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Post by Kasperthelost on Oct 10, 2016 12:32:28 GMT -5
Ok so hopefully one of you helpful people can help me and answer what could potentially be a dumb question. Anyway get on with it right?? Sorry, ok my question is can I use a big head valve on a stock 50cc cylinder and piston everything I read so far says yes but I'm yet to discover a video where someone is just changing the head and not doing a Bbk. I do plan on doing so but if I can just upgrade my head and get more power I'm all for it obviously. Also I have an a9 performance cam shaft I plan on installing with the head. Now I know how to do the job that's not my issue my issue is when I put the metal gasket which since I still have a stock piston and cylinder is 39mm when I line the metal gasket up against the head where the Center piston hole around the firing chamber I thinks called there is a bit of overhang is this ok? I just don't want to put it together and break my perfect running scooter. I'm sure anyone reading this understands. Please,please help me with these questions I have gotten loads of info from here before I even joined once I finally realised I could I did but you all always answer EVERYONES questions ? Thank you for taking the time to read this I appreciate any help I can get.
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Post by 90GTVert on Oct 10, 2016 13:27:10 GMT -5
 Most of the big valve heads are intended for larger bores. If you can find a BVH intended for the stock bore, that may give you more performance. If you use BVH for a larger bore on your stock bore, it will most likely lower compression so much that you'll probably be slower than before. With a stock bore, your best bet is to install the cam and wait till you get a BBK to use a BVH. Some even suffer from low compression with BBKs and BVHs. The right head gasket should match up to the bore. You don't want anything hanging into the cylinder or to not have the gasket near the edges of the bore.
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Post by Cincikid on Oct 10, 2016 13:29:51 GMT -5
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Post by Kasperthelost on Oct 10, 2016 13:31:48 GMT -5
Thanks that's basically what I had come to. I do plan on installing the cam though. Just glad I didn't take my bike apart to find out.
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Post by Kasperthelost on Oct 10, 2016 13:33:03 GMT -5
Although the bvh says its for 50 to 100cc. That's why I bought it I thought it would help until the Bbk.
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Post by 90GTVert on Oct 10, 2016 13:35:11 GMT -5
Although the bvh says its for 50 to 100cc. That's why I bought it I thought it would help until the Bbk. Many will describe it whatever way sells the most units. A head for a larger bore can fit and work on a 50, it's just not a good idea. Being a little skeptical of seller claims will serve you well . |
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Post by tortoise2 on Oct 10, 2016 14:13:15 GMT -5
Ballpark comparisons . . .
50cc displacement divided by 5cc stock head combustion chamber volume = 10:1 compression ratio
50cc displacement divided by 6cc big valve head with beveled combustion chamber volume = 8.3:1 compression ratio
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Post by Kasperthelost on Oct 10, 2016 17:07:21 GMT -5
Got a quick one. What do I torque the rocker arms and cam to? I have saw different answers so I would like to know what you think since I have been following your advice since before I was a member. Your info hasn't steered me wrong yet. 90.
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Post by Kasperthelost on Oct 10, 2016 17:09:44 GMT -5
And what do you think is the best setting for the valve lash? will I have to change it after I install the a9 cam?
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Post by humanshield on Oct 10, 2016 17:25:38 GMT -5
Got a quick one. What do I torque the rocker arms and cam to? I have saw different answers so I would like to know what you think since I have been following your advice since before I was a member. Your info hasn't steered me wrong yet. 90. I torque them (on a 50cc scooter) to 156 INCH pounds (not foot pounds  ) And the two side ones to 95 INCH pounds |
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Post by Kasperthelost on Oct 10, 2016 17:26:14 GMT -5
If I remove the egr can I still use the cylinder with the egr on it if I have the non egr valve cover?
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Post by Kasperthelost on Oct 10, 2016 17:27:19 GMT -5
I'm not sure what that means my torque wrench is in lbs.
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Post by humanshield on Oct 10, 2016 17:27:41 GMT -5
And what do you think is the best setting for the valve lash? will I have to change it after I install the a9 cam? I like .003 for both...others may have a different opinion. |
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Post by humanshield on Oct 10, 2016 17:32:05 GMT -5
I'm not sure what that means my torque wrench is in lbs. A quick Google search turned up quite a few easy conversion templates.... link13 foot lbs But I recommend an INCH pounds torque wrench because a foot pounds torque wrench can be off enough to make a difference on these small motors. |
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Post by Deleted on Oct 10, 2016 17:41:29 GMT -5
I'm not sure what that means my torque wrench is in lbs. A quick Google search turned up quite a few easy conversion templates.... link13 foot lbs But I recommend an INCH pounds torque wrench because a foot pounds torque wrench can be off enough to make a difference on these small motors. Exactly! A torque wrench that can do 100 ft. lbs is not going to be accurate at 13 ft. lbs. Bill |
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