250cc Zongshen rattles

[pitboys]

Hi guys,

New 250cc Zongshen motor that pretty much consistently rattles. The noise sems to be coming from the front end of the motor. It sounds like somethig is loose, like a loose nut that has a loose washer just rattling aorund waiting for the nut to fall off..(that would be me..

What could it be??

 

[Cactus Jack]

If it does it mainly while you are accelerating or under load ...... then that's detonation (sounds like marbles or something rattling in the pipe or the front of the motor) ...... in that case run your engine only on premium unleaded or octane booster in standard unleaded to see if it stops OR see if you can back the ignition timing off a bit ....... maybe you've just bought crappo fuel cut with too much ethanol or heating fluid ...... I've had the same problem in a Holden Commodore '87 model that was run on Cheapa XL fuel ..

Another thing is that some of them are pushrod motors ...... so excessive valve lash clearance could cause a rattling sound .....

 

[Matty]

so cactus would that work in reverse? cos i used to run mine with octane booster and since i stopped its started rattling like that...mine is a zongshen 125.. ill have to get some more octane booster and see what happens i suppose.

 

[Cactus Jack]

Yes , you've just said the exact same thing as I did but in reverse ....... running the octane booster would NOT have caused it to detonate when you went back to standard fuel .... all that's happened is that you can now feel it detonating . I'd say that's mostly what's causing all the serious engine damage problems that some people have had ....

The sound you can hear is the fuel exploding in the cylinder like a hand grenade and smashing the piston sharply like a hammer blow rather than burning cleanly , expanding the air and pushing the piston smoothly as far down the cylinder as possible . It's similar to copping repetitive king hits rather than repetitive shoves with similar resultant physical damage .....

 

[pitboys]

Hey thanks Cactus. I will try the different fuel however it does rattle even at idle. Could be the valves as you sugggest. Not having realy any knowledge in that area, is it a big job to adjust them???

Thanks

 

[pitboys]

Another thing is that some of them are pushrod motors ...... so excessive valve lash clearance could cause a rattling sound ..... [/QUOTE]

Hi Cactus Jack.

Can you tell me a little more about excessive valve lash clearance.....changin the fuel made no difference to the rattling??? Any help would be appreciated.

Thanks for your patience..