Why won't it run?!

So just some background, I bought an 81 xj550 seca that had been sitting in a garage for 5 years and would not start. Naturally the first thing I did was open up the carbs and clean them. In the process I broke the rubber on two of the float needles so I ordered rebuild kits. I also put in a new air filter.

After putting in new float needles and seats I have only been able to get it to run twice. Both times I held the throttle wide open and let the motor turn over for about 15 seconds before it would start. It would not stay running unless I held some pressure on the throttle the whole time even with the choke all the way open and the throttle response was very weak and slow. I decided that this meant it needed more fuel so I started adjusting the fuel screws on top from 2 3/4 turns to 4 1/2 turns out from bottom but I still had the same results. I turned all of them out one more turn and now it will not start...

I have given up for the weekend to try and wrap my head around it. Does anyone have any suggestions for me? I think I may try adjusting the fuel screws the opposite way and see what happens. I just really do NOT want to pull the carbs again.

Also, my rebuild kits came with 3 O-rings. One I used for the float needle seat but I didn't see a place for the other two. I thought maybe for the jets but I pulled them out and there weren't any there to replace... Any ideas?

Thanks in advance everyone!

 

You replaced the float needle but did you check the float height ? New needles might mean float height changes . When you stated you cleaned carbs but unless you did a full tear down and broke the rack (took cabs off the rails) and soaked carbs . Spray cleaner will NOT get into the small passages of the carbs if bike has sat . One more issue the float bowls have a tiny jet in the bottom it is probably plugged up this part of the choke circuit , backing the mixture screws out will not help please turn them back in to 2.5 turns. Try turning the idle knob in if it is backed out to much , then bike won't stay running . Have you opened the choke while trying to start? Cheers.

 

Checking the float height isn't something I have tried doing before. I'll need to do some research to figure that out.

I did not take the carbs off the rails...what do you suggest soaking in?

I'm assuming the tiny jet you're referring to is the long tube on the edge of the bowl that goes down through the bowl to the bottom? I will try adjusting the idle knob when I take them out again (crap). I did try starting the bike with the choke open and it didn't help but there was a change in engine speed when I had it running and opened the choke. That makes me think that the choke circuit is functioning and that maybe I just need to soak the carbs...

 

My favorite is Berrymans carb dip is a one gallon container and has a basket inside. You can purchase at AUOTOZONE . Be advised do your carbs right the first time and you should not have to tear down for a long while. Go to the upper right corner of the page xj4ever has the seals that need replaced as well as the fuel rail O rings . The butterfly seals need replaced after 30 plus years this is source of vacuum leaks. To do a full tear down and soak you can do this in a day . Is not as scary as it sounds a 4 separate bowls to keep all fasteners with same carb , a 10mm wrench or socket and ratchet, a small flat blade screw driver and a JIS screw driver . Look for the thread church of clean. Explains this more in depth , the only thing Mikuni carbs is to remove the butterfly plate the 2 screws are peened in place , a dremel you can gently grind down a bit and remove screws. Put new screws either fron xj4ever or ACE hardware these are small metric screws ,I went all out on my carbs , used stainless Allen screws, and a dab of blue lock tight. Cheers.

 

What pieces should I remove before soaking? Obviously the diaphragm but what about the float seat etc? Also, how long to soak?

I’ve looked through my service manual a little and only seen that it says fuel level: 2 +- 1mm... surely it’s not 1-3 mm above the carb body

 

A FULL tear down all the jets ,float, needle and seat , mixture screws and O ring , the butterfly plate removed this allows the throttle shaft to be removed and this is where the butterfly seals sit , even if they seem soft replace. Soaking the carbs with the seals installed will eat these seals ,and DO NOT reuse them period ( vacuum leak)

 

Alright, I guess i'll dive into this next week and just finally take my time and clean them thoroughly so I don't have to remove them again! Thank you so much for all the info.

 

Do not try to remove the diaphragm from the piston, piston should be cleaned by hand.

 

IN THE CHURCH OF CLEAN

Replacing your Hitachi throttle shaft seals

Setting the fuel levels

The Information Overload Hour

 

Update:
I took the carbs out and the idle jets were completely stopped up again so I'm thinking I'll need to clean out the tank soon. I cleaned the jets all out again and put it back together and attempting starting again. Yesterday on the first few tries it was the same before, it would fire maybe once or twice and then just keep turning over. I battled with it for over an hour and eventually decided to call it a night. This morning I walked up to it, turned the gas on and hit the switch and it fired up on the first rotation of the starter but was running super rich. I kept it running and turned the mixture screws down a little and stopped it from smoking and it actually idled for the first time! After letting it run for about 30 minutes I turned it off and went to doing other things. About three hours later I went to turn it on so I could ride it a little and yet again this problem persists... A couple of fires and then nothing...

I'm starting to lose my mind here but I think the ignitions coils may be the culprit now. I measured the resistance on the plug wires and one set read .8 Kohms and the other read 30Kohms.. way off from the 11Kohms the service manual says they should be.

Any input or suggestions?

 

My friend. You’ll continue to chase your tail if you don’t reel this in. Believe me, we ALL understand how tempting it is to want to throw your leg over your XJ and cruise on down the road.

You’ve not resolved your potential carb/fuel issues and now you’re looking at coils…

This will take time. Winter is coming (solid Game of Thrones reference). Click on the top right hand icon of any page here on the forum and start a conversation with XJ4ever. He sells everything you’d possible need.

My advice would be:

1.) Check your valves… No sense in doing anything else if your valves are out of spec. This wont cost you anything (unless you need to buy a feeler gauge of course) and you’ll know what adjustments you’ll need to make.

Here is a step-by-step…
https://www.xjbikes.com/forums/thre...valve-adjustment-with-pics-parts-i-ii.116006/

2.) Make sure your tank is clean of any debris.

3.) COMPLETELY rebuild your carbs.

See K-Moe’s Links Above… They are INVALUABLE to doing the work that lies ahead of you.

Stay the course. You can do it. You’ve got your hands on the right bike and you’ve come to the right place.

Take it from me. When I purchased my first motorcycle, it was a "non runner." By chance (and luckily), it happened to be an XJ. Then I found this place.

Be patient. Ask Questions. The answers are here.

 

Rechecked resistance through coils today and found out my caps are what need to be replaced. A full tear down and soak of carbs is in the works soon but the xj4ever kits are very expensive considering I only need the seals so while I wait I’m trying to solve my weak spark issue

Maybe I can just get the seals outside of buying the full kit...

 

You can buy the seals separately......chances are all you will need are throttle shaft seals, the o-rings and washer on the idle mixture screws, the fuel rail o-rings, and the butterfly shaft screws.

 

Side question. Is there a specific way to remove idle mixture screws? I tried backing one all the way out but it didn’t come out, it just kept clicking over on the top thread. I didn’t want to try and use too much persuasion at the time

 

I had same thing xj650. I used spray cleaner and 2000 grit wet sand on everything and it still took 3 attempts. I did not replace one part. Just took my time and got lucky I guess. After the 3rd clean it fired immediently with no choke and ran fine till idiot brother plugged headlight array into ignition plug.
(See my post)