my zx50 issues

[thebatman]

im havin issues with my carb...no choke or airbox at all...runs, not right by any means. took carb to shop, he changed carb and now is running but he says i need piston and rings to be correct. says bottom compression wrong.the fault of no airbox....is there any truth to what he says or just trying to work me for more? still the carb??...plz help. any and all will be greatly appreciated..

[Shaka]

There is no way to tune it properly without the airbox!  The first step is going to be getting whatever airbox or open filter you plan on using and then go from there.  You can then move on to dialing in the main jet size and getting the rest of the carb adjusted.  The only way to tell if the piston or rings are bad is by doing a compression or leak down test. If the motor is running you should be getting ok on compression, but if you find the carb is hard to get dialed in correctly, you may have a vacuum leak somewhere between the carb and the engine, or through the crank seals.  The only way to properly diagnose these is by doing a leakdown test.  Once again, the first step is to get an air filter on there!

[thebatman]

hey, thanks for the answer.. well the guy at the scooter shop did change carb, choke and airbox are in place now but running shoddy at idle or low rpm. thats why he said i probably need new piston, rings." its not bringing enough gas into chamber from bottom".. if i do that, THEN it will be right... whats the average life of a stock oem piston. want an exhaust but he told me its useless till i change/fix first, he is the seller of the exhaust .... said compression good on top, lagging on bottom.. ruined by my riding w/o the airbox,choke on previous carb.. ...see, im trying to learn this..lol. bought a manual but was told they are wrong sometimes, you just have to learn exper.....thanks for the help...

[Shaka]

It sounds like you are not getting enough vacuum to draw in the proper amount of fuel at low rpm's.  This is probably due to worn rings.  You may be able to just replace the rings and run a little extra oil in the fuel tank, but this may be just a temporary fix.  Really it sounds like you may be best off replacing the cylinder and piston.  I was running into the same symptoms with mine after about 10,000 kms.  I bought it used and it didn't appear to be well maintained.  I just replace my cylinder and piston with a 72cc big bore because it cost about the same, actually less than the stock parts.  With the big bore you have to replace many other parts as well though.  ie.  carb, exhaust, cvt parts.  It all comes down to what you want to spend and how fast you want to go!  Your mechanic sounds like he may be correct in his diagnosis though.  Typically these engines will last a very long time as long as you run a good quality oil in them!  I'm more than happy to help, offer advice, just keep posting!

[thebatman]

mine has 14,000 on it...its been good, but i want faster of course, only going 47 right now..was told that big bore kits are short term..have to change again in 6-8 mths. for longevity/reliability, change pipe,weights,springs, leave stock head,etc.. he told me today he was 98% sure thats whats wrong,(piston,rings) not the carb now.. said pipe useless right now,id think he was crazy when i put it on, woundnt run any better..

[Shaka]

Man, we need to consolidate these two threads into one!  Anyways, mine has a little over 14,000kms on it now and I think I put the big bore on about 7 months and maybe 5,000kms ago, can't quite remember.  Mine has been running strong!  I've gotten close to 55mph top and cruises all day at 50mph!  I still have some more work to do! 

[zombie]

The way the batman is describing it , Sounds like the bottom of the barrel may be scored. If a ring hung up on a down stroke it is possible there is a groove cut in the bottom of the jug. Can you pull your cylinder head to take a look? If you see anything odd, pull the cylinder next to inspect the piston/rings. At that point you can do the necessary swaps your self.

[Shaka]

Makes sense, that just the bottom of the cylinder may be scored.  Still seems unlikely due to the heat build up coming from the top side.  Maybe I will learn something new though!

[zombie]

Thats what i was thinking. Melted the top near the exhaust, hung a ring, and cut.

[Shaka]

Yep, makes sense to have the scoring below the exhaust port!  However, I just looked at my old stock cylinder, and I had scoring from top to bottom between the boost and transfers.  I'm pretty sure that was the end of the ring.

[thebatman]

hey man, thanks for the help out there. i will try and see. i hope i at least get my mpg back with the carb "fixed".. what have you done to yours so far?. i saw one on youtube i think, went 68mph.. thats better right there..lmao.. oh yeah, was also told that when i do put the exhaust on i will not need to rejet carb.. whats your take?. i live in the mtns...said i should get 55 without the big bore??

[Shaka]

Wasn't my youtube video, but 68mph is possible.   I have done a 72cc Airsal cylinder, Technigas Next R exhaust, Arreche 19mm carb w/ K&N Filter.  Malossi multivar & belt, CVT tunning, Motorio intake manifold & reeds, removed oil pump, and one of my favorites- Avon Viper Stryke tires in 130/70-12 & 120/70-12!  Probably more I'm forgetting!  I'm only getting about 50-55mph tops with the current setup, primary gears are next on my list!  If you put on a new exhaust you will probably have to rejet.  You should do an open filter along with the exhaust more max effect, which will definitely require rejetting!  Only plug chops will tell for sure!

[thebatman]

man, sounds like you have everything on there.. see, thats whats getting me.. you have some cash in the ol girl..only going 55.  i saw at scooterdepot.com, 150- for like 600. brand new and will go speed limit.i get discouraged with my zx, cuz its slower and harder to find parts.. dude said id get 55 with stock parts, just weights, pipe added... hows your takeoff? mine sux, but thats y he said piston,rings. wide open good

[Shaka]

My take-off is pretty awesome!  You definitely have to be holding on!  I can out accelerate just about anything on the streets, up to 50mph!  I had some lighter rollers in there, but it was hard to keep the front wheel on the ground from a take-off!   I had to detune it a little to make it more "daily" ridable.  Once I do the gears I should get another 10-15mph or so top speed!   You can just only spin the engine/rear wheel but so fast with the stock gearing!  Changing to lighter rollers and heavier small clutch springs will help tremendously with your take-off!

[zombie]

Forget about the 600 buck 150. The only way to get parts for them is to buy tree scoots. Parts for your zx are everywhere! 3-5 days shipping form all the shops we deal with here. Shaka hit all the hi points for you, and there are no drawbacks that i can think of. Mine is set up VERY similar to shakas. 47mm Malossi jug/head (70cc), technigas pipe, Malossi reed cage w/ Boysen reeds, Delorto 27mm carb, same tires as shaka, complete Malossi cvt, and polinni final drive gears (8.3-1) Forgot the racing coil/cdi/storage cap. With the gears I get 62 on the flat, and better down hill. Also whips a$$ on anything around here. It wouldn't make sense to do anything in upgrades till you find the problem you  have. If it is a jug then This is what I would suggest   http://www.malossiusaonline.com/CYLINDER_KITS_s/292.htm   I have the cast iron kit. 2+ years on the jug, and just replaced a piston (my fault I burned it). Keep us informed what you find, and we can get you back up to kick as$ performance in no time. Besides we need more zx's here. The Ag's are breeding like roaches.