8 replies to this topic

[crazy_scampi]

Hi guys, picking up my maniflow stage 1 kit at the weekend and was wondering should I switch jets? Got an 1987 advantage with HS4 carb on it. Needs a new jet so was holding off til I got the stage 1 kit to do it all at once. Should I get another wax stat jet or swap to a fixed as have read that it's easier to tune with a fixed jet. Know I can do the 2p trick but I'm just going to buy the conversion kit from sucarb.co.uk if I do change. And It will be going on a rolling road once fitted 👍 cheers!

[Craig89]

If your going to a rolling road shortly after fitting the exhaust then there's not much point buying a needle as the rolling road will more than likely change it anyway. The stage 1 will not make it undriveable on the standard needle is basically what I'm trying to say lol

[DomCr250]

The issue with waxstat jet's is that they have been known to malfunction - this moves the jet position.  I've not seen this occur personally, but the guy who used to run my local rolling road said he had seen it a good few times.

 

If you are going to replace the jet anyway then it's probably best to go non waxstat, at least it removes one uncertainty.  And considering you are going to get it set-up correctly you may as well spend a few extra ££'s and make sure everything is 100% before you go along.

 

I've swapped between the two and I don't seem to remember needing anything more than a non waxstat main jet and a bit of tinkering, did not use a kit, but that was a long time ago.

 

If you swap the jets the mixture may well be out, so just do the basic main jet set-up before you drive it to RR session.

Edited by DomCr250, 22 January 2014 - 05:34 PM.

[KernowCooper]

The jet replacement will be of the standard size and wont alter the mixture unless the old one was worn badly, in which case the mixture with the new jet fitted will be weaker, In the SU the needle is changed to alter the on road fueling, something the rolling road should do.

[crazy_scampi]

Ok that's cool so I'll just convert the jet to a fixed one. This is the conversion...

http://sucarb.co.uk/...ersion-r-h.html

I don't know what it's made up of but I read somewhere something to do with the choke maybe? Might be wrong about that though.
And as the engine is on 108k miles I was thinking of rebuilding the carb when I'm there too.

[ado15]

Ok that's cool so I'll just convert the jet to a fixed one. This is the conversion...

http://sucarb.co.uk/...ersion-r-h.html

I don't know what it's made up of but I read somewhere something to do with the choke maybe? Might be wrong about that though.
And as the engine is on 108k miles I was thinking of rebuilding the carb when I'm there too.

 

You are correct. The choke linkage is different so they use the earlier jet with a bracket to suit the later linkage.

[Dusky]

They normally supply a needle with a kit..

[DomCr250]

The jet replacement will be of the standard size and wont alter the mixture unless the old one was worn badly, in which case the mixture with the new jet fitted will be weaker, In the SU the needle is changed to alter the on road fueling, something the rolling road should do.

I take your point, and that's true if the waxstat has not gone - but if it's dropped down (as they sometimes do) and somebody has adjusted the mainjet up to correct it, then fitting a new main will make a difference. 

 

The mixture is controlled by a number of factors, one is the position of the mainjet in relation to the needle.

[KernowCooper]

 

The jet replacement will be of the standard size and wont alter the mixture unless the old one was worn badly, in which case the mixture with the new jet fitted will be weaker, In the SU the needle is changed to alter the on road fueling, something the rolling road should do.

I take your point, and that's true if the waxstat has not gone - but if it's dropped down (as they sometimes do) and somebody has adjusted the mainjet up to correct it, then fitting a new main will make a difference. 

 

The mixture is controlled by a number of factors, one is the position of the mainjet in relation to the needle.

 

What I was meaning to say was if you replace like for like at the same position on the jet, then the mixture would be weaker if the old jet was worn