Throttle Shaft Seals

Hello All,

I have a hanging idle. Once the bike reaches operating temperature the bike will hang at 2000ish RPM then drop down to a nice 1000 after about 5-10 seconds. I can also get it to come down with the clutch or by popping the throttle.

Checked the intake with some contact cleaner and low and behold, my throttle shaft seals are leaking... great...

Is there any quick/temp fix for them without pulling the carbs? I would prefer to have another few weeks before I make time to pull the carbs.

I also noticed via the Spark Plugs that cyls 1,2,4 are good mixture if not a touch lean. And cly 3 is very rich. So I turned in the mix screw on carb 3 by 3/4 to set it at 3 (1,3,4 are at 3 3/4 turns)
I will see tomorrow if that helps the cyl at all as it didn't change much from me running the bike at idle for a few minutes. Will see after the ride to work tomorrow.

Inspecting with the contact cleaner it seems that the outer seals are the worst. seal from 1-2 is slightly leaking, seal 3-4 is fine (no RPM change via spray)

And input on the mix or the seals would be appreciated.

Cheers
Dave

 

You can only get to the outer two without pulling and breaking the rack. Besides, if you're going to do one, you might as well do all eight.

On that note, I'll just leave this here.

 

Carb rebuilds are fun

 

No temporary fixes I can think of amigo, gotta do them right or you are just wasting time. Of course you could flood them with some combustable liquid as you ride down the road but that would probably be impractical.

 

That is great, thanks

I have no issue with doing the rebuild, it is the down time I don't like as I rarely have a straight shot of time to do it.

That is what I figured... and this whole issue is because I didn't think of them when I had the carbs out over winter.. So doing it right is how it'll be done this time...

Cheers
Dave

 

Either its a hole in one of the rubbers under your hats or dirty slide bores.
I had the hanging idle too till I polished the slide bores. It came back after one riding season so again i polished again. Cured mine.
While you are in there, blow them out seven ways to sunday with a few cans of carb cleaner. Set the floats at the proper level.

 

The float level was set but I will check again, My diaphragms shouldn't have holes as I checked before assembly, bores were also polished. I would think that the leaking shaft seals would cause it to run lean under load(high vacuum) but when the vacuum faids they'll re-seal, such why the idle runs, then drops and stalls. But who really knows, I just know that they leak, and while it is apart I plan on cleaning everything regardless.

Cheers
Dave

 

Nah....they leak the whole time. BUT they can only leak a tiny amount which makes very little difference above 3k rpm but makes it impossible to get the rack synced or adjust the mixture since depending on the exact position of the shafts and seals SOMETIMES they leak a lot, the next blip of the throttle and they don't leak so much.
One second #1 is leaking like mad and #2 is sealed up pretty good. You sync to that and then #1 seals and #2 leaks and your sync is way off.

But now you get to completely reset everything! but it's a definite requirement and it won't run right until you do it.
I would surely double check the float levels while its out just to eliminate that potential problem which will require the rack to come off AGAIN...

 

" I would think that the leaking shaft seals would cause it to run lean under load(high vacuum) but when the vacuum faids they'll re-seal, such why the idle runs, then drops and stalls."

Actually Azrael it is quite the opposite.

When you release the throttle and the butterflies close you are creating a restriction in the path of the airflow causing an increase in vacum.

The motor still wants X amount of airflow per revolution. If it can not pull that airflow through the throat of the carb it will start pulling it through the next weakest point. That being the shaft seals.

What this surge of air throught the shaft seals does along with the increased vacuum is pull a surge of fuel through the idle circuit in the carb. This temporarily increased fuel/air mixture is what causes the erratic idle problems.

That being said. Replace the shaft seals and you should be good to go.

Ghost

 

did you do a running sync? a temp fix might be to pack the cavity with grease but i don't know how long it would last

 

That makes sense. I still need to pay attention to what our teacher always said "Engines suck!"

I did, thought admittedly with no YICS tool. Might try the grease but do you think it could harm the engine/carb if it gets pulled in through the carb?

Cheers
Dave

 

Back in the "Golden Days of Rock-'n-Roll", ... all you needed to do was put a couple of Drops of TEAC Rubber Pinch-roller Conditioner in the Shaft Tunnel and rejuvenate dried-out Seals.

The latter-day equivalent is probably this stuff:

http://www.mcmelectronics.com/product/2 ... rm=200-200

 

Wow. That I will certainly try before tearing the carbs out. Thanks a lot Rick

 

Rick:
Do you think this would be the same? (local distributor)
http://www.rpelectronics.com/408b-125-r ... 100ml.html
Cheers

 

That is what I'm using on my rubber parts, it works pretty well. Smells good too!!!! (What are all of these pink elephants in the room for???)

 

It's likely the same; or better.

Browse. Look for the ones that have Precision Applicators.

Hold the rack vertical and put three of four drops of that Rubber Conditioner, work the Throttles and let it work.

Invert. Same; same!

 

So then if I brush this on and/or inject it into the seal it would stand a decent chance of re swelling the seal to make it good for a little while again?

Might it also be a good idea to brush on the boots before they crack?

Cheers
Dave

 

What, does that stuff smell like ditto machine fluid?

Where I work we usually have a gallon can of contact cement sitting in the fire cabinet for use in various places. Its distinct aroma caused one of the other mechanics to refer to it as "the happy can".

 

Wait whoa stop hold on.

TEAC tape decks and other electronic equipment's rubber parts aren't exposed to over 200*F operating temps like the various components attached to the bike's engine are.

What happens when everything gets nice and hot? What does the "magic elixir" do then? Make things better, or worse?

-Order all 8 seals.

-Since you know the outers are done for, replace those immediately (10-minute job, if that.)

-Don't apply anything to the seals that isn't at least "automotive" grade; I wouldn't apply anything myself.

-Finish the job correctly as soon as you can.

 

I would agree for most parts but my understanding is that carbs don't get hot. And printer rollers do actually get pretty damn hot. Nothing like the rubbers on the block itself, but comperable to the carbs I should think.

I have a parts carb so I will be repairing that one up vs fixing the one that is on the bike, but I would like to try something to temp fix the ones on the bike till I can afford the seals for the new carb ($90 for the kit)

How hard is it to get the butterflys off the shafts?
I was talking to our head tech at work and he was saying that yamaha peened over the back of the screws so you need to file them down or you'll screw up the threads on the throttle shaft... But no write-ups mention that.

Cheers
Dave

 

On the Mikunis, yes. On the Hitachis, no. A good-fitting screwdriver should do the trick. Probably a good idea to use a scratch awl to mark the back of the butterflies where they meet the shaft so you can be sure you reinstall them in the same position they came out.

Oh, and I did make reference to the peened butterfly screws in the Mikuni Carb Cleaning file.

 

$90 for the seals??? On a Maxim??? You NEED to get in touch with Chacal... his prices are MUCH lower than that.
And I'm all for you getting the right parts in there, reconditioning your old parts is just wizzing on a forest fire. You aren't buying much for the effort.

 

Chacal's price for seals is $32.00, and they're in stock (I just ordered mine last week). A big blob of vaseline on the seals will last for an afternoon as a temporary fix, but goops up your butterflies in very short order, although it provides a very graphic demonstration of which ones leak. Pretty tough to get enough on the inside seals to make it work too.

 

Parts are from Chacal... but note I said the Seal Kit (aka all the parts needed to be replaced when splitting the rack).

I really only want to do it once so the outer two are the only seals I can change without all the parts listed below...

seals: HCP38BSET8 $32.95
Screws: HCP1347SET8 $5.00
Shims: HCP3991SET8 $14.95
Screwdriver: HCP5901 $14.95 (JIS for the Butterflys)
E-clips: HCP2909SET2 $3.00 x 4
O-rings: HCP92SET6 $7.50 (Fuel Rail)
7.50 shipping

= $87.35

And chacal is the only person who has them regardless. I work for Yamaha and they don't split up the throttle shaft or butteryfly's in the fiche... So Chacal is the only place to get the Throttle Shaft parts from.

So I (and we all) should truly thank him as otherwise when these seals leak we would all be pretty screwed...

Cheers
Dave

 

Awesome, Thanks

Dave

 

Azrael be sure when you do put them back together you use thread locker on those butterfly screws.

 

That I will do.

So, I noticed today that she will hang when I pull to a stop, but if I give the throttle a good hard blip it will rev up but then drop down to a stalling idle... however if I turn the idle screw in more the bike actually starts to run away from me when I am coming to a stop 8O

Any input from the wiz's out there or is that still an atribute of the shaft seals? Any other input about other issues to look for before tearing the rack apart?

Cheers
Dave

 

All clamps tight on th mounts, carbs aligned in th mounts no cracked rubbers
or it's just time to bite th bullet and break th rack 'n do those damn seals. Synch' and adjust. They'll be good for a long time afterwards.

 

Well it looks like my troubles run much deeper than I thought... I had it in the shop so I decided to do a leak down as one of the other techs had a new tester from snap-on was dying to try it. Turns out cyls 1,2,4 have only a 2-4% pressure loss, but my number 3 cyl has a 60% loss and such is burning oil aka running rich... I knew she was burning oil but I figured it was just a little wear on all cys vs one really bad one... So I would assume it is a big factor in my running issue and will start on the repairs.

So I guess for now I will order a set of rings for cyl 3 along with a base/head gasket and adjust the valves after rebuilding.
Do you all think I should change the valve guide seals while in there?
and maybe lap the valves?

Kinda peeved but I guess that's how it goes sometimes...

Cheers
Dave

 

Don't put new rings in only one cylinder; and don't order rings at all until you've pulled it down and inspected and measured the bores. Otherwise don't bother.

By all means lap the valves and install new valve stem seals while the head is off.

Be careful of the valve spring coil orientation upon reassembly, it's important.

All that being said, have you done a compression test? Or are you basing your decision to do all of this expensive engine work on one leak-down test?

 

I have only done a leak down.
My understanding is that a compression test is essentially pointless if you have done a leak down seeing as compression tells you if you are losing pressure, where as a leak down tells you both if you are and where you are losing it. I could hear the wooshing coming out of the crank so my rings are bad. Running 100PSI on the test.

Open to any input though

Cheers
Dave

 

sort of, maybe but the regular compression test may tell you that the compression is fine and the leak down says it leaks at the rings when it leaks, it's got to leak somewhere

 

I'm inclined to agree with needing the compression test. You need to know if the cylinder is pumping volume. The leakdown could be in error (I've seen and done this so don't assume it is right the first time out). Use the compression figures to back up the leak-down test. It could well be a hung valve, or carbon on a valve face... Were you able to listen to where the air was going with the leak-down? You should hear the sound of escaping air either at the intake, the exhaust or the crankcase servicing port.

 

Ok, I will run a compression test then.

Yeah, it was coming out of the crankcase. Could hear it through the oil fill port.

 

So it turns out there is nowhere in the city I can rent a compression tester. So I guess I will see if I can borrow one from work tomorrow :roll:

Dave

 

Go to your nearest Canadian Tire and buy one for probably about $25.

Or "Google" "auto parts Vancouver, BC" like I just did, find your nearest NAPA and buy one (probably for about $25.)

Sears? It's a good addition to your toolbox. I have one that I've had for about 40 years now and one I bought a couple of years ago just to get the 12mm plug adapter in the kit.

 

So I got results of a compession test today.

4 3 2 1
180 140 170 175

(note: coldish engine, throttle closed)

and the leak down prove it is the rings so I guess I gotta look into tearing her down...

 

NO no no no...the throttle MUST be held open (carbs off is ok too). Engine temp is not a concern.
The result is skewed but in general you are right, #3 isn't as happy as the other three. Try running it for a week and try the compression test again to see if the numbers improve.

 

Ok, Did a comp test again today, WOT for all the tests

4 3 2 1
185 170 180 190

:?

I know I am leaking oil into cyl 3 so I ran the bike for a few seconds as I figured some unburnt oil/fuel may have sealed the rings. Then tested cyl 4 again and still got 165

I am confused to how it can fluctuate so much by opening the throttle...

Any input would be appreciated

Cheers
Dave

 

Based upon your initial leakdown and the subsequent compression tests, you do have a ring issue but I would not classify it as terminal. If you are not having any other issues, I'd just run it, the WOT compression is close enough that I wouldn't be concerned. Just check the numbers again in a week or two and see if they haven't improved. It may well be that the rings might, just might seal a little better with excersize but it is more likely that nothing will change. You can spend the interim time until it NEEDS the rebuild saving up for the new parts. And stock rings are NOT cheap.

 

So, I did a Valve Adjust/Carb Sync today...
The valves were so far off it isn't even funny...

First Check:
Cyl 1:
Intake: .05mm - 275 shim
Exhaust: .05mm - 260

Cyl 2:
Intake: .10mm - 280
Exhaust: .17

Cyl 3:
Intake: .10mm - 285
Exhaust: .10mm - 265

Cyl 4:
Intake: .8mm - 280
Exhaust: .11mm - 270

Set to:
Cyl 1:
Intake: .15mm - 265 shim
Exhaust: .21mm - 270

Cyl 2:
Intake: .14mm - 275
Exhaust: .17

Cyl 3:
Intake: .12mm - 275
Exhaust: .18mm - 255

Cyl 4:
Intake: .14mm - 270
Exhaust: .19mm - 260

Gotta keep an eye on Cyl 3 intake.
Do any of you think the .12mm on Cyl 1 Exhaust is a problem?

She sounds a lot better and we'll see how she runs tomorrow.

The only odd thing I that there was what seemed like oil in the YICS passage. Is that normal?

Cheers
Dave

 

"The only odd thing I that there was what seemed like oil in the YICS passage. Is that normal?"
I've noted this on a few of mine and chalked it up to leaking valve seals and coking. I'd like to hear a few other ideas fellas...

 

Our Yamaha tech actually thought that whilst there may be some oil in the passage, it is more likely just gas that settles inside and then has been boiled and re-boiled giving it the dark, oily viscocity. But that was just his specuation as it has been many years since working on these bikes.

Cheers
Dave

 

So, she is running much better after doing the Valves and Sync but still slightly hangs. Such I have ordered all the parts for carb rebuild from Chacal. Tore my spare carbs apart today and have some questions about if certain parts can be re-used...

Float Needles: The bike wasn't flooding before so I would assume they work, but there is a slight bump on them. Can I use these or do I need to get all new float assemblies?


Enrichment: Do I need to replace the boots on the top of the plungers?


Mains: I took the jets out a long time ago. These are the washers that go under the main jets yes?


Going to take the carb bodies to work to run through the agitator once my parts come in with the JIS screwdriver. Also re-jetting the mains while I'm at it as I have an essentially open exhaust.

Also got a colortune so I can set the idle mix right when they're done.
Does using a colortune on a cylinder that's burning oil damage anything?

Any notes or input from anyone about this rebuild?
Other tips I am probadly forgetting?

Cheers
Dave

 

The float needles are probably history. New ones are indicated.
The jet washers are reusable, just clean them up.
The enrichment plunger boots are unobtainium, treat them well and preserve.

 

I agree with robert. The needles are shot see the shiny part where it rubbed off the viton (i think thats what its called) that should be smooth with no bumps. They might not be leaking right now but they will. Hopefully you have them marked the wear marks are from it seating. If you don't put it back in its corresponding seat it will never seat again properly

 

May have a lead on some plunger boots, will try to replace them as they didn't come off very easy...

I have kept everything short of the choke plungers seperated into which body they came from. Will look into replacing them but might end up using whichever set is better from my old and current carbs.

Cheers
Dave

edit: Scratch that, found some keyster Valve Assemblies in a drawer at work for near free. Will be replacing them.

 

Indeed I have found some new Choke Plunger Boots adn 5 are on their way to me.

Cheers
Dave

 

If those plunger boots work, get a part number for us! I'd like a set!

 

I got them from Yamaha themselves. Sounds like I may have almost gotten the last set in North America...

Cheers
Dave