Signs of leaking throttle shaft seals???

What are the signs? Would it cause the carbs to race up rpms? If so, how much could it make it race up?

 

I found that if you spray electrical contact cleaner onto the shaft seals at idle you will get a NOTICEABLE increase in engine speed, unlike carb cleaner.

You want to give this test a go if you are having problems getting a rich mixture, or your idle creeps up a lot after getting warm, i.e. it idles fine, but it's hard to find the right speed.

I've found that other air leaks are more obvious. The shaft seals are insidious. It's hard to really tell there's a problem until you do that test. I did the test with carb cleaner and brake cleaner, and neither one gave me a positive test (positive that I had a leak, that is) even when I sprayed it directly into the air box. The electrical contact cleaner was quite conclusive, however.

 

Raven, I just rebuilt the bottom of my carbs (due to what I thought were sticking floats) and when I put them back on, first start the rpms jumped to 4-6k. I can feel some fuel leaking from around my throttle adjustment screw now as well. I was reading some pretty good posts when I searched the forum for "throttle loose" maybe you can check them out and find some good things to look at there.

 

From where??? The throttle adjustment screws are part of the linkage. Are you talking about from the end of the throttle shafts (you can only see the the sides of #1 and #4) or are you talking about the mixture screw on top of each individual carb?

The OP is asking about throttle shaft seals. Using propane or contact cleaner or starting fluid to "probe" for TS seal leaks is the only positive way to find them. Unless you pop the clips and nylon washers off the ousides of #1 and #4 and examine them to find those are toast. Then you KNOW they're bad.

 

Sorry, Fitz, I'm talking about the large idle adjustment screw on the back of the carbs, that's where I feel fuel dripping out around, but my throttle cable isn't "snapping" back into place now either and will keep the rpm's up to where you twist it to and stay there, so I'm looking at multiple issues.

 

If there's fuel dripping from the large main idle knob, you've got a leaky float bowl or fuel coming out an overflow somewhere. Nothing directly associated with that knob can leak, it's part of the linkage.

When you checked the floats using the clear tube method and gas, you should have discovered anything that would cause gas to drip from there. Having the rack out and mounted on the bench, being fed fuel, is the best way to find the issue.

Additionally, it sounds like the shafts or linkage are binding. That should have been discovered and corrected during the bench sync.

You need to pull the rack back off and get it right before reinstalling it. You skipped a lot or you wouldn't/couldn't have the issues you're having now. You can't just tear through it, and ignore the stuff you don't understand or that seems too complicated and hope it won't matter. It does. You're going to do it right, whether it takes once or five tries before you do. You know why? Because until you do it right it won't work.

All of which has nothing to do with throttle shaft seals.

 

Will take your advice and slow the heck down. Good luck Ravenz, keep us posted on what you figure out.

 

Well, I am still experiencing racing rpms. I am just thinking of all possibilities at this point. From what I read, it seems the seals are a common issue for leakage.

 

You could check the seals as Fitz described to rule them out...

Have you synced the carbs yet?

 

I just went through that racing RPMs and slow to idle down hard start after warm up.. I tried carb cleaner to try and find the leak with no luck. Used the propane leak test and found it right off the bat.

 

I just went through that racing RPMs and slow to idle down hard start after warm up.. I tried carb cleaner to try and find the leak with no luck. Used the propane leak test and found it right off the bat.

 

Ravenz, what exactly are you experiencing? From what I've experienced, an air leak gives "hanging" rpms, not "racing". By that I mean that the engine speed doesn't come down from a rev during hanging, but will go up with no input while racing.

Maybe I lack enough experience, but I haven't seen or heard of a "racing" engine cause by an air leak. Now, I have experienced a difficulty in setting an idle unless the engine is really really warmed up while I had an air leak. In that case the bike nearly dies at cold idle, so you increase the idle speed, and then it's racing once it's warmed up.

The air leaks I've had caused hanging speeds though.

 

Whenever I start it, it pretty much climbs immediately up to 6k rpm

 

Mine had everything clean and synced both bench and vac Color tuned. it was running like a top got about 100 miles on it and coming home I stopped at a red light the rpms went from 1100 at idle to over 4k for no reason. when I took off from the light it was running fine then started popping thru the exhuast. When I got home checked for leaks and found the shaft seals leaking. When I removed them they were hard as rocks.

 

Ravens, have you tried turning down the idle screw? Maybe a squirrel decided to go in there and mess with you.

 

Sounds like a boot is leaking, probably at the boot to carb joint. We see it often on the vstrom 1000 when a small backfire will pop the boot off connecting the throttle body to the engine...rpms scream and stay. Have had it happen on 2 strokes too and they will redline at idle and need to be choked to cut them off as the key will not shut them down...trust me, when it happens on one of them, you are moving faster and thinking faster then you ever thought possible so you can get it shut down before you grenade the engine. I've also seen when the owner wasn't quite fast enough....ugly, just plain ugly.....

Fairly easy to sort out either with wd40 or believe it or not, hairspray...it will plug the leak and leave your hair soft and manageable too!!

jeff

 

I have tried almost everything, the idle screw was the first. Unfortunately, turning it does nothing to the rpms.

 

Would polishing the piston bores be a cause of this problem?

 

I don't really see how, what were the results and method of the air leak test?

You've been around awhile, walk us through what happened so we can help you figure it out. Did this just suddenly happen?

 

Well....

Today I put the carbs back on after cleaning them again. This is not all of a sudden, I have just not figured out what it could be yet.

I made sure EVERYTHING was connected.
So I had everything on, including all vacuum hoses, boots, etc.

Would not start immediately, but a slight spray of starting fluid got it going, and it started right up every time after that. Immediately it just races up to 4-5k rpm and sits there. Before I put them back on, a few days ago I disassembled everything and pressure washed everything with the jets still in. I made sure to get all fuel passageways and everything sprayed out to get pretty clean. When I first cleaned the carbs, I ran them through a dishwasher a couple of times. So I figured spraying them out would be a good idea since the washer might have left deposits unseen. (I have used carb cleaner and compressed air as well)

New kits are installed, new pilot screws, o rings, washers, gaskets, float valves, etc. Float levels are set correctly. Pilot screws were turned all the way in and backed out 2 turns.

I tried various things today but nothing seemed to make a difference. I took off the vacuum hoses and put vacuum plugs on just to see if the hoses leaked-no change except maybe a slight bogginess revving up.

Turned pilot screws all the way in and out-no change
Turned idle screw all the way to the left-no change
Turned idle screw to the right, messing with it a bit-no change
Sprayed the entire carb assembly down with water, all hoses, rubber boots, mixture screws, and was having the sprayed down by my lady while starting it-no change whatsoever.

There is no cable hooked up. Hooking with the throttle has no affect. It does go down in idle when I press on the linkage.

I am at a complete loss on this. I do not think is a sync issue, the butterflys look way too close to be doing this. I did a very thorough bench synch and it kept racing up.

Boots look really good as well, putting on the rear boots was really easy, they were soft and flexible.

The only other thing I did to the carbs was polish the slide bores. Wet sanded with 800 and polished them so the slides could move with no resistance.

 

Let me ask...did you by chance remove the butterflys and separate the carbs?

It sounds to me that your pilots aren't having any effect because you A. have a massive air leak between the carbs and the engine, the other side of the carbs doesn't matter nearly as much or B. the butterfly or butterflys are partially open. You MAY NOT be able to tell by looking it they are too far open.

It sounds exactly what I did when I reassembled a set a while back and had not set the butterflys correctly first. I took the rack back off, fixed my badly aligned butterfly and instantly, my idle dropped back to zero so I could set it with the set-screw.

but these other guys know a lot more then I do.....


jeff

 

Or all that dipping and pressure washing and dishwasher action has completely blown out/ruined the throttle shaft seals and there are now massive air leaks through there...

When you bench sync'ed, did you start off with the main idle (knob) screw IN far enough so that you still have some "adjustment" left to turn it DOWN further? It sounds like you may have run yourself out of adjustment.

Other possibilities, more remote but still possibilities:

When reinstalling the rack, did you accidentally trap the linkage under the fins on the back of the head so it CAN'T close all the way?

What method was used for setting the floats?

What method was used for bench sync? (What "gap gauge" did you use?)

Why in the name of all things holy would you have someone spraying WATER on it while trying to start it?

 

I used the business card strips Rick talked about and have had to bench sync like six times due to not changing the shaft seals and they failed. Using the card strips when I put them back on and start it it idles at about 2k. A turn or two of the idle screw it settles down to 11k. Right now mine will start and idle at 800 rpms without the idle screw touching. I did at one point have the intake boot screw hold the throttle open my son tightened that side so he turned the clamp where he could get to it better and it hung the throttle open.

 

I used the business card strips Rick talked about and have had to bench sync like six times due to not changing the shaft seals and they failed. Using the card strips when I put them back on and start it it idles at about 2k. A turn or two of the idle screw it settles down to 11k. Right now mine will start and idle at 800 rpms without the idle screw touching. I did at one point have the intake boot screw hold the throttle open my son tightened that side so he turned the clamp where he could get to it better and it hung the throttle open.

 

I haven't messed with the butterflys, or separated the carbs.

The bike ran before, never idled quite right but it certainly did not race up rpms.

Turning the idle screw one way or another really doesn't seem to make a difference.

I used the tube method for the floats.

I did use the strips of card like Rick mentions

I read somewhere about the water, I guess it is not the best of ideas. In any case, I did not think there would be any leaks.

If the bike idled before, what need would there be for a bench sync?

 

The funny thing is, I took the carbs off my KZ750 and cleaned and polished the bores, it does the EXACT same thing.

 

Sound like to me JeffK is on the right track that your butterfies are not closed, I like to use the K.I.S.S. method have you checked the adjustment on your throttle cable?

 

I have installed both racks without the throttle cable just to eliminate it as a source of the problem. It races when there is not throttle cable installed

 

Have you popped the clips and nylon washers off the outside of #1 and #4 and checked the throttle shaft seals you can see?

 

No, not yet

 

it sounds a lot like mine when the shaft seals started leaking

 

Put some 20/50 Oil in an Oil Can and put a few drops of Oil on the Shaft Seals with the Bike running off a small Tuning Tank.

See if the Revs come down.

Make sure the YICS Plugs are tight.
Measure the Vacuum on each Manifold and see it there is a tell-tale great disparity.
ColorTune. See if each Carb is able to be regulated (Color change) or if there is an obvious leak.

 

Well turns out the 750 carbs had one of the rack bars installed backwards (PO), causing the linkage to not snap where it should.

It idles so beautiful now


Hopefully the Maxim has a similiar issue

 

The things Previous Owners do can be simple mindned but wind-up costing you plenty.

I had a Bike come-by here where the PO used Automotive Radiator Hose Clamps on the Carb Manifolds.

The Automotive Clamps sliced through the Manifolds and ruined the Intakes.

Feel good about finding what the trouble was and be glad it didn't cost you anything to "fix".

 

Ugh.... POs are always a nightmare.

Fortunately mine was not nearly as expensive of a fix as yours Rick lol