XJ700 funkiness

I bought an XJ700 a couple of months ago. Had it tuned up and it ran great for a bit. Stalled out going up a small hill and hasn't run since. It had way too much fuel in the carbs and was leaking out the leftmost carb. The shop said a fuel valve had blown and they put in an in-line switch. They also cleaned the carbs.

Now it only cranks with the choke wide open. Closing the choke causes it to die out. Rolling on the throttle also causes it to die out.

I'm out of money and tired of trailoring the damn thing so it's time to take matters in to my own hands....

Sounds like it's sucking too much air and I need to adjust the carbs. What tools do I need to get? A carb sync kit? The YICS blocker? anything else?

Any other ideas?

 

Get yourself a Genuine Yamaha Workshop Manual.

You need to:

Rebuild or get a New Petc0ck.
Remove Carbs and Overhaul & Clean them.
The inline shut-off is no more than a temporary stop-gap measure.

I'd buy a New Petc0ck
Order Carb Kits form XJ4Ever
Clean the Carbs
Set the Float Heights
Polish the Bores
Bench Sync and follow the instructions for Tuning the Bike.

http://www.yamahapubs.com/index.do?pg=search&category=3

 

Check for cracks in the intake boots or loose/leaking air boots as well.

 

Bonjour Mmcgee

without disassemble:test air intake
(with a brush dipped in gasoline)
if the engine accelerates passing the brush on the boots. = Cracked boots
alternative:replacement or heat shrinkable


if test ok do like Rick says

 

What exactly did the shop do to "clean" the carbs? Did they dissassemble and rebuild or dunk them in a vat of carb cleaner fully assembled? There are several ways to clean them but the above suggestion is really the only way to thoroughly do it and unless you paid a ton of money I doubt they did it this way.

 

Your shop gave you a load of BS.

Your carbs need a thorough disassembly, thorough cleaning, replace the fuel rail seals, and the throttle shaft seals, and the mixture screw o-rings.

Then do a sync, etc.....

You're not sucking too much air......you're not getting ENOUGH air AND fuel.

Let us know where you are.......chances are someone is close enough to help. I know that if you're close enough to central NY I'll help you do the total teardown and rebuild.

Once you do a carb set THAT way, you'll not have to worry about them again for a long long time.

'blew a fuel valve"...........I'll have to remember that one. Are you sure it wasn't the franistan? LOL Please tell us the name of the shop so we can NOT go there, either.

Dave F

 

If a Bike runs on "Choke" [Enrichment] ... and quits when the Choke is closed; that indicates a Fuel Delivery problem.

Even if the Main Fuel Jet is Brand New, ... the Nozzles [Emulsion Tubes] the Main Jets screws in-to may be clogged and no Main Jet Fuel is making it up and out into the Intake Stream.

There is a long list of reasons why a Bike won't run.
But the list when it runs on Choke and NOT when the Choke is closed points to Fuel Starvation.

Stuck Diaphragm Pistons
Clogged Nozzles
Clogged Beenie Screens
Stuck Floats
Incorrect Float Heights
Kinked Fuel Line
Air-bound Inline Filter
Petc0ck Filter Tower Clogged
Not enough Gas in Tank

 

Nobody's even mentioned valve clearances and the fact that they're a prerequisite for properly synchronizing carbs.

Betcha the shop didn't touch them, either.

 

That's because of the description the fellow gave. I don't jump right to cable when carbs are an obvious issue. I'm not ignoring the shims. But I'm not jumping right to the either.

 

Had the same problems with my XJ700N initially. I had my carbs's "cleaned" by a shop, but it still was hard to start and fouled plugs. Finally, I followed the process outlined on this forum--valves, carbs, wet set, sync, and got it running really well. Be patient. I have had my carbs off "several times" getting them really clean, replacing float valves and seats, and wet setting them. I also rebuilt the petcock. All parts came from Chacal. My bike runs great, however, I am still trying to get the set-up right so my gas mileage will improve--I'm getting about 31 mpg in town and 35 on the road. My bike is all stock, so I think I just have to keep tweaking until I get it right. This has been a learning process for me, sometimes frustrating, but always interesting. Good luck with your adventure.

 

I expected these problems to be more gradual. It stopped running so suddenly.Thanks folks. I'm going to get working on this as soon as the next paycheck clears

 

The fact that you have gas coming out of the carb says right away that you have a 'too much gas' issue. It indicates an issue right away with at LEAST the float needle. Gas is getting past the needle in order to overflow. SO....either the needle is hanging up and not closing, or the float is stuck and the needle is not closing. Therefore you're flooding. Now, if excess gas gets into the cylinder, it's probably going to leak down past the rings into the crankcase and pollute the oil, thin it, and if you do get it running, you'll risk overheating the engine, or blowing it up in a big ball of fire. THAT can be checked easily......open the oil fill cap and take a sniff. does it smell like gas in there? If not, well that's good. Fix the carbs before it becomes the next issue.

Now.....if gas is running through the float needle like that, it means that gas is flowing from the tank when it shouldn't. SO.........did you inadvertently leave the petcock on PRIME? If so, the fuel will continue to run even with the bike off. If a needle is sticking open, the fuel will flow. If all needles are closing well, the fuel will not flow. Is the petcock still on RUN or RESERVE? If it is, then you have a ruptured diaphragm or broken spring in the petcock. (Ah! Maybe THAT is what they were calling a "blown fuel valve") Even if that is the case, a set of floats that are working correctly will still stop the flow of fuel.

So.........you may have compound issues:

The petcock has failed, and you have leaky float needles.


Now........if the petcock has failed, that would give you trouble starting since the vacuum won't make the fuel flow at the correct amount to run. SO.......switch the petcock to PRI, wait a couple minutes and then try to start the bike. (DON'T do this if the crankcase smells gassy.) Remember, PRI is a free-flow gas supply, where-as RUN and RES are vacuum operated.

Give an update when you can..............

Dave Fox

 

So the petcock was leaking fuel when set to prime and the new shut valve was off. Other than that no problems. I took the pet cock apart tonight and all the rubber pieces appeared to be in great shape. The unit was remarkably clean on the inside. nothing was torn or damage on the shaft into the tank.

I didn't blow out the shafts to the fuel lines because everything appeared clean.

I'm thinking the petcock is not the problem, but is there something else in the petcock I should be looking for?

 

The petcock won't leak fuel when set to PRI....it will be full on, un-impeded fuel flow. PRI is a free-flow setting that bypasses the vacuum system..

So, to test if the petcock is leaking......Set the petcock to RUN. Disconnect the 'fuel OUT' line. Now take a paper towel and blot up the few drops that may be present from the end of the fuel line or the fuel nipple. Now......watch it closely for about 5 minutes. Do any more drops of fuel develop? If so, it's leaking. If not, cool. NOW.....set the petcock to RES and do the same thing all over again.

Make sure you hook the line back up when you're done.

No need to test the PRI setting unless you want to watch the gas just pour out.

If you can rule out the petcock, great. That's one less thing you need to check.

Now, it's time to go into the carbs and LEARN them inside out. They are NOT the deep dark mysterious jungle. It took me almost 10 years before I was willing to go into one........I wish I had let myself be convinced to do it a long time ago, as I would have saved myself a big hassle. Now, I'll tear a set right down to each individual piece before putting a bike back together.

YOU can do it. You CAN do it. You can DO it. You can do IT.

Keep keeping us posted..........

Dave F

 

I will check for leaks as you said. The leak I saw previously was due to the free flow of the prime setting being blocked by the shut off valve.