KT250 resto...help appreciated

Need help finding information or parts for that old machine in your shed? Someone in here will know!

Moderator: Moderators

FM350
Expert participant
Expert participant
Posts: 488
Joined: Thu Apr 14, 2011 7:04 pm
Bike: Fantic
Club: Otter Vale

Re: KT250 resto...help appreciated

Postby FM350 » Tue May 03, 2011 3:01 am

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.



Bigem
B grade participant
B grade participant
Posts: 53
Joined: Tue Jun 23, 2009 5:55 pm
Bike: Looking!

Re: KT250 resto...help appreciated

Postby Bigem » Tue May 03, 2011 5:52 pm

Thanks FM350,

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



David Lahey
Champion
Champion
Posts: 3536
Joined: Thu Jun 05, 2003 7:01 pm
Bike: Many Twinshocks
Club: CQTC Inc, RTC Inc
Location: Gladstone, Queensland

Re: KT250 resto...help appreciated

Postby David Lahey » Tue May 03, 2011 6:59 pm

Those type of Betors work properly the way they are shown in the photos


relax, nothing is under control

Bigem
B grade participant
B grade participant
Posts: 53
Joined: Tue Jun 23, 2009 5:55 pm
Bike: Looking!

Re: KT250 resto...help appreciated

Postby Bigem » Tue May 03, 2011 8:45 pm

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?



David Lahey
Champion
Champion
Posts: 3536
Joined: Thu Jun 05, 2003 7:01 pm
Bike: Many Twinshocks
Club: CQTC Inc, RTC Inc
Location: Gladstone, Queensland

Re: KT250 resto...help appreciated

Postby David Lahey » Tue May 03, 2011 9:11 pm

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.


relax, nothing is under control

Bigem
B grade participant
B grade participant
Posts: 53
Joined: Tue Jun 23, 2009 5:55 pm
Bike: Looking!

Re: KT250 resto...help appreciated

Postby Bigem » Tue May 03, 2011 10:58 pm

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!!



FM350
Expert participant
Expert participant
Posts: 488
Joined: Thu Apr 14, 2011 7:04 pm
Bike: Fantic
Club: Otter Vale

Re: KT250 resto...help appreciated

Postby FM350 » Wed May 04, 2011 9:57 am

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



shaunb
C grade participant
C grade participant
Posts: 42
Joined: Sun Nov 11, 2007 1:47 pm
Location: Gold Coast

Re: KT250 resto...help appreciated

Postby shaunb » Wed May 04, 2011 2:04 pm

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



David Lahey
Champion
Champion
Posts: 3536
Joined: Thu Jun 05, 2003 7:01 pm
Bike: Many Twinshocks
Club: CQTC Inc, RTC Inc
Location: Gladstone, Queensland

Re: KT250 resto...help appreciated

Postby David Lahey » Wed May 04, 2011 3:42 pm

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.


relax, nothing is under control

FM350
Expert participant
Expert participant
Posts: 488
Joined: Thu Apr 14, 2011 7:04 pm
Bike: Fantic
Club: Otter Vale

Re: KT250 resto...help appreciated

Postby FM350 » Mon May 09, 2011 8:13 am

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.




Return to “Twinshock & Classic Trials”

Who is online

Users browsing this forum: No registered users and 17 guests