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Discussion Starter #1
Hi All, so here we go... Just had to do an engine swap put :( and did all the grunt work myself. Bike started up 1st time and sounded great, took it out for a ride and found she was having issues in the 4-5k Rev range and seemed to be heisting with a constant blurb note coming out of exhaust system, give it some more rev's and noise went away, gun her and she flies all the way up no problem, little bit of back fire when dropping off power (but do have a different exhaust on, so sure that does not hide the noise like a stock pipe). Took her in to a repair shop to get carbs cleaned, balanced & jet's checked to see if that would solve issue.. picked her up today and still same issue:crap: the repair shop is a good guy who I have used before! So looking for some advice on what may be the cause for the issue in the 4-5k band.. (1998 carb bike has K&N air filter, Jetted, After Market exhaust that all worked great on my other engine) like I said she goes like a bat out of hell under power but does not like cruising in the 3-5k rev range feels very rough.. Thanks..
 

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Isn't this the classic "K&N air filters should never be used on a carbed 'Bird" syndrome?

Yep, I know you said it worked great on your old engine, but there's a lot going on down there. A lot of small variables that can add up. Try a stock air filter?

Everything put back together properly? No loose fittings or not-quite-pushed-back-on recirc. air hoses? Are the vacuum take-offs plugged back up properly?
 

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My 97 Carbie was acting like that last year and after a new air cleaner the problem disappeared. Is the filter clean?
 

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Discussion Starter #5
So ran bike with choke half open and it seemed to run better, so I am assuming that it is running lean?
 

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So ran bike with choke half open and it seemed to run better, so I am assuming that it is running lean?
This points even more to replacing the K&N with a stock filter.
 

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Discussion Starter #7
Blows my mind that two engines can act so differently with the same after market additions (K&N, Jets, Exhaust) old engine never had an issue... question is I just had carbs cleaned and balanced etc so adding the stock filter back in is that going to throw off that work? I am taking bike back to shop today so want to pick up a filter on way if you all think I should go that way? Cheers...
 

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Need to raise the needles a notch you can do it without removing carbs! When you crack it open your running on the main jets which are rich enough and make it run sweet but the mid range is lean, check and see if the needles are shimmed should have one washer from factory under needle if there are any more then someone tried, add 1 or 2 more i just installed a Sigma Jet kit to my 97 with K&N and Yoshi Slip ons and they rec and supplied 2 more shims to what factory provides , and when it was all said and done it screams smooth no flat spots any where! It worked for me, its the first place id start if i was in your shoes! Good Luck!
 

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Discussion Starter #9
Going to change out my needles to #45 for the pilots, spoke with jet kit company and it's one of the things they suggested especially with the K&N air filter letting more air thru. Running 150 on main jets, so waiting on jets and I am sure we are heading down right track.... Stay tuned
 

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Are you running every last bit of the stock airbox inlet trunking hardware as came stock from the factory? It's been noted before that the factory CV carb's need to have all the bits and piece (air inlet wise) in place your you may have performance issues going down the road. Key bits are the "Air Guide Plates". I'd double check airbox and related parts to ensure you've got all the parts in place before doing a jet change, but that's just me.

Tony
 

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Discussion Starter #11
Thanks Guys, Have all the stock airbox etc in place... she does not like being in the 3-4500 range with out the choke at least 1/2 way on, give her gas and she goes. Just think this engine runs a lot different than my old one and the #45 Pilot should solve issue greatly if not then bye bye K&N filter. not looking too get to a valve job.. fingers crossed.
 

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Thanks Guys, Have all the stock airbox etc in place... she does not like being in the 3-4500 range with out the choke at least 1/2 way on, give her gas and she goes. Just think this engine runs a lot different than my old one and the #45 Pilot should solve issue greatly if not then bye bye K&N filter. not looking too get to a valve job.. fingers crossed.
Checking valve clearances is always a good thing, but something of a PITA. Especially now the new engine is in the frame! Unlikely to cause such a rideability issue, in any case. Sounds like you're on the right track with experimenting with the carb internals, but that's a PITA too! Good luck!
 

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The air filter change back to OEM, although expensive, is still one of the easier un-mods to do to test for performance issues. And the choke,..it is more correctly an enrichment circuit although called a choke. It doesn't restrict air flow as did the old Keihin CV carb chokes from the 1980's era did. There is no flapper/choke plate in the throats of the XX's carbs.

Tony
 

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Discussion Starter #15
So took out K&N air filter dropped in oem air filter and what do you know... all that 4-5k sluggish gone! crazy to think that a brand as well know as K&N can cause such issues. Still may change out pilot jets to #45 just to see how perfect we can get her to purr...
 
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