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Discussion Starter #1
OK so I have started to get a serious loud knocking from just under the tank during hard acceleration and when coming off the throttle, there is no issue at idle or light acceleration and seems to get worse at the engine heats up, it kills the power also...............very strange

My theory as possible causes

1. I recently fitted a new set of plugs that seemed to be genuine and authentic - maybe they weren't, but no problem with them for about 1000km until now.

2. I fitted 2x inline DB killers that might have somehow got clogged up and are restricting the exhaust.

3. Bad fuel on my last fill - seems unlikely

No other symptoms or anything obvious I can think of

Has anyone else had a problem like this

Bike has 90,000km and up to now has run like a clock and to an extent still does

I recently changed from 10w40 FS to 20w50 FS both Motule and I am in a hot country so I don't see that as an issue, no warning lights or anything like that

opinions/experiences

regards
 

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Discussion Starter #2 (Edited)
not the exhaust - pulled out the DB killers

really weird and serious power drop and big knocking - has me worried now

Knock is definitely top end and no power under throttle and it is loud and very noticeable
 

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G'day GeoffXX,

I'd be suspicious of the spark plugs, or something about the reassembly ....... (are the plug leads mixed up?).

Make sure they are the correct part number as plugs come in all sorts of lengths and the wrong part # plug may be contacting the pistons and closing up the plug gaps.

I have worked on bikes that needed two crush washers on their plugs to keep their electrodes clear of pistons, so it can be possible the plugs are cheap knockoffs and too long.

I think the original plugs were an NGK IMRC9H, but a Denso IUH27 is compatible (I have used them before). There is a superceding NGK # that eludes me, but an ordinary NGK CR9EH9 will fit but won't last more than the usual 12,000kms vs the 40,000 kms life of an Iridium plug.

Don't be afraid to pay the $130 a set of 4 for Iridiums as you don't have to dig deep into the body work to change them as often, so that makes them very economical. I don't ride my BB much anymore so the basic $26 set of non iridiums will last me 2-3 years.

Someone on here should know the new NGK plug number...... or check the reference section.

(y)

PS 20w50 Motul...... I thought that was their mineral oil...... but any 10w50 or 15w50 oil like Motul 5100 or Motorex Top Speed is perfect for the bird - I tried Belray 20w50 semi syn once, and it was ok but felt a bit thick due to being a mineral fortified oil vs any of the latest mid strength full syn's.

The rating for oils is 20w = the viscosity of the oil when dead cold (eg at startup) and the 50 is the viscosity at full operating temp, so a smaller cold start viscosity helps get oil to all the parts quicker when 1st starting the bike and the thicker rating '50' helps keep the fully hot motor happy. If in a really hot climate, some use 10w60, but I live in Australia and our summers are near 40C and I have had no issue with 10w50 Motul 5100 - I just change it every 6000kms, and my 129k km BB still refuses to burn any oil over that 6000km interval (eg 4ltrs in, 4 ltrs out after 6k kms).
 

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Discussion Starter #4 (Edited)
The plugs are fine Iridium - exactly the same as the ones I took out - the issue with plugs is that there are fakes out there and they are hard to spot - as far as I could see these were genuine by all the markers I could find, the oil is Motul 7100 15/50 FS (typo check) so oil is not an issue

This problem is scary to say the least, believe me when I say this is a huge knock - and I am now scared to open the throttle it is so bad - when I do open the throttle it is severely underpower and and not revving the way it should, it is hugely laboured and I am honestly scared of damaging something trying to push it - it really is that bad

Idle is smooth an fine - no smoke at any point - starts on the button but wind that throttle and huge knocking sound from around the top of the engine - at first I thought it was intake noise as those throttle bodies can make a bit of noise especially riding with no helmet (for testing and listening) but that is definitely not the noise I am hearing

It really is alarming and the engine under load is hugely labouring and no power and will not rev as it should - when I removed the DB killers and took it for a short run I turned back after 300m actually worried about taking it any further

I am wrecking my brain trying to figure this out - it just defies anything logical

I'm going to pull the tank off today and get a good look in there and pull the plugs, I'm thinking either plugs or in fact my last fuel refill - could it be bad fuel (I wonder)

I don't think it is internal engine - no reason for that to happen and no smoke and idles perfectly in fact it drives perfectly as long as I don't wind the throttle and load up the engine, it has to be either intake - fuel - or ignition related all up top - it really is a puzzle.

also thinking that the fuel pressure could be low caused by a blocked fuel pump filter - that would make it run very lean and cause knock hmmmmm

PS - like yours my BB uses absolutely no oil at all from change to change and I change mine easily every 6k, I looked at the oil yesterday and it was still like new


a long time ago I removed the pair system and plugged them up - I wonder has something come loose around that area - that is a possibility also, will check it all out in a dew hours - 6am here in Thailand just starting to get light
 

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Discussion Starter #5
ok so pulled out 2x spark plugs and they are fine so I am starting to lean away from knock I now don't think this noise is knock at all since I have checked the sorts of things that would cause knock

something else is making this noise, possibly valve or something like that, it is only there when gunning the throttle, it is not as bad when the engine is cold and gets progressively worse as it warms up

Now at a loss as to what is causing this :(

still have to run the fuel down and put fresh fuel in but I don't think that is going to make a difference sadly
 

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Discussion Starter #8
not plug related and I don't think it is knock - thinking either valve related or something needs adjusted - it is really loud - something is slack or about to fail - run out of ideas TBH - it really is weird just to suddenly start happening like that
 

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Discussion Starter #9
I wonder about balancer shafts - could they suddenly cause a lot of noise - or do they fail and if so what causes the failure

clutching at straws here TBH lol
 

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Put your old plugs back in and see if problem still there. If the problem started after changing them, something was altered or they are shit plugs. Make sure primary wires on the coils are fully seated if you may have removed them. They push on very hard.
 

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Discussion Starter #11
Put your old plugs back in and see if problem still there. If the problem started after changing them, something was altered or they are shit plugs. Make sure primary wires on the coils are fully seated if you may have removed them. They push on very hard.
done 1000km on the new plugs - checked them and they are perfect - no issues whatsoever, they look perfect - it was a long shot that there was going to be an issue with them - I was leaning that direction because nothing else has been changed on the big except - plugs - oil and obviously fuel, like I said above I'm going off the idea that the noise is engine knock - it is pretty loud and sounds more like a hammer hitting the the engine somewhere - I really am at a loss as to what this could be but it is not plugs or oil, I've had this bike for 15 years through thick and thin - I know it like it was attached to me but I am running out of ideas - I might try and make a recording of the noise

It's funny that it does seem to be affecting power delivery but I could be mistaken as as soon I open the throttle and hear the noise I back off - still an outside chance it could be bad fuel - seems unlikely but I need to rule it out - it would sort of fit the symptoms but unsure, it is quite a worry when I open the throttle - Idles perfectly - starts perfectly - no smoke or anything like that and is as full of oil as the day I changed it 3 months ago
 

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Cam chain/chain guide/CCT about to kick the bucket? Sounds like the bike is trying to give you a message.

On second reading of your symptoms, it may be electrical in nature. Something is interfering with the proper operation of the ignition system? Check in no particular order, cam pulse generator, tip over sensor and the rest of the start stop circuit, wiring and all connectors. Good luck.

FI or carb? If FI check FPR.
 

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Discussion Starter #13
Cam chain/chain guide/CCT about to kick the bucket? Sounds like the bike is trying to give you a message.

On second reading of your symptoms, it may be electrical in nature. Something is interfering with the proper operation of the ignition system? Check in no particular order, cam pulse generator, tip over sensor and the rest of the start stop circuit, wiring and all connectors. Good luck.

FI or carb? If FI check FPR.
CCT is custom made with manual adjustment, I did consider the Cam Chain but cannot see how it would gradually break and cause the symptoms I am having - I'd expect the cam chain to snap and bang - end of

The sensors are all monitored by the ECU (F1) no warning lights, not FPR symptoms - would be running rich and smell of fuel would be obvious - like I said I have owned the bike for 15 years and thought of all the usual suspects but none would fit the symptoms but thanks for the suggestions
 

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"CCT is custom made with manual adjustment, " can you eliminate this non standard part and put original one back in? in order to eliminate it from suspect list
I think you can pull the side cover to inspect the cam chain/guide thoroughly in order to eliminate it from suspect list
Cam pulse generator can intermittently fail without triggering the FI light.
FPR can have an intermittent pinhole leak
What is your running voltage at the battery at idle and at speed?
 

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Discussion Starter #15
"CCT is custom made with manual adjustment, " can you eliminate this non standard part and put original one back in? in order to eliminate it from suspect list
I think you can pull the side cover to inspect the cam chain/guide thoroughly in order to eliminate it from suspect list
Cam pulse generator can intermittently fail without triggering the FI light.
FPR can have an intermittent pinhole leak
What is your running voltage at the battery at idle and at speed?
I am trying to understand how any of that would cause the symptoms I am having - there is no cam chain noise I know what it sounds like - FPR would not cause these symptoms either - running voltage is fine I have a volt meter on the dash and it sits at a steady 14.5 volts - battery is a healthy 13.4v, I have more or less ruled out these items - there is no fuel in the air intake - I had it apart today vacuum hoses are dry no fuel in there

CCT is working no adjustment needed
 

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Discussion Starter #17
Ok, what about the cam pulse generator?
not sure really - I would think the engine would be running like #### if there was that sort of problem, it runs ok (quite normal) until I open the throttle hard, going to take another look tomorrow in case I missed something.

Way early on I thought it was intake noise from the airbox - I'm going to check that the hose (that I blocked up) from the pair valve is still blocked up, it attaches at the front of the airbox (after filter) so it is open to the outside unfiltered and could be very noisy - that would fit with the symptoms - unfiltered air getting sucked in there would make for a free flow past the filter and loud noise from the intake - that actually makes sense - it would likely also mess up the fuel/air mixture making it run lean - like running without a filter, I should have looked closer at that when I had it all out, on my OP I mentioned "intake noise" which I have experienced first hand from one of my mates years ago had a tuned up cooper with twin webbers - the intake was like a hammer hitting the back of the dashboard they were so loud - part of that note we here from our bikes is the intake sucking air in although it is muted by the airbox - if somehow that was open to atmosphere it would be very noisy indeed - I am starting to think that this is exactly what I am hearing hmmmmmm, I wonder has that pipe become unplugged - it hangs off the front of the airbox with a big bolt plugging the end of the hose, I didn't check it or notice it today - should have, I lifted the airbox off and set it down, more I think about it the more plausible it is getting
 

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Discussion Starter #18
have you ever heard carbs sucking air in with no filter - they are very noisy and under load extremely noisy, Fuel injection intake is the same although you rarely hear it because the engine won't run with the airbox off (airflow meter)
 

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Discussion Starter #19
Thinking out loud here lol

The more I think the more I don't remember even seeing that hose on the airbox - it might well have been missing - it may have come off somehow, this is what lockdown does - stuck in my apartment now for 2 weeks alone with no interaction with anyone or the outside world lol
 

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I wonder about balancer shafts - could they suddenly cause a lot of noise - or do they fail and if so what causes the failure

clutching at straws here TBH lol
These only bang and clang about at idle........ mine make a racket as I haven't taken BB out for a decent ride and my fuel is over 6wks old....... but with a bit of throttle all goes quiet.

I'm leaning towards something nasty happening inside the cam cover........ maybe a cam bearing has stripped a thread and begins to knock around with revs - the cam chain makes a continuous roar/rattle if the tensioner has gone, but a bearing or a broken valve spring/collett or ??? - hopefully it's not, but worth a check while the airbox is off (y)

PS Don't wait to use up fuel, drain the tank into a container and check for crud in the bottom of the bucket/tank. Maybe a blocked injector might make the engine run rough enough to make some noises.

Sorry - just read the bit about intake hoses...... hope that's it :D
 
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