Bike Has no Power in low Revs

[Spike_R]

Hellooooooo

My bike has had a new top end put on and i got to ride it today its crap until you hit the power band has not even enough power to pull off on a hill.

I have tightened the the head and cleaned everything out but still no luck. It has had brand new piston rings etc but am not sure... someone said it could be that the carb inlet rubber is not tight enough but im not sure... i also tightened up the spark plug etc...

Cheers
____________________
Derbi supermoto with cr500 engine, niceee

[Keith]

You might want to let them know that the bike is a Derbi Senda with 70cc top end and 19mm dell orto carb.

You can only get useful feedback if you give good information.

Keith (Kickstart) may have some good information about how to solve the problem, after all, he knows almost all there is to know about 2 strokes.
____________________
Aprilia RSV Mille R Edwards Replica - Aprilia RS250 - Suzuki GSXR600 Supersport Race Bike

[Kickstart]

Hi

I don't know that much.

Anyway, I would expect a big bore kit to gain you low down power but it would be entirely possible that they designed the porting to work at high revs better than low revs. Does it take off like a scalded cat when it hits the power now (assuming you have run it in)? If so that suggests it is ported for higher rev performance and you are fairly certain to loose low down power by doing this (this is why power valves came into use, to allow you to use porting set up for top end power while still keeping the bike rideable at low revs).

Beyond that it might be worth having a play with the jetting. Maybe try lifting the needle up one notch to richen it on smaller throttle openings.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Spike_R]

well to be honest it is worse than i said, it will not pick up from the mark unless i start it in the power band, which isnt good for running in new piston rings. Im going to get some jubilee clips in the morning and tighten the carb on properly, if i have no luck with that im going to take it to the mechanic who helped me, if still no luck ill come back on here, then if no more luck its off to where i bought it.. lol
____________________
Derbi supermoto with cr500 engine, niceee

[Spike_R]

looks like the barrel is scored again!

what should i do cause its screwed can i get it re-bored?
____________________
Derbi supermoto with cr500 engine, niceee

[Kickstart]

Hi

Think the standard barrels can be rebored (same engine as the RS50?) but don't know about the big bore kit. Quite possibly the use a plated barrel and that would need replating (~£100 + piston, etc).

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[K!K @]

My mates was like that.
All you gotta do is screw te fucker to about 9000rpm then te powerband will kick in.
Try it and if it doesn't work fuck knows
____________________
Suzuki AY50 Katana
~Elite~Knights~