XJ650 sputtering after 30 min of riding?

I’m new here , just started riding last summer and bought an ‘82 xj650 maxim.
Put on about 1000 miles and I love it but I have one problem that I can’t figure out.

The bike starts up and runs great, very responsive till about 30 minutes or so into riding at highway speed (60mph)
Then it starts sputtering. it’s still able to maintain speed, but it starts popping and if you give it any throttle it sputters for a few seconds then takes off but is very inconsistent.
Problem completely goes away if you pull over, take the key completely out of the ignition, and restart it.
Seems to happen earlier if you hit higher rpms and the bike vibrates more.
Happens about every other time I take it out.

I’m not experienced working on bikes so I have no idea where to start.
Any ideas would be helpful?

 

Have you checked the valve clearance? Also check the vacuum hose to the petcock it might collapse when hot. It must be rated for vacuum. One more thing to try. The gas cap might not be venting. Try opening the cap and go for a ride.

 

Thanks for the reply!
Is it very complicated to check valve clearance? Would I have to take off the tank and carbs? Also wanted to clarify that when I restart it that I don’t let it cool down first, and it seems to run great for about the same time as if I started it cold. I’ve also tried turning the petcock off and on, just turning the key off and on without taking it out, checked spark plugs and boots. Only thing that works is taking the key completely out and putting it back in!

 

You have to take tank off, there are some good post if you use the search engine.

 

Valve adjustment thread instructions. You should buy a Haynes workshop manual for your bike too.

https://xjbikes.com/forums/threads/bigfitzs-airhead-valve-adjustment-with-pics-parts-i-ii.116006/

 

The first time you do the valve lash check procedure, use the bucket hold down tool, and put the valve cover gasket on with the sticky goo can be a little bit intimidating.

After you do it once it's a piece of cake.

The upside is that there is a good chance the valve cover gasket and the donut pressure washer things that hold it down are overdue for replacement, and if you replace them it will solve any oil leaks out of the valve cover.

Where abouts in the People's Republic of Minnesota are you?

 

Yeah I’m a bit intimidating by the whole thing, I’m pretty confident that I’ll figure it out though. I was thinking the same thing about the gasket and seals. I’m from the iron range, Embarrass to be exact.

 

Could start running lean from lack of gas when demand goes up? Does it have an inline fuel filter? Maybe the petcock screen is clogged.

 

It does have an inline fuel filter. Where would I find the petcock screen?

 

First thing is to make sure the inline filter is not partially clogged. Try running a replacement gas line from the petcock to the carbs to see if the condition persists. If so, get a new filter and reassemble. If not, remove gas from tank and turn tank on its side to remove the petcock. The filter is attached to the petcock and protrudes into the gas supply.
Fuel starvation may not be the issue but I would check it first.

 

there is one inside tank on top of petcock requires removal of petcock there is also one in the nipple that you can get to from outside tank.
Rebuilding the Yamaha Vacuum Fuel Valve w/pics

position of filter is important so it does not air lock.
if you are using a paper filter get a bronze sintered filter

1. HOW TO: Install a fuel filter

have you tried unlocking the gas cap it could be clogged
Your Gas Cap and You

incase it is the ignition switch
Clean and lube the ignition switch

valves
Bigfitz's AIRHEAD VALVE ADJUSTMENT with Pics - parts I & II

 

I won’t have time to take stuff apart for a few days but does anything stand out? I noticed the vacuum hose looks slightly cracked? The previous owner said he rebuilt the petcock and added the red shut off valve.

 

You have an aftermarket Petcock , I did not see the vacuum line running to it in photo. And why did PO fit a shutoff valve? This usually is a red flag to me that carb float needles are not sealing. A stock petcock shuts off once vacuum from engine stops . I had one of these fine Chinese aftermarket petcock went in the trash the fuel line was to large to fit the nipple and did not seem to flow alot of fuel. Bought a used petcock off eBay and an overhaul kit...no problems since. By the way have you tried opening the float bowl drain screws to see if any crud drains out?

 

There is a vacuum hose in the back , I just took it apart because I have a quick minute before I head out camping for the weekend. I could hear some pressure being released when I took the gas line off the petcock. Would that be a sign that something is clogged? Both the gas and vacuum line seemed to seal well. the petcock doesn’t leak in the on position with both lines disconnected. I think the previous owner had a problem with the stock petcock leaking and gas flowing into the carbs, so he replaced it with an after market one and added the in line shutoff for good measure, who knows? One thing I noticed is that with the fuel line disconnected, if you open the red shutoff valve the gas in the line flows straight into the carbs. I am not familiar with how this stuff works so I don’t know if that is a problem? It seemed to flow straight through the in-line filter as well so that doesn’t seem clogged? The little drain screws on the carbs are stuck. One pretty big thing that I forgot to mention is that when you first start it up , it will bog down if you blip the throttle, sometimes it dies. This goes away after you warm it up for a couple minutes. I don’t know if that is another symptom of fuel starvation or not?
I should mention that Im 19 and don’t know much about working on engines, other than changing oil and a couple other simple things. So if it seems like Im clueless about something its because I am!

 

I wonder why the PO didn't just repair the petcock instead of installing an aftermarket one.
Here is some reading material:

Inside your Carbs

IN THE CHURCH OF CLEAN

Clean Your Own Carb's - The Whole 9 Yards - by: Rick Massey

Why you should replace butterfly (throttle shaft) seals.

Replacing your Hitachi throttle shaft seals

Setting the fuel levels

HOW TO: Bench-synch your carbs

 

Yeah, that's a real amateur set up with the petcock and fuel lines you inherited. I would not ride it like that. So easy to do correctly. And jet fixer made a good point about shut off valve. You might want to disconnect the fuel line from the bottom of the petcock and see if the fuel leaks out with engine off with petcock positioned at "on". If it does you could have a carb problem. (sticky float valve) If it doesn't leak then I would follow Huntchuks advise and bypass the fuel filter and see how it runs.

 

Your fuel filter is old it shouldn't be yellow it should be clear. Another thing I don't like is the uphill curve in the fuel line to the filter from the petcock. Run your fuel hose off the key under the airbox and then up so that it's a straight downhill shot for the fuel. You can get air bubbles trapped in that filter and it will hydrolock on you or whatever they call it. I turn my fuel tea down on the cob pointing a little more towards the back of the bike run the fuel hose, then put the filter on and then run the hose to the petcock I like to have my fuel filter pointing up towards the petcock and a slight angle of course. Mostly I think you just need a new fuel filter it's been around the block a few times.

 

As far as that shut off he goes there's no problem with it being there unless of course it's hiding a problem when you disconnect your fuel hose see if your petcock continues to flow fuel with the bike off. Many people think that when their carbs overflow it is because of the petcock letting fuel through when it shouldn't your bike should be able to sit on prime all day long and not overflow your carbs. Of course I like to send a stand my bike so that there's no angle to the carbs while they're sitting there all day long. When the car is overflow or leak into the motor it is an evil valve assemblies at the floats that need to be looked at they should be able to stop any fuel flow. The only time I will say that they won't is if your bike is sitting out in the hot sun and pressure builds up in the fuel tank forces the petcock open and the fuel flows with enough pressure to push the needle valve down. But if you're fuel cap vent is working properly they shouldn't happen. The fuel shut off is a nice safety feature just in case

 

In the how to install a fuel filter link I provided you should find the part number for a fuel filter you can order it at any auto parts store may have it in stock they take a few days to get in but that's the first thing I would check as it is yellow and old. You may want to invest in some 6 mm ID fuel line. I like to get the translucent stuff so I can see the fuel flowing in it see if there's any air bubbles building up.

 

While you're at it it looks like you're vacuum line is old rubber vacuum line you want to get yourself some 4 mm ID vacuum line not fuel line and replace that vacuum line as well because it could be opening up a crack when it heats up and letting it suck air or it could be collapsing from the vacuum. So just to recap new vacuum line new fuel filter try to get it to flow downhill cheapest fix you're going to have you'll have instant results I change my fuel line every couple of years and inspect the vacuum line all the time. Both are cheap you can buy it in 10-ft lengths or shorter

 

Yep on a roll today sputtering could be a sign of lack of fuel from your description of when it's happening it's at the higher RPM. So after the fuel filter change and looking into the vacuum line. You may start to think of whether or not your petcock is inadequate flow.

 

Thanks! I really appreciate the pointers on what size and type hose to buy, very helpful! This is definitely going to be the first thing I try, is there any trick to reaching the fuel line and vacuum line where they connect to the engine and carbs? I can see myself having a really hard time getting down in there to put a hose back on.

 

easy way is with carbs off.
the fuel tee is between carb 1 and 2 should be easy to get to may have to remove 1 airboxx boot.
vacuum line remove fuel tank.
a little silicon spray will help slide hose onto fittings . spray fitting and end of hose.
I locate my filter on the back side of carbs just at the hose clip on the rack then a wire ty to hold hose to petcock to the clip makes for a stright down hill run for fuel to filter then filter to tee.

 

Do I need a hose clamp on the vacuum line ends?
I’ve searched every part store in my area and can’t find one that is that small, only ones that will work for my fuel line.
The old one just had tiny wire ones but they don’t seem to be doing anything.
Also how to I take the carb boots off to access the fuel line that runs to the carbs?

 

clamps needed the small wire ones are oem in a pinch you can twist a wire or use a zip tye.
I got a bag of them from china on ebay

 

airbox to carbs remove clamp at carb
if boots are hard heat with a hair drier to soften you should be able to push the airbox side in and into airbox.

to reinstall use hot water to soften

 

you don't want to do that, you'll never get it back on with the carbs on the bike.
just push the little caps on, they should be snug, no clamp needed

 

Just got it all together.
Having the petcock nipples facing down made it hard to get the fuel line running downhill. If I just misunderstood you xj550h then maybe you could send me a photo of how it should be. I have tons of extra fuel line to redo it. This is the best I could come up with. I also just noticed that I can’t even put the petcock into reserve, the grip of it hits the bottom of the tank.
I managed to get the new fuel filter running downhill by putting it between the carb boots. I have some zip ties to put on the vacuum line later. Haven’t tested it yet because I have the tires off the bike, just discovered this week after some research that they were from 2006! PO told me they were new and not knowing how to check I just figured they were. Not the only problem he hid from me! Ah well, I only paid $800 for the bike!
Question
When I took the gas line off the petcock the gas didn’t flow out of the line. But as soon as I opened the red shut off valve all the gas from the line drained into the carbs. Is that a sign that there is something messed up with the carbs? If so what do I need to fix/replace. I’m not familiar with taking carbs apart so please keep that in mind. Also I don’t have a manual yet (Supposed to arrive next Wednesday)

 

you may want to use this style filter.
xj4ever and ebay sell them

longer fuel line from tee add 90 filter for a strighter run to petcock
you want to keep the fuel line more level to shut off

or use a 90 degree shut off
install at the fuel line where the filter is, but higher ,add longer fuel line to tee then put the filter between shut off and petcock

 

Alrighty! Take two
Ran down to my local hardware store. Bought a couple elbow fittings for $1 each and put this together, I’m much happier with how it turned out. Tell me what you think?

 

Sorry epic fail , clear tubing is a major no no . Only use actual fuel line , it is reinforced. The other thing actual fuel line can take the heat from the engine , I would personally not use the setup you have .

 

looks good for the positioning fuel should flow freely with no air being traped.
I use the clear color lines (fuel rated) with out issue part of what i inspecs frequantly and change yearly.

the elbows I use are vacuum line elbows and are fuel resistant so find them for future use at auto parts store.
always check the line before you ride watch for discoloration and distortion.

 

next issue you brought up was fuel flowing to carb when shut off was opened.
the carbs have a port that goes directly to bowls and out the back throat , the fuel evaporates and goes out these holes . the hole is for some sort of pressure compensation in the carb bowl. allows fuel into bolw with out pressure bild up and allows air to be sucked out through hole when bike is running which may or may not hel fuel flow faster into the bowls when at higher demand.

as long as fuel does not keep flowing and filling your crank full of fuel you should be ok.
this would be a needle valve issue not stopping flow w

 

That was the one thing I was a concerned about Because with the aftermarket petcock positioned were it is, that shortest section of line directly off the petcock is touching the engine. I’m seriously considering getting a stock petcock, I found a new Yamaha, part number 3AL-24500-00-00 on sale for $78.00 from partzilla. Is that the correct one?

 

Yes correct number xj 650 petcock

FUEL COCK ASSEMBLY 1
3AL-24500-00-00

this link from partzilla shows photo and all other bikes that cross to you part number
partzilla is one of the remaining sites where you click on part number and it shows fitment to other bikes, nice for ebay purchased of used parts
https://www.partzilla.com/product/y...?ref=ac012c9e26c214afd9980b63e67de555d0c47457

 

Not long ago I bought a stock petcock off of eBay for like 25$ and a rebuild kit for 15$ so not a bunch of money . If you buy a used petcock , just make sure you rebuild it .

 

Do I need to get a kit with a tanks seal and new screws and washers? only ones I can find are only 4 piece kits https://www.ebay.com/itm/312645688003 if I can get by with this kit then my total would only be $53 for the kit and a stock petcock, and I would get to learn a lot in the process.

 

That looks like all the parts needed except for the screws that you would reuse. The large o-ring is the seal between the petcock and tank.

 

How does this petcock look ?
https://www.ebay.com/itm/283932666287

 

it is missing the intank screen.
you should read the thread on petcock rebuilding
Rebuilding the Yamaha Vacuum Fuel Valve w/pics

the most intresting statment in the post

"Now that the valve is apart, we need to examine it carefully to determine serviceability. Close examination of the valve seat will tell us if the unit is rebuildable or toast."

 

here is a complete unit on ebay
https://www.ebay.com/itm/133664129849?epid=1022894884&hash=item1f1f00c339:g:kVAAAOSwoWBgKBS0

you may be able to get a ysed one on this site in

For Sale, Trade/Swap, Wanted

start a post there

 

can we agree that in the pictures, it's on prime. if you take the fuel line off, gas should pour out. if not, drain the tank and remove the valve, take it apart and have a look. it might just have some guck in it and that's all that's wrong. don't spend money unless your sure you have to

 

I was thinking more about getting the gas line so it wasn’t sitting on the engine than the flow of the petcock. I think this is the on position?

 

put it on reserve and think about it minute

 

Before repairing my petcock I looked at new aftermarket stuff and determined they are all no good. Used OEM + possible repair kit seems the only way to go.

 

no the arrow on the handel is pointing down

 

The see-through line is fine. It just needs to be replaced about every year or two.

 

to go to RES it would have to go CW from 6 to 9 , there's a stop by the R, it looks to be at full CCW now
that arrow just points to the end of the handle

 

I ordered a new oem petcock from partzilla.
I just don’t feel comfortable with my gas line directly touching the engine. Also don’t know how that nylon elbow would stand up to the heat.
Probably could have rebuilt one but I didn’t feel that the price difference was worth it. I wanted to try but my gut was telling me not to. The petcock is supposed to arrive on Wednesday, and my new tires are scheduled to be mounted and balanced Tomorrow.

 

You're using the wrong pipe clips - get some spring ones of the right size.