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Old 02-04-2017, 06:01 PM   #1
workingstiff
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Default engine slap/knock

Been looking on this site for some time for info and was able to find what I need . But I have an engine noise coming from my 96 Yamaha G16a , JN6 011941 , motor Jn6 01003 . While cranking it ,sounds like a slap or maybe a knock sound . Not so loud while running . I do believe it is coming from the engine because while checking it out I could rotate the crank to a position ( I think bottom dead center) and move the starter belt back and forth quickly and hear a slap noise . It is definitely louder while cranking . So I think I had eliminated the primary clutch . My question , is there something on these that can create this noise or am I just domed with a rod knock . Just looking for some input so I pursue this further and diagnose .
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Old 02-04-2017, 08:12 PM   #2
sho305
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Default Re: engine slap/knock

In G2/G9 engines eventually the balancer bearing goes bad, mostly because there is no bearing it rides in the side of the case. You might be able to listen pressing an object on the case there and compare it to near the crank. Find a pic of the inside to see where the balancer is. They knock but keep running, rod knock type of sound though ones I heard were not that loud. The clutches can make a lot of noises the sheave only rides on a bushing and it is not a tight fit.
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Old 02-05-2017, 12:42 PM   #3
workingstiff
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Default Re: engine slap/knock

I have seen some talk about the balancer side cover going bad . This is a G16A . Not sure if this engine has one . I will have to look into it . I Plan on removing the primary clutch to be sure its not the problem .

The noise is not that bad once the engine is running . If it is a balancer side cover problem whats the dangers of running it like this . How long will last . Just trying to sort this out to see what direction to go or not worry about it right now . It just started doing this .
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Old 02-05-2017, 01:43 PM   #4
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Default Re: engine slap/knock

It will elongate the side case pretty bad and make a lot of noise. Never seen one go to a catastrophic failure. Caught early enough, Ive had a good machine shop weld it up and redo the hole. No new side case required.
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Old 02-05-2017, 03:47 PM   #5
workingstiff
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Default Re: engine slap/knock

Quote:
Originally Posted by Golf cart guy View Post
It will elongate the side case pretty bad and make a lot of noise. Never seen one go to a catastrophic failure. Caught early enough, Ive had a good machine shop weld it up and redo the hole. No new side case required.
Having it welded sounds like a good idea if that is what seems to be the problem. I dont know what material is around that area but do you think it could be machined an use a bushing if not to bad .

I will have the primary clutch off soon to rule it out and I will decide from there which direction to go .
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Old 02-11-2017, 11:51 AM   #6
sho305
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Default Re: engine slap/knock

People have tried to bush them but I don't know what success they had. Getting the cover setup in a mill is not the easiest thing to properly locate the hole. Likely need to make a fixture just for it based on a good cover, lot of time to do that. Machining it to a thou is the easy part.
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Old 02-11-2017, 07:33 PM   #7
workingstiff
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Default Re: engine slap/knock NEW UPDATE ON PROBLEM

Ok , I know what the noise was now . I was driving the cart today and all of a sudden there was grinding and some other noises and the cart just shut off . Tried to start it and it just free wheeled . Pushed it home ( Luckily was not far )
I decided to pull the engine and pull it apart . As it turned out the teeth on the crank and the cam was nearly all gone . I think there was only 8 left on the crank and about 5 on the cam .

( note ) this jn6 engine had bearings on both sides of the counter balancer
( note ) the cam did not have bearings on either side of the cam . Just plugged into both side covers .

Got the cam out and seems to have compression so I dont think the top end is hurt (no bent valve ) .

I will need a crank and cam . Question is would I be better off with a new engine price wise . I do not need major upgrades ( power or speed ) . This is just to bump around the neighbor hood and to go to my shop . So some what stock would be fine for me with a governor bump for a little more speed . My cart is bone stock . I have read some have been using the 2003 jr6 in my 1996 in place of my jn6 . I would like to hear opinions .
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Old 02-11-2017, 10:13 PM   #8
cgtech
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Default Re: engine slap/knock

Dang, that's a lousy way to find out. Oh well, damage is done.
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Old 02-11-2017, 11:28 PM   #9
sho305
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Default Re: engine slap/knock

You might get used parts cheap I don't know. I do know you can buy a 13hp clone all over for $300. They had powerlands on ebay for under 200. All you need is HD springs from vegas to run without a governor and get more speed than stock, though not a ton more. Springs are cheap, so is timing key, and you should put a free flow exhaust on it too. Anyway when I did mine it was 600 at the dealer for a rebuilt short block and no install. Really I should sell the two G9 engines I have as I will never get time to rebuild them, they both run great but burn oil. So I'd recommend you get one apart put new rings in. But yes putting a clone in is a project, its faster and easier to use a Vegas mount and parts. You also have to buy an adapter to fit the clutch. But we used an airbox and muffler from a car in a boneyard 10 bucks each on the first clone. Welded couple bars in to mount on both of them that was the easy part.
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Old 02-12-2017, 07:16 AM   #10
workingstiff
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Default Re: engine slap/knock

I think I would like to stay with a stock type motor . I would like to just bolt one back in . I have a local golf cart place close to me I can check on used parts which would be fine for me . I have read some have gotten the jr6 motor in place of the jn6 for my 1996 g16a . My under standing is the jr6 is a 350 something cc and the jn6 is a 301 cc and for close to the same money . Can any one comment on this so if I go to the dealer and talk to them I know it will fit ok .

I will try to get a couple pictures for you to show you the damage .

Also still looking for all options and opinions . Thanks for all that has posted
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