Bottom end noise...big end bearing?

[2smoke]

Finally have this thing running good after jetting... but!

If I am in too high of a gear and give it plenty of throttle and put a good load on it, I get a rattling/clunking sound until I let off the throttle- I can immediately hammer the gas again and it won't do it again unless I start the process over.

I pulled off the plastic cover on the chain side of the engine and get this noise when I turn the flywheel (not sure that's what that device is) - here is video-

I thik maybe it's the big end bearing? Or what am I hearing?

 

[Fast6hand]

May want to check compression. I know I can't turn my motor over that easy with my hand.

 

[2smoke]

On another note- I pulled the head off earlier thinking it was piston slap, but it's good and tight. And relatively clean even.

Also drained and refilled the gear oil, didn't help.

Again, not a constant noise, just when it's in the wrong gear and gets bogged.

 

[98blaster]

You sure its not detonating, bogging make cylinder temps rise, an if not jetted right can cause detonation, especially on modded engines, or advanced ignition timing

 

[2smoke]

I wondered about that, actually. I've got an FMF Fatty Gold Series mated to a Turbine Core 2 silencer. K&N filter, stock airbox w/ snorkel removed. 280 main jet, needle clip is on 3rd spot. I turned the air screw counter clockwise and it started running wayyy better after making the above changes (jet, needle, snorkel) - do I need to go richer yet?

 

[Blaaster]

The noise sounds a little suspect to me, possibly a big end bearing, even a wrist pin problem.

I would be taking the cylinder off and checking that play before I started the engine again!

On jetting, you need to set the float level, warm up the engine and set the idle as per specs and then perform a plug chop to confirm jetting.

 

[Larry's Shee]

May want to check compression. I know I can't turn my motor over that easy with my hand.

Maybe he had already taken head off?

If the noise seems more in the center, it might be the rod. If it's more towards clutch side, check the counter balancer drive gear. Things get ugly when that breaks

Because of the amount of rotation of the f-wheel between "clunks" (kind of like slop in gears)
it's your choice as to pull jug or clutch cover if you can't isolate it more

 

[Larry's Shee]

Crank the piston to BDC, and hold it with a hammer handle, then rock flywheel back and forth, should be able to feel it if the rod is bad.

Obviously no damage to cylinder from a puked brg?

 

[Fast6hand]

Maybe he had already taken head off?

If the noise seems more in the center, it might be the rod. If it's more towards clutch side, check the counter balancer drive gear. Things get ugly when that breaks

Because of the amount of rotation of the f-wheel between "clunks" (kind of like slop in gears)
it's your choice as to pull jug or clutch cover if you can't isolate it more

Agree. Didn't even thinking that.

 

[2smoke]

No damage to the cylinder - both the bore and the top of the piston were beautiful. No scores, no excessive build up, nothing. I did a plug chop over the weekend and I'm fairly happy with it, I think I may still go up a size or two to be safe.

Am I going to have to pull the entire clutch assembly to check the counter balancer gear? Please say no... I have some mechanical ability, but I really don't wanna screw with the clutch.

On a different note, same subject - can someone explain the air screw to me? When I back it out (counterclockwise), that's allowing more air in, correct? Which in turn makes the mix leaner overall? Yay or nay?

Now, on the balancer drive gear - what would make it make this noise? Do they just work themselves loose or is it likely cracked? I have read TONS of stuff on this forum, but haven't heard much about this specific gear.

Thanks for all your replies!

 

[Larry's Shee]

The gear is basically three pieces. The hub that attaches to the shaft, the gear that drives it, and a plate. The gear is sandwiched between the hub and plate and held by 3 rivits. On the rivits are oval shaped rubber cushions that are in oval holes in the gear.

Far as I know, I'm the only unlucky blastard on the forum that has one break. My son's friend was riding it at the time, so I have no clue if it gave any warning or not, or how long they may have rode it after it broke. Took only two seconds when I started it to know something was wrong. Shook like a whore in church.

I don't know if my gear broke which took out the bearing and chunked the case, or the bearing went first. I still haven't decided if the clutch basket is usable because the starter gear is chewed up. Sucks cause it's a relatively new one. The extra one I now have is grooved pretty good on the fingers.

Either get a Clymers repair manual, or find the download one on here.

 

[Blaaster]

N.

On a different note, same subject - can someone explain the air screw to me? When I back it out (counterclockwise), that's allowing more air in, correct? Which in turn makes the mix leaner overall? Yay or nay?

Thanks for all your replies!

Turning the air screw counterclockwise allows more air to mix with the fuel drawn through the pilot jet.

It is used primarily to adjust the idle setting and has very little say in the overall mix.

After the idle has been adjusted there is no need to mess with the air screw again unless you are having a problem up to 1/4 throttle opening.

Usually the air and idle screws are set and forget.

Above 1/4 the idle circuit is basically inactive, and any adjustments to the air screw is pointless.

 

[2smoke]

tore it down tonight.

clutch cover off, everything was tight and looked real nice. no noise in there.

got brave and took the top end off to check for play, nothing out of spec in there. the guy i got it from said it had a recent rebuild and he was being honest. wiseco piston, .050 over, everything inside is beautiful.

My noise must be detonation. I need to do a leak test and compression test. After putting it all back together, seems to have a lot more compression.

Different question, tightened my chain, wasn't thinking and set it without me being on it. loosened the adjusters to put some slack,back in it and it won't let the chain loose. Still too tight. Took it for a spin to try to,knock it loose to no avail. What do I do?

Thanks for everyone's help so far! This forum has so much information it's unreal. The KOR videos have been super helpful, too.

 

[Larry's Shee]

In your vid, was bike in gear?
The noise on vid is not deto

 

[Blaaster]

Definitely not detonation

.

There are 2 bolts that have to be loosened to allow the carrier to move.

 

[tfaith08]

Taking the clutch apart is a breeze, really. Just make sure you don't drop any parts down into the engine. The first time I did it was a breeze because of pictures/videos. Turn it up on it's side so that you don't lost any fluid and have to clean up.