Adventure Bike Rider Forum

got myself a crf rally 2017 I have recenlty done some work on my bike changed exhaust, tires, and done oil changes and filter changes qnd now for some reason i get between rpm range 4500-5000rpms a whoop whoop whoop continous sound until i get up into the 5500-6000rpm range ive checked chain slack and loosened a little more no change checked the bike free rolling clutch in and the noise disappears it only seems to be there at this rpm range while crusing along which is anoyying me can anyone give any feedback on what this could be qs its driving me mad ...

Have you got rim locks in the wheels? If you have this could be the source of your noise

Greetings Mike,

I assume that the noise has only suddenly started immediately after you changed those items? May I ask why you changed the exhaust? Perhaps the exhaust change has effected the breathing system and the noise might be an air resonance in the intake or exhaust system? Have you replaced the tyres for the same make/model/size/pressures?

Have you had anybody ride along side of you when the noise occurs, can they hear it, pinpoint the location; front - left side - right side - directly at the rear?

TTFN

Hugh.

Sounds like a fuelling issue, is the new exhaust a lot more open? and did you do anything to make the intake side more open also?
Most injection setups around these days run quite lean at mid-upper rev range for emission purposes and if you do mods to let them breath a lot better they can often need re-mapping with something like a power commander

the bike looks like its been through the "modders"--bottom fairing cut away, CRF250l Bashplate and other farkles etc--what is the history?--best get in touch with the previous owner to get a list of modifications. I certainly agree that fitting a straight through exhaust will have messed up the fuelling and it will need more baffling to get the backpressure back ,or an ECU change.

maby check the chain for a tight spot that could cause it under load ?

Is it not the tyres, they look like the sort of tyres that will induce some road noise. The Metzeler Unicross I used to have on mine played tunes

Checked the chain and slackened a little more aswell just incase my weight was the issue causing it to be a little tight underload but still the same ... the sparkles and farkles i did my self the bike orignally cone to me like this The tires are same i did use some different rim locks though once replacing the tires qnd changed the exhaust from standard to a yoshimura rs4 ... will ask previous owner if he had issues with this on has he took it off saying it was to load ... iam leaning towards feuling maybe now and the exhaust as when i pull the clutch in and free roll qt the same speed it isnt there its only when at 4500-5000rpm in 4th and 5th gear ... other than that everything is fine ...

Wouldn't the sound appear at same revs in any gear as they are only cogs on a shaft bigger cog higher speed thing... Do you known of any dyno shops near you so they could look at it for you..

Surely someone on the adv thread has used same exhaust as you?

strange ive got a spare wheel you can throw on to try see if its somthing to do with the tyre or the sprocket ?? let me know if you want to have a go