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Hi guys,

I have 2001 ET2 with stock Weber 12mm carb.

I have just bought 70cc Malossi kit (not yet installed) and what would you say, do you think I need to upjet or change the stock carb? What jet size should I go for?

There has been no other modificiation made on ET2 besides derestriction.

And does anyone know what is the stock size of the main jet and is it 5mm or 6mm?

I didn't found any useful topics using search option.

tnx
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Hi - did you ever get any further with this?? - I've got a very similar upgrade to do and any advice would be gratefully received
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Stock is 76. We typically go from 76 to 80 with a cylinder kit, and 82-85 with a kit and a pipe.
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is it 5mm or 6mm though i have a 2003 model
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I don't know what carbs came on bikes in the UK. Here in the states they are Weber carbs with 6mm threads.

We have to re-thread Dellorto PHBH jets. We have never been able to source the correct jets for the ET2.
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my brother whom is a car machanic has just fitted my polini 70cc kit , leo vince sp3 exhaust ( with restriction removed ) fitted the new rollers and clutch springs . as the stock jet is 76 i have upsized to an 84 . my et2 is a 2003 fitted with a dellorto carb.
upon removing the main jet i noticed it has 53 engraved on the side which has baffled me a bit as it should be 76 . after taking tbe scooter out for its first run it only goes 15mph now and seems way to rich to the point of flooding .
why would my scooter be fitted with a 53 jet before and will i need about a 60 now
any ideas thanks
⚠️ Last edited by wacka on UTC; edited 2 times
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wacka wrote:
my brother whom is a car machanic has just fitted my polini 70cc kit , leo vince sp3 exhaust ( with restriction removed ) fitted the new rollers and clutch springs . as the stock jet is 76 i have upsized to an 84 . my et2 is a 2003 fitted with a dellorto carb.
upon removing the main jet i noticed it has 54 engraved on the side which has baffled me a bit as it should be 76 . after taking tbe scooter out for its first run it only goes 15mph now and seems way to rich to the point of flooding .
why would my scooter be fitted with a 54 jet before and will i need about a 60 now
any ideas thanks
The 76 main us yanks refer to is for American Market scoots with Weber carbs. The Dellortos take different jets.

You'll usually want to go up about 8 points from where you were before.
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.

Which carb is it?...what does it say stamped on the side of the carb...there should be some reference number to denote this.

.
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its a dellorto 17.5
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.

I'm running a .84 Main Jet with an iron Malossi 70cc kit, 17.5 Dell and a Giannelli exhaust.

Mine is a 1997 model.

Hope this helps

.
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thats why i fitted an 84 because my set up is simular to yours fabio
but confused to why mine was fitted with a 53 as stock and not a 76 as the maunals state !
looking at most set ups simular to ours they go up about 8 sizes
im very confused
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.

When you went on the first run - what was the size of the main jet you had in, also I'm guessing the scoot is 'bogging down' and if so was it bogging at..... full throttle, or at 0 to 1/2 open, or at 1/2 to 3/4 open?

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i have only had the 84 in with this set up . i guess i could put the old 53 one back in but i dont want to trash my new 70cc kit.
After looking in the haynes manuals the lx50 is fitted with a 53 as a main jet !!
the plot thickens
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.

The LX50 - as in a 4Stroke??

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no a 53 is a main jet size for an lx50 2 stroke and most parts are universal to an et2 like exhausts a cylinder kits
is it possible mine is fitted with the lx engine i guess i will have to check my engine number now to find out !!
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.

In the Haynes Manual it lists the frame number ranges for the engines if that helps at all

.
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.

Here's a thought.... what airbox/filter are you running? If its running too rich as you think, then is it that the air filter is blocked maybe?

Also what setting is the needle clip at, in the carb?

And the Autochoke - is it sticking on?




Another thought too - is there a restriction on your scooter in between the carb and the manifolds (either inlet or airbox), some had a partial blanking plate I think i have read somehwere

Fabio

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mine did have a partial restricting plate on the carb but my brother removed it.
i will have to get him to look at the air filter and clip position as i am no mechanical wizz like yourself fabio
thanks for your help and advice i will keep you informed to our findings
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If you removed the air restriction, you're also going to have to change the needle to an A8. We've not been able to get those to run right without changing the needle as well. Your carburetor is a PHVA if that helps you source one.
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right just been into my local scooter shop and had a chat with their mechanics.they say take no notice to what the haynes manual says regarding stock jet sizes and have seen et2s with a 53 many times before.they told me they go to a 62 for a simple derestriction but recommended a 66 because i have a new exhaust and 70cc kit. so thats what i have bought , i also asked about the restrictor plate i had removed and the 2 mechanics were split on wheather it needs removing so i will try it without first but they did say i would need to alter the needle position .
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.

Good, I'm glad you've got some clarification on this.

My thoughts were that the removal of the restrictor plate (if its between the carb and the airbox) is allowing more air into the mixture than usual so that you'd need to upsize the main jet/change the needle clip position/fit a diff shaped needle (as Motorsport said) to compensate.

If the restrictor plate is inbetween the carb and the inlet manifold/engine then that's perhaps a different matter however.

Fabio.

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right was going to try and put the brass restrictor plate back in but i cant find where i put it. are these available to buy anywhere as i cant seem to see any on the net
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.

Hi Wacka


I've done some digging for you and I've found this thread that should be of interest to you....

2005 Typhoon 50 Carb questions

It describes the same problem that you're having (I think if I've understood you correctly) and also the solution

Hope this helps you

All the best

Fabio.

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thanks dougie
i guess i will have to try and adjust the set up as i have lost my restrictor plate hopefully the 66 main jet will do the trick once i get it fitted
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.

Yes that sounds like a good plan to me.

You can buy a box of Main Jets covering a range of sizes quite cheaply so you can work it out on a trial and error basis, just remember to start with the largest size first and work downwards whilst plug chopping.

See my wiki article here for some ideas about this...

Link.... 2-Stroke Carburetor Set-up Technique

Fabio

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right i have now fitted a 66 main jet and left the needle position as it was and it now ticks over just fine. taking it out on its first spin she now goes off the speedo which is 50 mph. i havent done a plug chop yet but first impressions seem good. i will have to get used to the new set up because the take off is quite different and capable of wheelies !!! i guess this something to do with the new clutch springs . i now seem to have a slight problem with the oil light flashing randomly even though the tank is full hopefully it will sort itself out after a good run out roll on the short british summer !!!
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wacka wrote:
right i have now fitted a 66 main jet and left the needle position as it was and it now ticks over just fine. taking it out on its first spin she now goes off the speedo which is 50 mph. i havent done a plug chop yet but first impressions seem good. i will have to get used to the new set up because the take off is quite different and capable of wheelies !!! i guess this something to do with the new clutch springs . i now seem to have a slight problem with the oil light flashing randomly even though the tank is full hopefully it will sort itself out after a good run out roll on the short british summer !!!
.

Fantastic news Wacka!!

Thank you for coming back to the thread and posting your results, it means a lot to us because we can see if were giving out good advice of not!!

I've just clicked you Karma button for updating us!!

All the very best

Fabio

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53 main jet is the standard size for a catalyst ET2 with dellorto carb... Ignore Haynes.

If you have removed the brass defusing plate from the carb bell mouth, and fitted a race exhaust youll probably need to go larger on the main jet, tend to need 72 to 75.

So before going too far do a few plug chops and check the colour!!
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cheekythomas wrote:
53 main jet is the standard size for a catalyst ET2 with dellorto carb... Ignore Haynes.

If you have removed the brass defusing plate from the carb bell mouth, and fitted a race exhaust youll probably need to go larger on the main jet, tend to need 72 to 75.

So before going too far do a few plug chops and check the colour!!
i only fitted a leo vince sp3 exhaust so i wouldnt really class it as a race exhaust.
i fitted an 84 first of all but it was way to large and the scoot would only go 15mph !
after speaking to the guys at my local scooter repair shop they suggested i use a 64-66. so i went for a 66 which has took the speed to off the speedo 50mph plus .
reading most people threads typically for basic derestriction and exhaust change people go up about 4 sizes , then after fitting a 70cc kit another 4 sizes.
fabio dougies set up has gone from a 76 to an 84 (non cat model) which is only 8 sizes and he has a home made race exhaust fitted so me going up 13 sizes i thought would be ample .
i guess i will only find out after another couple of runs and a plug chop though
i may also look at the roller weights as it revs quite high before take off - i fitted the ones that came with the exhaust
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update

i stuck her up yesterday and she started first kick so i took her out of the garage put on my coat and put my helmet on which took me about 3 mins. Just as i sat on her she cut out , i kick her off again and she chugged but cut out again.Then i was unable to get her started so i left it 10 mins and tryed again and off she went. I took her for about a 5 mile run and then did a plug chop. It didnt look too bad maybe a bit dark so i guess it maybe a bit rich , I tryed again today to start her today and again she ticked over for a few mins and cut out again.
Do you think it is flooding or the plug is fouling. Looks like i will have to try a 64 or maybe a 62 . Does going down just 2 sizes make that much difference ?
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.

Possibly needs the idle speed turning up a touch?

And if not that then perhaps the idle mixture needs tweaking slightly. See the wiki.... paragraph "Setting the idle mixture screw"..... Getting Your 2-Stroke to Run Properly


Fabio

.
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Fabio Dougie wrote:
.



Also what setting is the needle clip at, in the carb?

.
You have a special "sparky idiots guide" for this Fabs?
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Needle Clip

Needle clip setting....As you twist the throttle, the carb lets in more fuel by moving the needle in/out of the bore of the main jet, the needle lifts as you twist the throttle, this needle is adjustable and can be lifted or dropped by moving a clip up or down at the top of the needle shaft. The clip is mounted in the throttle slide and it's basically a kind of stopper.

Moving the clip up or down a notch can affect the richness of the mixture over the 1/4 to 3/4 throttle range. You could tell while running, if your scooter feels as if it has a flat spot on and around mid range, or it does not start to perform until the throttle is fully open, it will be too weak. If too rich the scooter will splutter at this position, but it will probably clear as you go onto full throttle. The needle must be dropped if the engine struggles to rev at all, if there's a strong smell of fuel or the engine pops or backfires.
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the scooter definately feels as if it has a flat spot on and around mid range, what does this clip look like mate and Ill have a pop tomorrow. I also bought the 76 and 78 jets today so gonna have a blast at that too!
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where is it here?
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Top end of the carb - under where the throttle cable enters.
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Is it that silver squared thingy magiggy?
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I know this is not exactly the same as your carb (but close enough for this puprose).......


Its under where the arrow is pointing.........
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