Replacing Throttle Shaft Seals on Honda Twins CB450 and CB500T

[@gordv1166]

Great video! Your "Signs that seals need replacing..." are exactly the symptoms that I'm experiencing with my Honda 450. Will definitely be contacting you regarding replacement seals.

[@gordv1166]

Just a follow-up... Contacted Dude's Garage to purchase a set of seals and within two days my seals were in the mail. Arrived 10 days later via snail mail. Purchase was made with PayPal. Very happy about that. Seals were of a high quality felt. Definitely a good, snug fit in the seal well and around the butterfly shaft. Used dielectric grease as recommended during assembly. Bike ran 10x better after everything was reassembled. Would definitely recommend replacing your felt seals on those older (classic) bikes

[@johnolepaulsen6101]

Thank you for the seals and educating video. Followed it step by step. My carbs are ok now and no carb air leakage anymore :)

[@badboybikerdude]

You're quite welcome, I'm glad to hear you're up and running again!

[@matthewmartens446]

I have a question about the throttle plate screws, if they are staked in, doesn't that mean taking them out will strip the threads? I even filed my throttle plate screws down to the throttle shaft, and they still have resistance while taking them out. I'm wondering if you think this is a problem, or if putting them back in with loctite solves that issue. Thanks.

[@weeverob]

great video, tx! the "junky screwdriver" looks like a paint can opener

[@dudesgaragedotcom]

+Rob Weaver It has been known to open a paint can or two in it's day

[@bestione761]

Hi there! I am trying to put my buterfly back on to the throtlle shafft after having my carburetors cleaned. Once I try to put the butterfly back in place it gets stuck, I can't move the throtlle shaft. I have taken apart evrmerything to check what could happened but I can't see what's the problem, any idea? Thanks

[@williamsimoninc]

ever done this on a Honda Ruckus? mine is leaking and i cant find the seals or instructions

[@mikeclower3711]

What about the choke shaft? Do you have a video for that?

[@nwjt]

No need for heavy gear oil to be soaked into the felt? Is Lithium OK instead of dielectric?

[@joshrandall8473]

Dude, is JIS different than metric allen wrenches? great tutorial btw. You are the first person i have seen even talk about these seals. I have rebuilt a bunch of these and never known to take the shaft apart to do this. I have seen yellowish gas residue around the spring before. Thanks for all the detailed info great job.

[@dudesgaragedotcom]

+Josh Randall Thanks Josh, I'm glad you liked it! JIS is different from american phillips and as far as I know, all japanese bikes use JIS screws. I've had much better luck not stripping screw heads off since i switched to JIS bit drivers. Not many rebuilders replace these felt seals but they should. New seals make synchronizing the carbs much easier and you end up with a smoother idle too. I used to have trouble adjusting Goldwing carbs just right and that is why I decided to create these seals. Since then I have used them on every Keihin CV carb job I've done and I've had great results.

[@evilsadvocate]

could a bad throttle shaft seal on a 79' CB750K cause low power and stumbling at high rpm? have not checked valves, but the carbs are very very clean. runs and rides perfect except for high rpm high load operation.

[@badboybikerdude]

Not usually, no. Once the carbs get off idle the other fuel circuits take over and the throttle shaft leaks no longer affects the bike like they did at idle. If the vacuum leak is bad enough to affect WOT the bike wouldn't idle at all. It may be an issue with the accelerator pump but that comes into play as you twist the throttle. Once you are at the top RPMs the accelerator pump has already done it's job. It's hard to diagnose an issue like yours without actually looking at the bike but usually low power at WOT is either a rich condition if it's just blah or a lean condition if you are getting backfiring/bucking too. If you don't have the stock airbox on it, that could cause your symptoms. A valve that's too tight might do it but I'd think the bike would misfire more often if that were the case. A clogged fuel filter or in-tank screen would starve it for fuel and would be noticed most at high RPMs. A bad fuel valve diaphragm would flood one cylinder and cause a loss of power and a restriction in the fuel system. A good thing to help you diagnose whether you are running rich or lean is to run the bike up to top RPM and then hit the kill switch while pulling the clutch lever in then stop the bike without letting the clutch out and pull the spark plugs. You can tell a lot about what is going on fuelwise by looking at the color of the plug insulator. They even make a tool called Colortune which lets you look inside the cylinder as its firing to see the flame color. Another thing it might be is bad ignition coils, A weak coil will show itself at high RPMs because the combustion pressure and coil firing frequency are greatest at high RPM under heavy load.

[@furkantahaolgun4534]

Nice and usefull video! How do you think about using O-ring and U-ring combinations instead of felt seal? I couldn't make it with felt seals on my 600F4's carburetors.

[@badboybikerdude]

Thank you! I've seen 0-rings used but I'm not so sure about using U-rings because the inside of the U would be the sealing surface against the throttle shaft and since the U has a gap, it would be a potential area for leakage. O-rings with washers or little cups like the CB450 carbs have would be a better bet IMHO. Are you running Keihins? Did they have felt seals originally? If so, the seals I use in the CB450 might also work in the 600F4. I'd need to know the throttle shaft OD and the seal cavity ID to know for sure but it is a possibility.

[@furkantahaolgun4534]

@@badboybikerdude Thank you for your reply. Originally it has felt seals. But only first carb has a special U-ring at one side of it. All of the carburetors has a normal hole at one side. But the other side has chamfered hole. And its almost all the way in to the shafts seating. Not suitable for U-rings. I tried after I write here. At normal side I used U-rings that U side facing out. I think it sealed that side. But I used O-rings at chamfered hole. Shaft isn't turning or its leaking depending on to the pressure that shaft makes on the O-rings. I'm just having trouble with chamfered hole side.

[@furkantahaolgun4534]

@@badboybikerdude I saw information just now. :D I will contact you through the e-mail. Thank you for your help and kindness.

[@badboybikerdude]

That chamfered hole is something I haven't seen yet, all the old Keihins had straight holes for the felts to sit in. If you could email a pic of the chamfered hole to me I'd appreciate it. If you use o-rings you should lubricate them where they contact the throttle shaft. That should make the throttles open and close without too much effort.

[@furkantahaolgun4534]

@@badboybikerdude I lubricated orings. But pressure that 2. and 3. carbs shafts making on orings doesn't let the throttle turn. I sent you an email that including a video of chamfered hole. Thank you for help.

[@Snurre86]

Should/could you take some sandpaper and remove the ruff edge on the shaft after you remove the butterfly to not damage the walls/seals as you take it out/in? 5:35

[@dudesgaragedotcom]

You could try rounding off the edges of the slot but the more material you remove, the weaker the throttle shaft becomes and the less area the slot has to grip the butterfly. I have thought about a tiny plastic sleeve between the seal and the shaft but it would have to be pulled outward before the shaft could seat correctly and there isn't a lot of room to do that once the shaft is installed past the slot. I also don't have the machinery required to make tiny plastic sleeves. The reason I twist the throttle shaft back and forth after installing it is to smooth out any anomalies that may have formed from pushing the shaft through the seal.

[@Snurre86]

Now I saw the other video you did where you say you can use sandpaper in the slot but I was thinking about the sharp edge outside the slot and the the screw holes. I am thinking about doing this on my CB600F 1998 (4x KEIHIN VP 49A carbs). I have completely rebuilt and cleaned the carbs except the seals and as I did a vacuum cleaner vacuum test of the vacuum pistons, to check there sync and after that I could see some black grease/oil running out of the seals.

[@dudesgaragedotcom]

Yep. I use sandpaper inside the groove to get rid of any burrs caused by unscrewing the butterfly screws. It makes the butterfly go back in easier and also makes it easier to center the butterfly in the carb bore. If you used a carb dip tank to clean them then the black liquid could be carb cleaner liquid that had soaked into the felt seals. For an OCD mechanic like me, changing out the seals is part of every rebuild but there is a way to test if the seal areas are leaking. With the carbs installed and the bike idling you drip WD-40 or similar around the seal are to see if the bike changes idle speed. If there are leaks, usually the bike will rev up or even die if the leak is big enough.

[@Snurre86]

Thank you, I was about to do the whole start spray test of any air leaks but I had a new float valve fail on my bench, even emptied the bowl twice to see, but it just continued to let petrol in to the bowl and overflow out the carb exit. But if there where no leaks before would you not make leaks by spraying start spray/WD40 on the butterfly shaft seals as it would remove the grease? Also I meant to ask about your silicone grease. I have heard that this grease can make AFR sensors/oxygen sensor go haywire. Not that I have this sensors in my bike but would be good to get confirmed.

[@dudesgaragedotcom]

First off, don't EVER use start spray (ether) to check for vacuum leaks. It is way too flammable/explosive to take a chance with. Second, the factory seals were not greased so there would be no grease for the WD-40 to remove. If you mean the silicone grease I recommend to use on my seals then no, WD40 will not dissolve it. Silicone grease is not petroleum based so petroleum products can't act as a solvent. I don't know if silicone grease affects O2 sensors or AFMs but I doubt it. Some RTV silicone sealers can give off fumes that mess up AFMs & O2 sensors but most RTV has been re-formulated to make it sensor safe these days.

[@weeverob]

really great video...any chance you could do a video for replacing the seals on a pair of Mikuni BS34 carbs [ for XS650 yamaha ] ? TX!

[@badboybikerdude]

+Rob Weaver I'll see what I can do. I think the Mikunis use a rubber lip seal though so I don't know if my seals will work on them. I will check it out, I do have a pair of XS650 carbs on the shelf.

[@weeverob]

Dude, i need your expertise! in a BS34 carb is there a part that is a 1/8th inch diameter ball bearing? a few months ago i replaced the needle valves on my two BS34 carbs [ for a yamaha xs650]. no problems. today i began to disassemble the same carbs to replace the 4 shaft seals. at the beginning of the disassembly i decide to remove the carb diaphragms to view the threaded tips of the butterfly mounting screws. i started with the left carb, removed the diaphragm cover, spring and diaphragm. i then tilted the carb forward and heard something fall on the table. it was the bearing. i looked everywhere inside and out and could not find an opening that would take this bearing. i repeated the same process with the right side carb but no bearing dropped out. is this bearing a foreign object that shouldn't be there? appreciate any insight you can give. tx!

[@weeverob]

+Rob Weaver i should have persevered.....the bearing was a part of the choke linkage, a rolling friction bearing that holds the choke shaft's position. evidently someone before me messed with the carb and omitted putting back the 2nd ball bearing and 2 springs. problem solved, adios.

[@badboybikerdude]

+Rob Weaver Sorry I didn't get to you earlier, I go offline on the weekends. I'm glad you figured it out though, good job!

[@oilinmyblood3906]

Hello brother, do you still sell your throttle shaft seals by chance?

[@badboybikerdude]

I do, just send me an email to [e-mail] and I'll get you taken care of, Thanks!

[@Snurre86]

8:40 Is the cup in the middle and not facing out to keep the seal from being sucked in and/or why do you even reinstall them?

[@dudesgaragedotcom]

The way it goes together is: carb body-seal-cup and the cup is installed with the rim facing the carb body. The purpose of the cup is to hold the seal against the carb body.

[@Snurre86]

How is the cup holding the seal against the carb body if it is facing out and is between the seal and the carb body from the factory?

[@dudesgaragedotcom]

The cup is not between the seal and carb body from the factory, the seal is between the cup and the carb body. Look at it this way, as a bologna sandwich. The carb body and the cup are the two slices of bread and the seal is the bologna. If you hold the 2 pieces of bread in place you can slide the bologna out of the sandwich. That is how I remove the old seal.

[@Snurre86]

OK I see now, it just looked like the seal was on the outside as you took it out first.

[@Lordywithus]

Are you still selling seals?

[@LeonKishchenko]

Hey dude super nice video !! Really need those seals for my project, do you still have some and can you ship to Belgium? :D

[@dudesgaragedotcom]

I do have them and can ship to Belgium! Just send me an email to [e-mail] and I will get you taken care of.

[@mikenixon4637]

It is extremely and deceitfully misleading to attribute any carburetor performance symptom to the felt throttle shaft seals. They are dust seals only, not vacuum seals. I know you started on this crusade because of an experience with your Gold Wing, but if after seal replacement the engine ran better that is a classic case of unintended consequence. That is, something else in the many steps of doing that task fixed your problem, not the felt seals.

[@badboybikerdude]

Here is what I know. Vacuum leaks of unmetered air cause idle and synchronization problems in motorcycle carbs. When I spray carb cleaner on the seal area and the bike revs up and/or dies there is a leak at the throttle shaft. After I replace the seals and repeat the spray test the bike doesn't react. That, to me, is proof that my seals are not "dust seals only" and do solve the problem. If you believe what you say, why have you bought seals from me in the past and why did you ask me to manufacture PD throttle and choke shaft seals for you?

[@mikenixon4637]

@@badboybikerdude First, spraying liquids onto a carburetor or intake manifold is an incorrect way to find vacuum leaks. The correct way is to do the less/more air test. It's conclusive and professional. Spraying the carbs will almost always result in changes to the engine idle, even when there is no vacuum leak, because carbs have several air vents and other entry points that can be affected. Second, there is no Keihin carburetor that relies on an absolute throttle shaft seal, and even if there were, a felt seal such as used on most Keihin carbs could not possibly provide it. Many Keihin carbs in fact, such as the GL1000, actually have vacuum leaks deliberately designed in by the factory. Some Mikuni carbs do as well, as evidenced by their exposed throttle shafts. And many carbs without exposed throttle shafts leak air around their welch plugs. Third, while you and others report improved engine performance after replacing throttle shaft seals, this is simply due to unintended consequences. That is, in all the removal, disassembly, reassembly, reinstall and adjustment, something or more than one thing ancillary to the seal replacement actually solved your performance issue. What I am telling you is well known in the industry.

[@badboybikerdude]

"What I am telling you is well known in the industry." That is a perfect example of the logical fallacy called appeal to authority. I notice you didn't answer my questions about why you bought seals from me and why you asked me to manufacture PD throttle and choke seals if what you say is true.