engine bogs down at top revs

JackT · Two Stroke Sniffer Joined: 19 Feb 2010 Karma :

Ive been struggling with this for months now. My 125cc kinroad cyclone has developed an problem when im in 1st gear or at the top end of a gear. When i open the throttle the engine coughs and splutters and seems to loose any power. I origonally though it was either a problem with petrol flow or air flow. So to fix this i have replaced the entire air system, (the filter, air box and manifold tube between the air box and carb. I removed the petrol tap to find no blockage in that and the tank is breathing so there isnt a vacuum problem. I then cleaned the carb jets with a soft bristle, cleaned out the entire carb. After the bogging kept happening i replaced the spark plug but that didnt work either. (you can imagine how annoying this would be getting). Finally i checked the exhausts for and back pressure problems but still the problem occurs.
Please please please help me. I cant ride the bike and i really need to get some experience for my test.
Thanks
Jack

WetSparks · Renault 5 Driver Joined: 05 May 2010 Karma :

Does this happen if you have the choke on slightly?

The other thing to check for is any air leak between the carb and the engine, a dodgy gasket or seal will let in too much air and run the engine far to weak.

JackT · Two Stroke Sniffer Joined: 19 Feb 2010 Karma :

Ive never tried with the choke, i'll try it tonight. And i checked the tubing when i took the carb apart, all seemed fine. Second look cant hurt though i guess

nightshaddow · Nearly there... Joined: 18 Feb 2008 Karma :

dose it have a choke cable, possibly the cable sticking,

also as sparks say airleak could cause it

also check your jets and your float again....
____________________
"WHAT DO YOU MEAN 100 MPH THATS IMPOSSIBLE Its chinese OFFICER."
Current rides CB 125 TDE(the next project) NS125RK ( now on the road ) CB125TDC (soon to be project 17) melody ( the nephews )

nightshaddow · Nearly there... Joined: 18 Feb 2008 Karma :

just as a thought also have you done the valve clearences lately,
____________________
"WHAT DO YOU MEAN 100 MPH THATS IMPOSSIBLE Its chinese OFFICER."
Current rides CB 125 TDE(the next project) NS125RK ( now on the road ) CB125TDC (soon to be project 17) melody ( the nephews )