Fuel delivery issue

I took my 85 XJ700N for a ride today and after about 8 miles it died on me. Acted like it was out of gas but I had gone only 55 miles since filling up. After trying to restart it a couple of times I set the petcock on Prime and it started right up. Got the the filling station and it took only 1.3 gal. I switched back to "on" and drove home with no problems. Any suggestions before I remove the petcock and filter see if I can find a problem?

 

Have a look at the condition of the vacuum line. If it's soft enough they can collapse when hot.

 

Do you have a inline fuel filter? Could be dirty...

 

Hadn't thought about the vacuum line collapsing but I'll check it. I'm pretty sure I installed a new vacuum line when I rebuilt the petcock, but I'll check on that also. I have an inline filter and plan to check it also, but it's only about 1 yr old. Hope it's something simple like that. I'll let you know what I find. Thanks for the suggestions.

 

Have seen many times that ppl use a rubber hose not intended for vacuum and it goes flat until bike quits

 

if your hose is good check tank vent hole valve in the gas cap if you go for a ride and the bike quits open the gas cap instead of using prime.
or go for a 10 mile ride with cap open. then ride home with it closed to see if it quits.
if you have a second key you can open the cap when it quits.

your gas cap and you
http://www.xj4ever.com/gas cap.pdf

 

I specifically bought vacuum line when I replaced it but I'm going to check it again. Hadn't thought about the gas cap vent. I'll check that out also. Thanks.

 

Finally got around to removing the tank today to check the petcock as well as the gas cap.
1. Petcock was clean and working. I found that the nipple for the vacuum line was facing to the rear so the vacuum line was fairly long. So I reversed it so that the nipple is facing forward and the vacuum line is about 4 inches long. Don't know if a longer line increases the chance for collapse, but now it's shorter.
2. The fuel filter flows very well.
3. Took the gas cap apart and all the vents are clear. When I put it back together I put the little metal ball on the side with what appears to be a fiber filter. Is that correct?

Everything appears to be working and the bike starts easily. Now I guess I'll take a ride and see what happens.

 

1. The vacuum nipple orientation does matter. You fixed that problem.

2. Yay

3. look at the link in the other thread.

 

Just rode about 50 miles and all seems well. I guess the longer vacuum hose must have collapsed but that still seems surprising to me.

 

Sure this wasn't the problem?

Gary H.

 

Often times there is not one single cause of a problem.

 

Very true and I'll venture to add that even in a case where it is one single cause the effect may be dominoeish (causing other components to be out of spec). Just a thought.

Gary H.

 

I've never had anything collapse due to nipple orientation

 

The orientation is more to do with the vent not being blocked.

 

My vent is not blocked

 

When I first rebuilt the petcock I situated the nipple to the rear so that I could use a longer vacuum line which made it easier to raise the tank to make adjustments to the pilots and when syncing the carbs. I had it that way for at least a couple of years. I didn't think it would matter because the vacuum plate could be installed only with the nipple facing to the front or rear, not up or down. Although the vacuum line was probably 3 times longer it was high quality vacuum line and I didn't anticipate any collapse. Who knows, but it seems to be ok now. I did notice that on the shorter vacuum line placement the vacuum line is very close, and may be slightly touching, the valve cover. I'm watching it to see if the heat damages the tubing.

 

I just went back and reviewed Bigfitz's instructions, with pictures, and low and behold the nipple should face the rear. Hell, I'm not going to argue with Bigfitz! I'll fix it tonight. I'm also going to look at the petcock and see if there is any reason--other than BigFitz--that it wouldn't seem to work reversed.

http://www.xjbikes.com/forums/threads/rebuilding-the-yamaha-vacuum-fuel-valve-w-pics.25058/

 

I wouldnt think that would have been the cause especially if its BEEN like that right along, and just recently started acting up .

 

+1. I know that it is possible to have the vacuum nipple face downward, but that may have been a petcock that was previously "modified" by a PO.