1P57qmj cly.head exchange By scoot (Read 703 times)

[scoot]

Hi everybody This is my first thread or ? so if I do something wrong please forgive me. my scooter is a 2008 Baja sc 150cc 1P57qmj will a 157qmj head fit the 1P57qmj engine I know the cam deck height is a little taller so I'm concerned if the stock cam chain will work or will the cam tensioner make up the difference.and is there any other concerns I should know about any help would be great.just as a side note I'm a retired auto mechanic but new to scooter repair (and loving it)

[Bashan]

I have used them interchangeably and never had any problem. I know they are exactly the same height but the P has a little bit wider valve seat. I had heard that about the cam height and supposedly that affects the timing but again, it never bothered anything I was doing. So apparently it's very subtle. I'd hate for you to get something and it didn't work though so lets get a few more opinions before you order. I got a BBK and swapped it for a P head. They never asked if it was a P or not when I ordered and I used the old cam chain, it worked fine.

[scoot]

Thanks,I'll wait as you said,but maybe I'm barking up the wrong tree is the 157qmj head better than the 1P57qmj head ?i.e. more performance ect.I was under the impression that the 1P motor was a lower performance California smog motor Bashan

[Bashan]

Ah the murky waters. It was my understanding that the P head was the better performer albeit marginally. The wider valve seats supposedly indicated slightly larger ports. Having said that, I had two identical P bikes and one was a screamer and the other a dog. No matter what I did to the dog it continued to play dead. It just goes to show the wide variation that occurs when quality control is an afterthought at most of the Chinese scooter factories. These are not Japanese or Taiwanese bikes, they are pure heart of China econo builds. Build 'em cheap and build 'em fast. One of the theories is that you don't know what parts are in them. They grab whatever they got to get them assembled. So you can't even believe what is badged or stamped on the bike. You take what you get and supposedly should be happy you got it so cheap. Forget the owner manuals and wiring diagrams, they're a joke. I don't know how many three phase bikes I've seen with a single phase wiring diagram.

[scoot]

Bashan Yea I've had the scooter for about a year now and I know exactly what you mean you get what you pay for scooters as well as after market parts but I'm having fun working on it and I'm ready to start hoping it up.after 30 odd years of auto mechanics I still get a kick out of tinkering (can't leave any stock)so big bore, cam ,ect here I come. thanks for the help love this site.