Replaced Battery,Bogs at 5k;now Eureka!!!!

[ScottS2488]

am I getting too much air through the K&N airbox filter? replaced the battery today and took it out for a test ride. slight miss at about 2500 then pretty sweet thru the power band til 5000....then pukes like crazy

signed
ready to cook marshmallows over the burning hulk

[ratbyk]

Pukes out at 5000

Have you pulled the plugs to see if you are too rich or too lean?
Your first check should be a plug check. If too rich jetting could be wrong or float level to high. If lean then float level to low or a blocked or kinked fuel line. If the plugs look good. Like a nice tan color just a bit of color I would not blame the carbs. Check out the ignition, particularly the pick up coil wires.
Ken/Sooke
78E Ratbyk
82 FT500 "lilRat"

[ScottS2488]

just another tidbit.....I got the same bogging when I put on those POS emgo individual filters...5000 rpm and end of story.....the wrench told me the plugs were still showing a little bit rich ( they put brand new NGK's in) the mains are 137.5s (maybe I should go up to 140????)

[ratbyk]

Bogging

Hopefully you do not still have those POS filters on. If they gone, then still pull the plugs. They will tell you what is going on. To rich, to lean, or maybe only one or two are not right telling you which cylinders are causing your problems and whether it is carb related or ignition. Really, a quick plug check will tell you a lot.
Ken/Sooke

[ScottS2488]

I had tried the individual filters 2 years ago and got the same result...sputtering at 5000 rpm...so I'm sure I'm getting too much air now.....when I had the old K&N filter on a month ago, it ran fine at highway speed, just way too rich at idle....now it idles just fine...thinking of moving the needles to 1 step rich

[ratbyk]

Bogging

Would not recommend moving the needles a step richer. The bike has run for 25 years with the needles in there present position. If you do you will likely be taking the carbs off yet again to move the needles back to there original position. Do some more diagnosis before you make any decisions. Know exactly what you are trying to correct before going helter skelter with fix's that may cause more problems than they correct.
Have you pulled your plugs yet to determine if your problem really is fuel related? Bogging down at 5000 may not be a fuel problem. Even though the last time you felt this same bogging down and it appears to be the same as when you had the POS filters on it may not be what you suspect.
A faulty pick up coil wire could be causing the same thing. At this RPM the vacuum advance may have pulled the ignition plate around enough to cause the wires to start to pull apart. Could also be 1 weak coil that is breaking down at that load/RPM. If you lost 2 cylinders at 5 grand the bike would again feel like it was bogging down.
Find out exactly what is wrong before applying questionable fix's.
Ken/Sooke

[ScottS2488]

Eureka!!!!

it's running way to rich still......broke down and pulled the spark plugs.....I never knew they powder coated new plugs....lol.....anyway first I lifted the needles up one notch.....damn near got stuck in the boonies....then dropped to 1 notch above normal....seemed a little better....then put the circlip on the very top.....now it's very close to perfect...if I could only go up 1 more notch......hehehe.

so now, is there any way to calculate how many jet sizes I should come down and put the needles back to normal?

[TopCatGr58]

Hey there Scotts,

I had to do a little searching to find your original thread, and since you're still talking about the same problem, it's best to keep the replies and followup questions in the same thread, so that we don't repeat info that we may have already told you, but couldn't remember when seeing just 1 post in new thread, even though you/we had talked about same problem in previous thread!

Okay, we know you're running the box filter, not individual filters, have moved the needles down as far as they can be set, and it seems almost right! This setting is making them much more leaner than they were! You say you have 137's in now. However, you didn't mention whether you checked your pickup coil wires? Will the bike rev past 5K now? Is your vacuum advance plate turning when suction is applied to it, are the centrifigual weights moving freely? Many performance issues can be ignition vs. fuel/carb. Where are your floats set? They may be too rich and just need adjusting?

I don't know of any formula for how many notches on needle equals 1 jet size?? But like RatByk said, you need to check out these other possibilities first! Changing the main jet size will involve pulling the carbs of anyways, so you can check and adjust the float height while in there, and tell us what it is/was!

[ScottS2488]

I had already set the float height as low as they would go because otherwise the gas would start overflowing.....

the bike revs over 5000 now...but not by much....on the bright side it is quite rideable now......doesnt bog down in the low end like it was

I was told that each notch on the needles = about 5 - 8% more or less fuel.....is that accurate?

[TopCatGr58]

Hey ScottS,

Well, according to the manual, the needle jet mostly controls fuel for the transition from idle thru midrange, but isn't that important in W.O.T.! Also, not going over 5Krpm as you have proved is NOT a matter of being too lean, (running out of fuel), since you were running rich to begin with, so I still think you're chasing the wrong thing here!

I still think you need to eliminate all of the other ignition possibilities before going further into your carbs. I'm no carb GURU, so hopefully someone else will chime in with similar advice, or contradict me entirely!?

If the timing is wrong, or the advance isn't working properly, it will definitely hinder the engine's ability to get to the higher revs!

I have not come across any notes regarding the % of increase/decreased fuel flow per needle notch position. I also don't know how the size numbers actually relate to the actual diameter of the main jets, but with 2.5 incremental changes, that equals to less than 2% change using just the change size over the actual size values!? If 1 notch = 5% change, then you would need at least 2 jet sizes per 1 notch using "Simple" math!?
Good luck, but still think it's an ignition/timing issue!?
T.C.

[chevy45412001]

glad to see

I sure am happy to see i'm NOT the most stubborn person on this site...lol

[skids]

Scotts, there has been issues regarding older model carbs (78 and 79) with the breather hoses. They can not be plugged-off or the gas can overflow. Since you took off the airbox, if you have the older carbs, I am assuming the individual cone filter do do have a place to filter the air to the vent hoses, so you might want to consider rigging-up filters for them somhow. I personally do not use cone filters, but I remeber some of the discussions.
Sid

[uk1.1s]

Hmmmm

I had already set the float height as low as they would go because otherwise the gas would start overflowing.....

That don't sound right....

If your carbs are overflowing and fuel is getting everywhere you also have a needle valve problem. This is the valve which shuts off the fuel once the floats...err...float high enough.

You shouldn't have to drop the float adjustment as low as possible to stop this... the carbs would have been designed to have the correct adjustment around the middle. There are well known float height values posted around on the forum or tech tips and it's around 25mm approximately. Moving floats to one extreme is not helping your diagnostics I'm sure.

Get yourself a float valve replacement kit (inexpensive) from someone like Parts n more...

Good luck with it

[Jacobite]

I was having low rpm problems - up to about 3000 rpm, and was getting terrible mileage (about 20 mpg). The bike was running way too rich. In talking to the PO, he said it ran rich the whole time he had it. After I tried just about everything else (including replacing floats & needle valves), I moved the clip on the needles from the middle to the top and it worked (thanks Don & Ken!). No low end bogging - lots of top end power, and mpg of 34.5.

Moving the needles may not be the solution to Scott's problem - but it seems to have been the solution to mine. I never had problems with high RPM - I can run it to redline with no difficulty (not in top gear - I'm too chicken!)

[chevy45412001]

scotts

just a tip if your still running rich (black plugs ) going down in jets will help.This is just an example of MY BIKE an XJ. Bone stock jetts 112.5 all 4 . I put on 4 individual air filters,bike fell flat at 5.000 rpm. I went up to 137.5 mains all 4 . bike will take 9,000 plus rpm"s now ,I need to go back down my plugs are still black (to much fuel) I'm going to try 130"s , every thing else in carbs is set to spec,i have no fuel leak probs or any other ill effects. You do need to read plugs though.guessing will not help your problems.Take note theese guys on this site KNOW what they are talking about. Just some friendly insight.