Hi all,

My CBR is giving me some trouble. My first time (since I bought it) on a serious round it drained the fuel tank within 120 km (about 80 miles). This was all high way at speeds of around 120 km/h (about 80 mile/h). And it had a huge flat spot under 7k rpm. In an attempt to solve this I bought a set of second hand carburateurs and a complete rebuild kit (keyster set CBR600, PC31 Bj. 95-98 | Keyster Vergaser Sätze | Honda)

After syncing the carburateurs and adjusting the pilot screw the bike is running better but not perfect. There is still a flat spot (sometimes it is, and sometimes it not). Currently the fuel consumption is (if i try to be as economic as I can) I can reach to about 15 km/l (35 MPG). If I start cruising on the highway, it drops to 12 km/l (about 27 mpg).

What are the common causes of high fuel consumption?

 

Hi All,

Today i noticed that the entire rear wheel (sprocket, rim and brake disk) is warm after riding. I am not sure if this is normal (Heat coming form the drive chain?).

 

Hi All,

I actually found the problem (by accident). Some ******** connected the throttle position sensor the wrong way around. You would suspect this is not possible because all automotive type connecters have a “key” and only fit one way (that is why I never paid any attention to it). In the case the connector has a removable “key” and that fits both way’s, hence, the connector can fit both ways. (see the picture)

After a quick fix the bike fired up like it never did before, the throttle response is much and much better…! It actually has some torque down 6k rpm. So, just some advice, if your bike is consuming allot of fuel while everything seems in perfect working order….? Give it a quick check….

Kind regards,
Sjoerd

 

Interesting, glad you found the problem. I would have never guessed that one.

Thanks for the insight, Ern

 

The moment I found that the connector was wired incorrect I knew that must be the problem. Looking back, all the signs where there. I always assumed it was running rich because it consumed allot of fuel. Although the classic tell tail signs where not there, signs like sooty pipe, sooty spark plugs, smell of petrol while running....

Typically if ignition timing if late it will lose power, but maybe more important in this case, the thermodynamic efficiency of the engine will drop. Normally combustion in petrol engine is taking place at "near" constant volume. If ignition is late it will approach a "near" constant pressure combustion. The result of that is the effective work of the engine will drop.

So, again: If you have a bike consuming to much fuel but not showing the classic signs of a rich mixture...check the ignition timing!