Chinese Scooter Club

thegraves · Sat Apr 26, 2008 9:36 pm 150cc Cylinder head removal

This is what worked for me, it will most likely work for you, but as always this is only a guide.

While doing this job, take care to notice things that are wrong. For instance, my carb only had one nut holding it on.

Put the bike on the centerstand and get ready for some work. If you aren't in the daylight, it is good to have a shop light handy. You will also need a ratchet with extensions, 8mm, 10mm and I think 13mm sockets, a long philips screwdriver, flathead screwdriver and some patience.

1. To start I took off the carpet B and body panels A, C and D. These are all just regular philips screwdriver items.

2. Open the seat and remove the cubby hole by removing the 4 nuts and the gas tank cover. then it just slides up and and off.

3. The Pain in my rear. The plastic cover around the motor blows IMO. It is 2 peices, top and bottom, and is held in by 5 or so philips screws. Locate and remove screws and pull these pieces out. (and I left them out) This is a good time to remove the spark plug wire as well.

4. Now to the exhaust. Start by removing the 2 bolts that connect the pipe to the head. These bolts are below the motor where the exhaust pipe reaches the head (just in case someone is really confused)

Then come out from under the bike and loosen both bolts that hold the exhaust pipe on. Once both are cracked loose then remove the rear bolt, then while holding the exhaust with one hand so as not to tweak it, remove the other bolt and set exhaust to the side.

5. Now you will be working on the top side of the motor. Looking in from where the seat was. You need to remove the air intake hose from the filter to the carb. Loosen the 2 hose clamps, one at the carb, and the other is under the filter. Then once those are loosened and the hose is worked free from the carb and filter box; carefully work this piece backwards and out. Be careful not to pull vacuum lines off, and replace them if you do. no biggie if you know where they go.

Next there are 2 nuts holding the carb on to the head. Remove these (long extensions are handy here). Working the carb out of the way is not too easy. The black frame rail gets in the way, but it will squeeze out with care. I left all the lines on the carb and simply set it to the side in the "engine bay" area.

6. Now we go to the front of the motor. Use some pliers (or just some strong fingers) and squeeze the retaining clip the holds the vacuum line on to the head. Remove the line from the head. There are 4 bolts holding the valve cover on. In my picture you can only see 2, but I promise there are 2 more in the area where the lines are going. After those are off, the valve cover will slide off. Set it down nearby with the engine side up (like a bowl).

Now you can see the cam, valve springs, timing chain etc...
I am not a OHV man as all my experience comes from pushrod v8's. But I imagine it is important to mark the timing chain and gear before removing it so it goes on EXACTLY the same way. So take a permanent marker and draw a line in 1, 2, 3 spots from the gear right up the chain. When assembling just make sure these line back up. If not your valve events won't happen at the proper "time".

Once the markings are done, you can loosen the chain. Back up on the top there is a chain tensioner (that I forgot to get a pic of, sorry) that is on the left side of the engine about 5-8 inches back from the head area. Use logic to know that is pushes down on the chain, so it must follow the chain for you to find it. There are 3 screws, 2 on the outside that hold the assembly to the motor, I just removed these 2 and pulled the whole tensioner out.
Now you can go back to the front and remove the 4 bolts and set the nuts and washers in the valve cover (bowl). Also, good to take note the it is marked I (for intake) and EX (for exhaust), so when assembling to don't put it in wrong. If you get confused, intake is on top and exhaust is on bottom. Work the camgear out from the chain with ease and set the cam assembly in the bowl.

PRESTO, the head slides right off.

gstraitman · Sun Apr 27, 2008 12:25 pm

well done thanks

Yellow Scooter · Sun Apr 27, 2008 2:05 pm

Nice post! :D
Boy, your carb was buried up something fierce! :shock:

Fox · Sun Apr 27, 2008 3:01 pm

Nice post! have a K+ gravy!

I have deduced from the pics that you are running your scoot w/out the fan shroud around the cylinder. Not wise IMHO. :|

thegraves · Sun Apr 27, 2008 4:07 pm

Fox wrote: Nice post! have a K+ gravy!

I have deduced from the pics that you are running your scoot w/out the fan shroud around the cylinder. Not wise IMHO. :|

Thanks.

Just to be sure, you are referring to the 2 piece black plastic part around the motor right? Being new to scooters, why is that not a good idea? I can't see what benefits it serves, but I am not the smartest guy in the world either.

Thanks
Justin

thegraves · Sun Apr 27, 2008 4:08 pm

Yellow Scooter wrote: Nice post! :D
Boy, your carb was buried up something fierce! :shock:

are they easier to get to on most other scooters :?:

Fox · Sun Apr 27, 2008 6:47 pm

thegraves wrote: Just to be sure, you are referring to the 2 pieces of black plastic around the motor right? Thanks Justin

Yes! They direct the air flow from the cooling fan around the cylinder to cool it. Without them, the motor is going to run hotter and will likely not last as long.

To each their own I guess? It's your scooter!

Scootin · Sun Apr 27, 2008 8:20 pm

Looks the same as my 150

pain in the ass to get the carb off. :x

thegraves · Sun Apr 27, 2008 9:31 pm

Fox wrote: thegraves wrote: Just to be sure, you are referring to the 2 pieces of black plastic around the motor right? Thanks Justin

Yes! They direct the air flow from the cooling fan around the cylinder to cool it. Without them, the motor is going to run hotter and will likely not last as long.

To each their own I guess? It's your scooter!

I haven't had time to get under it again, but what cooling fan are you talking about? I don't remember seeing a fan under there, maybe I am missing a part.

If there isn't a fan on my model, wouldn't that plastic contain the heat made by the engine, rather than let the air flow freely out, and let new air flow around? Also, please note I am only trying to understand not start an argument!! It helps me if someone can actually prove me wrong.

Thanks again for the help!!
Justin

Fox · Sun Apr 27, 2008 10:29 pm

thegraves wrote: what cooling fan are you talking about? I don't remember seeing a fan under there, maybe I am missing a part.

thegraves · Mon Apr 28, 2008 1:10 am

Fox wrote: thegraves wrote: what cooling fan are you talking about? I don't remember seeing a fan under there, maybe I am missing a part.

haha like a said earlier, I never said I was the smartest!! And now it is appropriate to say I am blind as well!!