Hard to start? Clutch wont engage unless I loosen spark plug?

[Member 30571]

Nice bike . Thats a 66/80cc motor

 

[skatevw]

thanks, so maybe put a fatter head gasket? Where can they be purchased?

 

[Chainlube]

thanks, so maybe put a fatter head gasket? Where can they be purchased?

Hold on for a sec, pull the head off and check it out first. Look at the mating surface and see if there are any machining marks. Like Damien says it could be the wrong plug. Only 4 nuts and it's off, 14mm I think.

 

[skatevw]

thanks, the plug is a weixing Z4C

 

[DAMIEN1307]

thanks, the plug is a weixing Z4C

That is the original Chinese made POS junky plug that came with the engine...They hardly ever work very well...I immediately throw them in the trash and replace them with an NGK-B6HS spark plug or the BR6HS if thats what you can get...You may well only need to replace that plug to solve your problem...DAMIEN

Amazon.com: NGK 7534 Spark Plug - B6HS, Each : Automotive

Buy NGK 7534 Spark Plug - B6HS, Each: Spark Plugs - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[skatevw]

Boy I wish. But as I say, if plug is tight, let clutch out, and the motor will NOT TURN OVER, it just slips from the clutch, only with extra air into the cylinder will it start?

 

[Chainlube]

Boy I wish. But as I say, if plug is tight, let clutch out, and the motor will NOT TURN OVER, it just slips from the clutch, only with extra air into the cylinder will it start?

If everything is in order, it will take some effort to turn the engine over. Pedal it fairly fast and then let out the clutch.

 

[digital_life]

Boy I wish. But as I say, if plug is tight, let clutch out, and the motor will NOT TURN OVER, it just slips from the clutch, only with extra air into the cylinder will it start?

You have to keep pedaling when you let the clutch out, You will also want to keep pedaling until you get to 5~10 Mph these motors need all the help they can get.

 

[Jacko1]

Hi, New to this site, Bought this beast over the weekend, been sitting and have no history on it. I sprayed starting fluid in it, and started it, cool.... then noticed the Plug was loose in head, so I tightened it, now cant get motor to turn over? let out clutch and will not engage motor, UNLESS PLUG IS LOOSE? Seems like too high of compression? with loose, runs good, but won't idle, and scared the plug will blow out if I really go out to ride it, Any Ideas??

I had the same problem but when I took the head off I saw nothing abnormal. after a few more tries it still didn't work so I put it down to a problem with the head and had a mate with a high compression head so I put it on and it started right up. I still do not know what happened but the new head fixed it. Plus it will give you more power. This has happened to a few people on other forums and they suggested this fix to me.

This is the one I used and it seemed to be the best value with the decent build quality.

Racing CNC Cylinder Head fit for 66cc / 80cc Gas Motorized Bicycle Bike Silver | eBay

66cc / 80cc Gas Motorized Bicycle. This is also why we can provide competitive prices that ensure you buy your spare parts at the right price, and in most cases better than our competitors. 1x CNC Cylinder Head.

ebay.us

 

[GreasyChris]

The higher the compression the harder it is for the spark plug to fire. If its not starting with the plug tight. I'd suspect the cheap plug you have or a weak magneto or cdi.