Agility 50 Big bore kit

[scooterman11]

with this kit do i have to have a bigger valve head ot can i use my stock head

http://www.provoscooter.com/airsal-70cc-cylinder-139qmb-50-4t.html

[whiteknight]

not sure with this one, i know the Naraku 72cc kit dosnt come with the matching head because the compression was too low if you were to use it, i use a naraku 50cc head with my cyclinder. but as i say, im not too sure with the airsal kits as i've never used them. maybe it is the same deal as the Naraku 72 kit and you may need to use the stock head but i would do some digging to make sure...or you could see what Wordslinger and Zombie have to say on the matter.

[whiteknight]

ok just done some diggin around and i found an older post on this forum about the Airsal 70 kit. apparently its best to use a high performance head to get the most out of it. i think its just the Naraku kit that needs the original head for it to work at its best.

[blue]

BIG BORE KITS ARE A WAST OF TIME AND MONEY. You well find your self walking the scoot home.

[Kenho21]

I have that exact kit and love it, although it is true once you install a BBK you're entering into a whole new world of tuning and potential mishaps, but sometimes I just like to break stuff... then fix it... then break stuff again...

But since I installed that kit I have gotten great performance out of it and really like the different it makes, the install wasn't too bad either. The only problem I had was tightening down the four bolts that hold the cylinder and stuff on. I wanted to make sure those were tightened down to spec so I took it to my old work where my buddy has a $500 torque wrench, just so I could have piece of mind.

Anyway, I would recommend it, just know that it's going to take some time and money to get everything just right, I still haven't got mine perfect yet, but I'm pretty close... I think.

[mono]

BIG BORE KITS ARE A WAST OF TIME AND MONEY. You well find your self walking the scoot home.

Must be a matter of luck then ? (or bad luck ?)

My no-brand 72cc is lasting for more than 9000km already, and when I took my engine apart some time ago (to try a 85cc) everything was still nice, shiny and tight as new, including crankshaft bearings, big end/small end, piston pen, etc...

It's not only my own experience, but the people saying that these small engines are tough enough to withstand a 70..80cc for a long time when fitted and tuned properly are mostly the guys with experience in the field - while most of the ones that warn of failure only mention one specific occasion, and some just seem to be repeating what other people say... You just never hear about it when things go right I guess...

By the way, I've recently driven a standard 50cc Agility for a while and the traffic around me scared the sh** out of me - a low-revving 2 valve 50cc 4T like this is simply not an option in traffic over here, no matter what the lawmakers think.

[scooterman11]

When you put a big bore kit on the agility 50 what jets  do you have to have to upjet the carb

[mono]

With my 72cc and standard airbox and carb, a jet 0.04mm larger than the jet that worked with the 50cc proved to be a safe bet.
After the 50cc -> 72cc upgrade I changed my 84 jet for an 86 at first, but it proved to be a bit lean, so I changed it for an 88, and it was OK again.

I also have an 85cc BBK which is a bit different in that it seems hard to tune correctly with the standard airbox. To give it the air it seems to need I had to drill the entrance of the airbox from 18mm to 24mm, and I removed some kind of "rim" in the tube between airbox and carb... After this modification (which also works brilliantly for a 72cc BTW) I had to add another 0.04 to the jet size to keep it from running lean....

It's always better to start with the largest jet that will probably still work and only try the smaller ones if your plug gets too dark. You don't want it to run lean, especially when you don't have the experience to recognize a lean condition while driving right away (some people have burnt a hole in their piston within minutes while running lean !)

[scooterman11]

what does my main jet and pilot jet have to be?
srry if im repeating my question i just need to get her going

[mono]

Read my post again. I know I write long stories instead of short comments - but my advice is in there...

Short(er) version : if your 50cc is running fine now and you don't change anything except for the cylinder, see what jet size you're on now and add "4" to that for the first try - but don't complain to me when it burns your setup, since something might differ from mine, such is the risk of tuning  

BTW, don't worry about the idle jet for now, just leave it until you're sure about your main jet setup, and you might find that it's idling and picking up good enough with the standard one...

[scooterman11]

Why is she so hard to start kick starting and wont even start with electric start

[mono]

Why is she so hard to start kick starting and wont even start with electric start

Dunno.... What did you exactly do to the poor thing right until now ?

I can't tell from here what parts you actually changed - and "hard to start" comes in a lot of colours... Did it already run for a short while, or hasn't it done even a single stroke on its own power yet ? Did you drain the carb and forgot to fill it up again ? Does the starter motor even try to turn around or is it completely dead ? Is kickstarting hard because it doesn't run after kicking 100 times, or is the compression just too much to kick it even once ?

[whiteknight]

my Ag is a bast*rd to kickstart and even the electric start has trouble but just about manages.

[mono]

Yep, the gearing of the kickstarter and starter motor are calculated for a 50cc. With a piston surface of about 1.5 times as large as that of the 50cc, their job is a lot harder with a BBK, even while the compression ratio itself is still about the same...

I never use the kickstarter because my electric starter always works, but often the starter motor stops at TDC and I have to release the starter button and press it again to get it through the compression stroke.

This annoyed me at first and I was scared that I might burn the starter motor, but nowadays I hardly notice it anymore - I just release and press the starter button a second time if needed, without thinking...

[scooterman11]

@mono
She ran for a while but only with a fight trying to get it running it was spitting out through the carb like it was flooding, but still will not idle on her own