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Re: KT250 resto...help appreciated

Posted: Tue May 03, 2011 3:01 am
by FM350
Make sure those shocks work properly mounted wrong way up. Emulsion type gas shocks need an additional oil/air separator piston for damping to work correctly wrong way up.

Re: KT250 resto...help appreciated

Posted: Tue May 03, 2011 5:52 pm
by Bigem
Thanks FM350,

I was not aware the Betors where supposed to be mounted inverted.

Re: KT250 resto...help appreciated

Posted: Tue May 03, 2011 6:59 pm
by David Lahey
Those type of Betors work properly the way they are shown in the photos

Re: KT250 resto...help appreciated

Posted: Tue May 03, 2011 8:45 pm
by Bigem
Okay, thanks David.

I know the Falcon's on my SWM have to be inverted and as I said I was not sure about the Betor's.

I tried Googling the damn things with no luck so went through some of the gallery pics on here and I would say 90% of the bikes with these Betors have them inverted.

Will it make much difference which way these are mounted?

Re: KT250 resto...help appreciated

Posted: Tue May 03, 2011 9:11 pm
by David Lahey
Pretty sure those Betors will work either way up. Some bikes benefit from the extra side clearance to the chain when they are fitted body to bottom because the body is smaller diameter than the spring. KT is one such bike.
Standard trials Falcons only work with body at top, but you can order them from Falcon set up to work with the body at the bottom for people who like the look of them that way, or need the extra clearance to the chain.

Re: KT250 resto...help appreciated

Posted: Tue May 03, 2011 10:58 pm
by Bigem
Thanks again David, much appreciate the advice.

As I am running a 520 chain/sprocket setup with the shocks in the conventional position, I will have to run a 2-3mm spacer top and bottom on the lh side to give me the clearance on the chain I like to have.

Brake side isn't an issue but I haven't fitted the pipe and muffler up yet to check the clearance around the shock spring.

All in all I am happy with how its coming together, just have to decide whether to bead or aqua blast the head and barrel, they are stained brown and it doesn't wash off!!

Re: KT250 resto...help appreciated

Posted: Wed May 04, 2011 9:57 am
by FM350
If the Betors have the additional piston required to separate oil/gas when shocks are run inverted, they will work fine. However any emulsion shock run inverted without the extra piston, will suffer from cavitation after the bikes being ridden for a while, which will mean damping that doesnt work that well. The 300 Fantic in stock form needs to have the shocks inverted to clear the chain, and the Falcon shocks supplied for this application, have the additional pistons fitted to allow them to work properly wrong way up.

I

Re: KT250 resto...help appreciated

Posted: Wed May 04, 2011 2:04 pm
by shaunb
I thought all gas shocks had the "mini" piston seperating the gas from the oil ?

I am only coming at this from experience with cars but pretty sure all Bilstion and Koni shocks have a piston to seperate the two.

Wouldn't pressurised gas on top of the oil actually not work without the piston? ie the higher pressure of the gas would actually try and emulsify the lower pressure (but denser) oil?

Just trying to understand this with my school boy physics.

Cheers

Shaun B

Re: KT250 resto...help appreciated

Posted: Wed May 04, 2011 3:42 pm
by David Lahey
Not all "gas" shockies have a floating piston. Some have a diaphragm, some have a piece of closed cell foam that contains the gas, and some, like the standard Falcon trials shocks, just have pressurised gas on top of the oil with no separation device between them. It's no big deal, they all work, but the ones like the Falcons have to have the rod at the bottom or the damping valve on the piston is above the oil level.

Re: KT250 resto...help appreciated

Posted: Mon May 09, 2011 8:13 am
by FM350
shaunb wrote:I thought all gas shocks had the "mini" piston seperating the gas from the oil ?

I am only coming at this from experience with cars but pretty sure all Bilstion and Koni shocks have a piston to seperate the two.

Wouldn't pressurised gas on top of the oil actually not work without the piston? ie the higher pressure of the gas would actually try and emulsify the lower pressure (but denser) oil?

Just trying to understand this with my school boy physics.

Cheers

Shaun B



Emulsion type shocks such as Falcon are designed to work in this way, and as the Betors are a direct copy of Falcons, I would imagine they probably dont have an extra piston to allow running them inverted. In general car shocks run with shock body at the bottom, so obviously single tube gas shocks need the extra piston.