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Weber Woes
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Author:  GeoffP [ Sat Feb 26, 2005 4:05 am ]
Post subject:  Weber Woes
gday all... I had my mini dyno tuned a couple of weeks ago by a guy that also does some of the historic racing mini's over here in Perth. He reckoned my main jets were fine but the idle jets were 4 sizes too big. They were 50F9, and he went 50F8, 45F9, 45F8 until he got the mixture right. The problem is it seems to have brought out the worst in my cam...

before, i could give the car a fairly healthy squirt right off the line and it always took off nicely, but now i need to either keep VERY light throttle till the revs are over about 2K, or ride the clutch until the 2K mark. anything more than super-light throttle below 1800rpm and it bogs down and goes nowhere. also if I coast between 2K and 3K and then put my foot down theres a momentary flat-spot before it picks up.
on the plus side it seems to be hugely more economical than before...

my dilemma is that i'm not sure if the way it drives now is because of the cam (wade 446b - 290* duration & .430 lift with 1.5 rockers) and maybe its supposed to be like that. My mate who set it up originally is of the opinion that you tune the weber to get rid of flat spots (it was certainly easier to drive) - but if that means running it way too rich on the idle jets i'm not sure if thats good in the long run

both the guys have had many years tuning webers on minis, but I would have thought a dyno tune would get the car running better than a manual tune, not worse... :?
Author:  drmini in aust [ Sat Feb 26, 2005 4:47 am ]
Post subject: 
It should not be a dog down low, if tuned properly for road use. This may mean making it a bit richer in the idle jetting.
Bear in mind that on the track they are always screaming its nuts off, they don't much care about low speed running. :wink:
Most Webers on Minis seem to need to run a bit richer down low than Dellortos do.
Author:  justminis [ Sat Feb 26, 2005 9:57 am ]
Post subject: 
Remember that the idle jets on a Weber influence the "progression" from slow running to the main jet system. In my experience of 20+ years with Webers on minis, 50F9 is not a rich idle jet. If you still have it, put it back in and try it, same with the other idle jets if you have them, try the. Your bleed back valve should be zero, ie, no bleed back and you shouldn't need anything other than 50 or 55 for acc pump jets. If you have small pump jets than this now, this may also contribute to your problem. Also make sure your float level is right and that you're not pushing too much fuel (pressure) into it. Steve
Author:  Candy [ Sat Feb 26, 2005 10:49 am ]
Post subject: 
I've got the same problem, got my mini dyno tuned here in Perth with that same guy who does the historics an race minis, bogs down on taking off unless I have given it a bit of a rev before letting the clutch out. I just attributed this to a the Wade 140 Cam I have in it which is a 295degree period.
Author:  Mini Mad [ Sat Feb 26, 2005 1:52 pm ]
Post subject: 
Just got mine dyno'd today and the air/fuel ratio was too rich, leaned it out with some 150 jets and it instantly gained a couple of HP all the way up, but I still had trouble taking off, couldn't do it without bogging down unless i had 3000 revs on tap..

My cam is an RE-13 which is about 290* i think on the exhaust...cam comes on at 2700 anyway, we changed the air jets as well and it went heaps better, but still boggy down low..

found my solution in the end..advance the crap out of the timing :lol: now 1500rpm takeoff's are no problems 8)
Author:  GeoffP [ Sat Feb 26, 2005 11:06 pm ]
Post subject: 
thanks for the tips... I can't remember if he gave me back my other idle jets, i'll have to check since it seems i might be better off putting them back in.
i did notice though that the plugs are staying a lot cleaner now. they used to foul up a bit. i think i'll be dropping in to pitstop bookshop next week to get that weber book so i have some idea of what's going on with it...
advancing the timing might be worth a try too but i'm concerned that if it starts pinging i won't be able to hear it over the sound of the weber :? is that likely?

is fuel economy affected more by idle jets or main jets? it might be a consideration too though i spose i'd have to weigh up the cost of fuel savings over the price of a new clutch since i'm sure it won't last too long with the amount of revs needed to get off the line smoothly...

Candy do you know if Darryl did any power runs to compare changes? I think with mine he just set the mixtures right then did a power run at the end. when i've had dyno's done on other cars they've told me what power difference the changes made so i could be sure it was an improvement. He says I've got 90hp at the wheels at 6000rpm, and while the numbers themselves don't mean much (i'm pretty sure his dyno reads too high), i've got no way of knowing if its any better or worse than it was before really... if there was any improvement afterwards it could probably be put down to the pulsar dizzy that went in while it was there... which reminds me... apparently the dizzy was very 'gunked up' so that it had practically no advance till about 2500rpm. he reckoned thats pretty common with jap dizzy's that have been sitting around for a while so if anyone has trouble getting theirs to run maybe thats worth checking
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