Hausheng 49cc lost its umpf - help!


New Member
Mar 27, 2008
After about 200 km of running great, my Hausheng lost its uumpf !

It starts fine, and runs good downhill (or on the stand), but on level or uphill it labours. Have to pedal where previously I got 30+ km/h ?

I think I may have pushed it to hard before being run in. Did about 150 km on fairly level ground before I went downtown with it. Going there is downhill all the way, coming back there is one very steep hill. I had to pedal hard, with engine fully open - barely made it to the top. On the following level stretch it didn't feel lively anymore. Next day worked fine downtown, but had to pedal all the way back.

Did I break something?

I have a small engine book (doesn't cover this engine specifically) and followed its instructions to check:

fuel flow
air intake
compression (thumb test)

I changed the oil at 150 km

On the stand it runs fine - sputters now and again at top revs (with small smoke puff), but it always hesitated when going over 55 km/h

How long before this engine is run in?

Please help!



Your engine should be well broken in.

Simple things first- check the fuel filter. To me, it sounds like a fuel flow restriction.


Check valve clearance.

Check valve clearance. .05 intake and exhaust cold . Enjoy the ride..


It does sound mixture related specially since it will run up on the stand with minimal hesitation but dies when its under load..

have you checked for air leaks and another thing - it might be worth checking the exhaust is free flowing and not blocked up (if its a 2 stroke engine)

Have you checked the condition of the clutch and drivetrain - also the spark plug is a good guide for mixture..

Jemma xx


If it starts and runs fine on the bench to me it's unlikely to be a valve clearance problem(check it anyway)
It sounds either fuel or air intake related so i'm afraid your gonna have to go through the motions of trial & error......start with fuel man.


New Member
Mar 27, 2008
Problem solved ! Thanks Homemade!.

I set the intake valve to 0.6mm and output to.10mm while engine was cold.

The output was 0.18mm before!

I wasn't to sure of the procedure for setting valves. So I turned the engine untill the valve gaps was at their biggest. Then adjusted the gap until the feeler gauge was a tight fit.

Maybe someone can explain the correct procedure?

Thanks for the help - was planning on taking the whole machine apart to hut for a problem.