weird nocking gets louder when warmed up

[pipeliner1960]

i have a 1981 atc 200. starts up one pull idles on its own. when you ride it around in it sounds like the timing chain is slapping or something is knocking. when it gets warmed up it gets worse. it does have a weisco piston and it blew a head gasket when i first got it. i dont know if the knocking would of had a reason for the blown head gasket. i pulled the flywheel out and tightened the timing chain.(i did it that way because i wasnt trusting the auto adjuster). it wasnt loose but i tightened it a little more to see if it was the problem. but it still knocks so what else could this be?

[shortline10]

A knock is usually either piston slap or lower rod bearing .

[neverdone]

personal experience if it gets worse as it gets warm it is a rod knock. Timing chains dont loosen up much when it warms up. Oil gets thinner though and will make your knock sound worse because it is not holding as much gap in the bearing.

[barnett468]

Hello


In addition to the items mentioned it is remotely possible that the piston is hitting the head or spark plug.

Did the top of the piston look flat to you or was there a dome on it?

Remove plug and see it it looks like there are signs of contact on the plug.

[fastatc70]

Where does the knock sound come from? Top end head,cylinder or is it from the bottom end crank area.

I don't have any experience with this trike so I am just trying to help. Dose this motor have a counter balancer?

I picked up a 250r for short money because it had a knock and it was the counter balancer. Bottom end knock.

[kb0nly]

Another possibility since you had it apart for a new piston and gasket is check your valve adjustments when cold. As it warms up you could be getting excess valvetrain noise if not set correctly. That is if the sound is coming from the top end.

[pipeliner1960]

The piston is domed ive set the valve lash at .005 on exhaust and intake. If it was piston slap wouldnt it smoke. I have a standard size jug and piston. Im thinking about swaping out jug and piston to see if its a jug problem. I started the bike and took the pull start off to see if the flywheel has a wobble but it looked good. I also remember when i had the top end off the rod didnt have as much play as my other 86 200s. If the jug and piston doesnt solve the knock i know it in the bottom end and ill just swap it out.

[pipeliner1960]

there were no signs when i checked the head when i took it off. the piston is domed and is a weisco. the valves didnt look like there were any spots or imperfections and the piston looked good. i did notice the piston did have a little heat tint on the top porton.(i dont know if thats normal). the spark plug didnt look like it was hit neather.

[manbearpig]

The piston is domed ive set the valve lash at .005 on exhaust and intake. If it was piston slap wouldnt it smoke. I have a standard size jug and piston. Im thinking about swaping out jug and piston to see if its a jug problem.

arent there issues with using forged (wiseco) pistons in a bore that was cut for a cast (OEM honda) piston? dont forged pistons react differently than cast when warming up?

[shortline10]

Might be as simple a spark knock meaning your in need of higher octane fuel . Which wiseco did you go with ? if its their 12:1 piston that's the issue if its the 10.25:1 piston , just high test pump gas if ok .

[kb0nly]

Ah yes good catch Shortline... If he has a domed piston he definitely increased his compression and could be detonation knocking.

[pipeliner1960]

well i swaped bottom ends with a 84 200s bottom end and its still knocking so. its got to be piston slap or something. the jug did look like there were some wear areas in the jug. does this mean the jug is too big for the piston and rings or is it too small? i always run 94 octane. anyway i think im swaping the piston and jug out with the standard one i have. im going to get the numbers on the top of the weisco and put em on here.

[barnett468]

Hello


Wow that was a lot of work, unfortunately the following needs to be measured which could have been done while you had it apart:

cylinder to piston clearance.

piston diameter front to back 1/2" up from bottom of skirt.

cylinder bore top and bottom in 2 different positions 90 degrees from each other. This measures out of round and taper. More than around .0015" in taper or out of round should be rebored. If you have .0015" taper AND .0015" out of round that equals .003" which equals unhappy IMO.

[pipeliner1960]

i figured it out. it was a 12:1 compression piston. and i just run 94 octain with a lil octain booster. it doesnt ping anymore and runs good. has got alot of power. too much actually because it slips the breand new oem clutches.

[shortline10]

Who figured it out for YOU ?

i figured it out. it was a 12:1 compression piston. and i just run 94 octain with a lil octain booster. it doesnt ping anymore and runs good. has got alot of power. too much actually because it slips the breand new oem clutches.