XJ700XS Fuel Valve Replacement & Now Stumbles or Dies off of Idle.

Hello Forum,

I am new to posting here, but not new to bikes or searching out solutions to problems. I recently acquired a 1986 Maxim-X. I have many things planned for this machine; first was to tackle the runs in one spot only fuel valve that net me a whopping 67 miles to the tank before running out on me (no res/on/pri options). So after much internet searching and deciding what route to take set forth to start getting this machine into descent running order for this summers enjoyment.

So I drain the mostly full tank and remove it from the bike, upon inspecting the fuel valve and comparing everything to what I had read on the net over the past 2 weeks turns out that there is no vacuum line connected, the vacuum port is capped off, the oem fuel valve has been modified (poorly I might add, it only runs in one specific spot near PRI.) so I order a brand new oem unit, some vacuum hose, new fuel line, new inline fuel filter and wait for items to deliver... I remove the current fuel valve to discover that the back plate is custom made, with a custom cut felpro make a gasket, rotating the valve has no stop and feels gritty inside, there is no longer an attached filter with proper tube lengths for RES/ON/PRI to function as intended (glad there is a current inline filter in place.

New parts arrive, I install everything including the now capable vacuum system now the bike idles fine, PRI doesn't seem to work much like I thought it would (when selected no fuel runs to the float bowls.). Now the bike stumbles and if not feathered will stall until 1000-1500 rpms then seems to run fine. I have not driven the bike yet the install took place last afternoon. I suspect it might be a vacuum leak so I will deal with that once time permits again, but I wanted to put this out there to see what input you all might have on the topic.

I plan on mimicking this members seat/fender mods*. I have ordered used ones (seat/fender) and the tail light off of the net so I can revert to stock if desired later; already have them here now in the garage. I also intend on some de-chroming replacing items with black or black chrome items where available, shooting for a midnight v-star like look.

Bike came with factory option sissy bar, a windshield, forward controls (which I want to re-install), some slimmer straight mufflers that look longer too (look like ones you find on a virago, or goldwing.), currently the stock ones are installed and I kind of prefer them as it adds a bit more of the muscle bike (v-max style) look to it.

*won't let me post links or images (might be because it is my first post.).

 

Paid $2000 for it.
Some pictures from the ad (sissy bar, and forward controls were not installed when I purchased it). I will add update pictures once I am riding it on a regular basis as for now it is a garage queen until I sort out the acceleration issue.

 

I suspect what you are going to hear is that you need to first adjust the valves, then go into the carbs and unless you have already done that it needs to be done. I have the air cooled XJ700 and I had pretty much the same issues that you have--except my petcock was standard. I got less than 30 mpg and the plugs were black and it ran poorly. After getting the valves in spec and cleaning the carbs (several times since I tried to shortcut it the first time) I now get approx 43 mpg on the road and about 40 mpg all around. A colortune plug will help you get the pilots screws properly set. Something is wrong with your petcock if it doesn't free flow gas when set to PRI.

 

Since the fuel petcock was poorly modified maybe the fuel lines to the carbs need to be looked at to see if they are in the right places. Possible the carbs will to come off to be lightly cleaned. Might be some trash in there blocking the jets.
That is a nice X, you rarely find a clean original one like that. Don't do too much to it

 

Any mods I make will be to item replacements so that if desired the stock look can be easily returned. (no frame chopping here).
user superluckycat (grrr; why can't I link to other threads from this site?) <-- I plan on doing the same solo seat and fender mod as his. (already have a spare fender and seat to mod on-hand).

 

Good,

 

Wheere did you get the replacement petcock from?

 

Yamaha parts department Part# 31A-24500-02-00

 

The reason why I ask is that the petcock should flow a ton of fuel when set to prime. Since it's a Yamaha part I suggest that you ask for a refund, credit, or exchange. You could open it up and see what's wrong, but that is an expensive part. It should work correctly out of the package.
I think that the stumbling is being caused by fuel starvation due to the new petcock not working correctly.

 

Thanks I will add this to the list of thinks to deal with as well.

 

to new to forums after so many posts you can start posting links. I think you are there with 6

 

In case you were looking for an update, PRI works well, and ON as well, but ran out of fuel the other night and switched over to RES and had the same issues. Put new filter and vacuum line on that is a little bit longer so waiting for nice weather and time to ride out this tank and see how it goes this time around.

 

Update: After spending some time on the bike and carrying around .5 gallon of fuel in two fuel bottles; I now have a better understanding of how these particular petcocks function. When I initially ran out of fuel and switched over to reserve and the bike would not run, I now realize it was because I had just starved the float bowls of fuel and needed to prime them again. On my way home from riding my fuel light came on while on the freeway, rather than wait to run out of fuel and the bike start to stall, I reached down and turned over to RES and made it home just fine without any problems.

Also past couple of days I was able to spend some time swapping out chrome for black, keeping what I take off in case the stock look is desired in the future.
Before:
https://goo.gl/photos/kPcmeH7cJ3Jix63a9

https://goo.gl/photos/THEY5Xf6FziDvqDo9

https://goo.gl/photos/eCCUvRxucWCWfG5Q8

https://goo.gl/photos/YkpYH86B5n8E5wpD6

After:
https://goo.gl/photos/J6jsiNKiKoqfj5G79

https://goo.gl/photos/8kDYXsV6yRiVQ9KY6

https://goo.gl/photos/fpJyZEDdNLSGNk1s9

https://goo.gl/photos/2tYUEieaXCJVtvDQ6

 

I did however run into a problem when swapping out the grips. I wasn't thinking about what I was doing and over rotated the throttle and now when I attempt to start the bike it is full on wide open to the rev limiter. I had to shut it down and turn it off as fast as I could, then started removing the seat, tank, and anything blocking my view of the linkage. Admittedly I am not 100% certain what I am looking at to fix this. I removed the throttle cable it seemed to have no binds in it and moved freely. Also removed the choke cable to make certain that had nothing to do with it.

Any insight would be appreciated (pictures help me too.).

Questions:
Is there a way to move from the cable choke to one that is a knob directly connected to the carbs?
Is there any stock exhaust in black that would fit this bike?

 

Hey all, I wanted to update you and let you know that I was playing with the linkage where the cable connects at the carbs using a hook tool I was checking the range of motion and it wasn't much, third try the hook tool slipped and it was enough to reset the linkage to zero and the range of motion appeared to be normal so I re-installed the throttle cable and the right hand controls. Now there was not nearly as much slack in the cable and range of motion again felt normal at this point I felt safe in starting it... All went well and it idled just fine.

 

Another update that is the saga of the XJ700X. So I had the throttle linkage issue (since resolved), but woke up to a house full of the smell of gas. I go out to the garage and there is a what would seem to have been left in my tank all over the garage floor (my fault, left it on PRI setting, I know, I know total NOOB!). I wasn't sure what he deal was since the afternoon before I thought I had ran the tank out of fuel on reserve after putting the new bars, grips, mirrors, shocks on the bike and removing the header mounted forward pegs (nice worn hole in there now, one more thing to fix.). So the next day I air out the garage, put more fuel in the tank res/on/pri don't work at this point I am considering selling off this thing as it is one thing after another with it. I might add NEVER buy anything an engineer has owned (they tend to make their own way instead of fixing it properly). Ok back to the fuel, petcock, carbs again; so at this point I say to hell with it and pop open the filler lid on the tank cup the hole turn to one side take a deep breath (petcock on PRI) and put a little pressure to the tank. I grab the flash light shine it on the fuel filter and it is filling up nicely then I hear this pissing sound all over the floor. Now I am totally baffled by this so I start to dismantle the bike, remove seat, tank, ignition box, move wiring out of the way and start looking around with the flashlight. Turns out this entire time the fuel line going to the float bowl distribution fitting was just hanging on barely and with my removal of the tank to fix the linkage was just enough to move it completely off the fitting. So with some screw drivers, some sweet and dirty talking I was able to refit the hose on the fitting and clamp it down. Re-assembled everything, put it on PRI no fuel flowing, did the tank pressure thing and the fuel she was a flowing quietly, the fuel filter filled up and then stopped after a minute maybe. Switched it back to RES fired up the bike and no more fuel leaks, smells, and my filter stays full of fuel and is no longer slow dripping off like before, I imagine this will improve my fuel economy slightly. Took it out today for a quick run to the gas station to top of the tank then down the block for new oil and filter for maint. Ran fine other than I lost the temporary bolt that was plugging the exhaust hole in the header.

Edit: Forgot to mention that one of the previous owners was an engineer and as such messed with way more than he should have, such as the homemade (engineered) foam air filter (soon to be replaced with a proper one.). A misaligned and adjusted airbox, three airbox to carb inlet sock clamps so loose that you could just move them freely by hand (since reset and properly tightened along with adjust airbox.). Doing some further research I realized that the top of the airbox had been modified (cut to maximum opening) with fine mesh screen glued into place from the inside and and a small plastic plate held atop all this with a small oval hole held in place with one screw and a small 1/4" by 1/4" aluminum channel. So the original oval down tube has been removed. Today I rode it with out the plastic plate in place and all it seemed to do was make it sound like it was going to suck my buddies through the seat at high rpm's under heavy acceleration. Any thoughts on this from you folks out there?

 

Oh yeah and the wind screen came in and i installed that on Sunday... I will get better pictures when I can....

 

I like the wind screen. Does it attach firm? Does it function well (at highway speeds does it help break the wind in the chest)?

 

There are many types of engineer: mechanical, materials, production, aerospace, train....

 

It attaches fairly well. Had it on the freeway at 85mph seemed to stay put just fine. As for the "breaking of the wind" yes a noticeable difference indeed.

Edit: Thought I should note that the back of my bike sits ~ 1.5-2" lower and I am 5' 11" in height.
So this wind shield deflects the wind toward the top portion of my helmet now instead of full on frontal blasting.

 

Yes K-Moe there are many types, but I prefer the ones that don't hack up the old paper filter and glue random foam in place, ones that use forma gasket versus a proper replacement (yes mine is leaking oil it seems from the valve cover.). Then mods the air box then tries to reverse it with mesh screening and a new piece of plastic with an oval cut into it; when a new air box lid could be found on the www. Puts 10" blown shocks that bottom out on nearly every bump, making it all but impossible for two people to place the bike on the center stand. I replaced those with 11.5" shocks and now with a small grunt I can center stand it solo. I am still discovering things as I go. Oh I did spot a white golf tee deep behind the cylinder wall in an area I have not been able to reach.. I hope that when I do pull it out I don't find out it was plugging something up. Not to mention the old petcock fiasco from post #1 of this thread. I have that still sitting here at my desk as a reminder to do my best to fix things on this bike proper.

Cheers Man,

Violator

 

Farmers . . . Farmgineering: What can I do right now, with the materials available, to makes this work until I have time to drive in to town?

 

My favorite sort.

 

Alright another update, these arrived last night so I installed them just now... Better tank clearance of the cables and brake lines versus stock and the previously installed 2" risers (came on the bike).

 

I am not fully satisfied with the mirrors though, can't see much behind for what it is worth. Might have to go with some bar end style, or maybe mirror risers not sure at this point. Any thoughts or suggestions? How can I go about moving most of the none petcock related posts to my own garage posting?