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Location:
Brisbane
Registered:
October 2002
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carburettor experts wanted
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Mon, 26 July 2004 08:45
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i am having a new problem with my car, it is an 18RGU, dead stock, twin solex's.
if i try to accelerate slowly its fine, if u need to go a bit more, it stumbles, and if its anywhere in the revs and it does stumble and i fully flatten it {even at 1500rpm} it just gets a real low grumble {cause of the WOT} and it just takes off, no stumbling or anything.
but it wouldnt do that today, it'd still stumble, sometimes all the way to 5500rpm, then 100m down the road i'd try again and it'd be fine.
all weekend it was cool, {i did 450km+} but now its shit.
also, when its cold, it idles way too low, stalls easily, but when its warm, it idles really high {1500+} and it really shits me, what causes that.
also, which way do u turn the mixture screws to richen/lean the mixture.
and the accel pump rod, where is i best to have the split pin located, lowest spot or highest {what location on the rod makes it do what}
now, if u can understand my gibberish, i'd be grateful for a reply
Phil
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Location:
Rocklea qld
Registered:
February 2003
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Re: carburettor experts wanted
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Mon, 26 July 2004 08:59
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I dont know heaps about them but turn all four screws for the mixture in as far as the go. and then turn each one out about 2 full turns and that should be about right for the mixture. The carbs might not be running at the same mixtures etc and thats the stumbling problem.
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Location:
Yowie Bay, Sydney
Registered:
June 2002
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Re: carburettor experts wanted
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Mon, 26 July 2004 10:46
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dont move the screws, they're usualy only for idle mixture
what makes u think its the carbs?
sounds more like an ignition problem to me
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Location:
Brisbane
Registered:
October 2002
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Re: carburettor experts wanted
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Mon, 26 July 2004 11:30
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why would u say its a ignition problem, sounds like its dumping too much fuel in at the wrong moment {way too low in the revs}
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Location:
Yowie Bay, Sydney
Registered:
June 2002
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Re: carburettor experts wanted
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Mon, 26 July 2004 11:37
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u say its fine if u accelerate lightly
ie. less load on engine = smaller spark required
more load on engine = larger spark required
if u have a broken down coil lead the spark will take the shortest path to ground and effectively make all cylinders misfire. trust me, it does feel like a drowning engine sometimes
but then again, i may be wrong!
anyway its easier to check ur ignition system than stripping and rebuilding a carb (or 2)
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Location:
Brisbane
Registered:
October 2002
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Re: carburettor experts wanted
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Mon, 26 July 2004 11:42
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sorry, i didnt fully explain my situation, i have a points dizzy and have just replaced my coil and coil lead, it has remarkably changed my driveability, but this small issue still persists.
when the load rate gets higher does it actually make a fatter spark.
but when i fully flaten the throttle, it only spits for a split second, but it doesnt really take off cause the revs r too low for the throttle position so i'm kinda drowning it
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Location:
Montrose, VIC
Registered:
May 2002
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Re: carburettor experts wanted
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Mon, 26 July 2004 13:29
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Hard to say really whats up without seeing the car, but what better excuse than this to take the carbs off, and drop them off the pier... for good! 
(kidding!)
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Location:
Brisbane
Registered:
March 2003
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Re: carburettor experts wanted
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Mon, 26 July 2004 15:26
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i have a similar problem with my 2TG, im runnin twin solexs and when i dump it it struggles abit and then takes off, but it isnt always that, i sometimes put my foot down real slow as if i was feeding it in, and the carbs just bog down heaps and then my engine dies altogether, does the same when i flat foot it.. i know that it is a fuel problem, not getting fuel fast enough into the carbs to fill them up.. bare in mind my solexs havnt been used for about 4years..
mine also does the exact same when trying to start cold idles like a bitch and when running normal temp sits on 1500.. again fuel problem, well for me it has been..
im not sure of anyway to really cure this, apart from mucking around with your distributor, loosen the bolt that holds the distributor in the block and while your car is idling, turn it counter clockwise first slightly and then pump your accelerator afew times, you may notice and improvement in throttle response, if not turn the dizzy the other way and soforth, its abit of mucking around but once you find the spot it stays like that for ages.. although im pretty sure most or all carbs have a Flat spot, even if its just a little bit.
hope that helps..
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Registered:
June 2004
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Re: carburettor experts wanted
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Mon, 26 July 2004 23:41
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check your timing. check your vacuum advance and the pipes from it. if they aren't connected i'd bet money that that's the problem. if they're connected, take the vacuum advance unit off and check it thoroughly, they can get a hole in the diaphragm and not work, giving your current symptoms. where is the split pin on the accel pump rod now? far away from carb or close, cause it's more likely it's not getting enough fuel if the problem isn't the ignition i just talked about.
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Location:
Brisbane
Registered:
October 2002
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Re: carburettor experts wanted
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Wed, 28 July 2004 08:42
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well, turns out thats not my only problem.
its all the way to the bottom {split pin}
i have no compression in cyl 2, i can completely block off the 2nd throat and it runs the same, when i shut the engine off, i get fuel vapour come back out of the throat 
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Location:
Perth
Registered:
May 2003
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Re: carburettor experts wanted
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Wed, 28 July 2004 13:03
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Have you done a compression test yet?
Tried pulling off No. 2 lead at idle to see if the RPM drops (becareful doing this).
If it is only No. 2 then it will be rings, burnt valve(s) or incorrect valve clearances. If it No. 2 and an adjacent cylinder then it will more than likely be a head gasket.
One of the causes of the stumble when you suddenly open the throttle is a momentary loss of vacuum. This is very noticeable with the side draughts due to the 4 throttle butterflies and a small intake manifold volume. The sudden drop in vacuum causes the dissy to immediately retard (something you dont want under acceleration). Once the motor picks up, the vacuum picks up and away you go.
I got around this problem to some extent by fitting a restrictor in the vacuum line between the manifold and the dissy. I used a small length of brass tube, soldered over one end and drilled a very very fine hole through the solder. Then cut the vacuum line and fitted in the tube.
This has the effect of slowing done the rate of change of the vacuum advance under sudden throttle changes (adds hystersis) but wont affect normal operation.
My accelerator pump linkages are in the bottom split pin hole (gives the most travel = the most fuel enrichment).
To set up the side draughts, properly balanced, you should use a proper vacuum gauge designed for doing so (it is different to normal vacuum gauges, it is a plate like device that sits over the end of the throat of the carb).
Hope this helpful.
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Location:
Brisbane
Registered:
October 2002
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Re: carburettor experts wanted
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Fri, 30 July 2004 08:46
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ok, heads fucked
got comps of 105, 55, 85, 55
heads coming off tomorrow, get my new one in 1 week
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I Supported Toymods
Location:
Glenmore Park, NSW
Registered:
March 2004
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Re: carburettor experts wanted
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Fri, 30 July 2004 09:12
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sad to hear 
on carbys tho... ive got a 2t with a stock fair cond. carby but secondaries dont seem to work.... vaccum adv does but not secons.
whats the most likely cause? i know it should be check properly but if i just knew what to look at on it roughly.
Cheers
Nathan.
PS dont mean to hijack, just thought while were here...
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Registered:
June 2004
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Re: carburettor experts wanted
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Fri, 30 July 2004 12:43
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ta-022, secondary doen'y work at all? it's not meant to come on till later in rpm range, it's not meant to come on too early, otherwise you get a great big dead spot. you can tweak the mechs of the carby to make it open when you want it to, takes a couple of trial runs to get right. should make your car go harder too.
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I Supported Toymods
Location:
Glenmore Park, NSW
Registered:
March 2004
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Re: carburettor experts wanted
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Mon, 02 August 2004 07:57
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how do i test if the secondarys are working?
definately doesnt feel like its getting a bit more power up the range? plus im too scared to rev past 4000rpm , just doesnt sound like its having fun.
Cheers
Nathan
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Registered:
June 2004
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Re: carburettor experts wanted
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Mon, 02 August 2004 08:46
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you'll have to take the air filter box shit off and get a torch and have a look at the barrel furthest away from the engine. open the carby right up, if it opens a bit, that's really all it needs and the engine will do the rest if it needs. you could do this with the engine going or not, if you do it when it's going, you'll have to let it get into high revs to see if it can open the secondary. if it can't, you could help it, by weakening the spring that holds it, or fiddle with the mechanisms of it to make it open. it's meant to be 'vacuum scondary' though', so if you force it to open too soon it'll kill the rev's and it'll feel like the car's gonna stall.
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I Supported Toymods
Location:
Glenmore Park, NSW
Registered:
March 2004
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Re: carburettor experts wanted
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Mon, 02 August 2004 09:15
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[quote title=joecoolmk2 wrote on Mon, 02 August 2004 18:46]open the carby right up, if it opens a bit, that's really all it needs and the engine will do the rest if it needs.quote]
when you say open the carby up you mean give it full throttle?
and when done it should slightly open the secondary butterfly?
and if not i can tweak the mechs till it just opens on full gas and the motor will do the rest when going?
lovely jubbly.
cheers
Nathan
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Location:
Rocky Mountains, Canada
Registered:
May 2002
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Re: carburettor experts wanted
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Mon, 02 August 2004 09:20
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Is the 2T carb secondary vaccum assisted?
If it is, then the diaphram that activates the second throat when there is enough vaccum could be perrished or have a hole in it.
The carb on my 18R had this problem.
I removed the diaphram assembly and replaced it with a solid link so that the second throat always opened > 80% throttle.
Worked very well... gave my 18R quite a bit more go.
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I Supported Toymods
Location:
Glenmore Park, NSW
Registered:
March 2004
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Re: carburettor experts wanted
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Mon, 02 August 2004 09:42
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secondary vaccum assisted: Check
Diaghram in working order: Check
well at least i suck on the hose and it works...ie moves some sorta arm connected to in running behind the acc. linkages.
but the previous carb had said arm that was attached to the diaghram... was instead like you said just solid mounted to the carby body at the top.
so with this in mind if i solid mounted where the diaghram is ie removed the diaghram, then at 80% throttle even when off the secondary butterfly should start to open and by 100% it should be completely open yeah?
Cheers
Nathan
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Registered:
June 2004
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Re: carburettor experts wanted
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Mon, 02 August 2004 09:51
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you don't really want it to open fully, it doesn't need to. the ngine will open it fully, as it can pull it open by forcing the spring. as i said before, at lower engine speeds, it will kill the revs, because it lets more air and less fuel through, so the engine isn't getting the right mixture for acceleration.
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