1.6 Xu / R1 Carbs - Jet Size?

[Guest sgratton]

Hi everyone.

 

I have spent the last couple of hours searching for the jet size to use in R1 carbs for standard 1.6 engine and cannot seem to find the answer, hence my post. Sorry if the answer is on here already...

 

I will have all the bits I need to get my carbs on this weekend, but would like to jet the carbs appropriately to get the car running and then get it checked out on a RR.

 

So I would appreciate it if any one out there with R1 carbs on a 1.6 could help me.

 

Thanks

Si.

[Richie-Van-GTi 70 2 Cars]

start with around 140's.

[Guest sgratton]

Cheers Richie,

 

I will go for 150 I think - I would rather it be rich then lean.

[clifton 0]

sorry for the hi jack but im going to be putting carbs on my 1.6 soon and what does jet size mean? and are all r1 carbs the same or are the different ones..if there is which should i go for?

 

thanx

 

ben

[Guest sgratton]

Not sure about whether there are different types of carbs on R1's, but on the main jet front... read on.

 

Basically carbs have a main jet in them, this is responsible for putting the fuel into air going into the engine when the carbs are open. Jets come in difference sizes and hence the bigger the jet size the more fuel you get. An R1 is only 1000cc, however it does rev very high - but the bottom line is that the main jets that are in the R1 carbs as standard will not be correct for the 1580cc XU engine.

 

Having the wrong jets will either cause the fuel mixture to be rich or even worst to lean (not enough fuel in the air) Both situations cause problems, being too lean would result in the head gasket blowing or a holed piston, because the fuel tends to ignite due to the heat before the piston has finished rising up the bore, this is called pre-detination (det or pinking), hence the exploding mixture has to go somewhere and this is usually through the piston or through the head gasket.

 

Hope this helps.

 

Si.

[clifton 0]

ahh yeh that helps alot thanx... but wat size jets do you use for a 1.6 then and how do you change them over?

 

ben

[Richie-Van-GTi 70 2 Cars]

hard to say what size jets exactly as lots of other factors come into play such as the set up, cam timing, manifold design, induction lengths ignition timing etc. The jets are only £8 for a set of 4 as weber DGAS jets fit straight in which are readily available on ebay etc. To fit them simply remove the float bowl unscrew the current jet and put the new jet in. Standard R1 jets are about 120ish IIRC, you want to start with a 140 jet and see what its like from there. You can mess with the pilot jets and also the main jet needle height so there quite a bit of area within the fueling to play with, if you get the jet size correct to within 5 you should be close enough to fine tune from there. IE, if the actual jet size required is 140 then anywhere between 135 and 145 should be capable of getting a pretty decent set up that wont cause any issues with pre det or bore washing.

[Guest sgratton]

Got my carbs on the car today - not started yet, but that was because I have no throttle cable - arms are not long enough to turn the engine over the reach the throttle