Race tech emulators - fill rebound hole?

[Icanopit]

I am about to fit RaceTech Emulators and K-Tech springs to my K9 front forks. Q: after opening out the lower holes on the Damper Rod's, do you leave alone or fill the upper REBOUND hole, having looked on 3 forum's there seems to be a differing opinion, What are Org's opinion or experience please. :confused:

JOHN

[johnnyrod]

No, don't do it, no need. Don't drill the extra compression holes either, just open out the existing holes a little.

[Lissa]

We didn't fill the holes either. :D

[Aiki]

I followed the racetech instructions and didn't fill in the rebound hole, I found there was not enough rebound damping, albeit for heavy track use. Having filled the holes in there's much more rebound damping and they handle much better. You may not need so much rebound damping for road use though.

[Luckypants]

No, don't do it, no need. Don't drill the extra compression holes either, just open out the existing holes a little.

What he said, drilling the extra holes can leave you with NO damping at the very bottom of the stroke. Icanopit is spot on to, it's not needed for the road.

[SV650Racer]

No, no need to do that..so as they say ^

[zadar]

Reason you want to close rebound hole is to get more rebound. Since rebound is controlled with oil weight you can than go to thinner oil which is better than thicker oil, more consistent and less sensitive on temperature changes.

[johnnyrod]

Sorry forgot to say, I've heard that the damer rods in teh SV have plenty of piston ring blow (wash) -by so you can indeed weld up the hole. I've not tried it but I do find the rebound damping is a bit weak as stock. Zadar's right you could do it and control using the oil weight, thinner oil works fine in the emulators which are adjustable anyway. TBH I made the mistakes of using progressive springs in the forks (alost impossible to bottom the forks, or even get much beyond half way), and also drilling the extra holes. With the forks off and springs out, when you pump them you can feel the lack of damping at full compression, but in the real world of road and track, they're way better than stock and enough to scrape the pegs, I think you can't go too far wrong.

[Spoon]

Interesting - so if you aren't closing the rebound holes what weight oil are you putting back in the forks - same as before the emulators or are you using thinner oil?

[zadar]

Yep, same as before. Rebound is main reason to use heavier oil.

[johnnyrod]

I'm using 15W but I weigh only 65kg nekkid. Probably 20W would be better. I would think having the rebound holes open would give you more consistent damping than relying on blow-by in which case you would expect more difference in damping betwen the two fork legs, which is bad of course.

[Icanopit]

Thanks to all for advise and observations. I have decided to make the changes progressively, start off with opening out the 4 damper rod holes and play about with oil rate and air gap (nothing drastic) and see if I find what suits me. Then IF needs dictate, close off the smaller holes (can always be redrilled) and again try oil's etc.
JOHN

[yorkie_chris]

you would expect more difference in damping betwen the two fork legs, which is bad of course.

Not really enough difference there to bother anything. There's a bleed hole in the emulator too IIRC

[SV650Racer]

We have always run 20w oil and never filled the damping holes in any of the minitwin forks we have prepped. Won plenty with them so they do work. Thats for the track though and hard use.

[Icanopit]

Not wanting to "hijack" another thread that's running, How to improve suspension? but a note on the lookalike emulators from the states. The alternative examples seem very good value but are rated for Harley's with a spring rate of 24 lbs/in as against the Racetech @ 64 lb/in SV, not sure whether the US ones are available with a better spring/valve rate.
Fortunately I purchased a set of R/tech off a fellow Orger at a simlar price as against from buying in from the States.
Just an observation for guidance.
JOHN

[yorkie_chris]

you mean the actual preload spring on the emulator?

[Icanopit]

Sorry YC, yes the emulator spring. Due to it's short length and already "tight" coils I guessed that there may not be enough left in the spring to get adequote increased compression to achieve much more?
JOHN

[yorkie_chris]

They are designed to pop off rather than moving progressively like a shim stack, so so long as you can get enough initial force on them I guess they'll be right. Roughly double the preload to get somewhere near.

[yorkie_chris]

Not wanting to "hijack" another thread that's running, How to improve suspension? but a note on the lookalike emulators from the states. The alternative examples seem very good value but are rated for Harley's with a spring rate of 24 lbs/in as against the Racetech @ 64 lb/in SV, not sure whether the US ones are available with a better spring/valve rate.
Fortunately I purchased a set of R/tech off a fellow Orger at a simlar price as against from buying in from the States.
Just an observation for guidance.
JOHN

Where did you find the info as to valve spring stiffness? Did i miss it somewhere obvious?

It appears the valve there is designed to pop off* rather than be progressive to me, so the only difference I could see you'd need is a bit more preload on the valve.


*If it wasn't, they would use a shim stack like the matris valves.

[Icanopit]

Morning YC, because the very good value alternatives if suitable are a HARLEY FITMENT, I am assuming they are a near direct copy of the RT item and specification!

Using the RT listing of specifications that I have, the Harley FX series is rated at Emulator spring 40 lb/in with 3 turns of spring preload, the XL series 26 lb/in with 4 turns of spring preload.
The SV requieres an Emulator spring rate of 64 lb/in with a spring preload of 2 turns, the spring preloads are of course all start points.

I reiterate though that figures are based on the RaceTech specification tables.
The RT list does indicate that it is ONLY Harley that uses a spring rate lower than 64 lb/in, it appear's that all other makes are guided at 64 lb/in ??

Hope I have not muddied the waters, JOHN

JOHN

[yorkie_chris]

Righto chap.

Lighter spring with more preload will be more digressive behaviour. I don't know how much difference there will be felt in practice.

[Icanopit]

My only thought was whether RaceTech would sell a spring as a spare part, but I am sure that, would eventually be priced unrealistic.
IF I can get one of my RT springs accurately measured I will, which I am sure a suitable altrenative could be sourced??

JOHN

[yorkie_chris]

They will be a standard part somewhere, but I doubt they be needed.

[zadar]

I have both emulators, springs are same length and same wire thickness.