Plogged idle jets, I think

[Waiex191]

My FJ was running horrible off idle.  I even stalled it once.  I yanked the carbs off and it looks like the #1 and #3 idle jets were plugged.  I haven't had a chance to test it, though it is back together.

Last year a float valve stuck and dumped gas on my floor.  While I was in there I checked them out, and they seemed ok.  They are new valves and seats from RPM that I installed when I rescued the bike.

[FJmonkey]

If it runs, I have had good luck with seafoam to open the idle jets with a long ride. But I don't think it will work if the jet is blocked.

[Waiex191]

I cleaned out the idle jets with WD40 and the air compressor.  Bike is running good again.

[Waiex191]

So this issue has been coming and going. I wonder:
1) Is my tank degrading?
2) Is the Kreem I put in there 30 years ago degrading?
3) Is my new fuel filter bad?
4) Do I need a filter after the Holley pump?

[Pat Conlon]

Cut open your fuel filter for a look see..

Kreem has given many people fits…..

[Waiex191]

I'm getting close to ripping the carbs out again.  I have a new stock fuel filter for under the tank.  I have an '89 with a fuel pump.

I'm having thoughts that it may be a float valve problem.  I did have to put a fuel shutoff on the bike.  Maybe the floats are leaking worse than I thought.  I replaced all the o-rings and needles with RPM parts when I redid the bike.  Could be stumbling due to richness at idle.  I've been getting about 41 mpg, and since the problem has been steady I've dropped to 37. 

I also bought a filter to put on the output of the fuel pump.  I'll check the plugs when I take it apart.  Any fresh thoughts on the issue are always welcome.

I'm hoping to get my GN400 roadworthy before I rip the FJ apart.

[Old Rider]

I'm getting close to ripping the carbs out again.  I have a new stock fuel filter for under the tank.  I have an '89 with a fuel pump.

I'm having thoughts that it may be a float valve problem.  I did have to put a fuel shutoff on the bike.  Maybe the floats are leaking worse than I thought.  I replaced all the o-rings and needles with RPM parts when I redid the bike.  Could be stumbling due to richness at idle.  I've been getting about 41 mpg, and since the problem has been steady I've dropped to 37. 

I also bought a filter to put on the output of the fuel pump.  I'll check the plugs when I take it apart.  Any fresh thoughts on the issue are always welcome.

I'm hoping to get my GN400 roadworthy before I rip the FJ apart.

Hello waiex191 
I recomend doing this test on the carbs .https://www.youtube.com/watch?v=Bxx5Iw1xoVw  Then you will be sure they not leaking when back on the bike.I have done this myself since you have a fuelpump you can maybe add some
pressure with the fuelpump ...on mine gravityfeeded i just try to blow into fuelhose

[Waiex191]

Hello waiex191 
I recomend doing this test on the carbs .https://www.youtube.com/watch?v=Bxx5Iw1xoVw  Then you will be sure they not leaking when back on the bike.I have done this myself since you have a fuelpump you can maybe add some
pressure with the fuelpump ...on mine gravityfeeded i just try to blow into fuelhose

I have always flipped the bank upside down and blown into the hose.  I did this when I refurbished the carbs, and they were good for a year +.  When I had them apart last month this check was good again.  I removed each needle and cleaned things up.

[Old Rider]

Hello waiex191 
I recomend doing this test on the carbs .https://www.youtube.com/watch?v=Bxx5Iw1xoVw  Then you will be sure they not leaking when back on the bike.I have done this myself since you have a fuelpump you can maybe add some
pressure with the fuelpump ...on mine gravityfeeded i just try to blow into fuelhose

I have always flipped the bank upside down and blown into the hose.  I did this when I refurbished the carbs, and they were good for a year +.  When I had them apart last month this check was good again.  I removed each needle and cleaned things up.

If you flip them upsidedown and blow into the hose i think they always will simulate that the floats shut off the fuel and giwe a false reading. You will have to place them in the positoin they
sit on the bike in a wice or something and fill them with gas .Then you can test on by one like in the video.If they not leaking then they will not leak on the bike exept if the bike is standing on sidestand and a float has get stuck

[Waiex191]

Step 1: get my GN400 back together so I can rip the FJ apart.
https://youtu.be/LB-_bQoedYA

I'd forgotten how close to WFO you are while maintaining 60 MPH on the flat.

[Waiex191]

So my GN400 was leaking gas when on the kickstand, but not on the centerstand. To make a long story short, the brass float on one side developed a leak. New float and it's like a new bike. This leads me to my FJ question - can the plastic floats leak and do the same thing?  I guess I can pull them out and weigh them, plus shake them to see if there is fuel inside.  Anybody have experience with float degradation?

I feel like the parts I got from RPM were top quality, but I didn't replace the floats. 

Off topic: flight 3. I've finally had the airplane faster than I've had the FJ.
https://youtu.be/lrPWXUGqVTc

[melloncollie]

I suppose anything's possible, I can't comment how likely it is though.  As far as testing the floats; do you think you'd see bubbles if submerged in water or rubbing alcohol outside the carbs?  You could swap them out blind but it'd be nice to know for sure if that's your culprit.

Do the stock carbs have an overflow for each carb?  My rs36s do, it takes some of the guesswork out of troubleshooting sometimes.

[racerrad8]

You need to full investigation starting at the tank. If the tank liner has failed and there is now rust getting into the carbs, plugged idle jets for sure. The drop in milage could be leaking needles or seats or restricted jets causing you to use more throttle to maintain the same speed.

This bike has very much of the same issues you are experiencing: https://fjowners.com/index.php?topic=18811.0

I had another one where the tank liner was getting in to the system as the filter was removed from the petcock in the tank.

It will be interesting what you find.

Randy - RPM

[Waiex191]

Thanks, I'll report my findings.  Last time I had the carbs apart they looked very clean, though it seemed I had to clear the low speed jets.  I have a new under-tank filter so I'll cut up the old one.  I also plan to weigh all my floats, including the very dry ones from my parts carbs. 

[Waiex191]

Progress - the GN400 is running great and the FJ is in the timeout corner.  The GN just finished a 2 year sentence there and now that the airplane is done I expect the FJ will be quicker.


Lots of broken toys in that corner - hovercraft, '73 Harley golf cart, mini pit bike, foam sailboat, and so on.