XJ700 sputters at high RPM.

Hello Everyone.

Sorry to make my first post a question, but I searched and couldn't find anything.

I have an 86 XJ700 Maxim with a problem. At about 6500 RPM the engine just looses power and kind of sputters. I will keep accelerating, but very slowly. First, is the redline really 11000 or so?

I replaced the air filter, plugs, cleaned fule filter. Took the carbs off and cleaned them. The floats were way off for some reason, like 5-6mm causing them to shut off early. I adjusted to spec (I think 14mm and they were at 19mm) thinking this was the problem, but no.

I have ordered a carbtune just to check the sync. I havent tried running on Prime yet, got cold again.

Any other suggestions? I also have an 81 xs400 I just restored and it almost seems faster than my 700. It seems to me the 700 runs ok at all other rpms and off the line, but just doesn't seem as fast as it should.

Mike

 

What did the plugs that came out look like?.

 

Wrong size Main Jets. (Too small)

Emulsion tubes (Nozzles) clogged.

Vacuum Pistons Sticking (Fail "Clunk test")

Vacuum Piston Diaphragm's Not "Set" -- Air Leak.

Search: Clunk Test ... try that first!

 

Sounds like the carbs are coming off again.

Thanks for the info and what to search for. Found enough to keep me busy for a day or two.

Thanks,

 

Also check the screens for the needle valves. I had the same problem on my 85 a while back, the screens were full of crud.

 

I took the carbs out and cleaned everything again. It seemed to pass the clunk test but I cleaned the pistons and boars anyway. The float screens seemed fine, cleaned anyway. The emulsion tubes seemed fine, cleaned anyway. I replaced the petcock vacuum line just in case, but it seemed fine. Diaphragm didn't have any holes or cracks I could detect.

Everything in there was stock. 107 main and 36.5 pilot.

I haven't been able to get it back out yet, but will follow up when I do. Next step is to sync the carbs. If it still isn't fixed can I run it on prime to rule out the petcock diaphragm? Does the air mixture screw effect high RPM's?

Thanks,
Mike

 

The pilot mixture screw affects mid range RPMs up to about 5 or 6K. Above that the main jet takes over. Running on "PRI" is ok just remember to move it to "ON" when done. You may have a vacuum leak. Check the intake boots for cracks. It could also be the TCI with a cold solder problem. If it is the TCI the electric tach will go haywire when the bike sputters.

 

Make yourself a screwdriver that FITS the Slot of the Pilot Mixture Screw - perfectly - NO slop ... Zeee-row! None!

Drip a drop or two of some really light oil in the Pilot Screw hole.
Turn it UP and Down ... easy ... but, get that Oil working for you.
Then, real easy ... turn it IN (Down) all the way ... until it Bottoms-Out.
Do it like your fixing a watch ... real easy.

After you get them Bad-Boy's ALL the way DOWN ... bring ALL Four back OUT.
Three (3) whole turns OUT.

It should idle NICE.
Use the Idle Adjust Rod ... shoot for 900 - 1000.
If it idles fast and the Manual Rod don't bring it down to 900 ...
Tweak the Screws in ... like from Noon to 12:01 ... down the line.
Eventually ... as you tweak off another minute ... the Idle will get nice.

A ColorTune Plug and Tweak will get you right on the money.

 

The mixture screws control idle and low rpm cruise (idle - 2000rpm),
Proper Float Level controls low rpm & acceleration (2000 - 3000rpm)
Proper Slide Needle Clip position into the main Jet
Controls midrange power and crisp acceleration (5000 - 7000rpm)
Proper Main Jet size is what you run on wide open, ( 7000 - +)

The Mixture screws are also what you adjust to pass emissions if you have to test, in your State I just went threw this the last 2 days. Too high HC's means too lean, back out screws to richen. Too High Co's, means too rich turn screws in to lower Co's.

I sat on my friends emissions sniffer to dail my 1100 in as I was surprized it failed yesterday. Even more surprized I had to set the screws at 4.5 turns out to lower the Hc's enough. Arizona's limit is 1800 on HydroCarbon's and 5.00 Co's, and at about 2.5 turns where I had them set I was burning 2370 Hc's. At 4.5 it dropped to about 800, and Co's came up from initial .18 barely reading to 3.23.
Man what a pain, I wish they'd do away with this crap for bikes. Arizona's pretty tough like California.

Now that's done I'll probably drop them back to about 3, as I can tell it's using more gas now on this tank.

 

Pre-1988's are exempt in Massachusetts ... pre-88 everythings!

Roll a Classic '55 Chevy into the Inspection Bay belching heavy, black smoke, like a old Spruance Class Destroyer steaming at All-ahead Flank laying-down depth charges to kill a Nazi U-Boat ... and the guy uses Windex to clean-up the windshield area before applying the new sticker.

Ride-in on a Harley leaking so bad all your saddle-bags are filled with quarts of oil and there's a Knucklehead being inspected and another one doing the test!

But let the new Accord be stuck on fast-idle because you were listenin' to some Jam's with the A/C Blastin' while waiting for the Harley-Valdez to get stickered-up ... and, your O-2 sensor not quite caught-up when he probes it ... and BOOM -- R E J E C T E D !

 

ROFLMAO :lol:

That cracks me up Rick, and your so right.

I saw a guys signature in another forum I was reading up on the FJR the other day, and I loved his signature,
it said, and I quote "98% of all Harleys are still on the Road Today, the other 2% actually made it home" LOL

Arizona is so screwed up finally they just past the law that cars 20 years and older won't have to do emissions if its covered under classic insurance. Which will be nice, except they're leaving it in the hands of the insurance company's to say yea, or nay on a given car.

So I'm going to be in the clear for my 71' Buick GS, but I'm making a clone Gran National out of an 86' Regal, so I'm wondering if the classic insurance will let me get coverage under collector car rules for that. I know the GN will be considered, but a clone I don't know.

 

Thanks for the correction. I wrote that in a hurry. The pilot screw is pretty much out of the picture above 3k and then it is a combination of the float level. idle jet and jet needle.

 

OK, finally got it out today. Still the same problem, but it might be a little better. Or maybe its just wishful thinking. I also tried running it on prime but it still had the same problem, starts cutting out around 7000.

I also got my carbtune and color tune today after I had it out. The sync wasn't off by much. I actually hoped it would be. The colortune showed the mix screws were in about 3-4 turns to much, but as I understand it that wouldn't effect full throttle at 7000 rpm's.

So, I'm not sure where to look next. The tach doesn't do anything abnormal at 7000. I checked the diaphragms very carefully for any holes, didn't find any.

What are your thoughts. I inherited this problem form the PO and have only had the bike for 4 months now. I have only had it out probably 4-5 times because of weather.

Thanks,
Mike

 

Here's where we need you to be as specific and descriptive as you possibly can.

"Cutting out" ... how? Fuel starvation or Ignition Breakdown?

If you think its fuel related ... go take it out and before you conduct the full throttle test ... reach down and switch the Fuel Supply to PRIME.

If your situation improves ... there's not much Shakin'-down to do ... to find-out why you aren't getting the supply of fuel you need for riding at the high-end of the tach.


If the Ignition is breaking-down ... we gotta find-out why.

 

Thanks Rick,

I did try running it on Prime but it still had the problem. I'll try to explain it. It's like a hesitation. It kind of stalls a little, jerks a little, surges, is not smooth at all. It continues to rev higher but very slowly. At first I would have sworn it was fuel related based on how it felt. If I were loosing a cylinder intermittently at high rpm do you think it would behave in this manner? If so it's possible I'm loosing spark on a cylinder, I think it would feel the same.

Since I think I have thoroughly been though the fuel delivery, what is the best way to check the ignition circuit at high rpm? BTW, I did colortune today and was getting solid spark on all cylinders at up to 4000 rpm from what I could see though the colortune plug.

Other information. This bike has about 4000 miles on it and it's an 86 so it didn't get out much. I once had a 4cyl Toyota truck with 80000 miles on it that didn't have much pep. After a while running synthetic oil the engine seemed to loosen up a bit and it would rev higher. Do you think something like this could be a contributing factor?

Thanks,
Mike

 

I'd make sure the bike didn't have a Rev-Limiter.
This happened twice in another forum.

I'd pull the left side Crank Cover and make sure everything in there is dry, clean and tight. Try moving the Rotor ... make sure its tight. Clean-off its face with a strip of 600.

Get a visual on the pick-ups. Clean them off with Q-Tips and alcohol.
Check the ring that the pick-ups are mounted on for tightness.

Follow the pick-ups lead to where it's connected to the harness undo and redo for a good connection.
(Use Aerosol Spray Contact-ReNew -- RadioShack -- Clean all the male/female contacts in the Quik-connects)

You clean all the ones in the two connections to the Ignitor ... and the ones to each of the two Coils.
Leave the Cam Cover off and run it with cleaned-up contacts.

Might / Might not.

I have (You might need) a spare Ignitor to hook-up and do a quick test.
Again: That would tell the tale.

Then you start the Multi-meter Festival and begin with the Coils and Wires.
You might want to upgrade the bike to better Coils ... I'll bet there's a few who'll recommend doing that right off the git-go!

 

Thanks for the tips, more to look at now.

Any easy way to tell if I have a Rev-Limiter?

Thanks,

 

the petcock has a screen up in the tank, take off the fuel line put a hose on the petcock and turn it to prime
it should make a big mess real fast

 

You'll find wires spliced-in at the Primary's on the Coils ... that's where the Limiter needs to go inline. Follow the wires to the Unit ... if there is one.
Battery box. Inside the airbox. Under the tank. Back in the tool-pouch void.
On top of the airbox cover.

There's not too many places to mount one.

Check to see that you have REAL VACUUM LINE running from the Intake Manifold to the Petcock Vacuum-Op Valve. If you have non-vacuum line getting sucked-together at high manifold vacuum ... it would allow the Petcock Vacuum Valve to relax and shut-off fuel flow.

Also ... check to see if there is an inline fuel filter ... and that the fuel line isn't too long and is routed such as to impede the gravity flow.

What's "The Read" on the spark plugs in it right now?

 

There is a real vacuum line to petcock. The sparkplugs look like a nice tan color, not to dark or light. No revlimiter located. No inline filter.

Question. How do I check the secondary on the coils? I checked the primary it was right on and the pickup coils were in spec (10 ohm under but within the +- 10%). I tried to check the secondary's according to the manual. Lead to R/W wire and the other to the output? I placed the lead on the R/W wire (and tried ground) and the other to the metal part in the spark plug boot. Couldn't get a reading, open circuit and all 4 so I must be doing something wrong.

I thought this was going to be easy. No spare igniter around, and they are kinda pricey on ebay.

Thanks,
Mike

 

Everything so far sounds like a fuel starvation issue. I was looking at your first post and noticed that you static set the fuel levels. I would dynamic set them using the clear tubing method. Another test is to run the bike until the miss starts and open the choke. If that helps then it is fuel related. I don't know it this bike had a rev limiter but I doubt it would kick in at 7K since the bike has a redline of 9.5K.

 

Didn't think of the choke. I'll give that a try next time it warms up and stops raining. I did try it on pri though, and I know the fule comes out pretty fast on Pri, so I don't think it's the petcock diaphram.

Would the bad secondarys on the coils cause this? I read an open circuit on both coils through all plug wires when I tested.

Thanks.
Mike

 

i'll second that float with the clear tube, at least do the easy outside ones for a quick check
you do have a inline filter up in the tank on the petcock
come to think of it there might be two, one for prime/run and another for reserve
if these clog up gas just trickels out
did you try running on reserve?
get yourself a clear inline filter

 

if they are original wires i think the caps screw off the wires then you can check right to the conductor

 

I checked with the caps off still no continuity. So either the coils or wires are bad. Do the wires come out of the coils or are the permanently attached?

I don't know if this is what's causing the problem though, I still lean toward fuel. I'll have to examine the supply better.

Thanks,

 

Just wanting to clairify the checking of the secondary coil......

With the caps off the plug wires, you put your test leads on the two plug wires coming off the same coil and take the reading with your meter set to Rx100 scale. You're looking for 11K ohms +- 20% at 68 F (20 C)

You should not get any reading between the primary and secondary leads as they are two separate coils of wire inside the housing.

 

Are you sure the fuel line hasnt got a kink in it?

Then my next guess would be the float settings, then I'd suspect the screen on the fuel valve.... Then the screens on the float seats might be restricted from some bad gas!?
The list goes on.... and on.

I agree, it sounds like fuel starvation.

 

Thanks Nick. I read the manual 10 times and it said to check between the r/w wire on the pri to the high tension wire on the sec. That didn't make sense to me either since I know how coils work and there isn't any contact between pri and sec. I checked between the two high tension wires with the caps off and both checked out perfect. Thanks.

Here is the page from the Yamaha manual. I read it again just to see, it must be wrong.

 

An awful lot of aftermarket Coils get bought after doing a Mult-test on the stock Yamaha Coils.

I've seen 'em read less than an ohm (1 ohm) on the Primary with the correct value on the Secondary and still work fine.

Go figure???

 

I just read over all this again, and I think your tank cap may be the problem. Some caps breath slightly threw the key slot like a 1 way check valve to allow air to replace the lowering fuel level, so pop your cap and leave it loose and go for a test ride.

If your not pulling the vapors out of the tank good enough and if your bikes cap doesn't have it's slight breathability and it clogs up, it will cause the same thing as fuel starvation as fuel won't be able to drain down to the carb bowls at the rate it should be.

You can soak a cap sometimes and clean it, just don't soak it long enough to destroy your rubber seal if it's not removable.

 

I just don't get it. I have looked at everything and am still having the problem. It pulls great up to about 6700 and then just starts jerking like it's out of gas. The carbs are clean, the petcock is clean, ran it on reserve, pri, and with the gas cap open. The carbs are stock as is the rest of the bike, but it sure seems to me that if the needles had clips they need to go up one or it needs bigger mains. If the carbs were running out of fuel it wouldn't run great up to 6700 when I shift down again and give it full throttle, it would still be out of fuel.

So electronics wise. The CDI is a tdi14-44. can anyone with an XJ700 85 or 86 confirm this is correct? I have been watching ebay but haven't seen one.

What about timing? Could the timing being off cause this?

Thanks,
Mike

 

Are you certain the right sized Mains are in there?
Are you sure the Diaphragm Pistons are not sticking?

Everything else you have to say would prompt me to try running it on a Known Good Igniter and seeing if that ain't it!

 

mgh333

I have a CDI box at home, I should be leaving work in a little bit & will look at it & get back to you.

 

mgh333
Just an FYI, My previous XJ700, had this same issue at or around 6500~7000 RPM, drove me nuts, wound up being a collapsed fuel line, hince starving it when it needed it the most.

I'll get back to you on the cdi though.

 

Rick, Yes I checked all the jet numbers 3 times, they are stock. And I checked the diaphragms and slides, they worked good, but I still took them out and polished them, they drop like a rock. I also blew in the inlet holes on the carb and they raised just like they should. I couldn't detect any leeks.
I'm starting to lean to the CDI as well since that's about all that's left. I have to figure out if it has the right one to begin with. Everything I see has been a TDI14-35, but that just might be an X and I'm not sure if they are the same. I have a TDI14-44 on mine.

Max, I really appreciate you checking for me. I have already replaced the fuel line with a good quality nylon reinforced line. You know, I could swear it's fuel starvation, like when it's time to switch to reserve. But I have had the carbs apart 3 times and they are very clean as is everything in the chain. The only variable are the diaphragms and I have tested them the best I could. I'm about ready to buy another set off of ebay just to make sure.

I still need to look into the timing, the last thing I haven't checked. It looks like the timing pointer is missing which makes it harder and makes me a little suspicious.

Thanks

 

The CDI box that I have, which came off of a 1986 XJ700 is a TID14-44. As you can see in my sig. I now have an "X" & can check the number on that one as well if you want?

 

Both the Advance and Timing are "Programmed" by how the Igniter gets signaled by frequency and duration of the Rotor as it rotates by the Pick-Up's.

There's usually a ... "Bracketed Area" ... marked-out, where the timing fires within the narrow band of advance needed for the engines best performance.

Some aftermarket "High-Performance" Igniter's tout adding a degree or two ... in non-specific language. They don't actually INCREASE the Advance beyond the Factory Maximum Advance LIMIT. They alter the CURVE getting the Igniter to Maximum -- quicker.

But, since their "QUICKER" is only about the duration of a Bolt of Lightning, the Claim is true. The reality is indistinguishable ... unless you take into consideration the addition of Pigtails which allows them to dodge the Yamaha Patent and Copyright.

 

Max, That is what I have on mine. I guess they are just harder to find. At least I know it has the right one on it.

Thanks again.

 

OK, problem found but I don't get it.

I have also been working on restoring a 1981 XS400. I noticed yesterday how much faster the 400 accelerated than the 700. It seemed like the slides were opening up faster. Since I knew the carbs were in top shape on the 700, and they were synced, and the butterflies were working, I decided to look on the side before the carbs since the only other thing that could be preventing the slides to open as quick and far as they should was air volume.

I took off the top to the air filter box, made a clip to hold the filter in place, and off she went. It runs like I would now expect and revs fine to redline.

Now what I don't get. All the jets in the carb are stock, I checked 3 times. So any ideas why it isn't running right with the air box lid on as designed? I will try running it with the lid on and the baffle out next to see if that also works.

Thanks for all the previous suggestions.

 

Also, is there any problems to running without the air box lid if it's running well? It was obviously starving for air before.

Thanks,

 

Because you have something missing that's allowing the seat to contact the lid.

If somebody did a Mod that has the seat making contact with the lid ... take-out the rubber intake port insert. Make a template of the opening on top of the box.
Make a piece to seal-off the OEM Cut-out and mount it.
Cut-out a new Port using the template someplace that won't get blocked by the seat.
Stick the rubber intake insert in the new opening and fly.