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Looking fabulous!

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

I guess I should bring this thread up to date... last October I managed to get the car through the "out of province inspection" which then allowed me to license the car for the road. Originally the car was sold in Ontario, but sometime after 1984 it came out west in pieces so was never registered here in BC. Obtaining the title was relatively easy, but did require some back and forth with ICBC (the insurance provider/DMV/dumpster fire). I did get a few days of driving in before the winter took hold, and all I can say is wow it's fast!

In December I ordered some one piece side windows from the UK, as trying to make they myself turned out to be a bit more difficult than expected. They have a compound curve, which I couldn't replicate. Anyways, they arrived and I spent the better part of January fitting them (weekends only):







Next up was this months purchase, a new cam cover. The engine bay went from this:



To this:



Unfortunately, it added weight, but it looks better in my mind. Other than that, I re-plumbed the fuel system two weekends ago as the motorcycle fuel pump didn't like where I had mounted it. So it was repositioned to just in front of one of tanks, meaning it's always primed (or flooded). This has made it less noisy and seems to keep pressure with less effort.

This past weekend I renewed the insurance and started back to the road testing. I played around with the carbs and timing but I can't seem to cure an off idle stumble. I'm running carbs off a CBR900RR so it will take some time to figure out. I have some theories that will get tested the next time I'm in the shop. I also noticed a weep of coolant from the thermostat housing which appears to be coming from where they're glued together, so a new one is on its way.

Anyways, it's sure fun to be driving it again and hopefully in a few weeks it will be reliable.

Rod

Weber 45DCOE's are famous for off-idle stumble on Zetecs, to the extent where they actually make one-off, brand new, model specific ones for the 2.0 "blacktop" Zetec.

I'm not an expert, but my understanding is that the Zetec breathes SO well, on the slightest RPM increase, that carbs have a hard time keeping up with fuel, causing the engine to run extremely lean for a moment & stumbling. The new version of 45DCOE's have extra progression holes to feed extra fuel during this critical progression.

Is it possible that a brief & sudden lean condition, owing to a situation similar to the above, is causing your issue?

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Scratch building, at continental-drift speed, a custom McSoreley-design framed, dual-Weber 45DCOE carburated, Zetec-engined, ridiculously fast money pit.

http://zetec7.webs.com/

zetec7,
So far that's my thoughts, a lean condition. I didn't have a good look at the carbs before bolting them back on, but I had hoped there was at least a progression hole that the butterfly uncovered when going off idle. Unfortunately, that's not the case. Had there been a progression hole, I would have tried some larger idle jets. So, the next step is looking at blocking off the air jet (or passage) for the main jet emulsion tube. Some guys in the UK recommend it for the Fireblade (or CBR900 in my case) carbs. It should be an easy test the next time I'm in the shop, just a bit of tape over the holes then try it out.

Good stuff!

_________________
Scratch building, at continental-drift speed, a custom McSoreley-design framed, dual-Weber 45DCOE carburated, Zetec-engined, ridiculously fast money pit.

http://zetec7.webs.com/

" just a bit of tape over the holes then try it out." DO NOT BLOCK OFF THE PORT HOLE TO THE EMULSION TUBE. Try just a piece of thin metal roll into a tube shape that you can slide over the emulsion tube. [more gas friendly] You only need a thin section, only the top two or three holes depending on the hole size and spacing. [some carbs have very small holes] you can also try a "C" section tube that allows some emulsion tube holes to be uncovered, while other holes blocked off.
Also look for kits that allow you to raise fixed needles on the newer style carbs.
You can also try getting slides with a smaller cut-away or machine a little off the bottoms of the slides.
The last option is restricting the air channel to the top side of the diaphragm, which can be tricky without fitting jets. Do not play with the springs, you will not get them all equal. You could possibly try spacers under the springs.
Davew

dave,
The plan isn't to block the holes on the emulsion tubes, but to restrict the air jet (orifice?) on the face of the carb. It's an easy thing to try as it only requires removing the airfilter and the plastic covers on the front of the carbs. I've read about blocking them from a few sources, so the thought is why not try it. If it works great, if it doesn't then it's back to looking for an alternative solution. Here's a stolen pic of what I'm planning on blocking (or maybe just restrict depending on how things go):



As far as needles go, the carbs already have dynojet needles and are on the middle groove. The main jets are 160's. At WOT it howls, at idle it's smooth, it's just getting off idle that's the issue.

Rod,

Your build keeps looking better and better. It's quite an accomplishment.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

I ordered some one piece side windows from the UK, as trying to make they myself turned out to be a bit more difficult than expected.

Well that's an unusual occurrence

Really like the look and the way they open.

Love that shade of blue.

Glad you got it registered without a last minute foul up.

Ron

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They say a journey of a thousand miles begins with a single step. By the time you finish the car it'll feel like you've done it on your knees.

Changing the Air Correct Port jet will affect the whole mixture range!
You only want enrichment at the transfer from idle to low needle setting.
You need to raise the needle or reduce the amount of air introduced at low needle settings i.e. blocking the emulsion tube holes at the very top.
The last option, You might be able to find needles with different taper and or smaller shank size, but that does not seem likely with the newer carbs. [in the old days you had 50 needles to choice from]
Davew

Can't see the pictures...?

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The B-3 build log: http://www.locostusa.com/forums/viewtopic.php?f=36&t=13941 unfortunately, all the pictures were lost in the massive server crash

The beginnings of the Jag Special,
https://www.locostusa.com/forums/viewtopic.php?f=36&t=19012
Again, all pictures were lost.

I guess these are keihins. If everything is clean and there are no vac leaks, if the idle mix screw is not happy close to 1-1/2 out, I'd look at a couple numbers larger pilot jet. Should be about $20 for four. Pilot aids at 1/4 throttle or less.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

I had the same issue on a Harley with that carb using the Dynojet needle. I tried everything - shims, jets, needle height... always had the same problem you are having off-idle. I went back to a stock needle - poof! Problem solved. Not saying that's your issue, just sharing my experience.

BEAUTIFUL build!

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My Haynes/Miata build: http://locostusa.com/forums/viewtopic.php?f=35&t=3774

I'm guessing these carbs lack an accelerator pump used on auto carbs to solve the off idle sag/stumble, correct?

_________________
Perry

'If man built it, man can fix it'
"No one ever told me I couldn't do it."
"If you can't build it safe, don't build it."

Perry's Locost Super Che7enette Build
Perry's TBird Based 5.0L Super 7 L.S.O
Perry's S10 Super 7 The 3rd
Perry's 4th Build The Topolino 500 (Little Mouse) Altered
Perry's 5th Build the Super Slant 6 Super 7
Perry's Final Build the 1929 Mercedes Gazelle

Large displacement applications with a single carb have accel pumps. One carb per cylinder apps don't.

Cs3tcr, a larger pilot jet will shift the best idle rpm adjustment, but the throttle transition is not controlled by the screw. If it did, there would be little point in having a larger pilot.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12