1984 fj above 5000 bogging

[JOWEINA]

Hello my 1984 fj1100 idles at 1000 perfectly accelerates to 5000 strong but then hits a wall feels like choke is on if i go through the gears it will go to redline in every gear but doesnt feel like a 1100 should want to pull your arms out of socket sync carbs ok valves ok i did notice when syncing carbs i attached a external tank and i kept getting air bubbles in the line if i tapt on the carbs could there be air bubbles in the carbs or do they work themselves out? and when i pull plug and check spark against engine yellow spark not blue but when i use inline sparkplug tester its ok thanks  in advance for any help
                                                                         JOEL

[Motofun]

Sounds like your fuel / air mixture when on the main jets is suffering.  Fuel:  partially plugged fuel filter, kink in fuel line, vacuum petcock not fully opening, jet needles not properly set.

AIR:  bad air filter, ?

[fj1289]

Hello my 1984 fj1100 idles at 1000 perfectly accelerates to 5000 strong but then hits a wall feels like choke is on if i go through the gears it will go to redline in every gear but doesnt feel like a 1100 should want to pull your arms out of socket sync carbs ok valves ok i did notice when syncing carbs i attached a external tank and i kept getting air bubbles in the line if i tapt on the carbs could there be air bubbles in the carbs or do they work themselves out? and when i pull plug and check spark against engine yellow spark not blue but when i use inline sparkplug tester its ok thanks  in advance for any help
                                                                         JOEL

Welcome Joel!

What's the background on the bike?

Did you just buy it?  Have you had it a while and it's always been this way?  Did it recently start doing this? Any maintenance Or modifications recently?

There is a lot of experience and expertise on this site - but internet diagnosis is always a bit of a challenge.  How does that phrase  go - Help us help you! 

[JOWEINA]

I did just get the bike a absolute gem looks brand new even though it has 34000 miles no mods bone stock the carbs look brand spank new i meen clean as hell dont no a whole lot about the jets and stuff but if i were to guess id say they were not modified i did take the tops offf and looked at the vacume diaphram looks brand new no holes fuel line is not kinked made sure that the y were the fuel lines split between the carbs is correct i know it is gravity fed just thought of something when i hooked up the external tank to synk carbs it did not have a petcock so the fuel in it was always on i went inside and when i came back out there was gas all over the ground like the floats did not shut the gas off with the vacume petcock i would have never known this hum could that have something to do with it i wonder

[fj1289]

These carbs are notorious for the o-ring that goes around the float seat drying out and causing leaks.   RPM (the sponsor banner) has a kit to replace all the o-rings and has allen head hardware to replace the JIS screws. 

Good deal on the slide diaphragms looking good.   

What altitude to you live at?  I wonder where to motorcycle lived most recently - it may have been rejetted for a different altitude.  No way to really know without getting into them...

The files section of this forum has a lot of great info - including quite a bit on carbs.   

These bikes are 30+ years old now.  Most have done very well to this point, and just a little TLC and refurbishing a few things that are probably due after 30 years will have them set to go another 30+ years!  Peacocks, carb o-rings, the "red connector", the voltage regulator, etc are all reasonably easy tasks for a leisurely weekend afternoon and will reward you with many trouble free miles in the future!


One last thought, what bike are you coming from?  Just want to make sure you are not confusing the top end rush of a modern 1000 with the expected rush from a fully stock three decade old 1100... but it should still pull hard enough to put a grin on your face!  Kookaloo!

[Mark Olson]

You may have a vapor lock happening . Try opening your gas cap and ride to see if it changes anything. If you use a magnetic tank bag that can also cause problems with gravity fuel delivery. Make sure fuel lines are routed correctly. Perhaps someone will post a pic of 84 fuel line route you can follow. Ride bike over a few curbs or speed bumps and that will sometimes help reset the carb floats. Temporary solution but you will need to pull carbs and deep clean to start at square one.
Good luck.

[Pat Conlon]

Perhaps someone will post a pic of 84 fuel line route you can follow....

Check in the Carb Files....there is a reason we saved it over there...

Other than the petcock screen in the fuel tank, there *should not* be a fuel filter on the system.