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Discussion Starter #1 (Edited)
This could be a "stupidist moment". If so, then enjoy and relish in my ignorance!

So I put dom-sports on, cut out the airbox, rejet (135/42/1 shim) and at lower speeds, through the power range, the acceleration is fantastic. But when I hit the highway and get to 60-75mpg, I get some sudden bogging in the power, which is intermittent.

Could this be a jetting problem? Or is it simply that I'm used to a sportbike with fairing which the wind does not affect to the same extent?

Jack
 

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It could be jetting maybe - seems the most common main jet setting for removed airbox and preds / doms is 140, so perhaps when you are opening the throttle and getting to higher revs, you are getting very rich.

Very rich a/f mixture can lead to a loss of power / "bogging" sensation.

I experienced exactly that when I had too large a main jet in my bike.

With the mods you list, you should not be experienceing a loss of acceleration at 65 - 70 mph. It should still be going.

EDIT: In fact a standard Bonnie should still be accelerating well at 65 to 70 mph.
 

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Discussion Starter #4
how many turns out on the idle mix?
No telling. I don't have the 'd' tool and the hose I tried to connect to the screw didn't fit snug enough--didn't try too hard, in any event.

Knowing the PO, I'd say it's exactly how it left the factory. He did nothing but change the oil on the bike.

It did idle high after getting warm but didn't race--lowered the idle to about 1k this a.m. It doesn't fart, pop, and smoke like it's running rich, but still could be wrong.

Thanks..Jack
 

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Discussion Starter #6
at just off idle (when you begin to open the throttle) in first gear from pulling from a stop, does it bog then? If so, you're rich on the idle mix.

153 might be a little rich, but I was running 150s in mine with your setup when I had stock carbs etc and it ran fine.
No, it pulls fine off idle. It's really only happened sporadically on the highway when at 65-75mph in top gear.

If you're around this weekend or next, maybe meet at joes and you can give it a ride?

I'll dick with the a/f screw tomorrow and maybe lean it out a bit; sounds like that's the way you're leaning--and you know that my mains are at 135, right?

PM me if you want to meet up...signing off for the night..Jack
 

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Your first post said the mains were 153 - I guess that was a typo - so you shouldn't be far off after all - maybe a little lean, but not much?

What revs does it bog at - do you know?

EDIT: Guess you got yourself an invite Sweat!
 

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Discussion Starter #8
You're right--I transposed the 135 to 153. Must have been the lack of beer at the time, which was quickly remedied later.

But...may have the answer: would an air leak in the header cause the problem?

I noticed the leak before doing all the mods and jbwelded it (on the weld between the cross-pipe and left header) when I was doing my pipes and chain.

Rather than letting it cure overnight, though, I couldn't resist taking it out for a drive about 2 hours after (jb)welding it.

Thinking back, I had driven about 15 miles at 65-75mph with no bogging or trouble until a sudden bogging--my thinking is that the crap weld broke loose at that time. I just now verified that air is leaking from the same spot.

Got the idea from a past thread--a guy who had an idle problem and mentioned that he didn't have an exhaust leak.

So what do you think?

And since I'm planning on having the headers ceramic coated, should I just have them spot weld the seam before they do the pipes? Any recommendations in Austin?

Thanks a lot...Jack
 

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Well,

You are now running up against the limit of my tuning knowledge, which in real terms is not a whole hell of a lot anyway.

My understanding is that a leak of that nature in the exhaust would tend to cause popping and backfiring - it is certainly not particularly good to have an exhaust leak, so if that were me I would certainly have that crack welded up.

Since you say the bogging occurred suddenly - maybe it is linked to the cracked weld, but I would strongly consider Sweatmachines advice.

So - if it were me, I would get the exhaust sorted out first, and then get back into the tuning once it is leak free.

I don't have any more to add I'm afraid, because I don't have enough experience on tuning matters and I don't want to send you off on the wrong path.
 

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Pull the shim off the needles after you get the exhaust leak sorted and see how it runs in the mid-range without a shim. I would suspect you may be too lean at 135 mains for much WOT running, so I would suggest sorting the main jets first after you remove the shim on the needles. Once the main jets are sorted, try for the best mid-range and add a shim if you have some flat-spots. Lastly, I would adjust the pilot screws for your lower throttle opening running.

If you have to have the headers welded anyway, I would suggest taking both off and having the welder remove the crossover pipe before you ceramic coat them--your engine will thank you by being more responsive at all rpm's, IMHO.:D
 

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135 is too lean, you should be at least 140 or as much as 150-155. 145s should be right in the median.

If you need to get them welded, call up to the South Austin Speed Shop and ask for Dave, he's welded up some pipes for me in the past and did it quick and cheap. The pipes are stainless and they'll have to be TIG'd:

http://www.austinspeedshop.com/

Austin Speed Shop
1414 S Lamar Blvd
Austin, TX 78704
(512) 693-7277

I'd be happy to check the bike out. I'm currently out of work :(, my bike is down :(, and my truck is down too :(. Not a good week!

The good news is that I have time to fix the bike and truck! Nothing major, an exhaust stud broke off the bike but I had to pull the head and get it zapped out with an EDM machine. I'm waiting on a new head gasket in the mail before I can reassemble. I'm hoping it will be here today.

The truck leaked out all the power steering fluid and the pump burned up. Another semi-easy fix...

Let me know when/where you want to meet up. The weather sucks today!
 

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Discussion Starter #12 (Edited)
tomorrow then? I decided to noob out and try another round of jbweld and let it cure properly. If it appears to solve the problem then I'll know to get the pipes done. Thanks for the name of the shop.

I gotta see your bike though.

As to the mains, Mike at bc was pretty damn adamant that 135 would be the right size but i'll get some biggers..richer is better in my book.

How about mid morning around 10 or so? Doesn't really matter what time, i have nothing going on. Probably get the smoker going tomorrow pm with a cigar so unless you're willing to get to my house (always a good beer and cigar) late pm is out.

Jack
 

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I'll let you know. If my new head gasket arrives today (fingers crossed) I'll probably work on the bike tonight or tomorrow as soon as I wake up. A couple of guys on the forum said they wanted to drop by to see me reinstall the head so I might be tied up, unless you want to come by my place. I'm in South Austin near Brodie/William Cannon.

My mail usually gets here around 5pm. The head gasket is due here today...
 

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Discussion Starter #15
FAntastic. If you don't mind I'd like to come by your house and watch, at least for a while. Just let me know when and where. I live pretty close.

Thanks...Jack
 

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Discussion Starter #17
I always bring beer to these things.

If you're offended by that, you're out of luck ;)

Please remind me to ask you where you got your pipes coated.

sitO
 

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Discussion Starter #20
Git yer ass to Texas and we'll show you bbq. Our smokers are so big we pull them behind our trucks in Texas.

You can show us beer. And ride your bike 50 weeks out of the year.
 
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