84 fj11 refuses to rev past 4000rpm,

[fj11.5]

Hi all, bike refuses to rev, have changed coils, ignitor box, coil pick up, checked for dodgy wires ect ect, only thing i havn done is take the carbs out , would float height blocked jets ect cause this, using air pods and 4 into one system, have also done the relay coil mod and had the advance 5deg plate on , was playing up before the mods , any ideas anybody ?

[irishluck]

carbs.

Use to own an 86 vulcan and it did the exact same thing, got carbs freshly rebuilt and rode like a champ

[fj11.5]

Thanks, at least im not the only one, ill tear the carbs out again and check float levels , im hoping she,s just starved of fuel, as it starts fine and idles when warm

[racerman_27410]

check the carb diaphrams for tears.


check the main jets and emulsion tubes for blockage..... those little holes are easy to get clogged up


KOokaloo! (i hope you get yours back soon)

[fj11.5]

diaphrams are like new, changed when i found holes before, jets are clear, hmmm emulsion tubes u say didnt even bother checking them just b4  , dam dam ***k , will pop the carbs again , thankr mate . . would a plug cap cause the problem ?, have multi metered them seem ok .

[racerman_27410]

the small holes in the emulsion tubes function right at the point where the engine goes into high RPMs so i would bet thats where the problem is.


Kookaloo!

diaphrams are like new, changed when i found holes before, jets are clear, hmmm emulsion tubes u say didnt even bother checking them just b4  , dam dam ***k , will pop the carbs again , thankr mate . . would a plug cap cause the problem ?, have multi metered them seem ok .

[andyb]

They'd have to be really, really plugged though.

Clean em and see, can't hurt to have more things clean within the carbs, it's another thing to check off the list!

[fj11.5]

Ok, on a roll, checked 2 before bed and both tubes had a few holes blocked , will sort out the other 2 today, thanks guys ,will report back to HQ when she lives again

[fj11.5]

Hi again, checked the other 2 emulsion tubes all clear, , maybe ive done the float levels wrong ? seems like its hitting a rev limiter with huge back firing, flamer out the pipe ect, on the plus side she starts and idles great haha

[Harvy]

Hi again, checked the other 2 emulsion tubes all clear, , maybe ive done the float levels wrong ? seems like its hitting a rev limiter with huge back firing, flamer out the pipe ect, on the plus side she starts and idles great haha

Mate, that sounds quite familiar, but in my case it was at 6000rpm. After replacing plugs and leads to no avail, I bit the bullet and bought a Dyna2000 ignition........all better now!

Harvy

[fj11.5]

Hey harvey, thanks mate, i may just have to end up doing something like that,

[Pat Conlon]

Hmmmm...'84 FJ ignitor uses a vacuum advance...so,
1) Is the vacuum hose hooked up to the igniter box? (off #3 carb)
2) If so, disconnect the line at the carb, stick it in your mouth and suck, does it hold a vacuum?

Not sure that's the reason, Even with the vacuum line disconnected the bike should rev past 4k....It's gotta be gas related...

3) Check your fuel line routing....follow oem, critical on early gravity feed bikes... This is a very common problem, pinched fuel line which causes all kinds of weird symptoms.
4) and make sure your carbs fuel bowl vent lines are open and not pinched or blocked. The bowls need to be vented to atmospheric pressure or the will not fill correctly

Finally, if the above 1 thru 4 is of no help...sigh, pull the carbs off and

5) Check your float heights. It sounds like your floats *could* be set too low.
A low fuel level in the float bowls will cause them to dry out at upper revs and the bike will go lean stutter and backfire....  

Report back....Let us know what you find. Cheers!    Pat

[andyb]

Wait, quick reset time:  Did you get this thing recently and it has never worked properly, or did the bike used to work correctly and since awhile ago cease to do so?

[fj11.5]

Hey again, tripple checked float heights , double checked all hoses and lines, vacume advance is on #2 carb as per manual can swap for 3 if thats any help ? , unless the problem happens again i may have fixed it ?? re,routed coil wires ,seems it was arking out on fuel tank, , tank off ran perfect , tank fitted problem came back, sort and heatshrink wires , all good ?  have had her for at least 7yrs , ,not used much lately dam it , thanks to all for the help , hope ive got it sortet

[Dan Filetti]

... stick it in your mouth and suck, does it hold a vacuum?

Let's keep it PG here Colon!

Dan