My new true blue KPX

[JerryHawk250]

Originally Posted by 4T_Goblin

I found a couple exhaust systems on Amazon but I only want the middle link pipe with the matching bend. The Amazon pipes come in 3 sections; header, middle, and muffler. Our KPX is a 2 piece exhaust

It's $100 for the system and I'm broke at the moment. Lol

I'm pretty sure this header pipe would have the right bends but you will have to have an O2 sensor bung welded on. https://www.orionpowersports.com/sta...-249cc-engine/

[4T_Goblin]

I would leave the stock header on and just use the middle pipe and a can. I already have a spare can, just need the middle section but it's hard to give up a bill for a middle section

[JerryHawk250]

Originally Posted by 4T_Goblin

I would leave the stock header on and just use the middle pipe and a can. I already have a spare can, just need the middle section but it's hard to give up a bill for a middle section

That would be the route I would take too.

[TominMO]

Originally Posted by 4T_Goblin

I found a couple exhaust systems on Amazon but I only want the middle link pipe with the matching bend. The Amazon pipes come in 3 sections; header, middle, and muffler. Our KPX is a 2 piece exhaust

It's $100 for the system and I'm broke at the moment. Lol

Links?

This one? https://www.amazon.com/Motorcycle-Sl...%2C117&sr=8-27

[4T_Goblin]

This is the one I would go with. I came across separate middle pipe pieces for $65 but they didn't have the right look about them, not like this middle piece in this link.

https://www.amazon.com/gp/aw/d/B09SH...RCU1HFV1&psc=1

[TominMO]

Started the process of consolidating all useful info into post #1.

[TominMO]

Weather forecast was partly to mostly cloudy with rain coming at 2pm. Went out to work on this at 8am. Figured I'd go for a little ride when done.

So as the rain thundered down on my water-resistant 1926 garage, I did the sprocket measurements and a little research. Used a cheap $20 digital caliper from Lowes, set to mm. Stock sprockets are 13 and 42 BTW.

Rear sprocket
Long story short, the JTR 279 is a perfect match. Same center bore, same bolt hole circle, two sets of bolt holes for different size bolts. The KPX uses the larger holes. The bolts are held on with a dab of what looks like red Loctite, and it takes a 16mm or 5/8 inch socket. I reinstalled with blue Loctite.
Amazon has a good selection of JTR279 sizes: https://www.amazon.com/JT-Sprockets-...13&sr=8-1&th=1

Front sprocket
The closest match I could find was the JTF270, as Jerry had guessed. However I can't recommend it until someone actually buys it and tries to install it.
Here are the specs on Amazon vs what I measured. Everything in mm.
The second image on this Amazon page is a diagram, to show you what I measured: https://www.amazon.com/JT-Sprockets-...ps%2C73&sr=8-1
Amazon........the KPX...........Dimension measured
18/20............16.85/19.83......mounting splines
34..................34....................bolt hole circle (two bolts)
4....................4.15ish............spline width (at bottom of spline)
8.5.................7.4...................overall thickness, including built-in "spacer" at rear
The stock sprocket is 13, and it is questionable whether a 14 could be used. The clearance to the swingarm pivot looks a little dodgy to go up a size. Front of sprocket looks like it would work for a 14, but close. I may buy a JTR270.14 just to check fit and clearance.

[TominMO]

Sprocket ratios

.........12........13........14
30.....2.50.....2.31.....2.14
32.....2.67.....2.46.....2.29
33.....2.75.....2.54.....2.36
35.....2.92.....2.69.....2.50
38.....3.17.....2.92.....2.71
39.....3.25.....3.00.....2.79
40.....3.33.....3.08.....2.86
42.....3.50.....3.23.....3.00 stock

[TominMO]

KPX valve adjustment. I am assuming you have done valve adjustments on bikes before. If not, go read up on that. This post is mainly about procedures for this engine.

Link to Jerry's YT vid on this:

Stuff you have to take off first--about ten minutes
Seat
Both tank plastics, and both middle plastics
Two bolts at rear of tank, to remove tank; disconnect gauge sending unit and fuel pump connection; remove tank
(Optional for more room) Horn, and connector between left and right tank plastics
Clip zip tie to move wires, and replace later with something removable like twist tie etc

Tools you really should have for this job
10mm and 8mm offset wrenches. I got a set similar to these at Harbor Freight for $21.
https://www.amazon.com/WORKPRO-Offse...NsaWNrPXRydWU=
OR, get a specific motorcycle valve adjustment set like this:
https://www.amazon.com/Baosity-Unive...ps%2C87&sr=8-5
A short breaker bar you can use with your 14mm socket, to turn the crank. NOT a ratchet.
I use a head lamp for lighting. Very helpful.

So you have taken off all the items listed above.
1. Next is the valve covers, 8mm, pretty easy. The offset 8mm comes in handy for the lower intake valve cover, but not strictly necessary.
2. Pull the spark plug so you don't have to deal with compression as you turn the crank. Remove the large chrome crank bolt cover on the side of the left crankcase cover, and the small round chrome inspection cover on top of the left crankcase cover.
3. Use the breaker bar with your socket on the crank. If you use a normal ratchet, you will not be able to control the crank when it hits a stage in its rotation where it just spins forward on its own. And of course that is the region that has the TDC you want, not the other one that's easy to get to.
4. Once you have it at the proper TDC, you can check the clearances. The front (exhaust) is a bit tricky. I removed the .10mm gauge from its set and used it alone. Seemed a little easier. Maybe try holding it with a needle-nose pliers to get more length.
5. If it needs adjustment, use the 10mm offset wrench to get down into the head. Offset wrenches tend to be longer than normal, so that is helpful too. I use a long needle-nose pliers to hold the square part at the top while I tighten the nut.

[JerryHawk250]

Thanks for the Valve adjustment warning. lol I was going to do that when I did my oil change. Sounds like it will be fun. I'll probably do a video.

[TominMO]

Originally Posted by JerryHawk250

Thanks for the Valve adjustment warning. lol I was going to do that when I did my oil change. Sounds like it will be fun. I'll probably do a video.

Great! If you can add any insights on how to deal with the intake valve, that would be nice too. You may have to slide your oil cooler down for access to the exhaust valve.

[buzz]

Nice Bike, like the blue. Could be next bike, waiting a little longer. think i can mine pretty easy. Keep us posted please.

[TominMO]

I gave some thought to removing the throttle assembly from the throttle body to get more access to the intake valve, but was not sure if that would then cause some other problem with reassembly, so held off.

[TominMO]

Ordered the 14T JTF270 sprocket ($24), some spare master links, a top box and a 10-pack of Chinese 112 oil filters with O-rings ($21). One K&N 112 filter is $9.

There were several choices on Amazon for the sprocket, and I picked the most expensive. One other one had a generic picture, and one had a photo but it didn't look like the one I ordered, which matches the one on the bike as far as how the mounting splines look. The 13T sprocket also has a generic picture, but at least they seem to be available.

[Boatguy]

Originally Posted by TominMO

Weather forecast was partly to mostly cloudy with rain coming at 2pm. Went out to work on this at 8am. Figured I'd go for a little ride when done.

So as the rain thundered down

I knew it!!! Never getting one. Ha ha ha.

The 2022 Lifan Rainmaker