Possibly dumb question - engine knock [Archive]

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rainman

23rd April 2008, 19:39

It's been a while since I posted one, after all....

Last Wed night I had parked my bike outside (in the cool air) at the BRONZ meeting. When I started her up afterwards I thought I heard a bit of an intermittent pop or knock (not a backfire) - about every second or two. As I had the helmet and balaclava etc on I wasn't sure and the noise went away soon after. Some of the guys there thought they heard it too but I was on the other side of the parking lot and it had gone by the time I got over to them to double check.

Bike's been running fine, still is. Hadn't heard the noise again, been busy and ignored it for the moment. This morning I pulled her out of the gargre and started up, same again. Lasted for less than a minute, and there's a knock every second or so until she warms up. Rode to work fine, and I didn't have a chance to get out to Colemans/Holeshot/... during the day - crazy diary disease. Parking at work is warm so she started up fine on the way home tonight.

The question is, is this a sign of imminent doom and I should proceed direct to the nearest spannerman first thing tomorrow, before the piston is ejected from the exhaust, or can I book in a more leisurely inspection after the long weekend? I have no long distance riding plans this weekend, but may head out to Muriwai for a coffee at some stage.

I realise noone can diagnose the actual fault over the internet but I suppose I'm asking what's the worst case scenario?

Bike is a 1997 Suzuki VZ800 Marauder, 37000ish km's.

Katman

23rd April 2008, 21:59

Possibly just a misfire from a slightly wet plug if you're starting it from cold with choke. Try throwing a new set of plugs in it.

homer

23rd April 2008, 22:08

could be just not the oil pressure being there as well , as it gets colder you may notice things like this

AllanB

23rd April 2008, 22:23

rainman

23rd April 2008, 22:45

Quick - check your oil level ...

Nope, oil's OK and was changed a few thou ago at most.

xwhatsit

23rd April 2008, 22:47

Quick - check your oil level - it may have dropped a bit and on a cold start its taking a while to get around the engine. Sometimes modern engines do burn a wee bit, and the big twins are often lugged around a lot.

Also when was it last changed? I've a Madza that loves clean oil - once it starts to get a bit old (6k or so of around town running) the first sign is a slight head noise on a cold start - clean Castrol and she's sweet again.

Shouldn't cause those sorts of noises though, lack of oil would make a lot of rattling top end noise.

My bike does similar things when it gets very cold. I think part of it is the occasional misfire due to it just being damned cold, wet plug or whatever who knows -- but the extra fuel ends up in the exhaust and gently ignites and makes an intermittent popping noise. Not the usual sort of backfire *bang* or spitting back through the carb thing.

sefer

27th April 2008, 01:05

I've a Madza that loves clean oil - once it starts to get a bit old (6k or so of around town running) the first sign is a slight head noise on a cold start - clean Castrol and she's sweet again.

It's probably got hydrolic lifters, so when the oil gets a little older and thicker it struggles to pump oil until it's warmed up a little.

skidMark

27th April 2008, 01:17

Possibly just a misfire from a slightly wet plug if you're starting it from cold with choke. Try throwing a new set of plugs in it.

What he said.

And holy shit, katwomen gave advice.

Good shit catwomen. credit where credit is due.(jew):laugh:

awayatc

27th April 2008, 01:40

My single cylinder performs in a similar fashion if I leave the choke on to long when it warms up stationary.......

fireball

27th April 2008, 02:07

my marauder made a similar sound before it blew itself up
ended up with a new top end so be wary of the knocking sound if it starts to sound worse spannerman it quickly