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.
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.
I cleaned out the idle jets with WD40 and the air compressor. Bike is running good again.
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?
Cut open your fuel filter for a look see..
Kreem has given many people fits.....
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.
Quote from: Waiex191 on June 23, 2022, 05:16:57 PM
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 (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
Quote from: Old Rider on June 24, 2022, 02:31:33 AM
Hello waiex191
I recomend doing this test on the carbs .https://www.youtube.com/watch?v=Bxx5Iw1xoVw (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.
Quote from: Waiex191 on June 24, 2022, 07:25:48 AM
Quote from: Old Rider on June 24, 2022, 02:31:33 AM
Hello waiex191
I recomend doing this test on the carbs .https://www.youtube.com/watch?v=Bxx5Iw1xoVw (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
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.
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
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.
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
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.
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.
(https://fjowners.com/gallery/12/6694_13_08_22_1_51_39_0.jpeg)
Lots of broken toys in that corner - hovercraft, '73 Harley golf cart, mini pit bike, foam sailboat, and so on.
Anything that stays in my "time out" corner for more than a year gets sold....well except for my '63 Riviera that's been there for 30 years.....Oh, and my trail 90....and I forgot the CB400F....
:Facepalm:
My FJ spent 16 years in the timeout corner! But then my kids grew up.
Quote from: racerrad8 on August 08, 2022, 08:54:31 AM
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.
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.
I took my filter apart. This is the outlet side according to the arrow on the filter.
(https://fjowners.com/gallery/12/6694_11_09_22_12_39_36_2.jpeg)
Here it is unrolled, showing the inlet side. Does not look too bad - definitely no tank liner degradation going on.
(https://fjowners.com/gallery/12/6694_11_09_22_12_39_35_1.jpeg)
A closeup of the worst spot on the inlet side shows a little sediment - dark colored. The Kreem liner is white. It looks good from the top when I shine a flashlight in.
(https://fjowners.com/gallery/12/6694_11_09_22_12_39_35_0.jpeg)
My thoughts are that it doesn't look too bad to me. The filter seems to be doing its job. I did notice some ugly corrosion on the fuel cap. Not sure if anybody has seen this before or has a recommendation.
(https://fjowners.com/gallery/12/6694_11_09_22_12_39_36_3.jpeg)
It took me a long time to get back to the FJ - I was working airplane issues. I have those mostly sorted and am up to 5.1 hours now.
I weighed the 9 floats in my collection. Four of them weigh 8g, the rest 9g. The floats that came out of the bike are immersed in gasoline currently. I weighed them down so they are covered. I'll re-weigh them another time.
The inside of the carbs and bowls look pristine.
I took out all 4 pilot jets. I couldn't see through any of them until I blew through them. Just my own lungs, no air compressor or aerosol can.
Here is what my float needles look like:
(https://fjowners.com/gallery/12/6694_12_09_22_8_25_53_0.jpeg)
The one on top is a new K&L. The one on the bottom was new from RPM a year or two ago. It looks pretty dirty.
Any idea what could cause that?
1) Alcohol causing corrosion or degradation somewhere?
2) Kreem liner making its way to the carb?
3) The pump making debris downstream of the filter?
My guess is that scaly build up is caused by the alcohol in the fuel combined with moisture. The same thing that is on your fuel cap. The carburetors on my son's truck start to look like that in a couple months after cleaning. My motorcycle carbs look ok on the same gas. His fuel tank has a small slit from previous rubbing against another piece of metal and it allows water to enter his tank when it rains (rarely in Nevada) . I think the water reacts with the alcohol to cause that build up.
Thanks - I'll try a clean up and I'll only use alcohol free gas. There are a couple of stations near me that offer it.
I finished pulling the carbs apart. I've been working airplane issues so it has been a while coming.
(https://fjowners.com/gallery/12/6694_21_09_22_9_39_38_0.jpeg)
New seats & needles on the way from RPM.
Yep....Bad float needle seat o rings are the most common cause of gas leaks in our FJ's
Quote from: Pat Conlon on September 23, 2022, 10:15:09 AM
Yep....Bad float needle seat o rings are the most common cause of gas leaks in our FJ's
Those were brand new o-rings from RPM just over two years ago! This alcohol gas sucks. My new parts should be here from RPM this monday according to tracking.
I do love riding the GN400, but it is no FJ. Hard to keep up with my kid when we ride together.
My new float valves arrived early - got them today. Carbs are together and on the bike. I'll chuck the airbox etc on tomorrow.
Just got back from a short ride. Went to the gas station to get some ethanol free premium then a loop around home. It's better, but not really good. Still stumbly between 1000-2000 RPM then suddenly smooths out. Also, as reported a long time ago in another thread, it is sort of wonky above 7000, like it is missing.
Here is what I'm thinking to keep trying stuff:
1) re-check the carb sync
2) Tweak the idle mixture screws
3) Maybe this is an ignition issue
a) check the condition of the kill switch
b) check the condition of the ignition switch
Anybody have any good ideas? When I reported my miss at high RPM somebody had suggested the kill switch or ignition switch. I never got around to that.
Quote from: Waiex191 on September 26, 2022, 01:23:59 PM
Just got back from a short ride. Went to the gas station to get some ethanol free premium then a loop around home. It's better, but not really good. Still stumbly between 1000-2000 RPM then suddenly smooths out. Also, as reported a long time ago in another thread, it is sort of wonky above 7000, like it is missing.
Here is what I'm thinking to keep trying stuff:
1) re-check the carb sync
2) Tweak the idle mixture screws
3) Maybe this is an ignition issue
a) check the condition of the kill switch
b) check the condition of the ignition switch
Anybody have any good ideas? When I reported my miss at high RPM somebody had suggested the kill switch or ignition switch. I never got around to that.
Along with number 3) Ale sure the battery and generator are both very happy - have experienced "ignition issues" that were battery related even though the battery would start the bike without issue. Think it had a cell starting to go.
Hey Bryan, I had a dirty run/stop switch that caused an intermittent power interruption to the ignition box.
It happened around 6k rpm. After checking all the grounds, I found the culprit by running a temp jumper wire from the battery + to the ignition box power input and after a ride, I noticed the problem went away.
Intermittent electrical problems are a pain to track down.
Tonight I popped out my idle mixture screws. Blasted out with carb cleaner, WD40, and compressed air. Runs great. I did open them up another half turn from the previous settings for throttle response. Why I didn't do this when I had the carbs out - I plead insanity due to a rough home situation.
Kookaloo!