Topic: Did I just F*** my forks up?.. 1980 CB900C

[Enstalled]

Was finishing up some adjustments to my rake when I went to tighten the crossover hose on my forks, and the right one made an audible snap sound and as i took it out, threads from INSIDE the fork came with it. Totally smooth in there for the length of about 1cm... Do I have any options other than replace the entire fork? I am feeling pretty stupid right now. 

[Bankerdanny]

(a) wrong board at this particular forum (your bike is DOHC), but the moderators will take care of that.

(b) Maybe. Does the hose still tighten? Does it hold air? The obvious risk is that if you don't have enough threads once the suspension cycles under load on a big bump that the fitting will pop out.

I know there is a DOHC Honda forum, that is probably a better place to get a definitive answer.

[Enstalled]

It does hold air, as in, it doesn't bottom out just sitting on the center stand.  I think the hose just makes sure that the forks have the exact same pressure when riding for better handling.. But I am no expert. The end of the hose sits loosely in the fork, but does not come out without force or counter turns/loosening the hose. The riding issue was my main concern. But I am really not sure as I have never encountered this type of issue on any CB I have worked on.

Also sorry about the DOHC/SOHC confusion, I just made the account to see if anyone knew the answer. But I am really more familiar with my 750F, which is why I came to the SOHC owners club forum. Lol

[Flyin900]

I am a DOHC guy and if you have stripped the threads in the top cap then that part is replaceable, as it unscrews from the top of the fork assembly. It is how you access and remove the fork spring and add new fork oil through the top of the fork tube.
You do need to fix that since a loss of pressure while riding will cause a height drop in the forks as a minimum along with other ride-ability issues and not something you want to happen while underway.

You can either helicoil or time sert the stripped hole and just screw the hose back into the assy. The hose fitting is a harder material than the aluminum top cap that accepts the hose and only minimal tightening is required, since there is an O ring on the hose fitting that supplies the seal. Check with Honda to see if the part is still available as new, or on the DOHC forum at www.cb750c.com in the wanted section forum.... a good bunch of members over there too.

[70CB750]

He could have a bushing made to thread in the damaged part and thread the hose into it but if this is the tube cap, it should not be hard to find replacement.

[Enstalled]

Awesome replies guys. Thanks for the advice. Sadly since I cant find the top cap on any OEM database by itself (if I am going to spend 299 USD on a new set of forks, might as well be something decent) I am going to have to save up a bit and just go with some Yamaha R1's. Bums me out.. I really wanted it to stay stock for the most part. 

Thanks for the quick responses, though!

[Flyin900]

Send me a PM and I can probably Time Sert the hole for a fix unless you are made of money!

There will be someone on the CB750 forum also who can help you too. Try Neiko67 on there he is listed under the for sale stuff, as he regularly breaks these bikes down into parts and sells them off.

[Enstalled]

Is a helicoil or time sert really "safe" on the fork cap? I just don't want to be riding one day and all of a sudden I am flying in a different direction LOL

[Bankerdanny]

They can withstand the pressure put on a spark plug so they can easily handle the FAR lower pressure from your forks.

[simon#42]

Is a helicoil or time sert really "safe" on the fork cap? I just don't want to be riding one day and all of a sudden I am flying in a different direction LOL

as long as it is done properly it will actually be stronger after it has been repaired , and i have no doubt flyin900 will be able to do it properly

[NobleHops]

++ to all the above. Many Honda DOHC bikes of that era used those, Honda specified a small amount of pressure in the fork to aid the suspension and the tube was there to equalize both sides.  Most guys do NOT in fact pressurize this, and so another option is to replace the fork cap with one that does not use the air fittings. But for sure, the fastest and cheapest solution is to buy a used one. Look up the part number on Partzilla then enter it into ebay search, or contact the good sellers in those boards - Neiko or grump32 are both great guys.

[Flyin900]

I see you sent a message to my email yet I am not sure the reply I sent back did get sent back to you, so here is a recap.

I would try to see if a new or used one is available from the CB750 site as suggested, or other options as new from Honda or EBay etc.

The fix would be stronger in a Time Sert as it is a carbon steel insert. That said the size of the thread pitch may be unusual as I recall it is very fine pitch and possibly under 1.0mm TP in size, so it may be hard to get a kit from Time Sert or Heli Coil in the correct size. My smallest Time Sert set is 6mm X 1.0 TP so it may be too large or coarse a TP.

The fix is easy with a kit even if you have limited experience, as long as you can find a correct sized kit. I don't have a hose available to measure the TP and diameter of the fitting.

My suggestion is don't be so quick to write off the suggestions of looking at another forum/website or used parts site or bike wrecker first.

[RAFster122s]

Contacting several bike wreckers/salvage yards/junk yards that specialize in bikes maybe a good alternative if the DOHC board members can't help.  Having the bike down while you have it fixed is just the price to pay that will be cheaper than a new set of forks.  Odds are another Honda of similar vintage with same size forks will have sme size fork tube caps.
They have some standardization by manufacturers and it is likely Honda sourced a lot of their forks from ine or two makers of the front forks.

Having fly fix it will be better than new.  Worse case you have a custom balance tube made for the bike and use a braided stainless hose with AN fittings on both ends. Can you post some photos of the balance tube and the fill for the air pressure?
A copy of the manual page that shows the air hose end of forks could be helpful as well. Post that up in the thread.  Using a banjo bolt is going to work if you size the hose large enough for the air to pass from side to side without restriction. Doing so is possible by matching the hose and banjo fitting internal diameter. But, with air as long as you aren't creating a choke point of much smaller diameter it should act normally.