this is my first time attempting something like the and im in the process of swapping over from the cylinder up onto another engine... how do i go about getting the cam and piston all timed up correctly... engine im swapping to has the cylinder and etc all off already.... thanks...any help appreciated

 

This comes up alot around here. [img]i/expressions/face-icon-small-happy.gif[/img]

Get the piston at the exact top using a screwdriver in the sparkplug hole. Then make the cam look like this while making sure the piston is still at the top. That's it. Can't be 180 degrees out of time. The sparkplug fires every TDC.



On the gasket surface at the top of this pic, don't put a lot of rtv and keep it away from the cam bearing area. If the rtv squeezes out on the cam bearing, it will wreck it. Try to get a very thin layer of rtv. It doesn't take much!



Also, there are 2 bolts that need to have rtv on their heads and washers or they will leak oil. If in doubt, put rtv on all of them.

 

thank you very much.... hopefully this helps me out... im going to begin this tonight after work.... ill probably be back on here with a few more questions.. again thank you

 

I'll be in n out this evening, so let me know if you need anything. [img]i/expressions/beer.gif[/img]

 

is this the same for a 125 lt motor, i will be doing it also.

 

I've never seen a 125 lt motor, so I can't say.

 

well i got the piston on last night.. after work tonight im going to try to put the rest together....time is tight this week.. a question about the two bolts you mentioned rtving.. im guessing you are talking about the two inner nuts that are near where the cam sits..had to take those two off to get the whole head off .. they each had a washer/gasket... when i pulled it apart there was no rtv just those washer things... or are you talking about bolts on the outside of engine confused..lol.. also can i clean off the everything with carb cleaner or brake cleaner? with everything i mean the piston top, valves, springs, head...etc.. wont harm anything will it

thanks for helping out a newbie to engine rebuilding....

 

Did you check the ring gaps? Should have been instructions with the piston and rings.

Get everything as shiney as you can get it.... Except the exhaust valve. Did you lap the valves? Did you replace any valves? The intake valve is pretty weak and if you didn't replace it, do so unless you're sure yours is good.

The 2 bolts are 2 of the many valve cover bolts. You're probably right about the 2 that have the washers. Usually the rubber part is torn, but if not, rtv it anyway. It will leak otherwise and a leak from the tippy top of the motor just makes the whole thing look messy. The factory service manual says to use rtv and not new washers. I usually coat the rim of the hole, then lay the washer on top, then coat the bolt head and tighten quickly before it has time to setup. Always tighten the bolts in the center first and work your way to the sides. 6.5-8 ft-lbs for the cover bolts. 15-18 ft-lbs for the head nuts. The smaller head nuts are the same as the cover bolts.

I use brake cleaner. Carb cleaner doesn't seem to do much and it leaves a residue. Brake cleaner leaves nothing behind.

Definitely check that intake valve though. Even if it delays reassembly for a week or two. If the hardness is worn off the valve seat, you'll never keep the lash in spec for any reasonable length of time. This will eventually result in hard cold starts and loss of power. Allowed to continue even further could result in the valve pulling itself right out of the head.

 

thanks for answering all my questions....the atv im taking everything off of ran nice.. was recently rebuilt by someone else... was just a big pile of **** other than the top engine... cylinder, piston, head, etc... im switching everything right over to mine... piston, rings, cylinder, head...etc.. do i still have to worry about ring gaps?? not sure what ring gap means actually...when cleaning everything up with brake cleaner, its alright to spray up the valves top and bottoms right

 

So, the rings are used? Not sure if the will seat when you try to use them again. I just don't know.... Never done it. But, the way I read about it is the rings rub against the cylinder wall and form a seal very quickly after you first start the engine. Once the rings are "seated", I don't know what will happen if you take everything apart and try to reseat the rings that no longer have sharp edges.

Ring-gap is the gap of the ring when inserted into the cylinder without the piston. Use a feeler gauge. Use the top of the piston to get the ring straight in the cylinder. I think its .004 for every inch of bore. So that would be .004 x 2.6 = .010. Too small and the gap closes under heat and expands into the cylinder and eventually seizes the piston. The top ring is most important.

You also have to pay attention to which side of the ring faces up. Usually the ring will have a marking on it. That side faces up. Also, you have to pay attention to the ring gap's orientation to each other. You don't want all the gaps to line up.

http://www.wiseco.com/PDFs/Manuals/RingEndGap.pdf