Throtte Shaft Seals a necessity to change?

Bowl gaskets - bare clean surfaces both sides.

Throttle shaft seals--I'll say it only once......whether they shrank or expanded, hardened, melted, etc...... They are over 30 years old. They need to be replaced. If you tear down far enough to separate the bodies, REPLACE THE SHAFT SEALS AND THE FUEL SUPPLY TUBE O-RINGSIDE. If you don't, you'll tear everything down again soon to do them and wish you did them the first time.'

That all said, it's up to you. Do what you want. We've recommended certain things to you enough times now

going radio-silent,

Dfox

 

No no no no I'm talking about the airbox to carb boots..... I've more than understood now that those throttle shafts need to be changed... and for good reason. Maybe they were sealing (ok) before the rack was broken, but after I broke it, POPULAR OPINION is they're useless.


I understand, I shalt repent of my sins.

 

I misunderstood, my bad.

Airbox boots-- if they've expanded, that's ok. Easier to fit--- lol. More likely, though, that the ring clamps have been stretched, so THEY aren't sealing correctly..... if the problem is the airbox side. Otherwise, check the manifold-side boots---- the thick heavy ones....

 

I apply RTV to the gasket and apply it to the bowl , let it dry completely and apply grease to the face of the gasket that faces carb body , Doing this the bowl can be removed without sticking to the carb body and stays attached to the bowl . I have removed bowls a couple of times and reinstalled no leaks either.

 

Hello, I am back.. after a long winter of a garage too cold to work in.

I hope you guys are still following this thread ( if not i'll make a new post).

I appreciate everyone's help thus far...


I have changed the throttle shaft seals, have bench synced the carbs (used two pins to set the butterfly valves all the same, and set the float levels to 3mm below the top edge of the bowl).

And the bike starts up, but same problem I had before... Extremely high idle.

So high, that I'm afraid to run the bike for more than a few seconds a time, in case i might crack the cylinder head, as the engine is cold, and hasn't run consistently in 10+ years.

**Video for reference:


From info I found online, and logic (hopefully), seems like there is a massive vacuum leak.

Things that I have ruled out:

1. Throttle shaft seals
2. Butterfly valves (the idle adjustment screw is pretty much all the way out, small little sliver)
3. Fuel levels ( i used clear plastic tubing to check the levels, they're 3mm +- 2 below the top of the bowl, I have read that high float levels can cause high idle, but even 3mm from the top of the bowl seems pretty high to me)

I checked the manifold boots, they look good, still flexible, but how they look must be deceiving. The leak is obviously not coming before the butterfly valves, as they are closed.
I bought heavy duty gear clamps that seal the boots pretty good, and checks the nipples for noticeable leaks.

Before I replace the boots, as they would cost me close to 600 bucks with exchange rate (damn the canadian dollar) , i want to rule everything else out.

Might be a poorly sealed head gasket, but there's no black deposits around the engine.

I find it hard to believe the engine runs this fast with just a vacuum leak. Where is it drawing the fuel to run? I would imagine this would be such a lean mixture the bike wouldn't even start.


What do you guys think?

 

I see you're playing in the choke. Just to confirm, are you trying to start it without choke and you receive the same results? how far out is your idle adjustment screw? I'd turn it all the way out to where you can get the bike to run at a decent enough range. from that you can then run your vacuum tests.

 

Have you sprayed starter fluid around to see where the idle might race more?

Have you backed the idle screw down?

Have you done a running sync?

 

me too
start looking at the throttle linkage. disable the ignition so it doesn't start, get a battery charger on the battery and do a running sync with just a starter.
15sec on one minute off, at least. two or three 15 sec shots should be enough to see if the sync is way off.
with the idle screw all the way out it should stall, try that

 

When the bike is cold, turning down the choke starts to stall the engine. After a few times starting it, choke up/choke down, does the same thing.

I want to check for leaks with starter fluid/propane torch, but I really don't want to run the bike for a more than a few seconds at a time.
I'll try to back down the idle screws and see what happens.

I currently have no battery, its hooked via jumper cables to my car.

You mean run a the carb synch tool? one with the gauges? I haven't purchased one yet.

Is this a synch issue? I understand if its running rough, but this just accelerates up like the throttle is open halfway. The throttles are close.

I was thinking to try to start the bike with a propane torch, and see where pointing the torch would cause difficulty starting.

 

Ah, I see what your saying. If one of the intakes produce much less vacuum than the others, theres a leak. Too much free air flow to produce a strong enough vacuum.

 

1. You won't crack the head by letting it run on like that, just don't let it go past redline for long (or at all if you can avoid it).

2. A vacuum leak can make the engine run right up past redline. I've had expereince with that.

3. Improper synchronization can make the idle quite high as well. I find that using pins is great for getting all the throttle plates even, but it's not at all good for getting them in the right place. They should cover about half of the idle fuel outlet in the carb throat. It's possible that you have the baseline set far enough off that backing the idle speed screw out won't let it drop to the proper idle.

4. There probably are multiple issues contributing to the high idle, so change one thing at a time and then see what effect it has before proceeding to the next item.

 

There is only ONE idle speed screw--- between carb 2 and 3. The knurled knob on the air box side of the carbs us what you need to turn counterclockwise to bring the idle speed down. If that's the cause, you're gonna have to turn it out quite a way.

If you don't have a carbtune, or similar, set of guages, you'll have a tough time balancing the carbs. No, we're not talking about the sync tool called the "YICS tool". You don't need that.

Is it a sync issue? Maybe... maybe not.

 

if you see a big difference it's probably your sync. count on getting some kind of sync gauge, dials, tubes, or water but you'll need one before your done

 

Back idle knob out if it is not touching then there is a problem .

 

If it's not touching, then most likely a butterfly is way out of wack and holding things open. I did get one carb rack to rebuild one time where a butterfly was actually bent and holding things open as well… A sticky shaft could also hold things open too. Any way you look at it, if The idle speed screw is not touching then you have other issues like jetfixer said---

 

Didn't finish typing had to catch train...if butterfly plates are not perfectly centered this can cause problems, first time I did carbs one plate was slightly off it does happen so please don't get insulted when asked . Did you do a bench synch with 2 business cards cut in half , put one under each butterfly adjust synch screw 1&2 till card has slight drag, do 3&4 same you will have to bring idle knob till you get a drag on all 4 cards , this should get you in ball park. A running synch will need performed I use a 4 vacuum gauge synch manifold adjusted till 1 and 2 and 4 equaled 1.5 hg and then adjusted idle knob up till all 4 read 1.5hg and idle was 1100rpm .I have no popping of the exhaust and runs great .....disclaimer your results may vary

 

Sometimes pictures can help. You should be able to back the idle screw out so that the result looks like the pic on the left, and all 4 should look this way with a good bench sync.

 

That's the way I'd do it, it will be close enough to ride if you take care with it.

 

It takes so long to bend the paper clips out, or cut the business card straps etc. etc.… I can have a rack bench sink by the time you get the business cards cut. You don't need to go through all that. Turn the idle screw in until carburetor number three butterfly top exposes the complete hole. Now it just the other three butterflies to just uncover the same hole in their carburetors. Now back the idle screw down until the holes are half covered , Then fine-adjust so all four holes are half covered now your bench sink. It takes only a minute or two to bench sync

 

I didn't see it before… Rooster explains it.