'85 700X lacking low end power

My 700X seems to be kinda doggy until I get the rpm's up around 6K....then it pulls very strong. There is a hesitation off idle and I have to feather the clutch a little on take off. Also, the rpm's are slow returning to idle. The valves are in spec, carbs rebuilt and sync'd, floats set, A/F's out 2 1/2 turns each, new plugs, new fuel filter and I'm running hi-test gas.

Any ideas on what might cause this?

Thanks.

 

use a butane torch around the carb-to-manifold boots, without the flame on. If there is a vacuum leak, you'll here the idle increase. Tentatively sounds like a vacuum leak causing a lean condition. Start with that. You'll learn something either way..... idle surges, you got a leak. Idle doesn't change, you've ruled that out--at least at that location....
Dave F

 

Thanks Dave, that occurred to me in the middle of the night, I'll give it a try this morning.

 

Hmmm, did the propane test, there doesn't appear to be any vacuum leaks, back to square one I guess.

 

spark plug boots? YOu may want to consider a colortuning to dial in the mix a little more if needed.

Dave Fox

 

Good call Dave, the plug boots are what....around 27 years old? No doubt they are years overdue for reconditioning.....thanks.

 

Awesome. Don't want ya breaking down on the way the the Carb Clinic!!!!!

Dave

 

Hahaha....not a chance!!

Jeez, I hope I don't have to eat those words!!

 

So was it the spark plug boots? Those are super tough to replace. Or did you just have to rewire inside of the boot? I am wondering how a boot issue would cause the problems you describe?

 

Ummm, Mike. They're really easy to replace.

They screw into/onto the wires; there's a threaded spike inside that screws into the core of the wire. Spin 'em off, lop off about 1/4"~3/8" of the wire and screw back on so they get a fresh bite.

There are also resistor cores in the "business end" of the caps that tend to come loose; if you look in where the spark plug goes you'll see pair of screwdriver slots on either side of the hole. Gently ensure they're not loose.

If you need new caps, XJ4Ever has them.

 

I'm in the process of converting to Dyna coils, 8.0mm ignition wire and Iridium plugs. Today I cleaned the plug cap components & removed and replaced the resistors with sections of brass rod.

Based on the condition of the cap components I think it's very possible that they were the problem....there was noticeable corrosion on the joining parts.

HAP is sending me down a coil hanger kit with some boots & connectors and as soon as they arrive I'll finish it up and see what I got.

 

Fritz,

The custom boots that fit the Maxim-X are very difficult, if not impossible, to replace unless you find a set for salvage, at least that was my understanding. The boots need to seal the top opening of the spark plug well, otherwise they trap all sorts of nice things which are problematic to the health of the engine. Perhaps you have better info?

And yes, the wires and other parts that go in the boots are readily replaceable.

 

85
Max-X
Spark Plug Wire Cap
YAM P/N: 2KT-82370-00-00 PLUG CAP ASSY

This Yamaha Part:
2KT-82370-00-00 PLUG CAP ASSY is also used on these models and components:

1985 FZ750N ELECTRICAL 1
1985 MAXIM X - XJ700XN ELECTRICAL 2
1985 MAXIM X - XJ700XNC ELECTRICAL 2
1986 FAZER - FZX700S ELECTRICAL 1
1986 FAZER - FZX700SC ELECTRICAL 1
1986 FZ750S ELECTRICAL 1
1986 FZ750SC (CA ED.) ELECTRICAL 1
1986 MAXIM X - XJ700XS ELECTRICAL 2
1986 MAXIM X - XJ700XSC ELECTRICAL 2
1987 FAZER - FZX700T ELECTRICAL 1
1987 FAZER - FZX700TC ELECTRICAL 1
1987 FZ700T ELECTRICAL 1
1987 FZ700TC (CA ED.) ELECTRICAL 1
1987 FZR1000T ELECTRICAL 1
1987 FZR1000TC (CA ED.) ELECTRICAL 1
1987 FZR750RT ELECTRICAL 1
1988 FZ750U ELECTRICAL 1
1988 FZ750UC (CA ED.) ELECTRICAL 1
1988 FZR1000U ELETRICAL 1
1988 FZR1000UC (CA ED.) ELETRICAL 1
1988 FZR750RU ELECTRICAL 1
1989 FZR1000W ELECTRICAL 1
1989 FZR1000WC (CA ED.) ELECTRICAL 1
1990 FZR1000A ELECTRICAL 1
1990 FZR1000AC (CA ED.) ELECTRICAL 1

1991 FZR1000B ELECTRICAL 1
1991 FZR1000BC ELECTRICAL 1
1992 FZR1000D ELECTRICAL 1
1992 FZR1000DC ELECTRICAL 1
1993 FZR1000E ELECTRICAL 1
1993 FZR1000EC (CA ED.) ELECTRICAL 1
1993 GTS1000AE ELECTRICAL 1
1993 GTS1000AEC (CA ED.) ELECTRICAL 1
1994 FZR1000F ELECTRICAL 1
1994 FZR1000FC (CA ED.) ELECTRICAL 1
1994 GTS1000AF ELECTRICAL 1
1994 GTS1000AFC (CA ED.) ELECTRICAL 1
1994 YZF750RF ELECTRICAL 1
1994 YZF750RFC (CA ED.) ELECTRICAL 1
1995 FZR1000G ELECTRICAL 1
1995 FZR1000GC (CA ED.) ELECTRICAL 1
1996 YZF750RH ELECTRICAL 1
1996 YZF750RHC (CA ED.) ELECTRICAL 1
1997 YZF750 - YZF750RJ ELECTRICAL 1
1997 YZF750 - YZF750RJC ELECTRICAL 1
1998 YFZ50RK ELECTRICAL 1
1998 YZF750 - YZF750RK ELECTRICAL 1
1998 YZF750 - YZF750RKC ELECTRICAL 1

$27 ~ 50-Bucks a pop.
I'd fire-off a PM to chacal.

::: In a bind, ... you could Fabricate some like the Old School Rodders did!
Drill a hole through a Rubber Ball.
Squeeze the Ball onto a Wooden Dowel
"Sculpt" the Ball by rolling it on the surface of a Belt Sander
Split the side of the Ball open along the side with your Switch Blade or Straight Razor.
Use your girl-friends nail polish to brighten them up. :::

 

LOL!

Thanks Rick,

a year and a half or so ago, I was told they were impossible to get/not made anymore and were only for this bike. I had to scrounge on eBay for a while to finally get some.

 

2KT-82370-00-00 PLUG CAP ASSEMBLY These are still available new from suppliers....you're gonna pay for them tho...$45±


Chacal has the best price I've seen on them.

 

Did some compression testing this weekend....looks to be well within spec.

#161
#159
#160
#160

 

NIIIIIIIICCCCEEEEE!!!!!!!!!!!!!!!!!!!!!

 

You can preserve those FANTASTIC Numbers by being "Extravagant" with Oil Changes and adding ::: Just the right amount ::: of a high-quality "Top Cylinder Lube" to your Fuel.

Become familiar with Marvel Mystery Oil.

M-M-O's Web Site makes for a fun visit.

http://www.marvelmysteryoil.com/

 

Hey DannyMax, if you have sparks in the sparkplugs you can rule out those cables...I got the same problem when I started doing a full carburation, my problem came with the carbs boots, wich were cracked. Once I puted the carbs together, in the low end I had to use the clutch to go over 2000rpm so the bike can take off easily. Make the long story short all the problems are in the boots wich are aftermarket and seems that they don't fit right so air is leaking. I don't know in the X models, but in mine ('85 XJ700N) there is a gasket between the cilinders and the boots check yours, repalce if needed, check your boots for cracks and seal any, make sure you have a tight fit between carbs and boots and carbs and airbox boots. Good luck..

 

That's a great idea Rick....MMO's been around since before dirt so it's certainly passed the test of time. Probly looking at about 1oz. per fill-up in the little X tank, a 16 oz. bottle would last half the summer!

Thanks, I'm gonna pick some up.

 

Thanks Rod, I did look the boots over and did the propane test also....all good there. It's not like the bike is embarassingly doggie....she'll light up the tire with ease, I just feel it should be a little snappier getting up to that wild 6500 rush! There was some corrosion inside the caps which I cleaned and thinking that plus the Dyna's, wires & Iridium plugs will do the trick.
Should know very soon....soon's the stagecoach driver waters the ponies and brings the Canadian mail bag in the roadhouse! :lol:

 

I finished the Dyna coils install today, it was cold and the dirt road we live on is a mess from the rain but it appears that there is a significant difference in throttle response and low end power....based on some speed runs up and down the driveway. :lol:

I don't know if the problems were with the OEM coils, wires or contacts inside the plug caps but....so far anyhow....I have to say that results are positive.

I'm hoping for some highway time tomorrow, see what I really have.

 

Pic of the Dyna install.

 

Putting those nice new Coils and Wires on a Max-X is a walk-in-the-park.
The Max-X has plenty of space.

:::::

If you find that you are still lacking Power in the Bottom-end, .... and YOU know the Emulsion Tubes are so clean a Marine would wear them on his chest, ...

Treat the Carb Diaphragm Piston BORES to a Performance Re-finishing.

Scrub them vigorously with SCOTCHBRITE Gray.
Dremel or Hand POLISH the Bores with Jewelers Rouges #5 & #6.
After Polishing ...
Number the 4 Diaphragm Pistons 1 thru 4 on the Bottom of the Piston w/ Magic Marker.

Experiment with exchanging the Diaphragm Assys in different Bores until you find the Very Best Combination which allows the Pistons to Float :::
::: EFFORTLESSLY ::: Up and down.

You want those babies to be heading toward the Top without coaxing when you roll-on the gas.

You should be able to get that 20 Valve bike wanting to pull the Handlebars right out of your hands.

 

It IS a cake walk Rick....actually, just about any work on this bike is really easy due to all the working room.

Bore polishing is a great idea, everything is 'clunk-test' approved, of course, and the 'E' tubes are certainly 'baby's bottom' clean but a far cry from what you're talking about.....a sailor would proudly wear them but never a jar-head!! :lol:

This goes on the to-do list at the next carb removal....that being the only exception to the 'easy to work on' sentence above, pulling those damn carbs! But getting easier each time.

Thanks for the tip.

 

Got a little meaningful time on the highway with the X today....very pleased with the results. Power delivery is strong right thru the entire range to about 8500, very, very smooth.

It seems so strong in low and mid range that the normal'cheek tearing' blast at 6500 ± is not that noticeable...it's there alright, just not that much different from the lower rpm's.

There's still a slight rpm hanging going on....seems a little worse after a lengthy 'spirited' run. I gotta do the propane test again....nothing showed up when I did it a couple weeks ago but it acts a lot like an air leak, maybe I missed it.

Over-all, I'm a big fan of the Dyna/Iridium/8mm wire mod on the X.

 

Spent the last few days messing with mixture, idle, sync and it appears that it is now really, really close. The hanging rpm thing is totally gone, rpm's return to 1100 like they should and that crazy power rush that kicks in around 6500 is back, and back strong. They call it the X-Factor, I found out, and it's quite a rush!

I'm amazed at how sensitive these bikes are with A/F mixture....Rick has mentioned it before and he's absolutely right....just a touch one way or the other makes a huge difference.

I'm close enough so I can live with it untill the Colortune that I ordered gets here.

Also, in between tuning sessions, I purchased and installed Len's spin-on oil filter adapter and Purolator filter. Very nice unit, excellent fit & finish....gonna make life much easier in the oil change dept., no doubt about that!