139QMB Valve spring size? By cdoublejj (Read 2,866 times)

[cdoublejj]

Any one know the 139QMB Valve spring size? any by any chance know how many LBS the springs are or how to measure that?

[cyborg]

Searching for spring pressure now

[Alleyoop]

Read this that should answer your questions. In the real world no seller that I know of will know very technical answers to specific questions unless they actually built the part themselves.
Alleyoop
49ccscoot.proboards.com/thread/415/1100-1284-150cc-valve-springs

[cdoublejj]

Mar 15, 2015 13:02:13 GMT -6 Alleyoop said:

Read this that should answer your questions. In the real world no seller that I know of will know very technical answers to specific questions unless they actually built the part themselves.
Alleyoop
49ccscoot.proboards.com/thread/415/1100-1284-150cc-valve-springs

Oh heck no especially given the state of of the "Performance" GY6 parts market. The trick is not the buy GY6 parts hence needing to know size and pressure or at least a good idea. it was nice to see the NCY stuff was stiffer. IDK why the heck ANY one would want Titanium springs. Titanium VALVES to reduce bob weight sure but, not springs.

A seller by the name of Scooters To Go, i think, actually tests there products, they are the ones who have the 139qmb stroker crank and decent gy6 crank installation video. They seem to know what they are talking about or have a good idea. not to say they aren't selling the some of the same stuff/products (not many), however they can least give you some info on them though.

[Alleyoop]

I know the size but pressure it all depends on the quality of the metal. Just keep this in the back of your head these are NOT precision made motors they are not made to tight tolerances. You can get TWO of the same motors and one may be able to develop more horsepower than the other, remember all come from CHINA. In china there are hundreds of factories that make and put out this stuff. Some use better materials and put out a better product but still not close to top quality.

So your saying Scooter To GO knows their stuff well then ask them the spring pressure question I would love to hear what they say.

[cyborg]

It all boils down to seat height,, valve stem length.keepers and retainers too it's not just the spring,,,

[cdoublejj]

Mar 15, 2015 19:45:32 GMT -6 Alleyoop said:

I know the size but pressure it all depends on the quality of the metal. Just keep this in the back of your head these are NOT precision made motors they are not made to tight tolerances. You can get TWO of the same motors and one may be able to develop more horsepower than the other, remember all come from CHINA. In china there are hundreds of factories that make and put out this stuff. Some use better materials and put out a better product but still not close to top quality.

So your saying Scooter To GO knows their stuff well then ask them the spring pressure question I would love to hear what they say.

They flat out stated they haven't sourced/found any thing yet. At least knowing the size is a start. I think it might be possible to find a quality set maybe NOT from China.

Your absolutely right. However All those finite details they look over is one more tweak i can make for a bit more reliability or power. I'm not going fora 120mph TT 50cc class here or any thing but, i am having a bit of fun tinkering and modifying.

Cyborg I'll try to take that in to consideration and learn what i can about that.

[jct842]

I wouldn't be surprised if the heavier springs take more adjusting. The soft aluminum of the heads and all.

[Alleyoop]

Not to mention if to strong breaking the rockers..LOL

[cdoublejj]

All VERY good points!!! I wonder what kind of tinkering can be done with the head aside from porting with stuff such as valve spring seating heights and what not. I bet that soft aluminum is why the valve springs shims are there! just like how titanium valves have caps on the end to keep the rockers/tappets from mushrooming the the end of the valve stem.

you know given all this i have to wonder if the lighter valves are the better answer. a couple ways to achieve that, most commonly the machine the out the center of the valve BUT, this increases the volume of the combustion chamber slightingly lowering your C:R. To have less weight and not hollow/machine out the center and keep C:R up some folks get titanium valves.

HOWEVER i'm not sure lighter valves change how the springs react, some react certain ways under certain frequencies. i swore one of the big valve spring companies had a cool write up on there website. it was talking about how certain metal alloy compounds make certain metal types and springs that perform certain ways under certain RPMs and frequencies. and say stock springs might not respond the same way with say, a higher lift, top end cam.

I think what you guys mentioned ALSO plays an important roll on such things. I think i have more research and or learning to do. For all i know the stock springs may already be over kill even at red line RPM.

[Alleyoop]

Least of your worries on a motor running those at high rpms you have to worry about the crank. A ported head with maybe bigger valves without more displacement is a waste of money. Displacement gets you more ponies and you then should get a quality crank(stroker or not) to take the extra power.

[cyborg]

Current thought on valve springs are ovate section wire nonprogressive wound and beehive wind profile,,, this stops alot of the occillations and surge waves that happen within the spring itself,,,this creates heat also with ovate wire the inertia mass of the spring is reduced,,, hollow sodium filled valves were an old trick from long ago,,, titanium wire springs, keepers and retainers further reduce inertia mass and higher rpm's are capable and floating kept in check,,,now valves are very thin stemmed even further reducing weight and friction on the guide/stem surfaces as swept areas are smaller,, 25% of the engine power created by the combustion is lost in the valve train and creates a lot of heat,,, one of the reasons ducati engines make great power is desmodromic valve actuation ,,, one cam to open one to close ,,,the valve is under continuous control with no valve springs to fight,,,

[cyborg]

And alley is also correct in the fact that you can have the best breathing setup in the world that doesn't mean a thing if the lower end is a stocker and can't stand the stresses of spinning fast with tons ( literally) of new lateral forces,, if it's not machined correctly and balanced ,,,,

[cdoublejj]

Mar 16, 2015 20:18:22 GMT -6 Alleyoop said:

Least of your worries on a motor running those at high rpms you have to worry about the crank. A ported head with maybe bigger valves without more displacement is a waste of money. Displacement gets you more ponies and you then should get a quality crank(stroker or not) to take the extra power.

Displacement is being increased. I've though about balancing. The stroker cranks are balanced fairly well according to the seller. That doesn't make it so of course. At least they do have a price to reflect that though. And they and maybe one other seller are the only ones offer such a crank, i might be inclined to believe that some since it's isn't some run of the mill fake titanium coated part.


All sports bikes are dual over head came these days. Too bad they don't make a dual overhead came 139qmb head. lol


On displacement... This is somewhat mild build but, these are Chinese engines. I learned all about too much breathing. One of the first things i bought was a150cc carb with manifold. I was very quickly educated on stupid that is my Dad and friends. Kind of hard to increase performance if you have no vacuum to draw in the fuel. So eventually the intake was ported, valve guided measure and cut from the intake port/runner. (plenty of length.) a second set of valve shims added and the exhaust port totally left un touched friend said not enough displacement and compression to do any thing with exhaust side. and the gob of chicken booger looking weld bead ground out of the exhaust pipe flange and the carb adjusted.

Results were and are QUITE positive but, as we all know if it's not broke your not trying hard enough. So picked a 60cc jug kit with all the need bits for about 35 bucks. I went with 60cc for a few reasons. First and foremost my buddy used to be a deal and i got to ride of those jonways that was really a 60cc and not a 50cc. Even with my port job the old Jonways still had a way of getting up to speed faster and still had a bit more top end.

Yeah the old jonway had likely a different CVT and small tires but, we can't deny the extra 10cc didn't help. The OTHER reason is these engines don't like BBKs how many times we get a help me tread because some crappy BBK kit or job went sour? These 139QMBs were not designed for that AND they are Chinese. And 3rdly I keep the same carb and exhaust, i don't want loud pipe or LOOK WHAT I DID vibe/look.

I plan to keep the original head, port the exhaust ans deck it. IF the exhaust guide is long enough it can be kissed by by from the exhaust port just like the intake. Will probably swirl polish the valves too. I am also looking at the A9 cam for a bit more top end. STG has one for 20 shipped. It has more lift and duration. Not sure how the springs would like that. I know these springs are somewhat common size for small OHV engines, so the quest to find some seemed interesting.

The only other weak point would be to have the crank balanced. On the upside new piston and pin shouldn't weight much more than the stock piston. Currently it's seen red line a few times. one of the biggest imbalances i believe to the be the rear RIM and probably Tire to. It dances on the stand when revved and rear hums quite notable 49.9 mph (GPS) which is also the top speed and also red line. IF only it didn't have to be steep down hill with a tail wind. Also why i'm on the fence with the A9 cam but, for 20 bucks we could just try it out compare with the stock cam and look duration and lift changes.

HOWEVER if you deck the head you have to account for lift that could mean if switching back to the stock cam having to get the head deck AGAIN. On the other hand that's all a part of the experience. The best part about it is that it's all super cheap! the A9 Cam and jet kits is no more than $40 bucks. The scooter was free and so is tinkering in the shop with friends on the weekend. :-)


EDIT: the 139qmb stroker crank is more than i want to spend but, would help displacement and isn't totally off the table yet. i think that would take it to some where about 66cc. the 60cc kit is actually 62cc from what i calculated.

[cyborg]

too much deck removal could also lead to detonation,,,the combustion chambers in these things are antiquated at best,,,and you are correct everything on the bike needs a balance job,,,this is one of the great shortfalls of these machines and is one big reason they are so inexpensive,,the manufacturers just don't put that in the equation so they save dough