Topic: Front Fork Damper Valve... anyone tried these???

[CrisPDuk]

Will these work on a '78 550K ? I don't know enough about the various SOHC forks to determine whether mine are the same as, or different from 750 items

[paulages]

Will these work on a '78 550K ? I don't know enough about the various SOHC forks to determine whether mine are the same as, or different from 750 items

yes

[paulages]

update here: we installed a set of mike's xs emulators in some cb750 K3 forks. i don't know if the O.D. of the little lip that sits inside the top of the damper rod is different on the race tech emulators, but we had to make an adaptor as per race tech's instructions to make these fit. we used 1" aluminum tubing, cut to about 10mm in length. this sits on top of the damper, and the emulator sits atop of the adaptor.

at first, i removed the roll pin in the top of the damper rod, and cut small pieces from it to align the pieces it had been holding, while allowing the locknut on the damper to fit in the middle. however, it was after doing this that i realized the ill fit of the emulator. i believe an o-ring around the part that is intended to protrude into the damper valve would have done the trick as well.

[Terry in Australia]

Rather than the alloy adapter Paul, couldn't you just machine a bit out of the top of the damper rod? That was what I was intending to do. Cheers, Terry.

[fuzzybutt]

pics please?

[paulages]

Rather than the alloy adapter Paul, couldn't you just machine a bit out of the top of the damper rod? That was what I was intending to do. Cheers, Terry.

yes, if you have the right tools-- but if i remember right, there was about 4mm difference in diameter, which is quite a bit of material to remove from the damper rod (which is probably only 3-4mm thick to begin with). plus, you still have to deal with the roll pin. i figure the spacer helps add pre-load to the stock springs anyway. i still think an o-ring around that bottom lip of the emulator would work well though. seems like the whole idea is just to keep oil from going anywhere but through the valve.

[paulages]

pics please?

sorry, i didn't have my camera. i'll try to take some of the next ones i install (i have three more sets to do soon, including my own).

[ceruzziracing]

Okay, so what do I do for the 37mm forks I'm putting on my 74 CB750 (1975 GL1000 forks)? Looked on racetech but couldn't find a listing for the early GL nor did I see them listed by size  This will be a mostly track oriented bike...

[Terry in Australia]

Rather than the alloy adapter Paul, couldn't you just machine a bit out of the top of the damper rod? That was what I was intending to do. Cheers, Terry.

yes, if you have the right tools-- but if i remember right, there was about 4mm difference in diameter, which is quite a bit of material to remove from the damper rod (which is probably only 3-4mm thick to begin with). plus, you still have to deal with the roll pin. i figure the spacer helps add pre-load to the stock springs anyway. i still think an o-ring around that bottom lip of the emulator would work well though. seems like the whole idea is just to keep oil from going anywhere but through the valve.

Sorry Paul, I'm missing something here, I'll go out to the garage tomorrow night (I'm working tonight, sadly) and try to see what you mean. BTW, thanks for the tank bashing info, it's coming up a treat!

[paulages]

Okay, so what do I do for the 37mm forks I'm putting on my 74 CB750 (1975 GL1000 forks)? Looked on racetech but couldn't find a listing for the early GL nor did I see them listed by size  This will be a mostly track oriented bike...

don't know what to tell you about the 37mm forks, though i bet an adaptor could be made. the O.D. of the emulator is quite a bit smaller than the I.D. of the fork tube. it seems what's most important is the seal between the emulator and the top of the old damper rod. i have some gl1000 forks in the shop-- i'll try to take them apart soon and see how they could work.

i'll definitely take pictures next time. here are some of the ones i installed in joe's 650 forks, that may clarify my previous posts. the "lip I.D" is what is supposed to fit inside the top of the damper rod:


note, that this is just a press-fit with no o-ring or other sealing device. on the 740 K3 forks i did, it wouldn't fit inside the damper rod, even with the roll-pin removed, like this (sorry, cell phone picture):


the adaptor i made was just a short piece of 1" aluminum tubing that went between the damper rod and the cartridge emulator, allowing the bottom of the emulator to seat firmly. i don't know how well this will work, but it is what race tech says to do with "flat top" or inverted top damper rods.
sorry, it's crude but you get the idea:

[ralt12]

Funny, there may be a difference in the rods. I didn't have a roll pin, and the amount of material north of the nylon bushing was a good deal more than in Paulages' pictures. I just machined the small amount out of the center of the rod to make these fit flush with the top.

[paulages]

Funny, there may be a difference in the rods. I didn't have a roll pin, and the amount of material north of the nylon bushing was a good deal more than in Paulages' pictures. I just machined the small amount out of the center of the rod to make these fit flush with the top.

are yours K0-1 forks? i know those are quite different. i don't know for sure what forks these with roll-pins came off of, but i think they were K3-5.

[ralt12]

Funny, there may be a difference in the rods. I didn't have a roll pin, and the amount of material north of the nylon bushing was a good deal more than in Paulages' pictures. I just machined the small amount out of the center of the rod to make these fit flush with the top.

are yours K0-1 forks? i know those are quite different. i don't know for sure what forks these with roll-pins came off of, but i think they were K3-5.

Ummm...I don't know. It's a 1975 CB550F. I know I should have taken pictures while it was apart, but I didn't think there was any reason to at the time.

[Terry in Australia]

Aha! You see, I was looking at a set of F2 dampers (my damper valves are going into them) and I thought that machining a little out of the top of the damper would have done the trick. Now I understand!

[paulages]

[

Funny, there may be a difference in the rods. I didn't have a roll pin, and the amount of material north of the nylon bushing was a good deal more than in Paulages' pictures. I just machined the small amount out of the center of the rod to make these fit flush with the top.

are yours K0-1 forks? i know those are quite different. i don't know for sure what forks these with roll-pins came off of, but i think they were K3-5.

Funny, there may be a difference in the rods. I didn't have a roll pin, and the amount of material north of the nylon bushing was a good deal more than in Paulages' pictures. I just machined the small amount out of the center of the rod to make these fit flush with the top.

are yours K0-1 forks? i know those are quite different. i don't know for sure what forks these with roll-pins came off of, but i think they were K3-5.

Ummm...I don't know. It's a 1975 CB550F. I know I should have taken pictures while it was apart, but I didn't think there was any reason to at the time.

Ummm...I don't know. It's a 1975 CB550F. I know I should have taken pictures while it was apart, but I didn't think there was any reason to at the time.

gotcha. thought we were on the subject of 750 forks at the moment. i thought that the emulators fit all 500/550/650 forks without modification, and that the 750 forks were what require the adaptor. i'll be installing some in my own 550 forks soon-- i'll take good pictures.

[CBJoe]

Thanks for all of the work and postings paul   

[ceruzziracing]

Thanks Paul for checking on the GL fit. I just got my GL forks today, one has a leaky seal so I'll be following this thread as I rebuild them!

[paulages]

Thanks Paul for checking on the GL fit. I just got my GL forks today, one has a leaky seal so I'll be following this thread as I rebuild them!

if you get yours apart before me, let me know and we can compare the critical measurements.

[ceruzziracing]

No problem, might get them apart this weekend if my kids will give me 5 minutes to work in the garage 

[eurban]

I sent an email to racetech a while back to see about emulator fitment for the GL forks.  They got back to me quickly requesting specific measurements so I took apart my spare fork and sent them the specs (twice).  Never heard back from them and I never got around to calling them.  Here's the specs that I sent them . . .

"I took a spare set of GL 1000 forks apart to get some info for you.  These are from the 1975/76 models . . .

Fork tube OD: 37mm
Fork tube ID: 29mm
Damping rod's head (piston like top with groove for ring seal) OD: 27.5mm
Inner diameter of damping rod: 15mm
Damping rod height : 214mm
Stock fork spring length: 514mm
Stock fork spring coil ID: 18mm

The damper rod's top is cupped but only very slightly. From the 27.5 mm OD to about 21mm it is flat.  It then steps down straight about 1mm and then is angled down till the center hole (15mm ID)"

I might be able to do a Pic this evening of the damper rod. . . .

[paulages]

i don't have anything in front of me, but 27mm is 1.08mm. the O.D. of cb550/650/750 emulator is definitely smaller than that, but the I.D. of the cb750 forks must be almost the same: the adaptor i made is from 1 inch tubing, and i remember the nylon bushing measuring just a bit over this. i have extra sets of the emulators in my shop. i'll take some measurements tomorrow. i'm willing to bet that most of the extra 2mm in the GL forks is in the walls of the fork tube.

[MRieck]

i'm willing to bet that most of the extra 2mm in the GL forks is in the walls of the fork tube.

Yes as Honda used them in their DOHC Superbikes

[eurban]

i don't have anything in front of me, but 27mm is 1.08mm. the O.D. of cb550/650/750 emulator is definitely smaller than that, but the I.D. of the cb750 forks must be almost the same: the adaptor i made is from 1 inch tubing, and i remember the nylon bushing measuring just a bit over this. i have extra sets of the emulators in my shop. i'll take some measurements tomorrow. i'm willing to bet that most of the extra 2mm in the GL forks is in the walls of the fork tube.

Did you get anywhere with those measurements?  Thanks!

[paulages]

i don't have anything in front of me, but 27mm is 1.08mm. the O.D. of cb550/650/750 emulator is definitely smaller than that, but the I.D. of the cb750 forks must be almost the same: the adaptor i made is from 1 inch tubing, and i remember the nylon bushing measuring just a bit over this. i have extra sets of the emulators in my shop. i'll take some measurements tomorrow. i'm willing to bet that most of the extra 2mm in the GL forks is in the walls of the fork tube.

Did you get anywhere with those measurements?  Thanks!

thanks for reminding me--i'll take some measurements this morning. i've been distracted by engine rebuild woes.

[eurban]

i don't have anything in front of me, but 27mm is 1.08mm. the O.D. of cb550/650/750 emulator is definitely smaller than that, but the I.D. of the cb750 forks must be almost the same: the adaptor i made is from 1 inch tubing, and i remember the nylon bushing measuring just a bit over this. i have extra sets of the emulators in my shop. i'll take some measurements tomorrow. i'm willing to bet that most of the extra 2mm in the GL forks is in the walls of the fork tube.

Did you get anywhere with those measurements?  Thanks!

thanks for reminding me--i'll take some measurements this morning. i've been distracted by engine rebuild woes.

Well?