Carb assistance

[arancara]

Really struggling with the carb, had two shims on the needle and a 130main jet, starting was very difficult but mid and top end was spot on, took shims up, played around with pilot, got it starting straight away with no choke, but mid and top felt bogged down. Now its a non starter where I have lost the sweet spot.

Its got the 156 big bore kit running so I need a rough idea what jets are used on a 150cc lifan engine at least.

[spencer2004]

I found that after I installed my big bore kit I actually needed to reduce my main jet size as the engine is sucking harder than before through the same sized hole so more fuel can flow through the jets.

As you have done a lot of mods you are very unlikely to find someone with the exact same setup who can tell you the settings that you need so your only option is to do a lot of trial and error.

Set your main jet and needle to what it was before you installed the big bore kit, screw your idle mixture adjustment in all the way then 2 turns out, if you cannot start your engine keep turning it out a quater turn until it starts then do a final adjustment of the idle mixture screw to get you the best idle speed. See what the top end is like and if it dosen't feel as it should then experment with both smaller and bigger sized main jets until you get the best result. After that if the mid rev range dosen't feel right experement with needle positions until you get the best result.

The 30mm carb is probably too big for a 150cc so it is very hard to tune, if you cannot get the fueling right I would suggest getting a smaller carb.

[arancara]

Well I've dropped down to a 115 and absolutely having no luck as to working out what is going on... I had the 30mm carb running spot on when it was a 125, just rich, with a 110 main jet...

But its now a more complex engine with the cams +1mm lift, ported inlet, the 156cc, oil cooler now working as well... The internet is not helping, some suggestions go as far as saying a 150 main jet on a 30mm carb, which I think is completely off the scale, from my first right up, my impression is top end is to rich when I managed to get the pilot adjusted, where as when pilot wasn't adjusted it worked well high up as the pilot is constantly active?

[spencer2004]

This chart may be of some help

jetchartSmall.jpg

As you can see when you change something such as the main jet it overlaps with another thing so it is really hard to get everything correct all at the same time.

[arancara]

I've been looking at diagrams like that all day and all i can say things don#t overlap in some situations as anticipated, any idea what the stock 150's and 200's come out in terms of jetting out the factory otherwise I think I will have to get it to a garage and let them tune it as I'm absolutely tired now and this is the last step I can't seem to solve, its already been off the road 4 weeks since I started the rebuild. My colortune has also packed up which adds to frustration.