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 :lol: 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.

[yaegerb]

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.

Uh....hate to be the bear of bad news, but 94 octane with octane booster WON'T work...read below. You need to run 110 octane, I suggest VP. By running 94 with an octane booster, you may be taking it to 95. Basically what you are hearing is pre-detonation which in time will cause some major problems for you.

"About Octane Boosters - Octane booster additives cannot turn a gallon of average quality fuel into a gallon of racing quality fuel. These additives are essentially flame retardants. That is, they raise the octane rating of a fuel by making it resistant to burning ... not by improving the high temperature stability. The end result is that they reduce detonation risk by reducing power output. An octane booster can make 86 or 87 octane fuel into a 89-90 equivalent (from a detonation resistance standpoint). However it can only raise 91 octane by one octane point or less. Given all this, we strongly recommend against using any octane boosters in a high performance two-stroke."

I know it says two-stroke in the article, but its from Klemm-vintage and that's all he deals with. The same can be applied for your four-stroke motor. If you want to get educated on fuels I suggest reading the whole article, pasted below.

http://www.klemmvintage.com/gasolines.htm

[pipeliner1960]

i took the weisco piston and jug into a ktm performance shop and they miked the bore and checked ring gap for me. they looked up the number on top of the piston and it came up as a 65.5mm 12:1 compression piston. they told me to run hotter fuel and it helped. now all i need is a performance clutch kit. which one do you recomend and what kind of special tool do i need to change clutch plates.

[barnett468]

all i need is a performance clutch kit. which one do you recomend and what kind of special tool do i need to change clutch plates.


One option is barnett plates or oem plates but both with barnett racing springs. sand metal discs usiung wet/dry paper on granite countertop or marble floor or just by hand to remove glaze, measure thickness for proper spec.

just oem on the centrifugal clutches, replace hub if it is grooved or feels irregular from clutch shoes.

[pipeliner1960]

If it doesn't work then whys it not knocking anymore. it feels great. runs good. i ran it all day yesterday and its fine. i got a thing of booster that said it could treat 32 gallons into 108 octain. i basically poured the hole bottle in a 5 gallon gas can of 94 octain fuel.

[pipeliner1960]

Who figured it out for YOU :) ? i appreciate the help man. thank you

[yaegerb]

If it doesn't work then whys it not knocking anymore. it feels great. runs good. i ran it all day yesterday and its fine. i got a thing of booster that said it could treat 32 gallons into 108 octain. i basically poured the hole bottle in a 5 gallon gas can of 94 octain fuel.

Just stating the facts. First bike i built a 200s with a 12:1, high duration web cams cam and diluted 93 octane with 108 octane booster and it ran great for about 3 months until I blew a hole in the piston from predetonation.

Do what you want, its your money.

[barnett468]

i got a thing of booster that said it could treat 32 gallons into 108 octain. i basically poured the hole bottle in a 5 gallon gas can of 94 octain fuel. If it doesn't work then whys it not knocking anymore.

Because you put a bottle designed for 32 gallons in with only 5 gallons, lol.

Did you read the article he posted?

Enter "toluene gas", "methanol gas" in your search engine and check it out.