A9 cam BBK 69mm valve PROBLEM HELP

[cutro64]

so i have a 139pqmb engine that came with a 2012 tao tao 50 .... i took my head apart and measured the valves and say they where 69mm so i ordered a 69mm vlave 50mm bbk with head and a a9 cam
i installed everything and had a very loud knock going on and large amount of smoke in the exhaust.. i trouble shooted and found oil in the exhaust do to the valve spring breaking and seal busting... this is after a short low rpm start.... so i rebuilt everything with new valve and seal and put int the stock cam everything works fine .... how can i get the a9 cam to work... do i need to use a 64mm valve n head...... or can i adjust the 69mm to workk... PLEASE HELP

[noday]

A9 has more lift on the cam lobes.

sounds like the valve was hitting the piston top ?

use some modelling clay on top of the piston. 4th pic down is an example

49ccscoot.proboards.com/index.cgi?board=4ttech&action=display&thread=417

turn the engine by hand. you may need to add some relief to the piston head with a dremel.

did you measure height of the old and new cylinder head, cylinder and piston( from top of wrist pin hole to crown) ? some times there is as much as 1mm difference from old to new.

did you turn the engine by hand after just the cylinder was installed ?

some pistons are 11mm from hole to crown, others 12mm.

if the piston is "taller" you can add clearance by adding base gaskets to the cylinder

[robertrayfield91]

Hii I have a 47mm 80cc big bore kit and need to no how to take out the valves in my original 50cc valves to put them in 80cc head

[noday]

thanks for joining 49ccscoot

welcome to this forum

:welcome3:


it is easy to take old valves and springs out, with just a C clamp and a socket

to put the new ones in, you need a tool made for the job

the link below shows one option

www.ebay.com/itm/Motorcycle-car-valve-spring-compressor-KZ-CB-GS-XS-550-750-tool-/330696033066?forcev4exp=true

after you change valves, the valve and seat need to be "matched" by using a valve grinding compound.

if you are posting here, asking this question, you probably should have this done by a machine shop & watch.

it is not hard to do, but apparent trivial details make the difference between success and failure.

[robertrayfield91]

Okk thanks a lot mate and do you know anywere we're I can get a strap wrench or a tool to hold the fly wheel want to change my rollers but need to wieght them before ordering new ones thanks.

[noday]

mate ? ...says to me you are somewhere down under ?

#1, you need an impact wrench to work on scooters, either electric or air

I use a 1/2" drive air impact, cost $25ish USD from HarborFreight. . . . . . BUT. . . . . I already had the air compressor for other things.

otherwise....... I would use

www.harborfreight.com/12-volt-1-2-half-inch-emergency-impact-wrench-92349.html

In the US, one can easily find strap wrenches or oil filter wrenches of the needed size, at most auto-parts stores, HomeDepot, etc

[vegaslightsss]

I saw a little "goody" the other day that fits along the bottom inside the engine case and fits the gear for the starter on the variator,you match it to the teeth so it slides in and then one of your standard belt cover bolts holds the pulley static so you can unbolt the wheel with a breaker bar. Myself I use an impact,much easier but for 9.95 the toot was really cool if you dont have access. here is the link
www.ecrater.com/p/14954780/gy6-50cc-139qmb-variator-locking
and a pic

Attachments:

[noday]

that tool scares me. too much stress on a single bolt into a thin part of the L crankcase.

[stepthrutuner]

Sept 2, 2012 20:11:09 GMT -5 noday said:

that tool scares me. too much stress on a single bolt into a thin part of the L crankcase.

Good point. All of those locking devices I remember seeing bolt on with two bolts.

[nitroman666]

Harbor Freight and other Chinese retailers sell 110 AC impacts for roughly $40-60. A must have for anyone working with scooters.

[stepthrutuner]

I use an electric impact myself but finicky purists say you can possibly tweak your crank wheels out of true with an impact. The Chinarellis seem to be prone to crank thread damage on the fixed face variator retention nut with frequent tightening/loosening using an impact gun. I try to use mine as gingerly as possible.

[nitroman666]

Sept 27, 2012 16:45:39 GMT -5 stepthrutuner said:

I use an electric impact myself but finicky purists say you can possibly tweak your crank wheels out of true with an impact. The Chinarellis seem to be prone to crank thread damage on the fixed face variator retention nut with frequent tightening/loosening using an impact gun. I try to use mine as gingerly as possible.

Agreed. When it stops, don't keep on torquing on it. It's safe as long as you do not keep on trying to tighten it.