OzVMX Forum

Clubroom => Tech Talk => Topic started by: dpt on June 22, 2009, 01:37:43 pm

Title: Decompression Lever
Post by: dpt on June 22, 2009, 01:37:43 pm

Hi Just bought my first bike XR 250 with a decompression lever please explain what this is actualy used for?

Thanks
Dave ???

Title: Re: Decompression Lever
Post by: ss2fly on June 22, 2009, 01:54:11 pm

Basically it holds open the exhaust valve slightly when your kicking it over to lower the compression = easier to start ( good when you flood it too.....)

I removed mine on the XR660 (Im 6'2" and 110kg) and starting it was not a problem.... ;)

Title: Re: Decompression Lever
Post by: dpt on June 22, 2009, 02:55:55 pm

Please don't think im stupid but should i be using the decompression lever when kicking the bike as i am having trouble starting it, its so much easier with my 2 stroke.

Title: Re: Decompression Lever
Post by: cyclegod on June 22, 2009, 03:11:30 pm

Decompression should be automatic (there is a small lever on side of the head connected to a lever behind the kick starter by a cable), check your cable adjustment.

Title: Re: Decompression Lever
Post by: dpt on June 22, 2009, 03:25:59 pm

If it is automatic why do i have a lever?

Title: Re: Decompression Lever
Post by: lms6201 on June 22, 2009, 07:21:52 pm

probably because it,s been modified !

Title: Re: Decompression Lever
Post by: brent j on June 22, 2009, 07:26:36 pm

The decomp is normally used to bleed off compression to get the piston passed top dead centre.
As God said Hondas normally have an auto decomp system that's worked from the kick start. I can only assume that the original system has failed or maybe someone has fitted an odd cam so a manual system has been fitted.
I'm told that some high lift cams can interfere with the auto system on Hondas.

On my XT500 Yamahas I push the kick start to get the piston approaching TDC on comp then open the decomp slightly and ease the piston just passed TDC than kick it. On a 250 it's probably not to bad but on a bigbore it makes it a lot easier.

hth

Brent

Title: Re: Decompression Lever
Post by: matcho mick on June 22, 2009, 10:15:30 pm

seem to recall a honda with both auto,& manual decomp,has it provision for 2 nipples/cable ends down on the lever near the k/start,might explain just the hand lever option,(easier to live with ??) ;)

Title: Re: Decompression Lever
Post by: dpt on June 22, 2009, 11:43:23 pm

Thanks for the advice it is a 2002 xr 250 so the lever is standard on them this is my first 4 stroke as i have a 1983 kdx and a 1983 yz100 very simple bikes but wanted a road trail for weekends.

Dave

Title: Re: Decompression Lever
Post by: Freakshow on June 23, 2009, 12:53:11 pm

is it a decomp or a HOT start ?  if the cable ends up at the carbi its a hot start or ANA -"shit i fell off restarter".  and it just give the carby a squirt of Juice I think.