use those on our race bikes without the box. (different bike and different carbs - they are just a good shape for our application.

Offline DreadRock

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Re: Motorcycle Carburetor Theory 101
« Reply #35 on: Mar 13, 2013, 16:09:57 »
 thanks for posting this as its very good info to learn from !

Offline Domiken

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Re: Motorcycle Carburetor Theory 101
« Reply #36 on: Mar 13, 2013, 17:07:07 »
Thank You!  Well done

Offline Qawls

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Re: Motorcycle Carburetor Theory 101
« Reply #37 on: Mar 20, 2013, 04:04:12 »
Good work thanks a lot!

Offline xxthegonzxx

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Re: Motorcycle Carburetor Theory 101
« Reply #38 on: Mar 26, 2013, 14:14:16 »
I think I might have found my problem. Thank you!

Offline Derwood

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Re: Motorcycle Carburetor Theory 101
« Reply #39 on: Apr 15, 2013, 04:22:44 »
GULP!!!!

That is a lot of info for this rookie. I will try to digest as I continue on my quest seek out the answer to which jets i need after removing the air box from my '78 CB550K.