Chattering noise at about 2k RPM

[Maryland Valk]

Hello friends -
I have a 99 Interstate with about 53K miles that has developed a chatter from the top part of the engine when under load. The noise happens between 1800 and like 2400 RPM and then disappears. The noise happens in all gears but most loudly in 4th and 5th.  The chatter is pitched with the speed of the acceleration. For example, If I am accelerating from 45 to 55 mph in 5th gear and am taking it easy... the chatter sounds more like a rattle. Under normal acceleration it sounds like a chatter, under fast acceleration it is more like a chirp. It doesn't occur when accelerating down a hill (as much).  What ever the noise it does not seem to affect the performance of the bike - but it is annoying.

So far I have changed the oil and made sure the tires are properly inflated thinking that resistance may cause an undue load- Not much help at all. I also switched to premium gas about 2000 miles ago - again - not much help.
Any ideas on what this may be... Would a valve adjustment or full tune up help????

Thanks in advance

DOUG

[98valk]

check the PAIR valves. The service manual mentions this. they are shut on decel.
ignore me if u have already de-smogged.

[Ricky-D]

When I hear that kind of description I immediately think of pre-ignition. (1)

The first suggestion is to change gasoline source and if you're not using premium, I would urge you to start using premium.

If you've added any kind of aftermarket ignition system parts, I would think they could be some of the reason.(2)

I would suggest you check to be sure you have a full compliment of coolant.

I would insure the cooling fan is working.

(1) You can check the plugs for this. (http://www.dragstuff.com/techarticles/how-to-read-plugs.html)
(2) Use your manual to check motor ignition timing.

***

[Valker]

You got some good suggestions, but I think the chirping is an indication of cracked vacuum hoses. Stick a small (1-2") strip of electrical tape to the bottm edge of the hoses where they meet the carbs. If this fixes it, your hoses are split.

[Maryland Valk]

Thanks Folks - - I'll try all of these.  Never heard of a pair valve but I was going to do a valve adjustment and plug change this weekend any way. I have a Chiltons manual I can look up the pair valve with.  The split hose is an interesting theory too.
I thought the timing was determined by a "Trigger wheel" and couldn't be adjusted. Is that incorrect?

[Rocketman]

Thanks Folks - - I'll try all of these.  Never heard of a pair valve but I was going to do a valve adjustment and plug change this weekend any way. I have a Chiltons manual I can look up the pair valve with.  The split hose is an interesting theory too.
I thought the timing was determined by a "Trigger wheel" and couldn't be adjusted. Is that incorrect?

The best location for info on pair valves will actually be this site's Shop Talk section.  There are two entries on de-smogging your bike, and how to do it, if you decide you want to.
I believe your comment about timing refers to the pre-ignition comment.  Pre-ignition is different than a timing problem.  It's actually caused by the fuel-air mixture detonating before the spark.  I can't describe the cause very well, but ignore the trigger wheel/spark timing for this issue.

Mark

[Patrick]

1. If the bike hasn't been 'desmoged ' then I'd too look at the vacuum lines.. If they have not been replaced in awhile then just replace them.. The 'key' was your statement of a 'chirp'..
2. Has an aftermarket trigger wheel been installed?? With todays lousy fuel there could be a detonation problem, but if higher octane fuel didn't help it may not be that.. That is if enough of the higher octane fuel was added..The higher octane slows the flame front[burn] and helps reduce the chance of detonation..
3. I think you can pretty much rule out a valve train/adjustment issue..
4. There could be a possibility of a bad valve[reed] in the pair assembly, plugging the vacuum lines on #3 and #4 intake runners and taking the bike for a ride will check that[and for cracked vacuum lines as well]..

[LadyDraco]

Strange chirping sounds can be vacuum lines..
They might look fine... But you really have to touch them to check on them..

[98valk]

also check loose exhaust manifold header bolts and/or bad exhaust gaskets.

http://www.z1enterprises.com/detail.aspx?ID=1597

[Ferris Leets]

What are you doing running at 2k in 4th or 5th anyway?  All right for coasting down hills but accelerating?  I know mine  does not like to be run at that low an rpm under acceleration.  I don't shift until at least 3k.  That drops me back to about 2500 and even that is pretty low.

[DFragn]

What are you doing running at 2k in 4th or 5th anyway?  All right for coasting down hills but accelerating?  I know mine  does not like to be run at that low an rpm under acceleration.  I don't shift until at least 3k.  That drops me back to about 2500 and even that is pretty low.

Don't forget our beasts will pull from 1100-1200rpm in 5th gear without a problem, albeit you don't want to necessarily crack the throttle wide open right away. Torque is a lovely thing...

But, I agree. I prefer to cruise between 2500-2800 rpm regardless of gear selection, unless I'm on the freeway of course.

[Valker]

What are you doing running at 2k in 4th or 5th anyway?  All right for coasting down hills but accelerating?  I know mine  does not like to be run at that low an rpm under acceleration.  I don't shift until at least 3k.  That drops me back to about 2500 and even that is pretty low.

I almost never downshift from 5th unless I am stopping. Mine accelerates cleanly from as low as 500 rpm indicated. If you check the owners' manual, Honda recommends shifting into 5th at anything over 31 mph. I may be odd with this, but I frequently idle through the offset weave in the MSF classes in second gear.

[Maryland Valk]

OK friends - - Here's the plan for the weekend.  Am I missing anything???
1. Change out and inspect my spark plugs.

2. De-Smog and replace my vacuum lines. (Can I use any automotive tubing or is there something specific I should look for?)

3. Replace my exhaust gaskets and check the studs / bolts. To be honest- I changed my own tires at the end of the last season and WhileI had the exhaust off I replaced the exhaust gaskets on the right side of the bike - on the left side I couldn't get the old gaskets out so I didn't replace them AND I broke one of the studs off while tightening the exhaust - I have never remedied that situation and just torqued the other 5 bolts / studs a bit more until the tapping stopped while at idle. This could be the whole issue as the sound seems to come from the left side of the bike. I really thought it was coming from the top end but I will be the first to admit that I could be wrong about that. I have the gaskets and a few studs that I bought to replace the broken one and the rusted ones so it's all good. Extracting that stud is going to be the hardest part of this project.

4. I have been using BP High Octane gas for about 2 months (I believe it is 93 Octane) I ride about 90 miles a day to work and put on a few extra on the weekends at about 600 miles a week. What gas do you recommend? I have seen Techron mentioned on this board and believe that Texaco uses that as an additive to their higher end gas. (I only use BP because it is convenient).

5. Finally - - I can't thank you enough for your advice and support. I am truly grateful for all your assistance.

DOUG
Living well near Frederick, MD

[woefman]

Questions I have is do you have any After Market Chrome ?  

i.e.   Chrome Radiator Cover  Tranny Covers ?  

Have you Checked or Tightened The Buzz Bolt ?  ( see Tech Talk "got a buzz")

I Experience pretty much the same thing as you, but our descriptions of the noise is different, yet same Rpm and gear range.

First I tighten the Buzz Bolt seemed to help , but now still have what I call a Vibration and or MOST ANNOYING NOISE . Yet motor feels smooth as glass.


Lot's of talk on Buzz Bolt and After market tranny covers making noise.

Mine feels/sounds like coming from radiator area . I just have not spent the time to figure out how to remove the radiator covers yet.

[DFragn]

Mine feels/sounds like coming from radiator area . I just have not spent the time to figure out how to remove the radiator covers yet.

The fasteners for the radiator side covers are under the amber reflectors. Use can use fishing line or similar  to slice through the 2-sided tape to gain access to the screws.

[Maryland Valk]

I have the tranny covers, a neck cover and those fork flames (Love the fork flames) I checked that all was tight and had the spacers / foam tape piece all in tact - - This is definately an engine noise If I accelerate slowly through the 1800 to 2500 rpm range it rattles - If I go through that range quickly (like in .1 seconds during a hard acceleration) It is a high pitched chirp. I REALLY like the exhaust gasket theory. Only because I have had the pipes off a couple of times and have all the parts I need. AND it sort of corrisponds well for timing. I fouled up the exhaust stud and gasket job at the end of the riding season (Like October / November 08) and only had it idle or reved in neutral in my Garage until I got it out to play in May 09. That's when I started hearing the sound.  I never made the connection until the gaskets were mentioned on this thread.  I am going to do major service this weekend though and check everything out... fix all the stuff mentioned in the posts here - - but I do the exhaust gasket and broken stud first to see if that solves things. 

You all are AWESOME

[Black Sled]

I almost never downshift from 5th unless I am stopping. Mine accelerates cleanly from as low as 500 rpm indicated. If you check the owners' manual, Honda recommends shifting into 5th at anything over 31 mph. I may be odd with this, but I frequently idle through the offset weave in the MSF classes in second gear.
[/quote]

I would be curious what your gas milage averages operating like this.  I ride mine pretty hard, and love the sound of the engine, but my milage certainly suffers...

[Valker]

I almost never downshift from 5th unless I am stopping. Mine accelerates cleanly from as low as 500 rpm indicated. If you check the owners' manual, Honda recommends shifting into 5th at anything over 31 mph. I may be odd with this, but I frequently idle through the offset weave in the MSF classes in second gear.

I would be curious what your gas milage averages operating like this.  I ride mine pretty hard, and love the sound of the engine, but my milage certainly suffers...

[/quote]
My lowest mileage ever was 24 and my highest was 53. Most of the time I get low to mid 30s. If I am just putzing along through the mountains of CO and NM, I usually get mid 40s.