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1/4 throttle issue

Old 06-19-2012, 03:21 PM
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1/4 throttle issue

Got my bike up and running but found an issue when i got on the highway for the first time... while riding around town in varied throttle positions the bike runs good for a rough tune pulls all the way no spikes no drop offs in power good temps etc... but when cruising at highway speed at 1/4 throttle it looses power backfires bucks and runs like **** only after cruising for 10-15 mins at first its fine pull over let idle for a minute and its good for another 10-15mins then it starts again... pulling the choke makes no difference no better no worse... when its bad it kind of feels like the petcock is hooked up wrong but I checked and its not... I assumeits in the jetting i have a fp ti jet kit with 50the pilots needles in the center 178 front main 180 rear... she pulls and will pull up the front in first and second on stock gearing and is good riding through town but hates cruising at the same speed any thoughts? I have mori cams valves je hc pistons dr honda velocity stacks and a stock filter pair removed...
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Old 06-19-2012, 04:02 PM
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The pilot jets are too large
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Old 06-19-2012, 04:22 PM
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I have to agree. Mine had 50 pilots in it when I got it with the FP jet kit. I think it had the same mains in it as well. I went through the carb thread and put 48 pilots and 75/78 mains in it, needle in middle position and screws 2.5 turns out and it ran perfect. In an effort to try to get a little better mileage I dropped the needles one position and it ran great everywhere except while cruising up to about 3000 rpm where it pops back in the carbs. Didn't seem to help mileage so I'm going to go back to the middle position on the needles.
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Old 06-19-2012, 05:18 PM
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I have keiln 45 and dj 45 pilots should i run either of these till the 48new pilots i just ordered come in or leave it alone because they will be too lean? Im assuming they will be too small and it will run lean...
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Old 06-19-2012, 05:23 PM
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I have keiln 45 and dj 45 pilots should i run either of these till the 48new pilots i just ordered come in or leave it alone because they will be too lean? Im assuming they will be too small and it will run lean...
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Old 06-19-2012, 07:47 PM
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I'd just wait till you get your new ones. No point in tearing it apart twice. What all do you have done to the bike?
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Old 06-19-2012, 08:28 PM
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It wouldn't hurt to run the 45s right now. You would be down on power slightly on the low end but it should cure the loading up issue you are having.

Though if you have 48s on the way it would be up to you if you want to pull the carbs twice or not.
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Old 06-19-2012, 09:17 PM
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Yea im waiting for the 48s it only takes half hour but its not worth it ive waited this long i want it right... gts I have basically built a stg 1 motor stacks pistons cams valves...
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Old 06-19-2012, 09:53 PM
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Have you done anything to the slides? With the stacks you can do one of 2 things to overcome the tendency they have to run rich in the mid-range.

Either drop the mains down 1 size or plug a lift hole in each slide.

If you read my carb set up thread it covers this and you really should do the slide mod if you want the bike to run properly.
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Old 06-20-2012, 01:33 PM
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Did the slide mod when i put the stacks in and I do have the stock needles ordered them just in case but I dont think ill need them...
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Old 06-20-2012, 01:56 PM
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No worries, just wanted to check because they can also cause the issues you were talking about by going rich in the mid-range.

Also you should have no real issues with the FP needles.

Last edited by 8541Hawk; 06-20-2012 at 02:12 PM.
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Old 06-20-2012, 02:09 PM
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I think I'd probably stick with the FP needles with your set up as they are easier to adjust if you need to and have a lost more adjustability as well.
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Old 06-20-2012, 07:20 PM
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Thanks for the info hawk and gts!! i will update when the new jets come in till then she will be in the garage!!!
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Old 06-28-2012, 02:06 PM
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So I got the jets in and its better at a cruise but when you try to go up it doesnt seem to have the punch it should... is that the needles?
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Old 06-28-2012, 02:12 PM
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Originally Posted by maniac2313 View Post
So I got the jets in and its better at a cruise but when you try to go up it doesnt seem to have the punch it should... is that the needles?
Generally yes. Whether it is rich or lean is what you would need to figure out.
Try the choke trick to see if it runs better with it out (a lean condition) or worse (a rich condition) and then adjust the needles.

Though by reading your first post it sounds like you have the needles in the center groove. So I bet you are rich in the mid-range and I would just drop them one notch as a start, but that is just me...
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Old 06-28-2012, 02:40 PM
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Thanks will drop them tonight! So down with the needle height leans it and raising richens correct? Sorry im not the best with carbs... the choke made very little difference but it was worse...
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Old 06-28-2012, 03:23 PM
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Originally Posted by maniac2313 View Post
Thanks will drop them tonight! So down with the needle height leans it and raising richens correct? Sorry im not the best with carbs... the choke made very little difference but it was worse...
Yes dropping them leans it out and raising them makes it richer in the mid-range
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Old 06-29-2012, 08:35 AM
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If you pulled fuel by going to smaller idle jets then you might want to consider adding a bit more fuel in the mid and upper ranges (needles and main). Like 8541Hawk said, use the choke to determine if you're lean or rich.

Also, double check your carb sync and that the tank vent hose is clear of obstructions and kinks. It just sounds a little strange that an overly rich idle jet would foul your plugs while operating in the mid range. Sounds like a fueling issue to me, like the petcock you mentioned, but you already checked that. Might try pulling a plug right after it happens to see if the plugs are really fouled.
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Old 06-29-2012, 01:42 PM
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The plugs arent fouled its just lacking the punch it should... I think its rich i moved the needles will ride it tonight to see for sure...
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Old 06-30-2012, 10:01 AM
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Its good enough to ride through the break in process... then i will do a fine tune on the dyno! Cant wait I'm happy with it now still have a few mods to go but im getting there!
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Old 06-30-2012, 10:03 AM
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Originally Posted by maniac2313 View Post
Its good enough to ride through the break in process... then i will do a fine tune on the dyno! Cant wait I'm happy with it now still have a few mods to go but im getting there!
Sounds like we got you close at least.... glad to hear it is running better for you
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Old 06-30-2012, 10:49 AM
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Its very close I cant wait for the dyno!! Thanks !!!
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