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checking tillison pop off pressure
#21
I know people have used plastic needles successfully in the past, but they've never worked for me.

David may be right. This carb may have been modified for alcohol.

Compared to running on gasoline, an engine running on alcohol requires a lot more fuel That;s why you can get away with an inlet needle that doesn't seal completely. Still not good.
Just buy a rebuild kit that includes the standard rubber-tipped needle.
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#22
actually reverting to gas on a properly modified alky carb is nearly impossible.
the reason is the passages have to be enlarged to allow the 60% plus extra fuel flow alky requires.
i've seen alky carbs run on gas successfully but they are very temperamental.

i see the needles and it is not the typical alky needle i'm used to seeing.
you may  be able to just replace the needle with a new vitron tipped needle.

but it is far better to replace both the seat and needle together to ensure a proper match.
at this point you don't want to add another layer of variables to the rebuild.
best option is buy complete rebuild kit that includes new seat and needle.

a better and more correct step would be to remove the fuel control needles and measure their respective bores before you spend the money to see if they are drilled for alky.
or easier check to see if there are three holes in the bore on the idle side of fuel flow.
actually this is getting kinda technical for a beginner
in fact i just had a thought .

yep i was right.
just checked what carb was originally made as and it comes up rupp.
theres an excellent chance you have an alky carb.

at this point you can get deeper into learning about carbs or accept a favor.
if you like send me the carb i'll mike it up and figure out alky or not.
if it's a gas carb i'll install the rebuild kit and seat do pop off ect ect for you since this is a great thread.
i'll post pix of what i do results and whatr was done to fix to finish thread.
we'll be saving for future members who'll need this info i'm sure.

if you like that idea pm me for ady though i think you have it already.
i actually am thinking i may have even sent you a carb possibly that one or am i having a senior moment?


or just ask to continue and i'll write up the next steps for you to try.

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Dave L.
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#23
Hi Dave yes that is the carb I purchase from you. I know all about senior moments lol. Did you look at the pics i posted in a earlier reply? I don,t know if looking at them would tell if its a gas carb or not. I know alot of people would want to run alky but I rather just run gas . If its a alky carb, it would explain why I,am having trouble getting it to run clean,. Thanks Dave for your offer, I let you know. Do you know what the stock hole sizes are if I want to measure them?
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#24
Uh-oh.

Mel, it depends on your wallet & how much patience you have, but remember, since you're running gas, a brand new Tillotson HL is only a phone call away and a bit over $100. Call EC Distributing.

(Yeah, I know guys, I should take my own advice!)

You said you're running an Mc5. Like Dave L said, whatever carb you run. Make SURE the pulse holes line up. [I don't know if the old flatback Mac carbs had their pulse holes in the same place as Tillotsons.]
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#25
Mel,

then that is definitely gas carb i used about six so far no issues.
the needle was probably something done back then as it looks like a stock needle but in plastic.
you need to just replace the needle with a modern vitron needle the taper will be fine as that carb was n.o.s. so seat shouldn't have much wear.
if you like just send back i'll redo it for free as it seems to be something i sent giving you fits.
or we'll keep going and you can learn more about carbs.
either way you need to get a new vitron needle from e.c carbs or a tilly dealer. get a new gasket diaphram kit too.
this one looks like it'll work

https://www.ebay.com/itm/RB-42-Carbureto...SwPhdVUvpS

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Dave L.
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#26
thanks everyone for the help. I,ve added a few more pics of my tillison carb., what does the m stand for on the inlet cover ?also does any inlet needle and seat work in all model tillisons? or do you have to match with model number.Dave thanks for the offer, but I don,t want to trouble anyone, and besides I learning things about carbs that I didn,t know. Just want to make sure I have a gas carb


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#27
you have gas carb. i can send you a needle if that's all you need send addy.
Dave L.
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#28
Was wondering what pop off pressure should I try to get for a Mc5 with gas carb and does different macs have different pressure. Also should fulcrum arm be level if you check with a straight edge. I know, I ask a lot of questions,but I learned a lot by asking and hope some other newbies will learn something
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#29
mel,

it's homework time .
your assignment is to read EVERYTHING on the thread i linked below. after reading everything return with further questions please!!

old thread with tilly rebuild advise by dave l

alot is for alky but tilly is a tilly so basic directions are the same.
most of the parts are the same to and remediation of poorly finished flat surfaces is a must for any good carb rebuild.
on gas tilly i think around 9# pop off good middle number but i've not run a gas tilly in ages so i might be off track.

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Dave L.
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#30
Dave  I use to hate homework, rather play, but I will. Where did you find that writeup? that,s what I,ve been looking for. you are the man and thanks aload. now I owe you a six pack  lol
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