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Knocking noise at idle

Old 05-08-2015, 04:48 PM
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Knocking noise at idle

New member here. I just bought a 1999 Superhawk and after getting it home I noticed a intermittent knocking coming from the front cylinder/head area. It did not do it until the bike was all the way warmed up. It didnt do it on the short test ride I took it on, but after a freeway ride home I noticed it. It only does it at idle, if you rev it at all it will stop. The bike only has just over 14k on it. Any ideas?
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Old 05-08-2015, 05:44 PM
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Need more data...
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Old 05-08-2015, 06:00 PM
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What other information do you need?
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Old 05-08-2015, 06:15 PM
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Does the bike have manual Cam Chain Tensioners?

Does the bike have an ignition advancer fitted?

How long since valve clearances done?

Is there an exhaust gasket gone?

Is it the slide rattling in the front carby?

There are that many variables when it comes to the engine in these bikes.
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Old 05-08-2015, 06:34 PM
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I say carb slides
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Old 05-08-2015, 08:26 PM
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If it only does it at idle then its the carb slides, nothing to worry about.
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Old 05-08-2015, 08:33 PM
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OK, Bike does not have an ignition advancer, has the stock cam chain tensioners, i don't know if the valves have ever been adjusted, but the guy I bought it from said he did some carb work recently, and it does have an erion racing exhaust system on it. How to you tell if the carb slides are rattling? And what would be the solution for that?
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Old 05-08-2015, 08:38 PM
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You can get a stethoscope cheap at most autoparts stores, prod around til you pin point the knocking. If is the carb slides there is no solution they are big heavy slides and its just the nature of the beast. And lastly get some manual cam chain tensioners, the factory ones tend to fail at no consistent point and when they do it usually means a new engine or atleast a new cylinder head.
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Old 05-08-2015, 08:44 PM
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Cool, I have a stethoscope and will try to pinpoint the source tomorrow. And will start looking for manual tensioners. Any brands that are recommended? Thanks to all that replied, I am feeling alot better about this purchase now.
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Old 05-08-2015, 10:39 PM
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Originally Posted by gti52 View Post
OK, Bike does not have an ignition advancer, has the stock cam chain tensioners, i don't know if the valves have ever been adjusted, but the guy I bought it from said he did some carb work recently, and it does have an erion racing exhaust system on it. How to you tell if the carb slides are rattling? And what would be the solution for that?

The carbs can be set up so the slides don't bounce at idle and if the PO messed with the carbs then I would bet that is the source of the noise you are hearing.

There is a carb thread, that some guy wrote, that explains how to cure the issue...... and a hint, it is coming from the front carb,

The CCTs are a big topic. Yes you should change them as you don't know how they were treated but the factory auto CCTs also work fine if you take a few easy steps.

Many will say they are just no good but I have run 100K miles with just factory stock auto CCTs with no failures.
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Old 05-09-2015, 05:03 AM
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Originally Posted by 8541Hawk View Post

The CCTs are a big topic. Yes you should change them as you don't know how they were treated but the factory auto CCTs also work fine if you take a few easy steps.

Many will say they are just no good but I have run 100K miles with just factory stock auto CCTs with no failures.
Have you modified the factory CCT's in some way for reliability or do you change them at regular intervals? I'm just curious. Personally I prefer MCCT's because they are a set it and forget it and something I dont have to think about. I like to check them at the beginning of the season when I bring the bike out of hiding, but like I said, I dont have to worry about them at all...
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Old 05-09-2015, 07:52 AM
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I haven't done anything to the CCT's yet. I literally just got the bike yesterday. How do you verify that the stock CCT's are functioning correctly?
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Old 05-09-2015, 08:54 AM
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I was asking HAWK, but you verify they are working by having a running bike lol.... its the type of thing that they either work or they dont and when they dont its usually devastation. The lucky ones have had it only skip a tooth on the cam gears. Which you would notice the timing being off the way it runs. The unlucky ones, new cylinder head or engine. They dont seem to like idling on the sidestand for extended periods from what I've heard
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Old 05-09-2015, 09:05 AM
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Superdutyd on the forum I believe still makes them send him a PM, I have a set of his and my disassembled factory ones if youd like me to post some pictures. Otherwise there are more expensive "name brand" ones on ebay. Its not necessary to go name brand on thess as they are fool proof
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Old 05-09-2015, 09:33 AM
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Theres also the option of turning your automatics into manuals (hence my disassembled stockers) for the cost of 2 carraige bolts, 4 nuts, and some washers
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Old 05-09-2015, 10:48 AM
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You can also use the stock CCT's and do the Stopper Mod (A.K.A. Failsafe Mod)
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Old 05-10-2015, 11:45 AM
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Ok after a bit of riding I have noticed this. When stopping at a light the engine seems to idle at either 1500 or 1000 rpm approximately. If it is idling at 1500 rpm you get intermittent knocks. At 1000 rpm no knocks. This leads me to beleive it does have something to do with the carb setup. What is the idle speed supposed to be? I have a set of manual cct's on order and will do the stopper mod to the stock ones once I have them out.
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Old 05-10-2015, 07:11 PM
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Originally Posted by gti52 View Post
Ok after a bit of riding I have noticed this. When stopping at a light the engine seems to idle at either 1500 or 1000 rpm approximately. If it is idling at 1500 rpm you get intermittent knocks. At 1000 rpm no knocks. This leads me to beleive it does have something to do with the carb setup. What is the idle speed supposed to be? I have a set of manual cct's on order and will do the stopper mod to the stock ones once I have them out.
The idle speed should be 1200 +/-100 rpm.

You might need to balance the carbs to get a steady idle, and there is also an adjustment to the throttle position sensor that makes for a steadier idle.

To balance the carbs you will need to install a vacuum take-off point in place of the blank screw on the rear right of the front head. It is easy to get to the fitting on the front head if the carbs are off. Once installed you can leave a length of vacuum hose connected and seal this off with a bung so you don't need to pull the carbs to do a balance.

The rear head already has a vacuum hose fitted which is connected to actuate the fuel petcock. I fitted a "T" into this line, and added a short length of vacuum hose with another bung, and with the permanent hose off the front head, balancing the carbs if now easy to do (if you have the right gauges).

You'll find the adjuster to balance the carbs on the left side of the rear carb.

The throttle position sensor should be set to 500 ohms when at idle, but from the factory they can be all over the place. The TPS is used to adjust the ignition timing. Mine was set to 960 ohms, but after re-setting it the bike is much livelier coming off idle. The TPS potentiometer is located on the right side of the front carb, and can be accessed once the airbox is removed.

If both of these items are set correctly but your idle issues persist then you'll need to delve further into the carbs to correct the problem. There are low-speed pilot screws that would likely come into play next.
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Old 05-10-2015, 07:35 PM
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service manual
https://www.superhawkforum.com/forum...-manual-11365/

TPS mod
https://www.superhawkforum.com/forum...n-sensor-9876/

MCCT's
https://www.superhawkforum.com/forum...pe-ccts-11275/

PAIR removal
https://www.superhawkforum.com/forum...-removal-9875/

Carb setup
https://www.superhawkforum.com/forum...-set-up-24769/


Damnit I'm turning into a nice guy... gotta stop this *****

check out the knowledge base section of this forum for everything you ever wanted to know about this bike til your brain hurts.

And I dont believe there is a sticky for sync'ing your carbs(correct me if I'm wrong) but if you dont have a sync tool I can show you what I use, costs less then $10 to make and will be your best friend lol
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Old 05-10-2015, 08:49 PM
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I do have a carb sync tool but I'm not sure it will work for this application. It is for syncing side draft Weber or S.U. carbs. What do you use? Guess I will be busy this week.
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Old 05-10-2015, 08:52 PM
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I've got a Motion Pro Syncpro, but all you are looking for is to get the vacuum in both inlets to match. Presuming the tool you have has at least two vacuum gauges or manometer tubes you'll be good to go.
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Old 05-10-2015, 08:53 PM
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Originally Posted by gti52 View Post
I do have a carb sync tool but I'm not sure it will work for this application. It is for syncing side draft Weber or S.U. carbs. What do you use? Guess I will be busy this week.
I have a Unisyn for balancing an MGB from 35 years ago and no it won't work on the Hawk.
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Old 05-11-2015, 02:50 AM
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Have a look at your plugs, they can give you a good idea of what is going on.

As far as knocking noises go get used to them as the VTR engine is noisy!

I am in the middle of doing my valve shims and obviously had to pull the plugs.

I was very pleased with what I observed with the plugs. A lovely tan colour which indicates to me that the jetting is spot on!



Guess what my bike has a knocking noise at idle and has done so ever since I did some major mods to the engine.

Bloody thing goes like stink and to date has never let me down.

I have my idle set at 1500 , but I have Hi Comp Pistons, free flowing exhaust, jetted carbs, 4 degree advancer , head and port work, lightened flywheel and a few other bibs and bobs.

I would be worried if my idle was erratic, that to me would indicate fuel or air issues.

You need to sync your carbs and do the TPS, while your at it check the air filter.

The VTR is very touchy when it comes to the air filter.

Factory is best!

If and when you balance the carbs make sure you do the mixtures at the same time!

Good luck mate, this all takes a bit of time but if you get to the sweet spot it is worth it.
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Old 05-11-2015, 03:36 AM
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my sync tool is a meter stick, clear tubing, zipties and some marvel mystery oil I believe...
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Old 05-11-2015, 02:45 PM
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Originally Posted by scottiemann View Post
my sync tool is a meter stick, clear tubing, zipties and some marvel mystery oil I believe...
I already had a fancy Syncpro because I also own a VFR, and it is a lot easier to balance a 4 cylinder with 4 channels of vacuum gauge.

However, I have to admire the simplicity of the oil in a tube type gauge for balancing just two cylinders...all you want is to know that they are drawing the same vacuum, there's no need to know the inches of mercury. If I had no other vacuum tool, it is what I would be using.

I suspect any oil would probably do the job, if it is a higher viscosity it would be more damped and a bit slower to respond to change, too low a viscosity and it would bounce around a lot. I'd guess that fork oil or ATF would be about right?
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Old 05-11-2015, 05:55 PM
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Originally Posted by Cadbury64 View Post
I suspect any oil would probably do the job, if it is a higher viscosity it would be more damped and a bit slower to respond to change, too low a viscosity and it would bounce around a lot. I'd guess that fork oil or ATF would be about right?
I recommend using either ATF or marvel mystery oil, your right though, thicker engine oil you wont get a good reading. The reason I use marvel is because it is of similar viscosity to ATF and if I happen to be way out of sync and are too slow on the kill switch or sync screw, the engine sucking some of that wont hurt anything.
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Old 05-11-2015, 07:06 PM
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Aha...Marvel Mystery Oil is a real product! I just assumed you had used an unknown oil that had worked well but you didn't know what it was.

Presumably this is what Tony Stark uses to keep his joints quiet???
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Old 05-11-2015, 07:20 PM
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Originally Posted by Cadbury64 View Post

Presumably this is what Tony Stark uses to keep his joints quiet???
ladies-"tony, what do you use for lube?"
tony-"mystery oil!"

He's gotta keep them ladies guessing lol

That stuff is an all around good product, not excellent although some people swear by it, but a good jack of all trades master of none type product
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Old 05-13-2015, 07:39 AM
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Ok, I changed the oil and the knocking seems to have stopped. The previous owner was running Mobile one synthetic motorcycle oil in it, and appeared to have it over filled. I decided to just do an oil change because it was new to me and had a cheap walmart filter on it. A new filter and a gallon of 15-40 oil and the knocking seems to be gone.
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Old 05-13-2015, 01:11 PM
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Overfilled with expensive full synthetic with a cheapo wally world filter? Nice

Im sure his overfilling was a lack of standing the bike straight up when checking the level...

I would check your valve shim clearance at some point
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