Blue Kymco ZX rebuild

[oldgeek]

I mentioned elsewhere that I took the Blue Kymco to the shop to find and fix a fuel leak. I got it apart and cleaned up for the most part, but then I started looking closer at it. The more I looked the more I found. I am pretty sure the fuel leak was caused by a worn float valve, I never seen one wore out like this one. I slapped a new one in and cleaned and reassembled the carb, fuel leak is hopefully fixed.


I decided to put the scoot on the lift and pull the CVT cover off, to clean it and inspect the CVT. Found the rollers well flatspotted, the variator guides worn out and the ramp plate cut into the rails on the variator so its ruined. The belt, clutch and rear pulley look pretty good. Then I noticed a bunch of gear oil and dirt on the bottom of the gear cover. I looked pretty closely and thought it was coming from the weep hole for the axle, great. I drained the very dark gear oil preparing to split the gear box. The exhaust has to come off to get the wheel off so I pulled it off and noticed it was cracked. No wonder this exhaust seemed so loud Lol My hearing it s*** anyway.

After getting the wheel off I split the gearbox and was surprised to find the gear oil was not coming from the weep hole, it was coming from the gearbox flange which did not have a gasket. I guess a PO split the gearbox at some point and just used some sealant to slap it back together. I am kinda pissed because I could have lived with that leak.

Next I pulled the spark plug out and it looks horrible. I think a year or so ago I accidentally dumped some gas in the gas tank that I had used to clean some gear oil out of a gearbox. I caught it pretty quick but I did not drain the gas and refill the tank, the scoot smoked kinda bad for that tank of gas LOL!

Now I am thinking about pulling the head to see how bad that is.

[aeroxbud]

You really have opened Pandora’s box!😲

[oldgeek]

May 23, 2023 5:18:15 GMT -5 aeroxbud said:

You really have opened Pandora’s box!😲

Yeah, from the info I can find its been 5 years since I did anything to this scoot other than a CDI swap and a front wheel swap due to a bad valve stem. I guess I had it coming to me!
Funny thing is that the scoot was still running and driving great!

[oldgeek]

Spent most of the day cleaning 2T grime off of the gearbox half and motor. At least all of the bearings and seals are in great condition. Had to cut my own gasket out for the gearbox, got everything clean inside and sealed it up. Added gear oil, here is my proof!

Decided to pull the head since the spark plug looked so bad. There was a bunch of thick carbon on the piston dome but hardly any on the head. I did not break the seal at the base gasket and was just going to clean the piston and head up and slap it back together but after cleaning the piston dome I could tell it was slightly sunk in. So I went ahead and pulled the cylinder to get a better look at it and the piston.





I assume the two soft siezes a month ago caused it to 4 corner the piston. I never noticed any power loss from it. I could just give the cylinder a quick hone and slap it all back together but what fun would that be? I have been spying the Athena kit and thinking maybe Treatland would have a memorial day sale, but then I saw a dusty box on a shelf and realized I have a near new Polini Corsa kit. It is the one I put about 3 miles on the first time I forgot to add gear oil to a gearbox. I pulled it off of the ruined motor, boxed it up and forgot about it till today. So I am pretty sure it will be going on this scoot again, coupled with a PG short exhaust. Ought to be good for 78 MPH

[aeroxbud]

That will be a nice combination of parts.
It's a good job you took the head off.

[oldgeek]

Spent most of the day working on the scoot. I am really surprised how much I got done considering how slow I usually work. It might have something to do with me not having a running scoot until I get this one back on the road. LOl I cleaned up the used Corsa kit I found yesterday from its previous install, made some squish checks and sealed it up. I put the rear wheel back on and checked fitment of the PG short exhaust. The pipe matched up well so I put the right hand side motor shroud on and bolted the pipe up. Installed a newish spark plug and the temp sensor, then started bolting up the gas tank and assorted brackets for the body panels.
I was trying to order a new variator from my normal place but they are out of stock, however while searching my shop for the missing piston rings for another motor I am working on I came across a used variator that will do just fine on this scoot for a while. To my surprise I actually had new ramp plate guides and even the correct weight rollers on hand so I cleaned up the CVT cover and put some grease in the places It needs it. The clutch and rear pulley looked pretty good so I packed some grease in the needle bearing and got the CVT back together.

A year or so back the valve stem on the front wheel cracked so I just swapped an entire wheel with a Duro tire on it for a quick fix. So today I broke down and put a new valve stem in the original wheel with the Power Pure SC tire on it so I can swap it back on this scoot.

The only major thing left to do is the intake, carb and airbox. I haven't decided which parts to use for that portion. I am leaning on using a Doppler aftermarket intake that is similar to the stock intake, a modified stock reed block, PHBG 19 or 21 carb and of course a stock airbox modified to work with the PHBG.
I could use one of the CT style intakes that allows you to use one of the bigger reed blocks but I think I am just going to see how the modified stock reed block works first.

[oldgeek]

Started off the day with swapping out the front wheel, that went easy enough. Spent the next 4 hours trying to decide which reed block and intake combination to use. So many issues with both setups, but in the end I settled on the CT style intake and reed block. I ended up making an adaptor on the lathe that allows me to mate a PHBG carb to a 28mm intake meant for the PWK carb. I was even able to figure out a way to keep the stock airbox using the CT intake setup, which is something I have never been able to figure out in the past. All that is left to do is seal the intake stuff up, make some tabs to relocate the airbox a bit and put the body panels back on.

[aeroxbud]

Very tidy install.
Having a lathe is such a help with stuff like this.

[oldgeek]

I finished up the odds and ends today, it really came together well. I was going to use a 21mm PHBG carb but to make things simple I just went with the 19 mm that was working perfectly with the other kit. This is absolutely the first startup of this scoot.

[oldgeek]

I know somebody here knows about the PG short pipe. I haven't used the pipe much but I recently read somewhere that there is an insert at the Stinger that can be taken out. Under what conditions should you remove it? it's barely tack welded in there and it wouldn't be hard to put back in if necessary. TIA

[aeroxbud]

That pipe has a nice tone to it. I'm liking the street style pipes more and more.

[oldgeek]

I ended up back over at the shop for a moment this evening, Its been raining off and on here for two days. There was a momentary break in the rain so I took the scoot out for a quick ride up and down a side road in the industrial park. Some CVT tuning is most definitely needed, this motor/pipe combo is dead down low compared to the other cylinder. When it does get on the pipe the hit is rather abrupt. I did not hold it WOT very long, I just wanted to see if temps were safe and they seemed to be ok.

[oldgeek]

My hopes of getting this CVT and carb tuned up fairly easily today were were crushed. This motor and pipe combination is way different than what I had on this scooter. I had the clutch and torque driver apart several times to service it and make changes I have the stiffest Springs in the Dr pulley clutch and it still seems to engage a little too early. I lightened the weights in the variator to 28 G total weight and I still need to go lighter. I tried several different needles and slide combinations in the carb to no end. The pipe has nothing to offer at all below 6500 RPM's, it's horrible. If you can get on the pipe it hits really well and pulls hard. I finally got frustrated and gave up. When I got home I started searching some old threads about the PG short and sure enough what I'm describing is just the characteristics of that pipe. I am pretty sure lighter weights will make the launch bearable so I can get on with and finish tuning this setup but I'm afraid I'll end up with a light switch kind of ride it's either on or off and that is not really fun IMO if I really end up not liking it I can always throw the TK pipe on or the V8 and be happy.

[190mech]

49ccscoot.proboards.com/thread/29366/yamaha-vertical-yasuni-honda-conversion

[oldgeek]

May 28, 2023 22:42:58 GMT -5 190mech said:

49ccscoot.proboards.com/thread/29366/yamaha-vertical-yasuni-honda-conversion

Oh, now I remember! Amazing how much of this stuff I forgot about. Thanks for reminding me

Spent a while on tuning the CVT and carb today, went with some rollers with a total weight of 25.5g and moved up to a 99 MJ.
I still almost have to flinstone the launch but at 15mph it comes to life and goes! I felt confident enough to take a longer ride so I went over to Ocean Blvd for a brief ride. There and back it screams reading 62mph on the scoot O meter (actual is probably like 58). I saw 340 on the temp gauge at the end of a mile long WOT so temps are in check. However stoplights were hell and cruising on the Blvd. was tough. I dont mind being loud at all, but being loud and slow aint cool! Its a good thing I did not have to drag any rental scoots off the line cause they would have embarrassed me.

I think I will be swapping the Polini variator out and shimming the drive boss a bit to try and fix the launch. The clutch is not helping either but I dont have anything else on hand that is lighter that I can find in this disaster shop at the moment.