31K Carbs on 1UA barrels

[woodentopp]

Has anyone any experience with 31K carbs on 1ua barrels. My bike was bought as a 31K with these 1ua barrels and I am having a pigs own job to set up the carbs. Main jets are now 310 and it's still lean on a plug chop .

Any ideas please!!!! Is it worth finding 1UA carbs instead of going furthur with 31k's?

[wonkywheel]

I'm no expert on the set-up between the carb differences. Yet i can tell you the porting is different between the barrels.

[nige]

Got 1 ua barrels on mine standard air box and pipes with 31k carbs (just fitted) . Standard 31k jetting and it far better than the pj carbs. Mains 240 . Not running rich.

[nige]

Not running lean I mean sorry

[nige]

What throttle position is it running lean ?

[billyboy]

you will find it's even more pi$$ing about with the p/j carbs , is it standard ,or are you running filters ? are the ports tuned ?

[nige]

Give up p#ssing around with my pj and put 31ks on it better response

[woodentopp]

Am running the standard air box with the siphons removed and TSA pipes. Have sorted the pilot jet and air screw so it starts fine but it just revs through to top in 3rd and wont go past 5500 rpm in 4th, 5th or 6th. I took a plug chop with 300 jets and it showed lean. The bike wasn't a runner when I bought it and had 300 jets fitted.

I have checked all the joints so i don't think its sucking in air from somewhere else.

Anything else i should check?

[nige]

Had that trouble with mine not going past 5500 was fuel level in carb. Occasionally it would rev out but then just die. Would get to about 5600 and die back . Prated around with levels for ages till sorted it. Bloody carbs knew there own way off .

[woodentopp]

Did you increase or decrease the fuel level?

[nige]

Increase the fuel level it is starving itself of fuel hense running lean . look on tech all float heights jet sizes etc under jetting carbs.
Think thx to norbo

[nige]

Another thread going re float heights :-)

[woodentopp]

NIGE, THANKS FOR THE HELP ;D

[dusty350]

Hi,
I've read a lot of threads on various forums regarding the setting up of powerjet carbs, and particularly the difficulty of getting them right with any set up that is not standard. I sold my powerjets and bought some 31k carbs for my F2 engine in an Lc, as it has individual pod filters and I believe the PJ's are more difficult to set up with these than non PJ's. I've yet to get the bike up and running, so cant help there, but hopefully the 31k's will be easier to get right.

Dusty

[nige]

Seemed like. Messed around with my pj carbs for eternity to get levels right. Took next to no time to set up my 31ks. Don't know if the 31ks are more forgiving with regards to fuel levels or wether I just got lucky ? I doubt that though as if it wasn't for bad luck I'd have no luck at all.

[woodentopp]

Saw on Norbo's technical site that the float level should be 0.5mm. Any idea where this is measured from?

[nige]

I used the clear pipe method.
Fit clear pipe to over flow on carb. Loosen bleed screw. Fuel in pipe will raise to fuel level in carb. This should be .5 below join of carbs. If you start with this method you will get an idea of fuel height in carb (to low or high).
Can be done via measuring tilting carb till needle shuts and measuring from face of join. There a thread for this method with Picts in advice and help.

[classicjap]

It could of course be fuel starvation not caused by the carb float level setting - pipes and fuel tap OK ?

[nige]

It could be but is easy to check levels with clear pipe on over flow with bike still complete. Would have thought best place to start before starting take bike apart.

[nige]

I went through all that with my bike . Cleaned fuel filters, replace fuel lines, cleaned out carbs seemed like a thousand times, changed the fuel and flushed tank, and it turned out to be fuel levels were not right . They were not far out and I didn't think it would make that much difference but it did it seems like a fine line between over flowing and to low.