Knock after re-build...

[fireburns99]

I just got my cylinder back from Neil after being bored and honed. I installed the new piston and cylinder, used the 1211 three bond with only 1 piece of the stock head gasket being used. After letting it sit for a day, i started it and it fired right up. After listening for a second there was a faint knocking sound.

I looked at the oem service manual, and under the troubleshooting for knock it lists:
1. Carbon buildup in the cylinder (fresh cylinder, so not this)
2. ignition timing to far advanced, such as for with a bad CDI
3. fuel air mixture too lean
4. Worn out piston and cylinder(fresh bore and piston)

I turned the choke on at idle which would have richened the mixture, and i could still hear the knock.

The specifications are as follows:
'86 cylinder that has a clean up port
thin head gasket (thin piece of stock trx gasket
38mm A/S-50 pilot, 165 main, CEJ needle middle clip
VP 110 fuel mixed 32:1 w/ castor 927

So is this slight knock normal until the rings seat etc? Or is there something you can recmmend? Thank you,
Nick

[Aceman]

Squish clearance too tight?
What's your compression?

Have you ran this cylinder/head combo before with a 1 piece gasket?

[86250rrider]

i also have a ported jug by him same head gasket, carb, and im using a 182 main,50 pilot on my 38mm a/s.you kinda lean im thinking .

[fireburns99]

Originally posted by Aceman
Squish clearance too tight?
What's your compression?

Have you ran this cylinder/head combo before with a 1 piece gasket?
Yes this cylinder/head/gasket combo was run previously with no knock.

The only new thing is the 38mm A/S.


86250rrider
i also have a ported jug by him same head gasket, carb, and im using a 182 main,50 pilot on my 38mm a/s.you kinda lean im thinking .
Even if i was a little lean, do you think it could cause a knock that could be heard? And when i turned the choke on, wouldn't that have richened the mixture enough to stop the knock if it was indeed lean?

And another note. I replaced the crank seals, and while at it tested the crank bearings. Everything seemed tight. The connecting rod also had no movement up and down.

[86250rrider]

my compression is only 185 psi and will detonate on anything lesss than straight 112 octane.i really dig the power though! im thinking you shoulkd at least be using a 175 mainand at least a 48 pilot. how many turns are you at on your a/f screw ?

[fireburns99]

Originally posted by 86250rrider
my compression is only 185 psi and will detonate on anything lesss than straight 112 octane.i really dig the power though! im thinking you shoulkd at least be using a 175 mainand at least a 48 pilot. how many turns are you at on your a/f screw ?
Well with th same setup i used to run 91 with 210 psi of compression. It only detonated once when i ran it extremely hard.
In regards to the jetting. I actually have a 50 pilot, i was mistaken. And the main jet isn't a factorright now because i'm breaking it in, and its only idling. I'm at 2 turns out on the a/f screw.

[atvmxr]

if its at idle, or just a hair more than that, almost every R I know has a knocking sound in nuetral/clutch pulled in. not sure what it is, shift forks rattling or something.....



but from the others post above, appears that your jetting is off compared to theirs

[fireburns99]

Originally posted by atvmxr
if its at idle, or just a hair more than that, almost every R I know has a knocking sound in nuetral/clutch pulled in. not sure what it is, shift forks rattling or something.....

but from the others post above, appears that your jetting is off compared to theirs

So then the knocking at idle in neutral is normal?? I can't tell if its always been there and i've never noticed it, and i'm just noticing it because i'm looking for something. Or if there is an actual problem. But i've thought i've thoroughly checked crank bearing etc...

And the main seems to be off substantially, but the pilot is comparable. I've used the jetting recommended by other people. But when i get it moving and broken in some more i'll start tinkering with it.

[250r4life]

sounds like the notorious R knock to me... youre just more aware of it right now since it is a new motor...

[fireburns99]

Originally posted by 250r4life
sounds like the notorious R knock to me... youre just more aware of it right now since it is a new motor...
So it is a common problem. Thats making me feel much better. Thanks for the input guys.

[250r4life]

Originally posted by fireburns99
So it is a common problem. Thats making me feel much better. Thanks for the input guys.

more of a common occurance... not really a problem...

[Jason Hall]

Might want to check the Counter balancer shaft bearings. They can destroy cases If they blow apart. One I repaired forced the bearings through the cases Into the sides of the crank. It destroyed the right side case, I welded the left side. Also check the outer bore (where the outer bearing race contacts the case) on the right side. My buddy bores the case out & presses steel Inserts In to save a worn case. The balancer shaft can be removed & both bearings can be replaced without splitting the cases. The counter balancer is an offset weight, that Is there to remove viberation. At low RPM's all the gear slack can make the balancer knock. 20 years of soaking up viberation can trash the bearings & the right side case.

[Rich250RRacer]

Originally posted by 250r4life
more of a common occurance... not really a problem...

On an R, I think I'd be more concerned if it DIDN'T make any noise at idle. :D