Rattle/Ping noise on CRF450R when coming out of corners

[Spokes574]

My engine was running fine, then I added:
-1 tooth to rear sprocket and a new ignition CDI Rev box.

After about 1hr the engine started to make a rattle/ping noise when coming out of corners, and only when I come out of corners. Once at high speed no noise.

So I put full race gas in, still rattle/ping.
So I put the stock CDI box, still rattle/Ping.
I checked the pipe bolts and they are tight
I check the spark plug and its light brown.

The bike runs great other than the rattle/ping noise when
coming out of corners and I know that is not good.
I am loss as to what else to check.

Any ideas as to what could be the issue?

Thanks,
Spokes574

 

[Rich Rohrich]

Check to see if the chain is slapping .

 

[Spokes574]

Check to see if the chain is slapping .

Rich,
I am assuming the chain you are referring to is the timing chain? How would a lose timing chain make pigging/rattling noises coming out to corners?

Also, now after losing sleep over this, this noise did start after installing the after market CDI/rev box - though I did put the original back in now and still have the problem.
I still left the 1 tooth larger sprocket, guessing thats not the source of the problem.


Another question for you. With the aftermarket CDI/Rev box the bike takes 5-7 kicks to get on, but when I have the stock CDI box it takes only 1-2 kicks? I turned the fuel screw out 1/2 turn but still the same results.

Thanks for responding. Its 3:30am and I am up thinging about this problem.

 

[Rich Rohrich]

I was referring to the drive chain. CRFs are notorious for making weird drive chain noises that run through the frame and sound like they are coming from somewhere else. You changed the sprocket and now you have an mysterious rattling sound. Just a thought. ;)

As for the starting issue. If you think about how CDIs work, it's clear that the ignition box has a major influence on how the stator output is stepped up to secondary voltage. It sounds like the box you have just isn't stepping the voltage up high enough at super low revs (200-400 rpm) being turned during kick starting. If it starts right away by push starting it from a reasonably high speed, I would look hard at that box. It's worth talking to the vendor of the box and explaining the issue you are having.

 

[Spokes574]

Rich,
I dropped the bike off at my mechanic and they put it on the dyno and did not hear any rattling/pinging. They said they ran it in the parking lot and did not hear anything either. The only thing they said they could find was a very loose kick starter which I do not think is the cause of the ping/rattling I hear coming out of corners. I told them to ride the bike at the track, so we are to meet up on Sunday at the track. Why would the bike not make the noise on the dyno?

 

[Rich Rohrich]

If my hunch is correct you'll find that the noise isn't present because the suspension is static on the dyno and the swingarm angle is fixed. Likewise riding it in the parking lot won't move the suspension either. Once you are riding at the track the swingarm moves through it's normal arc in the corners as the suspension compresses and the chain slaps and your noise reappears.

 

[Spokes574]

Rich,
So I am guessing that you feel its the chain/slap and not the engine since its runs fine on the dyno and parking lot?

How about if the engine is not effected until a suspension puts a load on the front sprocket as the swing arm moves. What are your thoughts on that?


SO I guess I should re-ajust the chain and just ride the bike as ussual?
It's at 3 fingers out as ussual I am not sure what other way to adjust it.

Thanks

 

[Rich Rohrich]

How about if the engine is not effected until a suspension puts a load on the front sprocket as the swing arm moves. What are your thoughts on that?

I think you might be reaching now. :)

 

[Spokes574]

Rich,
went to my mechanics shop with my helmet and road my bike myself down the street taking off in 2nd, then taking off again in 3rd and sure enough no pigging/rattling.
So you are correct that the chain must be having an effect when the suspension is in motion! I will adjust my chain this weekend and see what happens. Who would of figured that chain slap could sound like its coming out of the header?

 

[lwsmithjr]

You may have checked this already, but on my CRF, this noise got very noticeable all at once....and I had not changed anything. I just happened to pull up the chain one day and look at the rub guard. It had worn through and the chain was rubbing -- and slapping -- directly on the swingarm. The chain had made two very nice grooves in the swingarm from the rubbing. But if you did not pick the chain up off of the swingarm, you couldn't tell it was worn through.

 

[Spokes574]

Thanks for that info on the chain glide wear, I will check that also.
Funny how other things on the bike can make you think you have an engine issue.

 

[Spokes574]

I checked the swing arm this weekend and noticed that the mud flap was a tad bit chewed up from the chain. I never have seen this with the 48 tooth sprocket, only now with the 49 tooth sprocket, so that instantly told me that yes there was something going on with the chain for sure. The chain had about a little more than 3 finger ajustment, so I ajusted the chain to exactly 3 finger slack, and the noise went away. So yes in deed the chain can make noise that seems to make you think its coming out of the header like a lean jetting ping. i have been riding bikes for ~10yrs and never ran into this before.

Spokes574