Starting after top-end rebuild and new carb

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loadedscooterist
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Wed Sep 12, 2018 4:30 pm

Hi, Just a quick update - went and played round with carb settings today (first chance I have had) so now running on :
Pilot - 45
Atomiser - 5699-2
Main - 118
Starter Jet - 50

So once fitted it started 3 / 4th kick - so a decent improvement, However after about 30 seconds died on me and it was tricky to restart. Progress of sorts and will be working through fine tuning as suggested above. I am wondering whether the choke is working correctly as well?

Thanks for your input all!

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sunrisemac
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Wed Sep 12, 2018 8:49 pm

how long do you run with the choke on? Is the choke cable too tight so when it's off the choke is still holding on a wee bit and flooding the engine?

loadedscooterist
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Wed Sep 12, 2018 9:13 pm

That's a good point and I will need to look at the adjustment. I have a few things to look at and don't think I am far off from sorting this out. To answer your question the choke was on when it died.

Thanks

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sunrisemac
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Thu Sep 13, 2018 8:45 pm

Did you try to restart with choke off and a bit of throttle?

loadedscooterist
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Fri Sep 14, 2018 9:26 am

Hi mac

I haven't had much time to go back to the shed. What I was going to try was playing with the mixture screw first as had been suggested but want to fine tune as much as I can with the other suggestions that have been made. Will report back once I have had time over the weekend. Thanks for taking time to input

johnny650
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Sat Sep 15, 2018 6:13 pm

I've just had the same problem with my 185cc budget cylinder kit rebuild for the past 6 weeks !
I have finally got mine starting 2nd kick and running very strong with the following .

AF Clubman 42mm
Jetex 22
slide 200cc
Atomiser 5899-2
Main 122
Pilot 48
Choke 50
mixture screw 2.5 x turns out

This setup is running very strong with good throttle response and strong acceleration .
There is still a slight power loss from 1/2 to 3/4 throttle but if i back the throttle off slightly and then nail it it will rev right through to WOT. Still a little tuning to do.

Now the reason my scoot was so intermittent on starting and running was this .

Firstly there was an airlock in my fuel pipe between the petcock and the filter . ! .
Once I had filled the tank to create more head of pressure and removed the fuel bowl to drain the fuel pipe the air lock disappeared. The effect of this was the engine would start eventually and run very rough with some 4x stroking but would cut out immediately the choke was put off . This is why I would recommend that when testing a non starting rough running scoot you fit a clear fuel pipe otherwise its near impossible to diagnose

The other reason for poor starting which was so difficult to find was a slight air leak between the carb and the inlet manifold. Because the Jetex carburettor is so close to the petcock shaft joint it is prone to binding when the throttle is opened up so I hadn't been fully seating the carburettor on the manifold stub to avoid a sharp bend in the shaft.! it was only about 1/4" off of fully seating but that allowed air to be drawn in between the carb and manifold along the splits in the plastic bush .
I now use a block of hardwood and a hammer to make sure the carb is fully seated

loadedscooterist
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Sun Sep 16, 2018 3:41 pm

Hi Johnny, Thanks for the update and your answers.

So I spent the afternoon yesterday trying to sort out my starting issue based on the suggestions provided in the thread.
I went with the following set-up:
Pilot Jet = 45
Atomiser - 5899-2
Main Jet - 118
Starter - 50
Mixture screw - 3/4 turn out
Air Screw - 1/2 turn out
Spark Plug - NGK B8ES

So choke on - 2nd kick and it starts. Great! However, it then dies after about 40 seconds and then refuses to start.

I then clean the plug and then got it to start again (within a few kicks) but didn't want to idle without my assistance on the throttle. It was also quite smokey at this point.

When I took the plug out there was smoke coming out of the barrel - not masses (think vapour level of smoke) but enough to see. I also seem to have a sprung a leak of oil which looks like its coming from the exhaust header but this was there when I stripped the old barrel off. So I have an internal engine issue - e.g. broken seal as well as the starting issue.

I am now at the point where I have wasted so much time sorting this scooter out (as well as money) in all the time I have owned it - just over 12 months (and have only been out on it once and there is no fun in that is there!). I now have a hard decision to make as to whether its worth ploughing more time and money (which I don't have masses of) on it or just simply get shot of it (at a loss). At present the second option is more preferable.

I am going to take a little while out and think next steps. In the meantime thanks to everyone who has input and spent their own time giving me answers.

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