Topic: 750 Fork Lowers - Did They Change?

[OldSchool_IsCool]

My winter project this year was to install forks from a 750 K2 onto a 550 K3.  The 750 forks bring with them a larger brake disk which should improve braking.  And since the forks I got are nice and shiny, they look way better them my original borderline 550 fork tubes.

I've run into a problem with the dust cap.  I was planning to use the dust cap from my 550 forks, but found them to be too small.  So I ordered up a set of dust seals from Pyramid-Parts.com.  In the picture below, the left-most conical cap is off my 550.  The disk in the middle is NOT the oil seal, but rather the plug-type dust seal I received from Pyramid.  Since the circlip is so near the top of the 750 fork lower, there is no way the Pyramid seal is going to work.  DON'T BUY PYRAMID FORK SEALS!!

Anyway, on to solving my dust cap problem.  I checked the parts fiche and found that the dust cap from my '77 550 has the same part number as the dust cap from a '78 750.  The forks I'm installing are from a K2.

QUESTION:  Did the 750 fork lower change between the gaiter'd years and the capped years?

[Don R]

I have seen some that are longer on the alunimum part but I can't really elaborate on years etc.

[bwaller]

That looks like the dust seal for 77-78F model 750s. The one for your 550 is from the 77-78K's and maybe all the 550 F's as well as 77-78 750K's.

The 72 forks you have used gators obviously.

 

[OldSchool_IsCool]

Does this mean there aren't any caps that fit K2 forks and I should be looking for gaiters instead?  I'd rather run with caps and keep all that shiny chrome viable, but if I gota do gaiters then I gota, no big deal.

[the architect]

Your dust boots look just like mine did, when I rebuilt my '75 with '77 model forks.  The caps took some gentle persuasion, but they went over the fork lowers without too much fuss. 

Does your new boot have a ring/lip, just inside it?  Mine did, and this fits into the groove on the fork lower.  I had to push and wiggle it    but it went on [queue jokes here].

Since my '75 came with gaiters instead of boots, I ordered the cap-style boots for a 500 twin -- Parts N More.

[KeithB]

Just a note ...you will also find the brake caliper mounting bracket and the fork mounting holes of the '72 are different from the following model years.
Don't ask how I know...

[OldSchool_IsCool]

Your dust boots look just like mine did, when I rebuilt my '75 with '77 model forks.  The caps took some gentle persuasion, but they went over the fork lowers without too much fuss. 

Does your new boot have a ring/lip, just inside it?  Mine did, and this fits into the groove on the fork lower.  I had to push and wiggle it    but it went on [queue jokes here].

Since my '75 came with gaiters instead of boots, I ordered the cap-style boots for a 500 twin -- Parts N More.

Thanks Arch, the boots/caps from my 550 do not have any metal on them, just firm rubber.  I'll work with them some more to see if maybe a little more effort is all that is needed.  Don't wana stretch or tear them, so maybe a little heat.

Just a note ...you will also find the brake caliper mounting bracket and the fork mounting holes of the '72 are different from the following model years.
Don't ask how I know...

Good to know Keith.  The forks, disk and caliper came as a set off of one bike from a forum member here.

[MCRider]

Does this mean there aren't any caps that fit K2 forks and I should be looking for gaiters instead?  I'd rather run with caps and keep all that shiny chrome viable, but if I gota do gaiters then I gota, no big deal.

There are dust caps that fit pretty close. Went over this in my build thread. They are early 35mm harley caps or there is a Honda part number, I'll get it for you but I won't be in the shop till Sunday probably, if you care for it. I think its an early XL250.

They are just a bit sloppy in the groove, but unless you pointed it out to someone, it would not be noticable.

To answer your question, yes the legs changed. The top of the lower leg diameter changed, tho both still used gaitors. The length of thelower leg changed but idon't think that affected the dust caps. But late model dust caps will not fit early model lower legs. I don't know exactly at what K series what happened, just know in general.

[OldSchool_IsCool]

Does this mean there aren't any caps that fit K2 forks and I should be looking for gaiters instead?  I'd rather run with caps and keep all that shiny chrome viable, but if I gota do gaiters then I gota, no big deal.

There are dust caps that fit pretty close. Went over this in my build thread. They are early 35mm harley caps or there is a Honda part number, I'll get it for you but I won't be in the shop till Sunday probably, if you care for it. I think its an early XL250.

They are just a bit sloppy in the groove, but unless you pointed it out to someone, it would not be noticable.

To answer your question, yes the legs changed. The top of the lower leg diameter changed, tho both still used gaitors. The length of thelower leg changed but idon't think that affected the dust caps. But late model dust caps will not fit early model lower legs. I don't know exactly at what K series what happened, just know in general.

There is a difference between the early 750K lower and the late 550k lowers as well.  This is as close as I can get a late 550 cap to squeeze on:



I did some measurements.  The diameter is within a millimeter, so that shouldn't be too big of a problem.  The real issue is the thickness of the upper shoulder.  It's thicker by 2mm.  the troth inside the boot just isn't wide enough to slip over the extra 2 mm.  Guess I could shave it if I had to, but I'd rather not.




If you can dig up the part number from the other Honda bike, I'd appreciate it MC.  There is a Harley shop across the street.  I'll stop in and let them snicker a bit at the old guy with his old Jap bike, but if they have the right boot in stock, I can take it!

[754]

There are 4 different fork lowers for 750 K between 69 and 78.


 The HD cap that firs should be FX forks from77-80ish, in thsat range.. Drag Specialties used to make really nice chrome cpvers that fit over the rubbers see if they can get them.. the HD seal should fit your forx too..


 Hope you didnt order from England when you could have walked over and got them..

[OldSchool_IsCool]

 Hope you didnt order from England when you could have walked over and got them..

+100 there 754!  They took 3 weeks to get here and the envelope was marked "MISSENT TO AUSTRALIA" so if indeed the smug wrenchers across the street have what I need, then these little biscuits circumnavigated (almost) the globe for nothing! 

[MCRider]

Old School: The HD cap and the old Honda dirt bike cap are in my mind the exact same part. HD was using Jap front ends in that era. They fit the tube perfectly, pop onto the lower leg perfectly (don't look like they were forced onto the leg and bulge like in your picture.)

They leave a little bit of the groove exposed. When the cap is sitting down the groove is covered up. It will slide up a tad and reveal about 1/16 to 1/8 of the groove.

A forum member here suggested I fill the opening with a black Oring from the hardware whichi did and no more groove exposure. Let me know (again) if you need the honda part as the HD guys likely have what you need.

[754]

Showa made the Honda 750 legs and the FX dual disc forks.
 Before that HD used Kayaba, they were very thin around the seals(broke easily) you dont want the erlier Kayaba caps..

[OldSchool_IsCool]

I called Ed and Terry at Western Hills.  Told them I'm converting a 750K2 from gaiters to caps and that a XL250 cap was suggested.  Terry said they should fit fine and that he had a couple on the shelf.  They are now in the mail working their way from Ohio to Michigan.  Hopefully they won't have to visit Australia on the way!

I'll report back on how well they fit once I get 'em.  MC, don't go out of ur way, but if you could scare up that part number just in case, I'd very much appreciate it!

[OldSchool_IsCool]

UPDATE:  Ed and Terry came through!  Part number 91254-435-003 caps the fork lower quite nicely.  It slips into the groove without the annoying bulge.  A bit of the groove is left exposed.  As MCRider suggested, an O-ring trims out the remainder of the groove quite nicely.



Thanks all for your help!!