How fast should my ZX50 be going after mods?

[Shaka]

I think I have done about every upgrade I can to my ZX50 and I still can't get more than about 50-52mph as indicated on the speedo! 

What are others getting?
Am I missing something, or is that just all it will do?

Set-up:

-  70cc Airsal cylinder kit
-  Arreche 19mm carb w/ 115 main jet
-  K&N air filter (open cone type)
-  Technigas Next R exhaust
-  De-restricted CDI via green wire splice
-  Malossi variator, tried w/ various rollers from 6.5-9gr
-  Malossi kevlar belt
-  Stock clutch w/ green springs
-  Running premix 92 octane @ 38-1 ratio w/ full synthetic

Any input is greatly appreciated!

[rgy]

my two zx 50's run 47/48 mph.  The place I bought them from did the original mod and had them to low 40 and then another shop took out the rev limiter.  i'm close to your speed and i'm still at 49.9.cc

[Shaka]

That's what I'm saying!  With the 70cc I expected to be up around 60mph.  It seems like the engine just won't spin any faster, like something is limiting it.  Could it be the CDI?  I took off the wire splice to test to make sure it was de-restrictig and it did about 47mph.  You could definitely feel it limiting the RPMs.  I put the splice connector back on and still only got 50-52mph max.  It didn't seem like the CDI was limiting it though.  My other theories are the reeds or the carb just isn't tuned right.  The carb seems to be real close though.  It's definitely not perfect, but it runs pretty good.  It has somewhat of a "sweet spot" at about 1/4 throttle where it will accelerate like it does at about 3/4 throttle.  Other than that it's seems good.  If I up-jet it bogs.  I'm reluctant to go smaller as I don't want to run too lean.  It just doesn't seem like less fuel would give me another 10mph top end either.  Am I wrong?  Any other ideas?

[zombie]

Hey shaka< the only difference between our scoots would be I have a 27mm delorto w/ a 95 jet.I cut down yz-80 carbon reeds to fit (cut the thick end),I did a little porting on my jug (mostly clearing out mounds of metal that was causing limited flow), Take the stock packing out of your pipe, and replace it w/ 4 turns of HEAVY fiberglass (fab mat is what it is referd to) And install a 130x60 rear tire. these should get you the extra 10 mph. I think the first 3 things made the biggest diff. Maybe a smaller jet w/ a thinner needle will help your carb problem. The smaller jet will help your top end bog, and the thinner needle will still give you the sweet mid range. Your carb manuf. will be LOTS more help than the dealer. If only all of lifes problems were so easy!

[Shaka]

Zombie-

How do you get the packing out of the silencer?  I don't recall seeing any way to take it apart.   

Will the 130 60-12 rear tire fit with the inner fender?  Clearance looks really tight already!  That fender is acting as the only divider between the sand thrown from the tire and my air filter.  I'd like to keep it if possible.  I even made a bracket to hold it with the new exhaust.  I tried running with out it and my filter got covered in sand after 2 days!  I live at the beach!  I was going to get new tires anyways though, my back one is overdue!

I have looked into the Malossi reed cage with carbon petals.  Do you think this will give me the results I'm looking for?

Thanks!

[zombie]

On my silencer there are three 8mm cap nuts facing the exhaust tip. When you remove them the cap, tip, and packing all come out together. I have a Kenda on the rear that is a squeeze, but it fits. I had to use a die grinder to remove a small bung on the bottom left engine case. My tire was getting a rub line after running at top end for a short while, also had to back the brake shoes WAY off to get the angle to re-install the tire set up. I also have the malossi cage, and tried the malossi reeds, I don't think they had a very good flex rate. I had a loopy sort of idle w/ a VERY snappy sound at top end, kinda like a lean mix sound. I bought a set of reeds made for a yamaha yz 80 which are thinner over all (also too long) but much more of an even bend. or flex to them. So I used the malossi as a template to trim the yama. thick ends, leaving the thin end untouched. I used a scribe to mark them, and did the trimming w/ a table sander. After getting the shape I used slow cure epoxy to re-seal the raw edges. Back to the tire a 130x70 would not fit but the shorter 60 does. In the front I have a Kenda 120x70 which is the same height, just a little narrower. If you have a welded silencer, I would drill a series of six, 3/8" holes just before the tip (outlet).  It Will improve the scavanging w/out that anoying two stroke dirt bike pop. Some things work, and some don't. I just like trying different stuff. Since the speedo only goes to 60, there is no way to send a pict., but trust me 65mph can be hit. It only will run there for about 200 yards, and will fall off to a steady 55-58. I am assuming the 2 ring piston swells enough to limit time at speed. It could be fixed w/ a 1 ring set up, but I would be buying them by the case. I forgot to mention the cdi i am running was custom programed by Suitai. They used the same ign. curve used by the kymco race team. (back in the day) I believe it is 10%to 3500/15%35-4600/18%46-7500/15%75-13500. They can program it and get it to you in about 2 weeks. It starts off below street specs. but tops out above

[Shaka]

Zombie-
Thanks for the in-depth reply!  That gives me quite a few things to consider and work towards!  My silencer doesn't have bolts on the outlet end, just 3 where it attaches on the inlet side.  I don't really want to drill holes in it.  I think I will try the reeds and look into the cdi, tires as well!
Thanks again!

[wordslinger]

On my silencer there are three 8mm cap nuts facing the exhaust tip. When you remove them the cap, tip, and packing all come out together. I have a Kenda on the rear that is a squeeze, but it fits. I had to use a die grinder to remove a small bung on the bottom left engine case. My tire was getting a rub line after running at top end for a short while, also had to back the brake shoes WAY off to get the angle to re-install the tire set up. I also have the malossi cage, and tried the malossi reeds, I don't think they had a very good flex rate. I had a loopy sort of idle w/ a VERY snappy sound at top end, kinda like a lean mix sound. I bought a set of reeds made for a yamaha yz 80 which are thinner over all (also too long) but much more of an even bend. or flex to them. So I used the malossi as a template to trim the yama. thick ends, leaving the thin end untouched. I used a scribe to mark them, and did the trimming w/ a table sander. After getting the shape I used slow cure epoxy to re-seal the raw edges. Back to the tire a 130x70 would not fit but the shorter 60 does. In the front I have a Kenda 120x70 which is the same height, just a little narrower. If you have a welded silencer, I would drill a series of six, 3/8" holes just before the tip (outlet).  It Will improve the scavanging w/out that anoying two stroke dirt bike pop. Some things work, and some don't. I just like trying different stuff. Since the speedo only goes to 60, there is no way to send a pict., but trust me 65mph can be hit. It only will run there for about 200 yards, and will fall off to a steady 55-58. I am assuming the 2 ring piston swells enough to limit time at speed. It could be fixed w/ a 1 ring set up, but I would be buying them by the case. I forgot to mention the cdi i am running was custom programed by Suitai. They used the same ign. curve used by the kymco race team. (back in the day) I believe it is 10%to 3500/15%35-4600/18%46-7500/15%75-13500. They can program it and get it to you in about 2 weeks. It starts off below street specs. but tops out above

..dang................

[Shaka]

I haven't really done anything recently to the scoot, just riding it as is.  I keep getting this feeling that my CDI is behind my lack of top speed though!  Could my CDI be going out slowly?  I was getting about 50-52mph a couple weeks ago, now I'm lucky to get 50!  It has just been nagging me!  I feel like I have put a sh*t ton of money into this thing and haven't really gotten the results I was looking for!  I keep hearing of other people getting 60mph out of their 70cc kits, even with just upjetting the stock carb!  I have never had the a CDI go out on me before, so I don't really know the symptoms.  I was also thinking of getting some type of tachometer to check how fast the motor is actually spinning.  This might indicate the CDI gradually decreasing it's max, if they do that.  Anyone have any experience with bad CDI's or installing a tach?

[zombie]

Find the New width of your belt, and compare it to yours. That would be MY guess. The cdi will either die, or run till it gets hot, and shut down. I don't believe they will get corrupted programing. Also may be time for a set of rings. New rings, and cylinder combo's tend to wear in VERY quick.

[Shaka]

What do you mean by new width of the belt?  Check for wear?  I guess that rules out my cdi slowly going bad.  One thing I just remembered is that the base gasket between the crankcase and cylinder over hung to the inside a bit, slightly restricting the intake flow.  I'm gonna try and get some time this weekend to pull it off and do some trimming and inspect the rest.  Will post back w/ results.  Thanks!

[zombie]

The NEW belt should be approx. 17mm WIDE, as It wears it will get thinner. I mean across the top of the belt. The spec. for the new one should be no more than 2.5mm bigger than what yours is now. Say yours is 13.5 it would be time to replace it. (these numbers are just for example) Find the dimensions for the new one and 2.5mm is the rule. Believe it or not, when I mount intake, exhaust, or cyl. gaskets I found LIPSTICK on the mounting parts will transfer to the gasket, and show where you need to clean things up. Just try not to leave it in your tool box. (the buds tend to laugh) Some may even give you a little wink.

[Shaka]

Ok, I found the oil leaks, posted under oil pump thread.  I also pulled the cylinder and head off to inspect.  Everything inside looked alright.  There is a slight bit of scoring, mostly visually on the exhaust side, I couldn't feel it though!  Most of this was from when I first installed the big bore, I had the carb hooked up wrong and didn't get any oil for a little bit!  It still had at least 100 psi of compression at that time, I don't have a tester to check right now though.  The rings looked alright also.  I did trim the gasket around the intake ports while I was in there.  Also replaced the spark plug, and "faced" it.  I have done this on my car and it seemed to make a slight improvement, so I figured I try it on the scoot!  Basically just aligning the opening of the plug with the exhaust port.  I just fired it back up and it seems to be running well, possible improvement on throttle response!  I'm gonna go for a quick ride, then pull the cvt cover and check the belt width.  Will post back.

[zombie]

You may want to richen your idle jet 1/4-1/2 turn. the exhaust port is where the piston will burn on de-accel. It's ALWAYS better to be on the rich side of the tracks.

[Shaka]

How do you do that?  Do you open up the carb and physically turn the jet?  I thought you just replace the jets with a different size, or are you talking about the mix screw?