Scooterotica

Having a few issues with my S3 Li.
It's got a 175 conversion, scootrs exhaust and unfortunalty a 22mm jetex.
It starts and runs fine but i get a stuttering at certain throttle settings. i'm concious of how much trottle i'm giving it as i have rebuilt the engine. So say if i'm doing around 35mph in 4th it stutters but if i give it i touch more throttle it's fine.
This rough running occurs in each gear at different speeds and again open it up a bit more and it runs well.
I dropped the main jet from a 130 down to 125 and the problem is still there.

Any offers gent's?

Thanks.

Could be that 35mph in 4th is too low revs for your very revvy exhaust. Unless you're whanging it you may not be even using main jet, that doesn't kick it until you're over half throttle, so unlikely that just dropping main jet will have much effect. Try a clubman type exhaust. Is your Jetex fitted with a 150 slide? .... and not a 200 slide.
Any idea what gearing you're running?

Hello mate.
i got the carb off ebay and 'apparantly' they are suitable for 150cc-200cc.
The scoot is an LI125 so it's got the original 125 gearing. Currently got the air scoop off and it is difficult to start if i remove the air hose.

Just been out on it and thought it was going to cut out at one point. All of a sudden it became really bogged down, it was as if i was going run out of petrol. Had to pull clutch in and rev it. I wondered if it was due to the cold weather?? ( it has never done this before)

It starts and ticks over nicely but It's a bit tempremental at junctions sometimes, i have to have my wits about me to ensure it won't cut out as i slow down or come down the gears.

Cheers.

sounds like its 4 stroking at low RPM. The main jet shouldn't have any effect on the running of the motor at those RPM's so I would consider dropping the pilot jet.( the main jet should be in the 123 area as well I reckon)

You need to be around 45 ish on pilot I would say

Chris

Great thanks for the tip.
I think i've got a 45 lying around so will give it a try tomorrow.

I'm still quite the novice and caburation is a black art to me!

Cheers.

Agree with Corrado, try a Clubman type exhaust. 45 pilot, 123 main and maybe a 16 tooth front sprocket and you will see a big improvement.

Rich'

Never been below a 48 pilot jet on the jetex .

Dean

Corrado is right. 22mm Jetex carbs can be bought jetted for 200cc or 150cc. I used to have a 175 conversion with a 22mm Jetex and Clubman and it went really well, but I changed the slide to the one used for a GP200 which is a 7895-1. The 22mm jetex for a GP150 has a 7895-2 slide. Also check the atomiser some Jetex GP150 carbs come with a 5899-4 atomiser, others come with the GP200 atomiser which is a 5899-2. Mine was fitted with the 5899-2.
I tried the 175 with a ScootRS pipe and it never went as well as it did with the Clubman.

Ok tried changing the pilot jet and it made a slight difference but the problem is stil there. Opened up the throttle today and it was maxed out at 40-45mph in 4th and felt like it was being strangled.
So i will definatly go for a clubman and might be able to get hold of a 16t sprocket.

Now stupid question time, why/what difference does a different type of slide fitted to a carb make?
And what sort of engine set up is the scootrs exhaust suitable for.

Thanks.

Fit a 5899-2 atomiser ,a 200 slide with no cut out in it,48 pilot,and anything from a 118-123 main jet all this will work if the engines built correctly with no air leaks and is timed up correctly.

If you use the 150 slide (no cut out) then it will seize up at cruising speed (quarter throttle) after 5-10 miles probably going up a hill when the engines runs at its hottest.

Remember to start high a work down when setting the main jet.

Dean