Has anyone ever tried this to check throttle shaft seals

Has anyone ever tried smoke testing there throttle shaft seals to check for leaks. The only reason i am wanting to check them this way is because the carbs are off the bike getting ready to go thru them completely this is what i am planning to do. I have a 6 hp shop vac i am going to make adapters out of rubber hose and pvc. Hook them up to the intake side turn it on 1 carb at a time . Take a piece of news paper roll it up light it blow it out go around every seal moving the butterflies back and forth if they leak should suck the smoke right in. I used this method on big 60 million gal a day water pumps that were hooked up to a prime vac supply pulling 25 hg vac. It was the most accurate way to check for an air leak these mechanical seals cost over 10k just for a repair kit. My outer seals are soft and pliable. If i find any leaking at all i will go thru the hassle of filing and splitting everything and doing it. I just hate to go thru all that work if there is nothing wrong. I would have checked them on the bike but it sat to long and wouldn't fire. The carbs are really clean looks like there was some water in the gas every needle is stuck in the seat. The plate and mounting screw were really rusted All the jets even mixture screws came right out Just got done pricing out the rebuild stuff from chacal parts page its almost $250 without screws

 

I would just go ahead and replace the throttle seals while you have the carbs off. I just removed the carbs on my 82 maxim 750 because I could not get the bike to idle. I also felt like it was running lean while using light throttle. I checked for throttle shaft leaks before removing carbs and found no leaks. But while I had them off I pulled an outer seal just to see what they looked like. It was soft and pliable also, but I figured that was the way they were supposed to be.

After completely cleaning the carbs, clunk tested and bench sync, reinstalled, bike fired up fine after playing with main throttle adjustment.
I even got a half way decent idle, went for a quick ride to warm up for the vac sync. The revs started hanging when letting off the throttle.

When I got back and started checking for air leaks, lo and behold, the throttle shaft seal I pulled to check was leaking. So I went ahead and ordered new ones from Chacal, along with new butterfly screws. New seals were not nearly as pliable as old seals. Installed last weekend but did not have a chance to put back on bike.

Installing them was not as difficult as I thought, I would suggest getting the JIS screw drivers, they did fit the screws on my carbs much better than standard Phillips. And loctite for the butterfly screws.

I found a complete how to on this site that was very helpful.

Good Luck!

 

I probably will but mikuni carbs are much more of a pita then hitachis .You have to file the peened over screws most of the time hitachis take very little effort to get the screws out

 

@ BigT

Can you provide some info on how the new seals "feel" on assembly, i.e. do they sit loose on the throttle shafts like the old ones, or do they sort of fill the space between shaft, carb body and washer better?

 

JIS Screwdrivers ARE very helpful.

But, you can Fabricate Screwdrivers to use for Main Jets, Pilot Mixture Screws and MIKUNI Pilot Fuel Jets from old screwdrivers that need a new life.

Using a DREMEL, you can sculpt some Screwdrivers to use on Carbs Only.

One Tool you should "Make" if you are going to get into Fine Tuning and Plug Chopping is a: "Mini-Tweaker"

Using the Small CRAFTSMAN Screwdriver with Pocket Clip:

Grab a Hack Saw.
Cut the Handle of the Screwdriver leaving 30mm of the Handle on the Shank.
Chuck the Shank in your Drill and Sand the Handle "Smooth and Rounded-off" with various grits until you can Finish it with 800.

Cut the Shank almost in half.
A little more than half, ... leave 40mm's of Shank on the Handle.

Using Sanding Drums, Grinding Stones and Cut-off Wafers, ... Sculpt the end to have a PRECISION Fit into the HEAD of a Pilot Mix Screw.

Lastly:
Put the TWEAKER in the Vice with the Newly Fabricated Blalde in a VERTICAL configuration.
Using the Hack Saw, ... Make a "Channel" in the Handle on the Center Line.
So the Channel "INDICATES" the position of the Blade Tip.

Paint the CHANNEL with White Paint.
Use a Pin dipped in paint and add White to the Hack Saw Blades cut Channel.

This Tool will fit under the Tank and allow you to Plug Chop without REMOVING the Tank.

 

Once you remove a seal it will never seal again they wear spots over the years you have to replace them.
I have ran into 1 problem with 1 of the carbs looks like it was done along time ago. Someone snapped off part of the float stand halfway around the pin the pin still fits tight and never had problems with leakage so i think i am going to leave well enough alone. (looks like the tried to put the pin in backwards) but after i gather parts will make sure its ok before re assembly. Figured if i have to i can fix it

 

I forgot about the butterfly screws on the Mikuni carbs. That does sound like a PITA. Glad I got to skip that step. I got real lucky with my carbs, everything came apart pretty easy, even the idle mixture screws. I replaced the o-rings and washers underneath them because the o-rings looked a little distorted.

Plan on putting carbs back on bike tomorrow, hopefully for the last time for a while.

 

The old seals that I pulled were very soft and pliable. Did not hold thier shape at all. The new seals were much more rigid and were a tight fit on throttle shaft, used a little lithium grease to help. They also tightly filled the cavity on carb body, had to apply a little bit of pressure to pop them in, again a little dab of grease to help.