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Discussion Starter · #1 ·
Hi all, We just bought a C90 08. I have 250 miles on it I noticed a not sure if it is a knock or valve noise while engine is under load such as rev up in each gear. If I put the bike in neutral and rev it up I can here what sounds like the valves. Never having a C90 before I am not sure if this is normal or if there is something wrong with the engine. Hope someone can help with this.
 

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Next tank of gas, buy premium (high octane) and if the engine knock goes away, it was pre-ignition not valves.
If the noise is still there it "may" be the valves.
Hope that helps,
John
 

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Discussion Starter · #3 ·
Next tank of gas, buy premium (high octane) and if the engine knock goes away, it was pre-ignition not valves.
If the noise is still there it "may" be the valves.
Hope that helps,
John
OK thanks John, I was thinking the same thing myself even though the book calls for 87 octane.
 

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My C50 will sound terrible on anything less than premium JJW has a good suggestion.I don't know how much different a C90 is than a C50.
 

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IMO higher octane will do nothing. This engine has been designed to run on 87. Putting in higher octane could decrease your performance, mpg. 92 octane is a slow burn and primarily for higher compression engines. 87 is a faster burn and primarily for lower compression engines. You probably just got a bad batch of fuel.

Your bike is brand spankin new so there really should not be anything mechanically wrong. You say you have only 250 miles on the clock????? You are sure??? If the problems persists after running a new batch of fuel you had better go to the dealer. Another 200>300 miles you will need your 1st service anyway.

I would: check oil level just to make sure she is lubed properly. The dealer could have screwed up!! Are you familiar with checking oil on the C90? Run the bike for 3 min. Shut down let stand for 3 min. Check oil with bike on a level surface and standing upright. If you cannot see the site glass get some help. I usually have my daughter do this while I check.

Try adding a fuel stabalizer for a couple of tanks. Some C90 riders use Marvel Mystery Oil a few times a year. BTW what oil are you using. Some LC/C90 riders have had knocking issies when using Amsoil. After your 1st dealer check, I would not do more than 1, switch to RotellaT syn 5-40. Great stuff and can be had in any Walmart.

For some good info go here and here
 

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Discussion Starter · #7 ·
Thanks all for your replies, Been riding bikes for close to 50 years on and off but this is my first C90. The only thing I can see is the dealer has to much oil in the bike. I always put the bike on a jack to check the oil and I noticed the whole inspection window was full. How much over I am not sure, this was done by the dealer when I picked up the bike, Not sure if this would be the problem with the what seems to be a valve noise at high rpm. I did call the dealer and told him so next week when I bring it in for the 600 mile they will check it out.
 

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I always put the bike on a jack to check the oil and I noticed the whole inspection window was full.
To get an accurate reading, the bike needs to be straight up AND level, front to back. Putting it on a jack may not keep it level and might result in a wrong reading. When viewed properly, it the level is just barely up to the top of the glass, that should not cause a problem.
 

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i have a noise in my 90 also ,i took it to the dealer and a factyory rep came and checked out. he claims this is normal for the 90. so im riding it and if anything happens its under warranty till2011 .the rep said with the hydralic valves there is no adjustment so you get what you get. also i tryed every brand and octane of gas there is in the poconos pa. it still makes the noise.....even switched to suzuki synthetic oil!!!!
 

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What conditions does the knocking occur? Only start up or just under load. I have been reading up on this a bit. If only start up then possibly using certain synthetics, Amsoil seems to be the worst on cold startup for knocking on the 90, could be the culprit. Others that have had this problem say that it takes 200>300 miles for the condition to stop. I don't know cuz my bike does not knock so I know this is not a normal condition. I would go here and ask all the experts.

If the oil doesn't flow properly on start up, it can cause some issues.
The most wear an engine will have is on a cold start up if the oil doesn't pressurize fast enough. My understanding is that Rotella 5W-40 oil will flow a lot faster than a 10W oil. The other thing to consider is the valve lash adjusters that some call lifters.These are oil filled cushions between the rocker and the valve stem. When they empty them self, the cushion is gone and that's where you will hear the knocking. Once the oil warms up and gets thinner, the lash adjuster will fill up with oil and remove any slop between the two. That could be your problem so trying the Rotella will tell you if it is or not.

Other possible causes, valve clatter from Clymer

  1. air trapped in hydraulic lifter (this could cause the knocking under load)
  2. defective hydraulic lifter (always)
  3. decomp. cable my need adjusting (knocking at startup)
  4. weak or broken valve spring (always)
  5. worn rocker arm and/or shaft (always)
  6. worn crankshaft journal (always)
 

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Discussion Starter · #12 ·
Interesting enough it does not make the nose until the engine gets warmed up, it is quiet when I first start and a few minutes later.
 

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My C109RT is doing the same thing..When I go from 3rd --> 4th it's very noticeable..I'm running premium fuel as recommended and I only have a bit over 1800mi on her...The dealer has done all the recommended service.
 

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Fuel recommended for a c50 is 87 octane.But everytime I've used it I get a ping in my engine when I start off.I started using premium and have had no more problems and still get from 48 to 50 mpg.The last time I checked my plugs they were clean as a whistle.As long as this works I don't mind paying a little more for gas.
 

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Discussion Starter · #15 ·
Goes to show all things are not created equal. I will be taking it to the dealer for the 600 mile check soon so I will let them check it out so they can put it on paper for posible future problems.
 

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mine makes noise after about 15 >20 miles out on a ride, the hotter the outside temp. the louder it gets. put on cobra pipes no longer hear the noise.but then again cant hear the wife either...................
 

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Discussion Starter · #17 ·
mine makes noise after about 15 >20 miles out on a ride, the hotter the outside temp. the louder it gets. put on cobra pipes no longer hear the noise.but then again cant hear the wife either...................
LOL, More than one way to skin a cat.
 

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Are you sure it is engine knock and not just a rattle? I have had rattling noises that took me some digging to find, and it sounded like engine noise. Ended up being my hwy. pegs bouncing up and down. Also if you header bolts are loose you may hear a "ticking" sound, on mine it sounded exactly like valves ticking, usually accompanied by backfire on decel.
 

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Discussion Starter · #19 ·
Are you sure it is engine knock and not just a rattle? I have had rattling noises that took me some digging to find, and it sounded like engine noise. Ended up being my hwy. pegs bouncing up and down. Also if you header bolts are loose you may hear a "ticking" sound, on mine it sounded exactly like valves ticking, usually accompanied by backfire on decel.
No, It's definitely a knocking sound, we will give it some time to break in and a couple oil changes to see if it goes away.
 

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before anything try checking the fule door lock you might have some play in it. had same engine knock on 06 c90
 
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