SuzukiSavage.com - Engine knock

TheNaughtyLemur

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Engine knock
09/09/17 at 08:43:16

so my engine now has this horrible loud engine knock that I can only describe as rod knock. You can hear it a little while idling, start to really hear it when giving the engine a quick rev, and then can hear it from 2 blocks away when you put the engine under load (such as starting out in 1st).

I've read up on a couple threads here of people with similar problems and am going to prepare myself for the worst in a bearing being bad and hope that I'll be pleasantly surprised it's something far simpler. I plan on dropping the engine soon and figuring it out from there. My only snafu being that I'm having surgery on my shoulder on the 19th and won't be able to work on it during the initial recovery period.

The bike has relatively low miles (under 8,000) and when I checked the cam chain tensioner (at 7,000 miles) it looked brand new. I don't let it idle on the side stand, but when I did first buy the bike I went through several tanks of gas without realizing that my petcock was toast. After I changed the oil after replacing the peacock it reeked of fuel, so that's where I'm assuming the damage is from. I'm using Shell Rotella T-6.

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06 Suzuki S40 - 140/90-15 Rear Tyre - Raptor Petcock - MAC 2" Header and Exhaust Kit

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Ruttly Serious Thumper Offline Thumpers Rule Posts: 4997 Manteca , CA Gender:	Re: Engine knock Reply #1 - 09/09/17 at 20:14:54 Check Warranty and/or Bank Balance That sucks ! I see a rebuild in your near future or get another engine / eBay
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justin_o_guy2 Serious Thumper Offline What happened? Posts: 55279 East Texas, 1/2 dallas/la.	Re: Engine knock Reply #2 - 09/09/17 at 21:14:40 I'd hope for a loose flywheel and be ready to hunt a used engine.
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kojones Full Member Offline SuzukiSavage.com Rocks! Posts: 223 Finland	Re: Engine knock Reply #3 - 09/10/17 at 09:49:56 Mine had similar knocking, turned out that the balancer driving gear was missing a dowel pin at the crankshaft, so the balancer was hitting the con rod.
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LANCER

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Re: Engine knock
Reply #4 - 09/11/17 at 10:01:37

I had a knock that developed in my '96 after making a move from SC to OK. The bike sat for a period of time without being started while we were looking for a place; about 6 months or so. During this time some rust developed on the rings and cylinder wall and when I did start it (I neglected to squirt some oil on the piston in advance) the rust caused the piston to yank sideways and damaged the piston slightly. It would start and run but in the slow range you could hear the knock while in the upper range it disappeared. I rode it for a little while hoping it would work itself out but of course it did not.
When I pulled the head & cylinder. The head was fine, the cylinder needed a little clean up but was ok. I just had to replace the piston thankfully.

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TheNaughtyLemur

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Re: Engine knock
Reply #5 - 09/11/17 at 10:41:49

LANCER wrote on 09/11/17 at 10:01:37:

I had a knock that developed in my '96 after making a move from SC to OK. The bike sat for a period of time without being started while we were looking for a place; about 6 months or so. During this time some rust developed on the rings and cylinder wall and when I did start it (I neglected to squirt some oil on the piston in advance) the rust caused the piston to yank sideways and damaged the piston slightly. It would start and run but in the slow range you could hear the knock while in the upper range it disappeared. I rode it for a little while hoping it would work itself out but of course it did not.
When I pulled the head & cylinder. The head was fine, the cylinder needed a little clean up but was ok. I just had to replace the piston thankfully.

Sounds pretty similar to my situation. I hadn't ridden it in a couple months, heard the sound and then stuff came up and I hadn't ridden it for another couple of months and the sound got much worse. I let it sit for another month and a half and decided I wanted to ride it again before I have shoulder surgery and can no longer ride for over 4 months. And now I came to the conclusion it is not going to get better by itself.

So my project for this downtime that I will be out of work is going to be sorting this out. If this is going to cost me any significant amount of money I don't think I will fix the bike. As a student who is usually broke, I just don't think it is worth it.

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06 Suzuki S40 - 140/90-15 Rear Tyre - Raptor Petcock - MAC 2" Header and Exhaust Kit

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LANCER Serious Thumper Alliance Member Offline Savage Beast Performance Parts Posts: 10601 Oklahoma Gender:	Re: Engine knock Reply #6 - 09/11/17 at 14:21:33 If you can get the head, cylinder and piston out so they can be looked at we may be able to help.
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Dave

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Re: Engine knock
Reply #7 - 09/12/17 at 04:33:09

Before you take anything else apart......look to see if it is the nut that holds the flywheel on. If that nut comes loose the flywheel bangs on the crankshaft splines, and it makes a noise that can be heard from a long distance away. It is not possible to listen to the noise and determine exactly where it is coming from - as the flywheel is mounted to the end of the crankshaft and the "banging" force is rotational and doesn't move the engine block in a way that helps to isolate the source. My bike started doing that and the noise was horrendous, and it was worse at idle and would get less noisy at speeds. I tore my bike apart and unfortunately, I didn't find the loose nut until after I had taken the entire top end apart looking for a problem. One other member on the forum bought a very nice bike with a horrible knock to part out - and long after the bike was torn down he discovered the same "loose flywheel nut" to be the only problem with the bike....unfortunately there were too many parts gone to consider putting the bike back together.

Checking this nut requires removing the left side engine cover, using a puller to remove the stator, then using a 46mm deep socket and a flywheel holder to tighten the nut. I cleaned the oil off mine and used a permanent threadlocker on it to be sure it didn't come loose again. (Permanent threadlocker can be removed when needed.....it just takes a bit more effort).

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