Any leads on the engine rattle?? - Honda CBR250R Forum : Honda CBR 250 Forums

Tahir · 11-26-2012, 08:00 AM

I had my mechanic look again at the rattle today.. removed every bit of plastic and tightend all bolts..with the fairing and headlights removed, the sound gets even louder.. we opened up the clutch side of the engine as well as the head.. everything seems normal.. the mechanic says the noise is due to the connecting or the primary gear.. any idea???

gromit · 11-26-2012, 10:11 AM

I had a rattle that sounded very serious (metal on metal) coming from the upper engine area. I tracked it to the polution control (smog) emissions system. On the engine valve cover there is a small cover plate with a rubber air hose going into it. Under that is a reed valve then a port plate (the one with all the holes #2 in the parts diagram). The port plate is not supposed to move but mine was loose and rattled very badly at various engine speeds. On the actual photo you can see three location points that are worn from the plate moving around. I removed the plate and the engine rattle was gone. Your mechanic should be able to easily check and repair this.

Turbo DV8 · 11-27-2012, 12:26 AM

And the plate serves what function? And the removal of the plate affects what?

Tahir · 11-27-2012, 03:58 AM

Quote:

Originally Posted by gromit

I had a rattle that sounded very serious (metal on metal) coming from the upper engine area. I tracked it to the polution control (smog) emissions system. On the engine valve cover there is a small cover plate with a rubber air hose going into it. Under that is a reed valve then a port plate (the one with all the holes #2 in the parts diagram). The port plate is not supposed to move but mine was loose and rattled very badly at various engine speeds. On the actual photo you can see three location points that are worn from the plate moving around. I removed the plate and the engine rattle was gone. Your mechanic should be able to easily check and repair this.

i removed the metallic plate ( the one in the middle of the picture) and test drove the bike...it didnt help either...

Aufitt · 11-27-2012, 12:51 PM

I'll give you a lead-

Its got one spark plug.

gromit · 11-27-2012, 01:44 PM

Quote:

Originally Posted by Turbo DV8

And the plate serves what function? And the removal of the plate affects what?

The port plate helps dirtribute the pulse pressure to the pair (pulsed air induction reed) valve which is directly above the plate. It is part of the exhaust emission system which reduces unburnt hydrocarbons into the environment. Removing it would make it less efficient BUT if you have an aftermarket exhaust (slip on or full) the entire system has been rendered totally useless because the catalytic converter was removed with the stock muffler. The catalytic converter must be present to reduce hydro carbons.

**MotoMike** · 11-27-2012, 03:04 PM

Quote:

Originally Posted by gromit

The port plate helps dirtribute the pulse pressure to the pair (pulsed air induction reed) valve which is directly above the plate. It is part of the exhaust emission system which reduces unburnt hydrocarbons into the environment. Removing it would make it less efficient BUT if you have an aftermarket exhaust (slip on or full) the entire system has been rendered totally useless because the catalytic converter was removed with the stock muffler. The catalytic converter must be present to reduce hydro carbons.

The PAIR valve still performs its function to inject air into the cylinder head exhaust port, regardless whether the bike has its stock exhaust or an aftermarket exhaust installed. I agree, the cat must be present to take advantage of the air being mixed into the exhaust to reduce emissions.

BTW, I checked my port plate when I did my second Valve Clearance Inspection... the port plate wasn't loose in the cylinder head cover. It is held in place by the reed valve assembly when the two screws are tightened down. Those three shiny spots on the port plate are just point of contact areas, which are not discolored by exhaust blow back, as is the case on the surrounding areas of the port plate. The reed valve itself could be a source of noise at certain rpm's, which in any case doesn't concern me. After 6000 miles, my bike runs better than ever.