50cc camshaft removal.

[zbuck]

How do you get the chain off the cam with the engine still in the scooter? I need to pull the head and this is the only thing holding me up. thank, Don B.

[theswede]

Hi Don, and welcome to the forum!

In order to lift the cam chain and be able to remove the cam shaft, you need to remove the cam chain tensioner. This gives the chain enough slack to allow the cam to be removed.

On this page, www.49ccscoot.com/bbk.html, you can find a complete tutorial for how to tear down and rebuild the top end of a 139QMB engine.
The cam chain tensioner removal procedure is about 9 pages down in the instructions.
Also, this guide might be useful (describes doing the same thing, but without removing the engine), cam chain tensioner removal is on page 6: guldburken.gote.org/scooter/TopEndInstallGY6.pdf

Good luck,

Otto

[zbuck]

Hello Otto, You are welcome. Thank you for your reply. After some effort I was able to get the chain off the cam. I though I had a burnt valve. But when I pulled the head, their was oil all over the head gasket. My firist though, was bad rings. But on further checking, it seem to be the oil seal on the exhaust valve. I am going to check the valve guide ID and see if it is in spec, if so I need to find some valve guide oil seals. Don B.

[Rebel]

Welcome to the forum.

I assume you had the timing marks all lined up when you took it apart. Makes it a bit easier in my opinion, when you put things back together.

[zbuck]

Rebel, Thank you for the welcome. Yes I had the timing marks lined up. Exhaust valve guide is out of spec. Now I have to decide if I am going to replace both valve guides or just by another head. Don B.

[Rocketdog]

Cheaper to buy another, unless your doing the machine work yourself. Here's a shameless plug for Enviro. enviromoto.ecrater.com/product.php?pid=3369563 And I believe Rebels get 10% off. There was free shipping at one time. And Enviro's as good as his word, which is first rate.

RD

[zbuck]

rocketdog, Yes I have dealt with Jeremy and you are right in what your saying and he still has free shipping. I have a friend that owns a automotive/ small engine machine shop, as I have alot of small engine work done there I get a pretty good rate. The Chinese maching on this head sucks. The carb insulator ID does not match the intake port ID, insulator being a smaller ID. I don't know if this is a form of Chinese restriction on this engine. Maybe I would be better off getting a new head, we will see what my friend has to say today. Don B.

[Rocketdog]

"The Chinese machining on this head sucks." Not just yours. hehe

"The carb insulator ID does not match the intake port ID, insulator being a smaller ID. I don't know if this is a form of Chinese restriction on this engine." Now there's an interesting theory. I thought it was just pitiful work. lol

I'd go with your buddy who has the shop. Smooth the ports a bit, blend the bowls to the valve seats, and match up the ports while your at it.

RD

[Enviromoto]

Thanks for the vote of confidence guys I really appreciate it

[zbuck]

You are Welcome Jeremy. Rocketdog, After further review with my Buddy, I think I will buy a new head and use the old one for R&D. One thing I noticed on the carb insulator, if you try and port match to the intake manifold and the head intake port you are getting awful close to o-ring landing. Another thing, when they tapped the head for the spark plug, where there tap broke thru into the combustion chamber they did not chamfer the break thru just left a raw edge. Who knows were the spark was going. Don B.