Hi all,

The short story is that one of my mates recently bought a rebuilt CBR600FK (1989) with custom fairing. The guy said he'd totally rebuilt it and it was great blah blah.

Well, when we went to see it... it wasnt..

Basically it had an oil leak on one of the oil pipe unions but the bolt was rounded off so we went to take the sump off to get a better grip on it and found that 2 of the exhaust header bolts were mangled and one had snapped off in the cylinder head.

Got that off to get it fixed and took the cylinder block off as well to replce the gasket and noticed one of the pistons was cracked!

Replaced that and rebuilt the engine with the new piston and rings, all new gaskets, etc.. and got it back together.

This was done with the aid of another mate of mine. Now neither of us are mechanics but we're pretty mechanically minded and work on our own bikes (although rebuilding an engine is probably the biggest job either of us had done) but we worked through the manual and got it all back together.

Filled up with fluids, got her started and she sounded great Took her for a quick ride to blow out the cobwebs (5-10mins ish just make sure everything felt ok) and thought we'd done a good job.

A day later my mate (the owner) had a quick ride on it for a few mins with no problems just to make sure it was still ok and that was that for the day.

The next day he was going to come meet me for lunch (15-20min ride) but on his way to meet me the bike started making a tappy noise.

I heard it but wasnt entirely sure what it was, he wasnt losing power, it just didnt sound nice.

Today I went round there to make sure the spark plugs were tight as id heard this can cause a similar noise but they seemed ok so i decided to record a quick video and ask you fine people if you know what it can be.

[youtube]z9UFIE544qo[/youtube]

the sound appears to be coming from the rear of the engine, could it be an air leak on the carbs? or perhaps the CCT?

whats weird is it doesnt seem to change speed when revving.

oil is fine, and up to proper levels

the noise just suddenly started and im thinking if we'd put it together wrong we'd have had noises and problems from the word go but as said it has been ridden for a day or 2 without any problems, it just started.

any help greatly appreciated, apologies for the wall of text

many thanks

 

That *IS* weird. I can't think of a single thing whose motion isn't directly affected by engine RPMs. . .everything that moves at idle increases its repetitions as RPMs increase. . .

 

I'd check the CCT first. Remove it and see if it's moving properly.

 

thx for the suggestion, when i get a chance i'll be doing just that

 

That almost sounds like a fuel pump problem - you know the fast clicking that you hear as the bike is running out of gas, and you need to flick over to the reserve and let fuel flow to the engine. As the other poster replied, it would seem to me that it is not an internal engine component - but maybe an electrical or vacuum fed item?

 

I have to agree.Not the CCT.

The fuel pump is under the left sidecover. check that. it is pretty loud, not a normal noise.

track it down by using a long handled screwdriver. put one end on the suspected noise generator and the other against your ear. you should be able to track it down quickly.

KongBastard

 

If it was the CCT, the noise would increase as the RPMs did. NICE CALL on the fuel pump. +1.

 

thanks for the suggestions guys, been very helpful

i'm hopefully popping round there on saturday to have a look at it, was gonna get the tank and airbox off so i can get to the CCT just to give it a look over and a clean, also, if it is an airleak then it sounds like thats where its coming from so perhaps one of the carb air pipes wasnt tightened up properly when we rebuilt the engine.

i really dont think its the fuel pump, the noise isnt coming from there, sounds more back of the engine than being as far back as where the pump is. although we did have a wiring problem with it (loose connection to the relay meaning it wasnt coming on) which i fixed. pump itself is fine i believe but i'll definately have a good listen to it.

might actually take the fuel pump of my trackbike ('97 FV) and do a swap to test it.

thanks so far guys..

 

You can get to the CCT with just the left side fairings off - and with a deep socket you can get it off in about 5 minutes... I had my old one off and on quite a few times - that video clip is probably not as good as hearing the noise in person, but I have a hard time believing that it is the CCT - when one of these is failing, it is allowing some chain noise to be heard, more of a rhythmic rattling sound.. not so much of a tapping

 

The pump isn't even necessary for what you're doing, here. You can bypass it completely, and just run the fuel hose right into the carbs.