'91 FJ1200 won't rev past 5k rpm under load PLEASE HELP!

[racerrad8]

Randy, do the 155 pilot air jets actually measure 1.55mm? (0.060")

No, the 155 fits a #51 (.067") pretty nicely, but a #50 (.070") will not fit.

I pulled a 160 jet and it too fits the #51 which is sloppy and the #50 will not fit.

The #53 (.059") drill bit which is as close to .060" I have is really sloppy in both the 155 & 160 jet.

Randy - RPM

[Pat Conlon]

Randy, do the 155 pilot air jets actually measure 1.55mm? (0.060")

No, the 155 fits a #51 (.067") pretty nicely,

Ok, so the #155 pilot air jet is actually 1.70mm in size (0.067")

Sounds like there is no correlation between the Mikuni jet numbers and the diameter (other than larger is bigger)

[FJ12IRL]

Hi All,

Just an update on how she's running post re-jet.

I took her out for a long spin and an "Italian Tune Up" (revving the nuts off it) and she is pulling cleanly all the way from idle all the way up to 6.5k then pulls hard all the way to the redline in all the gears just like my old FZR1000 Genesis.

I have re-installed the JDM clocks and it was great to see the needle go past 180km/h and keep going strong until I ran out of road!!

Carbs have all stock jets installed bar the 112.5 mains, so I can say with extreme satisfaction my FJ is fully de-restricted!

Once again thank you all for your help getting my ponies back.

[Pat Conlon]

Congrats Nigel!

See?  It all worked out and you helped us learn something to boot!!

[FJ12IRL]

Congrats Nigel!

See?  It all worked out and you helped us learn something to boot!!

I have a lot of experience with older (80's & 90's) Japanese motorcycles but I have to say the JDM model FJ with all those restrictions really tested me..

When I posted originally, I was at the end of my tether, about to call it a day and sell her back to the Breakers I'd bought her from and now, having learned from the members here and resolved the issues I had with my FJ, I'm really glad I asked for help.

I hope to help some of you out in the future if I can.

Cheers

Nigel.

[aj52]

Hi All,

Just an update on how she's running post re-jet.

I took her out for a long spin and an "Italian Tune Up" (revving the nuts off it) and she is pulling cleanly all the way from idle all the way up to 6.5k then pulls hard all the way to the redline in all the gears just like my old FZR1000 Genesis.

I have re-installed the JDM clocks and it was great to see the needle go past 180km/h and keep going strong until I ran out of road!!

Carbs have all stock jets installed bar the 112.5 mains, so I can say with extreme satisfaction my FJ is fully de-restricted!

Once again thank you all for your help getting my ponies back.

Hi there

So the speedo has no effect then on the restriction?
From previous posts you mentioned that you changed the ECU and airbox as well.
Could you see the difference between the JDM airbox and the 'new' airbox?
I want do derestrict both of mine too,now that we have an idea where the restriction lay.

Thanks
Hannes

[FJ12IRL]

Hi Hannes, The restriction in the airbox is in the horn of the cover. You could remove the plastic and that would do the trick. I needed the carb rubbers so i bought the whole lot from a breaker.
The rev limiter is in the CDI igniter box, when you replace it with any other non-JDM box the speed limiter in the clock is disabled.

[aj52]

Thanks a lot for the pics.
I need to open that other block off piece then.
So now the search starts for the ECU here in RSA

Hannes

[FJ12IRL]

There's loads of them on ebay Hannes.