Valve lash / clearance numbers

22 posts in this topic

Posted (edited)

Heya gang,

        Far too often I see people tossing around bad numbers when it comes to adjusting the valves.... 

        Not all GY6 150cc engines have the same valve lash, but the good news, the scooter itself should have the valve clearance listed on the maintenance/emissions plate....

         So, if you're curious as to what you should set your valves at, DO NOT ask some random person on the net, just look at your scooter...

         I snapped some pictures of the engine plate and the corresponding engine ID stamp (not to be confused with VIN or manufacturer part number)

      ***ALSO NOTE**** These sizes are in metric, not SAE.

01_Bintelli.jpg

02_Bintelli.jpg

03_157QMJ.jpg

04_157QMJ.jpg

05_1P57QMJ.jpg

06_1P57QMJ.jpg

GY6_150cc_Engine_Stamp_Location.JPG

Edited by DMartin95
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Posted

Dan

With all the GY 150cc Scooter motors you have been into have you ever found any differences that would warrant these different lash specs?

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Posted

Agreed, Dmartin95.

Dan

With all the GY 150cc Scooter motors you have been into have you ever found any differences that would warrant these different lash specs?

I wouldn't be surprised if the better engines had tighter lash. I think it has to do with how much valve seat creep is expected. The better the head casting, the less seat creep expected, the tighter lash recommended. Just a thought...

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Posted (edited)

Dan

With all the GY 150cc Scooter motors you have been into have you ever found any differences that would warrant these different lash specs?

Yes.

The heads are different.....For instance, 157QMJ, 1P57QMJ and  bn157QMJ all have different compression ratios.Also have different cam cradle height.

Edited by DMartin95

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Posted (edited)

I should have been more specific.

I do understand the different heads etc, but does any of that warrant all these different lash spec's?

Take for instance the common 157QMJ, I see different comp ratios advertised but have you seen any combustion chamber volume or Piston Volume difference in any of the common 157QMJ?

I'm just trying to figure out what really warrants these different specs, even with the different heads,cam cradle I'm not seeing anything that warrants it.:thinking:

Edited by pistonguy

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Posted

I should have been more specific.

I do understand the different heads etc, but does any of that warrant all these different lash spec's?

Take for instance the common 157QMJ, I see different comp ratios advertised but have you seen any combustion chamber volume or Piston Volume difference in any of the common 157QMJ?

I'm just trying to figure out what really warrants these different specs, even with the different heads,cam cradle I'm not seeing anything that warrants it.:thinking:

I keep forgetting the difference in the heads. Those differences would make for different lash settings, but I wouldn't think that could be the difference between 0.003" and 0.006". Too tight a lash is worse than too loose a lash, right? Cheap engines with loose tolerances need extra lash just in case so they don't risk burning a valve seat. Good Honda engines and the like can have tighter lash to reduce hammering on the valve and the dreaded clacking noise.

Once again, I'm just speculating.

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Posted

I keep forgetting the difference in the heads. Those differences would make for different lash settings,

Ya but I'm looking for the "Why" I don't see what would warrant it.

For instance, I know with a Plated bore vs a Iron Bore I can run a tighter piston to cylinder clearance and also more compression for a given octane just because it dissipates heat so much better, so I can understand that. 

I also do not find these GY's have loose tolerances,  I do complain but the product for what is is isn't all that bad, and the Taida appears to be the premium product out there.

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Posted

Ya but I'm looking for the "Why" I don't see what would warrant it.

I also do not find these GY's have loose tolerances,  I do complain but the product for what is is isn't all that bad, and the Taida appears to be the premium product out there.

Taida is the best out there I know. They have closer tolerances than Tong Jian for instance. Also, the aluminum Taida uses in their heads is much less porous and is cleaner than Tong Jian. The seats in the porous head will move quicker and farther than the ones in the Taida. The porous head will also tweak and stray from dimension more than the Taida. My dad saw this with exhaust manifolds on his 5.4 Ford. The OEM manifolds would crack every 10,000 miles or so. He tried running one for 1,000 miles and then put it on a surface grinder to make it flat again where it bolted up to the engine. That manifold has 40,000 miles and counting.

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Posted

Dan, this is a great thread, what valve lash does Taida recommend for their cylinder heads?

I run my intake at 0.002" and exhaust at 0.003". I check my lash every two weeks, last night when I checked the exhaust was at 0.002" and worked perfectly. Intake stayed in place at 0.002".

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Posted

Taida is the best out there I know. They have closer tolerances than Tong Jian for instance. Also, the aluminum Taida uses in their heads is much less porous and is cleaner than Tong Jian. The seats in the porous head will move quicker and farther than the ones in the Taida. The porous head will also tweak and stray from dimension more than the Taida. My dad saw this with exhaust manifolds on his 5.4 Ford. The OEM manifolds would crack every 10,000 miles or so. He tried running one for 1,000 miles and then put it on a surface grinder to make it flat again where it bolted up to the engine. That manifold has 40,000 miles and counting.

You have worked with or have the Taida product vs Tong in Hand to make this determination?

A actual problem with porosity is going to come from gas or a shrinkage issue and your only going to find that with x-ray or cut the thing in half looking for gas pockets.

I am by no means any type of authority of metallurgy but I professionally have worked with similar  materials in the field.

The  three most common Aluminum Alloys for Cylinder Heads for there properties of Castablilty, Machineability, Finishing and Weldability, these also must meet a criteria of Hardness and Strength at were high temperatures are required, they are 2420 and A2420, many cast pistons and air cooled cylinders and cylinder heads are cast from these alloys.

The other alloy is 356.0 this is widely used for engine blocks and liquid called cylinder heads with a heat treat condition of around T5-T6..

Either or Any manufacture is using one of the three alloys because they are the only alloys that work, and None are more or less porous than the other.

 

 

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Posted

You have worked with or have the Taida product vs Tong in Hand to make this determination?

A actual problem with porosity is going to come from gas or a shrinkage issue and your only going to find that with x-ray or cut the thing in half looking for gas pockets.

I am by no means any type of authority of metallurgy but I professionally have worked with similar  materials in the field.

The  three most common Aluminum Alloys for Cylinder Heads for there properties of Castablilty, Machineability, Finishing and Weldability, these also must meet a criteria of Hardness and Strength at were high temperatures are required, they are 2420 and A2420, many cast pistons and air cooled cylinders and cylinder heads are cast from these alloys.

The other alloy is 356.0 this is widely used for engine blocks and liquid called cylinder heads with a heat treat condition of around T5-T6..

Either or Any manufacture is using one of the three alloys because they are the only alloys that work, and None are more or less porous than the other.

 

 

I was just using Taida vs. Tong Jian as an example. I know Taida is good and Tong Jian is so-so. I have a Tong Jian in my basement right now and a Taida in my dreams (for now):rofl2:. I have read numerous other forums saying the valve seats move until the head (heat treats) itself. Many people complained about a certain brand of cheap Chinese head (it started with a G and it wasn't Glixal, that's all I remember) needing the lash readjusted too often and they blamed it on the poor casting and cheap aluminum.

I should have said this the first time around.

 

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Posted (edited)

I was just using Taida vs. Tong Jian as an example. I know Taida is good and Tong Jian is so-so. I have a Tong Jian in my basement right now and a Taida in my dreams (for now):rofl2:. I have read numerous other forums saying the valve seats move until the head (heat treats) itself. Many people complained about a certain brand of cheap Chinese head (it started with a G and it wasn't Glixal, that's all I remember) needing the lash readjusted too often and they blamed it on the poor casting and cheap aluminum.

I should have said this the first time around.

 

This is just pure internet parroting bunk..

Not one of them ever sent off a Cylinder head to be cross sectioned and X-Rayed to make such a claim.

This is down to Alloys so for one to blame "cheap aluminum' is showing ones complete lack of knowledge of Castings and Finish machining Aluminum..

Also realize Few to None of the se manufactures actually owns and operates a Foundry for there castings, almost all of them use the same Foundry for there castings.

It does not pay and is not good business to own and manufacturer every component of news engine.

The specific manufacture may own the tooling to cast in there logo but thats it.

Here is the real deal, I have product in hand,  61mm cast pistons from both Taida and NCY  they use the same foundry and this same foundry can supply a raw casting to be machined or a finished product. 

So someone can't tell me that the Aluminum in the Taida piston is better than the NCY piston..

There is a ton of private labeling done out there and so much of it is manufactured from the same supplier..

254-61mm-pistons-taida-cast-vs-ncy-cast-vs-taida-forged-high-comp

Edited by pistonguy
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Posted

This is just pure internet parroting bunk..

Not one of them ever sent off a Cylinder head to be cross sectioned and X-Rayed to make such a claim.

This is down to Alloys so for one to blame "cheap aluminum' is showing ones complete lack of knowledge of Castings and Finish machining Aluminum..

Also realize Few to None of the se manufactures actually owns and operates a Foundry for there castings, almost all of them use the same Foundry for there castings.

It does not pay and is not good business to own and manufacturer every component of news engine.

The specific manufacture may own the tooling to cast in there logo but thats it.

Here is the real deal, I have product in hand,  61mm cast pistons from both Taida and NCY  they use the same foundry and this same foundry can supply a raw casting to be machined or a finished product. 

So someone can't tell me that the Aluminum in the Taida piston is better than the NCY piston..

There is a ton of private labeling done out there and so much of it is manufactured from the same supplier..

254-61mm-pistons-taida-cast-vs-ncy-cast-vs-taida-forged-high-comp

Umm, you should lighten up. Even if you have some insight into this subject, you're coming off very abrasive and frankly, just rude. There are different ways to make your point.

Anyhow, NCY and Taida are both Taiwan products. You should try comparing an actual Chinese casting to one made from Taiwan. They are NOT from the same foundries, nor is the metal quality the same. Who needs an XRAY when you can see micro cracks and brittle metal with your bare eyes?

--------------------------------

Take note, metal quality is only one concern. 

China uses slave labor wages that leads to unskilled workers, this in turn leads to quality control suffering... This is on every level, from casting to assembly. 

There is no comparison.

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Posted (edited)

Ya but I'm looking for the "Why" I don't see what would warrant it.

For instance, I know with a Plated bore vs a Iron Bore I can run a tighter piston to cylinder clearance and also more compression for a given octane just because it dissipates heat so much better, so I can understand that. 

I also do not find these GY's have loose tolerances,  I do complain but the product for what is is isn't all that bad, and the Taida appears to be the premium product out there.

The "Why" - 

The heads are different and the engines have different compression ratio's. The combustion chamber is different on the engines with the "P", gives it a compression ratio of 10.5:1 as to where the standard 157QMJ is only 9.2:1....  The engines with the "P" have an additional 1 HP just from this slight head modification...

So, 2 dif engines, different specs..

 

 

Edited by DMartin95

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Posted

The "Why" - 

The heads are different and the engines have different compression ratio's. The combustion chamber is different on the engines with the "P", gives it a compression ratio of 10.5:1 as to where the standard 157QMJ is only 9.2:1....  The engines with the "P" have an additional 1 HP just from this slight head modification...

So, 2 dif engines, different specs..

 

 

I'm just proving thought and discussion..

Ya, ok so a slight bump in compression and hp I don't see why that warrants a different spec.

For instance, in general, any late model 250F MX'r comes out of the box with a oe comp ratio of around 12:3-1 and makes roughly 36rwhp.

Now I install my max comp 14:1-1 piston, reshaped combustion chamber, Ti valves, Beryllium Copper seats blah blah and now she makes a solid 42rwhp and the Valve lash remained the same. there was no reason to change it.

Kinda funny I checked my own placard on my Scoot and compared it to the paperback manual included and guess what? the paperback says 90 octane or higher with 10w/40 oil...My placard states 91 octane or higher and 15w/40... Oh, oh what do I do now? lol,  I see one of your placards reads 10w/30 for oil.. 

As far as I can see all these specs appear to be copies of copies of copies of copies, I would venture to say so much is based on when the GY was originally born and the manuals from scoot mfg to scoot mfg have gotten blurred, since then we are working with updated tooling, materials and workmanship, and theses manuals appear to have never been updated. but really why? my Scoot brand new was $749. plus $120 freight, Ill go ahead and write my own manual.

I could see why for instance Bintelli may have "added" some clearance for insurance purposes, safer on the warranty claims to have to general consumer set a slightly larger lash as they are not capable of consistently measuring and adjusting there lash to .002, add +.001 or so and the Scooter consumer can't jack that up to bad, but actually they do..

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Posted (edited)

Sorry I was just spit-balling some ideas. I wasn't really taking a scientific approach at my statements. I'll think a little more before I post next time...

I see the question you were asking, @pistonguy. Sure the compression ratios are different, but that would affect head volume/shape and deck height and not valve lash (to a certain degree).

Manufacturer politics has much to do with it too. Heck, we all know the engine will run just fine with a plug gap of 0.020" or 0.030" but one manufacturer might prefer 0.026"-0.028" and another 0.022"-0.026". That would also have to do with compression ratio, probably more so than valve lash but you get the point.

And I run 20W-50 in the fall on my GY6.:laugh:

 

 

Edited by TheDullCarbide

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Posted

Ya, ok so a slight bump in compression and hp I don't see why that warrants a different spec.

 

NO.

Those were just examples of differences in these engines that I know of first hand and trying to illustrate the point that these engines are not all the same, they're different.

I have not profiled all the the OEM cams to see if they're different.... I'm thinking the cam profile is what ultimately will determine the valve lash, I just don't remember off hand.... But again, I don't have the cam profiles to prove it..... However, I do have the engine math books and can look any of this up.... 

What I know is this (for a fact) Not all these GY6's are the same. There are subtle differences and in my opinion, it's best to err on the side of caution and go with the plate stamped on the scooter.

--------------------------------------------

The whole reason this thread exist is an attempt to stop the non-sense like this..... Time and time again, I see people recommending valve lash be adjusted to .03mm-in/.05mm-ex... This is what is recommended on most of the 50cc stamps I have came across....I have never seen a 150cc with anything lower than a .05mm on the intake valve.... After these thing heat up and thermal expansion takes place, if the valves are too tight, the thing won't run.... 

So really, I am at a loss for what kind of point you're even trying to make.... If I understand your intention, it's to tell everyone to ignore the engine stamp that comes on their scooter and "write their own"???? If so, (and I hope you don't take this as being rude, not my intention) I find that to be misguided.....

And take note, I do understand emission plates and manuals have their errors.... But not ALL of them.... Especially when it comes to the higher quality scooters.   

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Posted

Umm, you should lighten up. Even if you have some insight into this subject, you're coming off very abrasive and frankly, just rude. There are different ways to make your point.

Anyhow, NCY and Taida are both Taiwan products. You should try comparing an actual Chinese casting to one made from Taiwan. They are NOT from the same foundries, nor is the metal quality the same. Who needs an XRAY when you can see micro cracks and brittle metal with your bare eyes?

--------------------------------

Take note, metal quality is only one concern. 

China uses slave labor wages that leads to unskilled workers, this in turn leads to quality control suffering... This is on every level, from casting to assembly. 

There is no comparison.

Ill go with a Blunt response.

My showing NCY and Taida using the same piston mfg, was only a example of what is going on, lets stick to comparing apples to apples and you will find the same thing is going on in the slave labor camps in China, many mfg's using the same foundry and maybe  there own tooling to cast a logo in it.

Micro cracks are a different issue altogether than a proclaimed cheap porous inferior materials, Cool  then someone show me either or..

 

As far as my response from the get go as far as I'm concerned mr carbide speaks with a forked tongue, from its earlier post I had to ask if one had ever even held the product in his hand and as I ventured to bet was correct, never.  

When this is continuously presented to me Im being called a idiot and I find that not only rude but highly insulting, I don't roll that way and I won't roll with others who roll that way..

 

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Posted

Here's the question though. I have a 1P57QMJ and I just did the 63mm BBK 180cc upgrade. It came with a new head but I'm still on factory rockers and switched to an A9 cam. I have no idea what the factory cam was. Should I go a couple thousandths wider than factory spec and just adjust the lashing based on valve train noise?

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Posted

Here's the question though. I have a 1P57QMJ and I just did the 63mm BBK 180cc upgrade. It came with a new head but I'm still on factory rockers and switched to an A9 cam. I have no idea what the factory cam was. Should I go a couple thousandths wider than factory spec and just adjust the lashing based on valve train noise?

NO!

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Posted

NO!

Well thats a very emmpowered "no". I'm assuming there is more to that. So even though everything on the top end is totally different, I should stick with the factory spec?

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Posted

Well thats a very emmpowered "no". I'm assuming there is more to that. So even though everything on the top end is totally different, I should stick with the factory spec?

Yes and Correct ,keep to the spec..

              Cheers..

 

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