Engine knock, knock, knocking

[HardInThePaint]

Yo I got a guy wanting to sell his CB but it got an engine knock. I've heard of engine knock but haven't dealt with one before. My question is what the hell causes that? And how much work do I have to put in to handle that? He selling the car for $500 so I'm still debating if its worth it depending on what you guys say about the knock.

[PIMPCORD]

Possibility is rod knock & piston slap when the piston is moving freely when it has little compression in the cylinder bores.

[JoshM]

If the interior/exterior of the car is worth $500, then don't worry about the knocking and just swap in a better motor. $500 for a running (even poorly) CB is a good deal if the body is pretty straight.

[wed3k]

there's a place named JIC that does remanufacturing and a f22 bottom end will sell for around 500 bucks, completely rebuilt.

slap on a good cylinder head and oil pump and you should be good to go.

[xkjnboix]

not hard to find let alone swap another f22a# in. they are a dime a dozen. as long as the rest of the car is ok go for it

[randomcustoms]

assuming it is a rod knocking, heres what youd have to look for and fix, first of you need to determine whether the cylinder walls are ok to be honed or whether thed have to be bored to be fixed, if honing will do, all you need is new piston rings, rod bearings and main bearings, and full gasket set. i'm in this situation right now, or if you needed to bore it add pistons to that list and machine shop time! but for the price its worth it if the body and interior are decent

[HardInThePaint]

Right on for the help guys.

[rob_is_legend]

Ive got a nice knock too, but no money. :/ any small things I can do to prolong the life of the motor outside or regular oil changes and that nature?

[N9netwoAccord]

Ive got a nice knock too, but no money. :/ any small things I can do to prolong the life of the motor outside or regular oil changes and that nature?

run thicker oil. marvels mystery oil.

[nostringz]

higher octane fuel should help too. clean carbon deposits up. Shell V-power for a tank or two...

[johnl]

higher octane fuel should help too. clean carbon deposits up. Shell V-power for a tank or two...

Don't confuse detonation or pre-ignition (manifest as a 'pinging' or a rattling noise, but also known as 'knocking') with rod knock, they are utterly different things.

Rod knock is a regular and usually fairly loud 'knocking' noise that rises and falls with rpm and may be constantly apparent but may also only be apparent when the engine is under load (even a light load such as revving in neutral). Combustion 'knock' is usually quieter, 'rattlier' and usually only apparent when the engine is under heavyish load.

Rod knock is terminal, combustion knock can be be fixed if you can locate the cause.

[CB7Man]

So my knock sensor is bad and at 3K if I give it a good amount of gas, it makes this rattle noise, let off the gas it goes away. It only happens between 2.8-3.4K

Also my engine runs way better before the CEL comes on...

[deramansa]

So my knock sensor is bad and at 3K if I give it a good amount of gas, it makes this rattle noise, let off the gas it goes away. It only happens between 2.8-3.4K

Also my engine runs way better before the CEL comes on...

this happens to me today..CEL comes ON..engine runs better..

[johnl]

So my knock sensor is bad and at 3K if I give it a good amount of gas, it makes this rattle noise, let off the gas it goes away. It only happens between 2.8-3.4K

Also my engine runs way better before the CEL comes on...

So the engine is also running poorly when it's 'knocking'? Does the engine 'knock' occur before the CEL comes on?

I'm pretty sure my CB7 (Australian delivery) doesn't have a knock sensor, I'd be surprised if any of them do(?). Without hearing it it's hard to diagnise just what sort of 'knock' your engine has, but 'pinging' and rod knock each make fairly distinctive noises. I think you need to have an experienced person have a listen, and check out what CEL you have.

A combustion 'knock' (ping, rattle) can be caused by a number of things:

Fuel too low octane causing pre-mature 'auto-ignition' from the heat caused by compression (unlikely with low compression US market F22a engines)

Over advanced ignition timing

Engine running very hot (ccoling system problem)

'Hot spots' in the chamber, i.e. unwanted sources of auto-ignition caused by e.g. carbon deposits glowing red hot, spark plug electrodes glowing red hot (plug is wrong heat range, i.e. too 'hot' a plug), exhuast valve glowing red hot. Hot spots could be caused or worsened by a lean condition (lean mixtures burn much hotter than rich or 'adiabatically' correct mixtures).

[slammed91cb7]

my old 91 cb use to do that. it would run like shit then the cel would come on and it cleared up. unfortunately the guy i sold it to drove it for about a week and the engine died.