help plz with 4stroke info

[Divy]

ok well ive had enough of my pitpro 138cc ive tried to adjust carby mixtures, needle, irk timming an no luck so i am going to pull down the engine an check out the internals
but like i said before im a 2stroke boy i can tear apart an rebuild 2strokes easy but ive never owned 4strokes before so never got to play around an learn how to build them

so first of all i will be taking off the barrel an head to check the valves an so on so can any one that knows how to tear down a 4stroke please give me some pointers on what to do eg: how to take off cam wheel an chain what do i need to mark so it goes back in the right timming an so on

thanks in advance steven aka divy aka Mr.NOIDEAOF4BANGERS

p.s i know some will say dont try if you dont know but if i dont how will i learn an plus the up side is if i farrk it up i can just buy a 140cc

 

[BLOFLY]

im with divy on this one .... HELP ....

 

[Flarry]

What the hell is wrong with it??

 

[Hillz]

yeah did it start & run b4 you put the IRK on?

does it start with th IRK?

if so what problem? backfires etc.....

 

[Cactus Jack]

ok well ive had enough of my pitpro 138cc ive tried to adjust carby mixtures, needle, irk timming an no luck so i am going to pull down the engine an check out the internals
but like i said before im a 2stroke boy i can tear apart an rebuild 2strokes easy but ive never owned 4strokes before so never got to play around an learn how to build them

so first of all i will be taking off the barrel an head to check the valves an so on so can any one that knows how to tear down a 4stroke please give me some pointers on what to do eg: how to take off cam wheel an chain what do i need to mark so it goes back in the right timming an so on

thanks in advance steven aka divy aka Mr.NOIDEAOF4BANGERS

p.s i know some will say dont try if you dont know but if i dont how will i learn an plus the up side is if i farrk it up i can just buy a 140cc

I'll help ya' dude ! NO need to stuff a motor up learning ! They're 2 year old kid stuff to work on ! But first - what are the symptoms you are experiencing ?

All that you really need to learn and remember is that the cam MUST have the rockers on the base circle (heel) with the specified valve clearances set , when the piston is at top dead centre on the power stroke , which means that the "T" mark on the flywheel rotor will be aligned with the timing mark on the engine cases . The cam sprocket has an "O" mark which must be at the 12 O'clock point (90 degrees to the head gasket surface , facing straight up to the centre of the head) with the timing marks aligned when you put the cam chain back on . When you take the timing sprocket off the cam - you ALWAYS put it back on with the "O" mark pointing away in the opposite direction to the cam lobes . "O" MARK UP AT 12 O'CLOCK , CAM LOBES POINTING DOWN , ROCKER CLEARANCE SET , FLYWHEEL TIMING "T" MARK ALIGNED WITH PISTON AT TDC ! SIMPLE !

You need to maintain rocker clearances at all times ! Failure to keep them adjusted will result in loss of compression , burnt valves , burnt rocker arm wear pads and cam lobes ! The clearance allows the valves to close and dissipate their heat build up thru the valve seats - it also allows oil to get between the rocker pads and cam lobes . If the rockers ride the lobes continually , they act like window wipers , squeegying out the oil .

The bottom right hand cylinder stud goes thru the oil suppy gallery to the head , so it HAS to have o-rings at the gasket faces and has the copper washer beneath the nut to seal in the oil pressure ! The copper washer expands with engine temperature to maintain tension on the stud and keep the gallery sealed . The head bolts need to be tensioned in stages in a cross hatch pattern - just like any head on any other engine .

 

[BLOFLY]

What the hell is wrong with it??

my bike starts fine idle`s beautifully sounds tough but i cant crack the throttle open ,evrytime i do it splutters and i gotta rev n rev to get it to rev and then it still wont rev out i put all stock stuff back in but no difference maybe i should try the carby off of the mrs bike ive ripped carby appart twice now to make sure its ok. and it seems to be fine ive put irk and oil sling back in ive moved e clip up i think it made it worse...

 

[Flarry]

Well I was asking divy actually but ok...

 

[Hillz]

Well I was asking divy actually but ok...

LOLersk8s......

 

[THUMPY125]

Divy i wouldn't pull it apart i would be taking it into a motorbike shop and having a talk about the problem and showing them whats wrong ie, start it up. They could then point you in the right direction or if the price is right do it for you.

 

[Divy]

the problem is its hard to start i have to give it a few kicks with the throttle open almost full an when it starts it sounds very very ruff an i can hear a knocking sound from the head area it takes the bike about 5-8 minutes to get warmed up an then it will idle but it will only idle with the air screw screwed in alot so the idle revs are really high when its warm an i ride it there is no power its flat threw all the gears an in 3rd an 4th it doent want to make power it stays at one speed an rpm an no mater how i accelerate

 

[Flarry]

This happened to my old bike it might just be a warn engine but I think its the carbys clogged up, anyway im buying a new engine but keepin the carby so we'll see...

 

[Divy]

thanks cactus for the info it will help alot ill let ya know if i need more help when i tear it down

 

[Cactus Jack]

the problem is its hard to start i have to give it a few kicks with the throttle open almost full an when it starts it sounds very very ruff an i can hear a knocking sound from the head area it takes the bike about 5-8 minutes to get warmed up an then it will idle but it will only idle with the air screw screwed in alot so the idle revs are really high when its warm an i ride it there is no power its flat threw all the gears an in 3rd an 4th it doent want to make power it stays at one speed an rpm an no mater how i accelerate

Check your valve clearances ! If the valves aren't seating slightly it'll be really hard to start and run better as it warms up and also lack power ! Also too rich a mixture will make the engine run flat and not rev out ! If you've over revved it in neutral with the inner rotor , it's possible that you've bent a valve ! The valve head cocks at an angle in the seat and the added rocker clearance makes the knocking noise . I hope it's just something minor tho' !

 

[Divy]

judging by what you said i reckon im gonna see a bent valve
ill hopefully check it all out tomorrow an let you know what i find

if it is a bent valve does any one know who sells valves??

oh thanks again cactus jack

 

[BLOFLY]

if i cant find a part i look on ebay for someone that sells the same motor and ask them for a buy it now price for parts i havent been knocked back yet, hope thats a help

 

[Divy]

here is a pic of the head to me every thing looks okay what do you think??
could i tell if a vavle is bent by the way it sits or do i have to take it out an see

 

[Divy]

also there was quite abit of carbon build up around the vavles an piston but i dont know if this is normal for a 4stroke

 

[Hillz]

that ain't shit all carbon build up!

check to see if the is any marks on valves from hitting the piston..... but they look ok....

 

[Cactus Jack]

here is a pic of the head to me every thing looks okay what do you think??
could i tell if a vavle is bent by the way it sits or do i have to take it out an see

It's hard to tell in the pics but the exhaust valve looks like it's been getting too hot and that can be caused by it not seating properly . If the inlet valve was being held off the seat you'd have had popping and backfiring thru the carb and the inlet port would have carbon in it - the inlet port should ALWAYS look clean and carbon free !

Make sure the rockers are on the base circle of the cam with the lobes facing down . You should feel slight play in both of them ! If not - loosen the adjusting nuts and back the adjusters off until you CAN feel play - they should have 2 to 3 thousandths of an inch play ! Then tip the head up and pour some fuel in each port - one at a time to see if anything leaks out around the valve seats into the combustion chamber ! If nothing seeps out then your valves and seats are sealing OK ! You'll be able to see by looking at the valve pockets in the piston if the valves have been floating and hitting it !

The symptoms you described were similar to what would happen if you had low compression . Unleaded fuel can cause valve wear and quick loss of clearance so you should check your valve adjustment regularly and correct it if necessary - it only takes a few minutes ! Use valve saver in your fuel !

 

[foolsp33d]

Use valve saver in your fuel !

Interesting! iv been wondering about this... asked a while ago in the fuel thread, about adding moreys etc.. will start to do so if its worth doing! Am running a moreys bottle in the zuki.. wonder if a similar setup can be done to the pitty... hmmm..