Pull clutch in, release throttle grip -- revs stay UP

85 Maxim 700X. I've been tinkering trying to get the right setting for the air/fuel mix screws that I mistakenly removed during a carb clean. Have now got the machine so it will start, hold steady idle near the recommended idle speed. I don't believe I have it correctly adjusted as yet, however. During two separate test drives, I've found that when I pull the clutch in, the revs stay up, even when I've released the throttle handle. When I let the clutch out, revs go back down to idle. When I've looked at stuff with tank off, I can't see any signs that either the throttle cable or the choke cable, are somehow being affected by the movement of the clutch cable. Does anyone have an idea what might cause this symptom, and of course, what could fix it? This "gear-grinder" thanks you.

 

". . .trying to get the right setting for the air/fuel mix screws that I mistakenly removed during a carb clean."

That's not a mistake - It's one of the MOST important, AND overlooked spots on a carb re-build / cleaning. What you were SUPPOSED to do was record how far out they were by turning them in, before removal.

Re-set to 2 3/4 turn out from lightly seated ( you serviced the 4 washers and "O" rings, re-installed correctly??) and then fine-tune based on actual plug color (drive - inspect - adjust - repeat)

a short list of what causes a hanging idle -
Boot clamps not tight
no slack in throttle cable, or routed wrong
cracked boots or boot caps
worn throttle shaft seals
incorrect throttle sync
Gremlins

 

That's the cause of most problems on a bike

 

Also, don't forget the throttle slides not going CLUNK! A very important clean-tuning part of a carb rebuild. Search for it "slides go clunk"

 

Being a "Gear-Grinder" ... as long as everything else is visually OK (installed right, no cracked boots, etc) i'm gonna suggest throttle shaft seals first. Did you replace your throttle shaft seals and put them in with silicone grease? Let your bike idle, then spray a quick shot of carb cleaner near your seals, and see if the revs increase.... Those seals can be a big PIA on these bikes....

 

FLOAT LEVELS first;

bench sync

running vacuum sync.

You're only part way there. And we're assuming your valve clearances are in spec.

 

Lot's of good stuff to chew on in these replies. Thank you all. I've seen several references to "throttle shaft seals, but must confess I do not know what those are. anyone have a relatively straightforward explanation? To my knowledge, I haven't touched them.

 

Throttle shaft seals are the proprietary (special cross-section makes them different from regular o-rings) seals located inside each carb body, one on each side, on the throttle shaft itself. They are "trapped" by each carbs' individual throttle linkage; the only ones you can access without completely breaking down the rack are the two "outside" ones. The other 6 are buried until the above disassembly has been performed.

The fact that these seals are "buried" in the carbs is why it's not a good idea to submerge partially-assembled carbs in carb cleaner or other solvent.

Before you start getting too worried about throttle shaft seals, take care of the other basics first. Then if you still have the symptoms of a vacuum leak after everything else is right, you can look there.

 

Bigfitz... Thank you! I think I get what you are talking about, and it sounds like extremely dicey work. My "cleaning" was done with the carbs remaining in a rack. I did not submerge carbs, I dipped a brush liberally in carb cleaner and gave everything a good wipe down. Used compressed air for the various openings, jets, etc.

I am inclined to think that I need to re-look at many more apparent and accessible potential problem areas first.

 

HOPE you are all still listening...

ended up checking valves, which do need adjusting. Nearly all intake valves have too little clearance. Since this requires carb removal, have done that. Re-cleaning carbs, special attention to throttle shaft seals (replacing all o-rings, will grease upon re-assembly. replacing the o-rings on the fuel-air mix screws with new 1x3mm. My question involves float height check. The manual's explanation of "tilt the carburetors by 60-70 degrees, so the valve isn't held down by the weight of the floats" is confusing me. If I tilt one of the carbs by 60-70 degrees, nothing discernible happens with the valve. If I tilt it by more than 90 degrees, then the hanging valve comes fully up and out of it's little spot (but doesn't fall off the tang). It seems strange to me, that float height would be measured in that postion.

I'm hoping someone knows a less confusing way to get a clear reading on float height. As always, thank you.

 

In all honesty wet set the float levels, XJ4ever as many good tutorials, one of them how to set the fuel levels. Keep in mind the one I refer to in the link below is for the Hitachi but the procedure is pretty much the same. You'll need to know the factory spec for your Mikuni's (I believe that's what the X has) but again, the procedure is going to be very similar.

http://www.xj4ever.com/

 

Valve clearance adjustment also requires camshaft removal on the "X" so I hope you've tracked down a manual.

All that silliness with tilting the carbs, etc., is just for getting a dry setting. Dry setting is only the starting point, you need to WET SET the float levels anyway. http://www.xj4ever.com/setting%20fuel%20levels.pdf

 

Is it not possible that his idle screw was set way too high? That was my first thought, could someone explain to me why no one else's thoughts went there? Curious what I have wrong in my thinking.

 

have had the manual for some time on CD rom. Awesome resource, except for when it gives bad advices on valve check intervals and/or float check

 

to fintip. the increased revs happen only when clutch is pulled in. When the bike is started and idling, it is not racing. problem occurs after throttle has been used.

 

At this point I am a bit confused as to where you're at. Have you replaced the throttle shaft V-seals (they're not o-rings)? Are the valves in spec? Perhaps if you reiterate what has and hasn't been done it would be easier to diagnose this.

The revs continuing to stay up after the throttle is released is a sign of a vacuum leak or possibly your throttle butterflies not closing completely. There's air getting in somewhere.

 

Huh.

 

Valves not in spec, next on list. I'll confess that I thought o-rings were okay for the throttle shaft. carbs not yet together, so this can be remedied, if o-rings cannot be used . After carbs go on, I need to reset fuel-air mix, and carb synch has been disturbed, so that needs to be done.

 

The throttle shaft seals are proprietary parts and cannot be replaced with common o-rings. The mixture screws need to come OUT and probably get their tiny o-rings replaced.

While you're working on the carbs, be sure to WET set the float levels; the more accurately the better.

The more thorough you are in getting the carbs right, the less likely they'll need to come back off again.

You'll need to have the valves in spec to get a decent vacuum sync.

 

Thank you for the advisories. I did go to The XJ forever forum and found the parts list. Will be ordering. I'm in Denmark, so there will be a bit of a wait, but I am very grateful that they are willing to ship overseas. I reached the same conclusion about the smaller o-rings, and it makes a whole world of sense to be as thorough as possible while stuff is apart, instead of rushing to get done and having the work be compromised.