125cc stroker bogging down

[ro51znw]

Hay all. Im pete and a newbie........ Been lurking for a while and now need a hand, hope you can help.

I bought a derbi senda baja from ebay as a non running project, i fitted a Chinese engine from a zongshen arizona as the old one was fubar.

The new engine runs fine until im out riding, its has a horrid bogging down feeling and wont go much more than 40mph.

Bizzar thing is, going down the slightest of hills and its fine but up the slightest hill and it boggs.... Most of what i have read online suggests that it could be running rich at higher rpms.

Would yoi guys and gals agree.

Its driving me mad not getting out and riding and i really hope it can be fixed.

[ro51znw]

http://tapatalk.imageshack.com/v2/14/11/30/b76f62f16687d60d0eb560b19a4abfb7.jpg

http://tapatalk.imageshack.com/v2/14/11/30/1818e3c3c3ccf9ae5a960ec014e2edd3.jpghttp://tapatalk.imageshack.com/v2/14/11/30/79283434eba55e6249cbf701cd79e163.jpg

Some pics to help out ( we all love pics) made the cradle my self at work

[Joeman]

try switching the fuel off and see if it picks up as it runs out...

what ignition system are you using? could be that its not advancing enough at higher RPMs...

[ro51znw]

Its the original zongshen cdi ignition. Never thought to shut the fuel off, good plan will try that...

The carb is the zongshen one too with the original needle however i have put the throttle cable from the derbi into the zongshen slide, would tjis affect the needle hight?

[Joeman]

needle height is normally adjustable with a little C-Clip... if you're running rich, lower the needle...

[ro51znw]

Yeah it is adjustable, i think i will try to lower it a notch and see if it helps, i just don't want to run it lean and damage the engine

[Grumpy Old Git]

Have you checked the air intake - Filter, etc.? Colour of the spark plug?

Simple checks may give you more clues to go on.

[ro51znw]

It was running to lean after all i have richend up the carb by raising the needle a notch and its performance is much better now

Still had to push it home two miles after the clutch cable snapped

[ro51znw]

Thanks for the help everyone

[Classickid21]

Helloo dude you have had a look already but air leaks

Are you running a standard air box or k&n if the after market pod filter put a sock over it and try see if this helps it stop bogging as much

If you are running a pod filter what jet do you have fitted

If this isn't the case.

What is the spark like weak or bright blue

And what sprockets are you riding on may be some of the issue

Kin regards