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Post by jet4125 on May 6, 2016 11:39:54 GMT -5
I'm going to buy a 160 big bore kit for my sym jet 4 125.
What else do I need to buy? Kit comes with everything. But it says I will need to up jet. How much bigger do I need to go?
Standard carb and exhaust.
What else will I need to do?
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Post by 2stroked on May 6, 2016 12:14:47 GMT -5
An assortment of larger jets would be a wise purchase. What kit did you order, could you post a link?  What's the true cc of the new cylinder??? The bore size?? A port and polish job on the head may give a performance bump almost as large as the BBK!!! Some have said that the port and polish was their best mod as far as performance wise. |
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Post by jet4125 on May 6, 2016 12:27:39 GMT -5
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Post by 90GTVert on May 10, 2016 6:08:07 GMT -5
As said, get a selection of jets. You probably won't have to go up too much in size, but it's good to do a tuning process vs swapping one in and hoping it works. I have a 112 main in my 155cc with a K&N pod filter. That's what I ended up with when tuning for max power. Mine runs hot though, so I'll probably have to upjet just to keep it cooler. Most people report using a 120-130 with open filters. Still, just use this stuff as a general reference and tune yours. Stay on the rich side to keep it cooler. Take a look at the carburetor section here : www.49ccscoot.com/faq/faq.htmlI didn't get a big increase in power, because mine only went up ~5cc, but you may with a larger jump. If so, there's a chance that you need to swap rollers to get the most out of it. It may work just fine as-is though. |
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Post by jet4125 on May 10, 2016 12:21:17 GMT -5
How will I know with jet to use?
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Post by 2stroked on May 10, 2016 13:15:43 GMT -5
Okay, find out what size jet you have in right now. Then order a five or ten pack of jets from somewhere like PFS or JetsRUs. Start with the next size up from what's in there now and go up from there.
Nobody can tell you exactly what jet to get, because each bike is a little different. We can only tell you a ball park estimate. Your safest and easiest bet is to order a tuning pack of ten or so.
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Post by 90GTVert on May 10, 2016 15:29:26 GMT -5
How will I know with jet to use? Look at the link provided above your post. Lots of info there about jet selection and related links including a video showing an easy process. |
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Post by jet4125 on May 22, 2016 2:53:12 GMT -5
Right I've got my bigbore kit I've also bought a face air filter and a new exhaust.
I've had a look at the carb and it's main jet now is a 110 where should I start when tunning
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Post by 90GTVert on May 22, 2016 6:44:42 GMT -5
Put a big one in there and work your way down, seeing where you find the best power. I'm only using a 117, but some people say they use up to 130. You could start at 130 to be safer. Mine was sputtering at 125.
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Post by 2stroked on May 22, 2016 13:55:14 GMT -5
Get the assortment that has at least a 140-145 as its biggest. The new bbk, will need an upjet, the new filter will too, and the same with the exhaust.
MAKESURE TO ONLYCHANGE ONE THING AT A TIME, I.E. BBK, then tune, then FILTER, then tune, then EXHAUST and do your final tune. Doing it one change at a time helps to eliminate the WTF gremlins.
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Post by houseoffubar on Jul 16, 2019 1:36:49 GMT -5
You have a head for a 150 coming too?
The 125 will almost certainly have much smaller valves.
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Post by SMALL CC TEK on Jul 16, 2019 12:49:08 GMT -5
You in the Us cause we never had that model ? Or are you in possibly florida they seem to get all the wild one off scooters ! lol
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Post by bi6foot666 on Sept 28, 2019 21:54:56 GMT -5
Doesnt sym use ceramic coating on their pistons? They make good shit.
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Post by 3strokeengine on Sept 30, 2019 12:00:20 GMT -5
I live in florida so take into account im at sea level elevation with temperatures in the 80-90*F range.
For 150-170cc with the stock 24mm carburetor anything over a 115 is way too big. Ive often found with wideband tuning a 112 main jet on a A9 cam 150cc 24mm carb, pod filter with a run of the mill performance exhaust produces air fuel ratios of about 14:1 cruising and 12.5 AFRs during WOT.
The same setup after the 170cc kit installed with the same 112 main jet would run 14:1 AFR crusing and around 11.8:1 AFR WOT.
In other words with the same 112 main jet and carb and not even 2 hours later the same day the 170cc actually runs richer than the 150cc go figure.
With the 30mm carbs that all goes out the window. I didnt do many 170cc 30mm setups but with mine i ran a 122 mainjet. Just know that even tho the engine gets bigger doesnt mean the jets need to be bigger (in most cases smaller!)
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Post by bi6foot666 on Sept 30, 2019 12:58:50 GMT -5
A kymco people 250 runs a 108 jet. The 250 S tho runs a 104. My agility 125 has a 105main.
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