Engine Knocking!?!? Please help!

[300ridr]

Hey guys, my motor has been sitting in pieces for the past few months and i finally decided to try and get it fixed. it was knocking really loud, so i adjusted the valves, NOTHING! still knocking. i checked the oil, LOW!! very dumb on my part! i put oil in it, and the knock grew louder still! the performance started falling and the bike would cut out like mad. i adjusted the carb i dont know how many times and it still failed! i then tore it apart, thinking ROD BEARING! i tried jiggling it, NOTHING! it would go side to side but no actual movement up and down or any other sign of a bad bearing! would it be noticable? SMR, you did tell me a while ago it could have been piston slap. sounds logical. now im faced with a decision...buy a piston and hope it fixes it, take it to a shop and spend $500+ that i might not even need to spend, or buy an old parts bike with a good motor? i know this is a novel but i really need you guys' help and opinions on this one!

[dman66]

If you suspect piston slap on the valves or the head, you can tear down the top end again, leave the jug and piston on,bring up the piston to TOP DEAD CENTER, wipe off oil on top of piston,and put some modeling clay on the valve reliefs and maybe 2-3 spots on piston top. Reassemble the top end - in perfect timingspecs,rotate the engine a couple of times by hand, re break down the top end and anylize the clay thickness to see what clearances you have. It's alot of work, but your time is free compared to a shop charging you. Hope this may help - I learned this with car engines.

[300ridr]

Ill have to give that a shot! At this point, anything will help! Thanks dman!

[400thacker]

You need to check where the wrist pin goes through the piston and the bearings on the bottom end. If the valves were hitting you would more than likely have a bent valve and not enough compression to run.
It could also be extreme timing chain slap.

I would take the cylinder and the piston and check for a disfigured piston or cylinder. they can wear in a oval type form and cause loss in power and possible noise.

basically, it could be a thousand things and you need to start at the bottom and work your way up.

main bearings, rod bearings, wrist pin, and valves are the things I would think of to check first.

like mentioned above, your time is free and shops are not so it's worth a shot if your budbet is limited lilke most of us here. :D

[300ridr]

My timing chain felt really tight. If i tear apart my bottom end ill end up puttin everything in there, maybe even a crank. Would i be okay to buy a used crank setup from a reputable company? I found an 05 bottom end for $135, so maybe that would be a good choice, that is, if mine is all worn out! Either way, i intend on putting a wiseco and hotcam on it so maybe i should just get the bottom end and the piston and cam.

[400thacker]

I don't know what year your is but if the reputable company promises that it's good then thats what I would do.
fixing yours would be cheaper but ALOT more time consuming.
if you haven't done it before then get a manual and TAKE YOUR TIME if you plan on splitting the cases.

[400thacker]

did you check your rockers and cam and cam bearings for excessive wear?

IMO it's more than likely in the top end

[300ridr]

i looked at them but i couldnt tell you if theyre worn. if i decide to keep mine, ill just buy that bottom end, put a new piston kit, and install new cam, bearings, and chain. but now im starting to look at 400ex's. i can spend 5 or 6 hundred and fix mine, or spend 1300 on a decent 400 then sell mine as is

[dman66]

It all depends on what you want to do, and your mechanical ability. I have a 87 250x, and love this quad for trail riding, but would like a little more speed, so a 400ex would be the next step. I had a chance to ride my neighbors Kawasaki Prarie 360 4x4, and that machine pretty much goes through any thing you through at it. Now I'm thinking of buying one of those. The guy who owns the 360, often says he misses the 07 trx250ex he used to have. It's up to you.

[smr]

Originally posted by 300ridr
i looked at them but i couldnt tell you if theyre worn. if i decide to keep mine, ill just buy that bottom end, put a new piston kit, and install new cam, bearings, and chain. but now im starting to look at 400ex's. i can spend 5 or 6 hundred and fix mine, or spend 1300 on a decent 400 then sell mine as is \\

look at the rocker arm wear it rides on the cam. If it's worn it will be shiny and real flat. (should be concave to fit on cam lobe)

[300ridr]

rocker arms were shiny, and were not flat but rounded a little. the rocker arms' dont look anything alike? is that how theyre supposed to be? ill try to post pics

[300ridr]

this is one arm

[300ridr]

and here's the other. sorry they're a little blurry, but it gives you an idea. is this how they're supposed to look?

[400thacker]

they should all look about the same. I can't tell anything from the pics.
they should all be slightly rounded and if they are not then thats your problem or atleast one of them.

[300ridr]

Ya sorry for the pics. One is like rounded outward and the other inward with almost a chunk missing! Ill see what i can do on paint to show you guys what they look like

[300ridr]

this is what the faces that touch the cam lobes look like. one is perfectly contoured and the other has like two different contours. not sure if this helps you guys any but thats about all i got:(

[sm00th026]

By your pic. if that's the face side that go's on the cam yes you need a new rocker arm and you may want to check your cam lobe for wear too

[300ridr]

Ya the face side goes on the cam lobes. Maybe a worn csm is sn excuse for a hotcam:) my dad is takin the motor to a shop just to see what the mechanic thinks

[300ridr]

Thanks to you guys ive diagnosed my problems! I ordered parts yesterday. Dad took it to the shop, they said rocker was trash, piston needed replaced, intake valves were cuped, cam worn, and i am getting cam chain and slides and a fresh hone! Going with a std bore wiseco and hotcam, should that increase anything?

[300ridr]

Thanks to you guys my motor is up and running like a champ. Started it up about a half hour ago and she ran like a champ! Cant wait till its broke in:D