Status Update!

If it's broken or just needs tweaked

Moderators: Volker_P, tidd650

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DammitDan
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Status Update!

Postby DammitDan » Sat Jul 15, 2006 3:30 pm

I got my new mains (122s up from 118s) and the bike takes off like a jackrabbit now. No sluggish response anywhere except up past 5k RPM, where I get no torque at all. It revs all the way up to 9k, and in the low gears i can burst past this mark, but when I'm cruising it will just top out at 65mph. I wouldn't have a problem with this if it weren't for my speed-demon nature.

I'm gonna be getting new slows (38s up from 35s) next week, but do you think I should now get even larger mains? It's gotta be a jetting problem, since I'm still getting little pops on deceleration and I hit the wall at 65. Before I put in the larger mains, I hit the wall at 60. And if I do get new mains, should I jump even higher into the spectrum? Like 128 or 130?

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Ibsen
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Postby Ibsen » Sat Jul 15, 2006 3:37 pm

Take a look at the spark plugs first. If the colour indicates that the carbs still are running lean, you should try larger main jets.
If you have put on a 4-1 exhaust there is a chance you have to live with some popping in the exhaust. It is not uncommon.

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DammitDan
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Postby DammitDan » Sat Jul 15, 2006 4:27 pm

But shouldn't the fact that I can't go faster than 65 make it clear I'm running lean?

I'm nervous to check spark plugs, cause I've crossthreaded 2 sparkplugs now (and I think my #1 is starting to, too).

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Ibsen
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Postby Ibsen » Sun Jul 16, 2006 2:22 am

You don't have to take them all out. The two outher plugs should do just for checking changes.
And yes, it should indicate that it is still running lean, but when you reach the point where it is running too rich you will loose power as well.

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DammitDan
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Postby DammitDan » Sun Jul 16, 2006 11:55 am

You know, you're right.... If the jets are the same size across the board, there won't be much difference between the jetting indications at higher throttle settings. Woot! I'm gonna go do a plug chop! :D :D

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DammitDan
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Postby DammitDan » Sun Jul 16, 2006 3:43 pm

Hmm... Well I did a plug chop and it looks like it's running very rich now. I went WOT for about 20 seconds with a brand new plug and when I pulled it it was totally blacked with carbon.

I'm so damn confused...

I was reading on the SOHC forums that perhaps my lack of top end is a restriction in fuel flow... So I chopped a new gas line and installed it without an in-line filter (The tank is clean and coated, so I don't need to worry about it for this test). Unfortunately, as soon as I put in the new line, the #2 carb started leaking from the overflow. DAMMIT!!! I tried tapping and poking, but it didn't do anything.

I Hopefully can take the bowl off without removing the carbs.

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DammitDan
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Postby DammitDan » Sun Jul 16, 2006 5:36 pm

IT CAN BE DONE!

Turns out you can take the bowls off to do stuff while the carbs are still on the bike (although not without a fair share of cursing and frustration....)

One thing I would suggest... next time you take your carbs off, replace all those stupid phillips head screws with bolts. I had to use a socket wrench with a phillips attachment, and it took me about 40 minutes to remove/replace two bowls. Even longer if I had done all 4. It would have gone much smoother if I had been working with bolts instead of screws.

Anyways, I "fixed' the stuck float (I think it was a stuck float...) so it doesn't leak all over the place anymore, but unfortunately putting in an uninterrupted fuel line didn't fix my top end problem.

Is it possible, with my WOT plug reading so rich, that the bike is simply bogging down from the main jet? Should I cancel my order for new larger slow jets and get smaller main jets instead?

Other than the top end problem, the bike seems to be running like a dream. Up until the point where I try to accelerate past 60 or my RPMs go up past 7k while accelerating in any gear (it sounds like it's missing or something).

Damn I'm confused...

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DammitDan
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Postby DammitDan » Sun Jul 16, 2006 9:13 pm

Here I am talking to myself again, but I'm crazy anyway, so...

I did a little more searching on the SOHC forums and found that if you take off the air filter cover (not the air filter itself) that it might help out. Well, I did just that and lo and behold

I GOT IT UP TO 85! I think I can get it even higher with new plugs.

So, what does it all mean? I have no earthly idea. I can only assume that the cover was limiting airflow, making the mixture so rich on the top end that it was literally drowning the cylinders in vapor.

Now I just gotta do a plug chop, and maybe... just MAYBE... drive it in to work for the first time in a year!

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Chris
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Postby Chris » Mon Jul 17, 2006 1:08 am

Yeah, that kinda makes sense. If you uncorked the exhaust, I guess you would need to uncork the intake as well to keep it from choking the engine. Very interesting. I think I've read that thread before about removing the air filter cover. They used washers on the screws to hold the filter in the box? Maybe it was that guy up in Wisconsin that posted that one, I can't remember. Sounds like you're gettin' there. :)
1980 CB650c

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Volker_P
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Re: Status Update!

Postby Volker_P » Mon Jul 17, 2006 1:14 am

Hmm, how old is your air filter? :)

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Chris
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Postby Chris » Mon Jul 17, 2006 10:58 pm

Yeah, this is where I saw that washer trick on the air filter: http://home.wi.rr.com/kgebauer/cb650problems.htm
1980 CB650c

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Volker_P
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Re: Status Update!

Postby Volker_P » Tue Jul 18, 2006 1:14 am

Just an idea, I do not know if it is possible with the CV carbs:
Can you rise the needle position instead of using larger main jets? Maybe the present position is too low and the compensation with the larger mains works too coarse. But first check/clean/blow out your air filter or try a new one before you spend more money on jets and time on playing around with them.


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