150cc peace sport tpgs 804, piston By fox83 (Read 7,489 times)

[fox83]

hello all,
I'm a long time reader/tinkerer.first time poster. My question is I just can't seem to keep my bike running at a proper idle area or even around 2-2.5k rpms. I've changed out my carb,head.but still no luck.oh also adjust valves.what I was wondering is would a scored piston cause trouble starting and staying running?I've already ordered one to install because this scoot has a lot of miles anyway so I figured way not. But if this isn't the cause what else could I look at.

[czmdiver]

If you Scuffed/Seize a Piston you have will have compression Loss resulting in it being Very Difficult to Start.
If this happened you would have lost your clearance and it would rattle at idle. called piston slap.
It Would most Likely have Damaged your Cylinder also if you scuffed a piston.
In the installation of a new Piston and Ring you will need to a Cylinder Hone of 400-600- grit and know how to use it.
A Simple Compression check is cheaper and easier then doing the above.
Lets chill and systematically go thru what you got going on
How many mies on her?
What did you adjust the valves to? did you double check them?

[cyborg]

just a shot in the dark,,is the idle erratic? if so i suspect an air leak,,,i would check intake manifold to head bolts and carb clamps and all vacuum lines associated with the intake tract

[Alleyoop]

I think Cy is on it from the start, the motor has low compression and for it to keep running you need to have it idle quite a bit higher.
Alleyoop

[fox83]

I think your both correct. I was having both problems hard start and up n diwn idle. I adjusted valves to .004-.005. And just put new carb and new head and new batt. Tonight I'm adding a new piston and cylinder.also putting all new gaskets.she is a old girl. 2007 with 8k plus kms. Do you think the new cylinder and gaskets should fix my problems?

[kagetenshi]

I have heard that .005 is a bit much for a valve lash (even though it's a minuscule difference). But I'm no pro at this.

[fox83]

Also the guy I got the scoot from tore the baffles out of the muffler and it had no airbox. I have been shopping for a muffle but just not sure what to get. The new carb had a #35 and a #107 jets. My old carb had 35 and 115. Which set should be ran till I can get a uni air filter and muffler?. Sorry I know I'm going many directions at once.

[fox83]

Also my new cylinder kit came tonight. I don't need to do anything special to the jug correct? Just check the rings gap?

[czmdiver]

Aug 3, 2015 20:04:16 GMT -6 fox83 said:

I think your both correct. I was having both problems hard start and up n diwn idle. I adjusted valves to .004-.005. And just put new carb and new head and new batt. Tonight I'm adding a new piston and cylinder.also putting all new gaskets.she is a old girl. 2007 with 8k plus kms. Do you think the new cylinder and gaskets should fix my problems?

Make sure you Properly clean the new cylinder prior to assy.
There is only One way
Hot Soapy water (dish washing det). run a wash cloth thru the bore in the Hot soapy water.
Disperse water with WD-40 or similar.

[fox83]

Ok I got new piston in but when I put everything back together the exhaust rocker arm has zero play in it even when I back tappet all the way out. I'm sure that's not normal so maybe I put the cam in wrong.also I haven't put the exhaust pipe back on yet cuz its a pain and wanted to make sure she would run before I did all that...would that keep the engine from starting.? I got to get this squared away its my only way to work

[czmdiver]

Aug 4, 2015 16:41:55 GMT -6 fox83 said:

Ok I got new piston in but when I put everything back together the exhaust rocker arm has zero play in it even when I back tappet all the way out. I'm sure that's not normal so maybe I put the cam in wrong.also I haven't put the exhaust pipe back on yet cuz its a pain and wanted to make sure she would run before I did all that...would that keep the engine from starting.? I got to get this squared away its my only way to work

Check your Cam Timing, Something is wrong.
should be a Tutor in this engine section
Turn engine by Hand Slowly. dbbl. check your timing and your valve lash adj.
The Motor Will start just fine with No Exhaust. fire her up shut her down install exh.

[fox83]

I'm at a lose. I know I'm at tdc big holeon cam facing out small holes are level with head. I got it started. Was some white smoke. Shut it off and tried to restart and just turns and turns. I give it gas and the turnin picks up but no start....could it be the stupid spark plug. Omg imma feel like an idiot if it is.but rpms stay steady when I had it going but would die below 2k

[Alleyoop]

If all is good it should idle good around 1500-1800 rpms. Have you adjusted the carbs Fuel Mixutre?

Right now check for spark take the plug out or use a spare and stick it in the boot and hold it against the valve cover and crank it if it is sparking then it's not electrical.

I would check your timing align the cam with the two little holes even and then look at the timing mark on the flywheel and see where the POINTER is align with on the flywheel.

Also since you mentioned you had no valve gap even with the stud all the way out WHAT MOTOR DO YOU HAVE you may have the odd ball motor and would need to swap the ROCKERS from the old head onto the new head. The Rockers are bigger on the odd ball motor.
Alleyoop

[fox83]

Ok update..plug was blacker then tar. So I put a spare in and she started idles great eight above 2k. But I ran her up to about 6 and cut her off and plug is getting black again. I put a 115 jet in because that's what I had before but the carb came with a 107. Should I put that back in?

[fox83]

Pretty sure its just a 157qmj. The intake still had its normal wiggle.