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Discussion Starter · #1 ·
I got an x7 a few weeks ago, i have already had to replace the tires, carburator, fuel filter, fuel lines, battery, and spark plug. The engine was running great but I noticed a loud rattling kinda sound, and huge lack of Power to the ground. So i decided to check the clutch and engine components. They end up looking good( my photos will be posted when i get to a computer) makes me a little worried it could Be a tranny issue but I'll worry about that if it ends up to be the issue.

However the road block ive hit is; I'm stuck with where I should go from here before I piece the engine together, i dont want to look into porting myself yet, I'm still learning. from searching around a bit it looks like I don't have many options when it comes to engine performance upgrade kits.

I was going to buy this 52cc bbk but I've been reading h
ere that it's not worth the money and not a true upgrade?
http://www.minibikepartsnow.com/x-7-performance-parts.htm

What would you suggest as some good performance mods for the engine that I can purchase then get this bike on the road?

I figure after that I can start planning some custom work of my own for this bike, thanks for all the help, ive learned so much from these forums.
I'll post some pics of the bike and engine soon.
 

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French Fries N Cheese
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Looking good. As far as performance goes theres lots you can DIY like porting your cylinder, lightened the piston, polishing and deburring the sharp edges on the cylinder. bluepring the inside of the crank case, but dont take too much out because the idea is to minimise case volume. Lighten up the flywheel by trimming the fins, then balance it. Lighten up the clutch and upgrade for a stronger spring to increase the lock up RPM.

Things you can buy:
A good rev pipe to help the engine breathe
Timing advance "rocket" key
Woodruff key for the clutch
bigger fuel lines and filter
Foam air filter and Vstack
Full Circle Crank
thin quality piston rings
windowed piston

Carb upgrade is always an option. there are many different carbs you can swap in to these, but yours is fine, just get a wt603 rebuild kit from walbro to make it work at it's best. you can even modify it.

Hope this helps.
 

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Discussion Starter · #5 ·
Yes you have been a big help, I'm going to order some parts today. A lot of good ideas !!

I figure I'll get the big Bore kit for now and then port my stock setup while it's off, maybe I can compare the two setups.

I ended up buying a real walbro 603 so it should be working well, the intake manifold will be in this next order.

I'm going to search for that full circle crank and windowed piston.
 

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Discussion Starter · #8 ·
Nylon sounds like a good idea.

I never thought about restriction , I figured the volume of that tube would be plenty for the suction of that carb and any pressure created should flow smoothly because of the open filter cap. But that's all out of my own @** lol.

I'm gonna run some tests and see if I get some improvement from the nylon only.

Thanks
 

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If your talking X7, there is no FC crank, CAM2 did a bunch of mods and put an Cag FC in his piston port. Do not want a ported piston either, that's for a reed port Cag engine, like the yellow bike.
That's piston looks ok. But it really needs cleaning and polishing and cleaning up the edges inside the cyld. Raise the exhaust port ceiling in a football shape up 1/8", do the same on the intake but go down 1/8" in a football crown shape up or down to the center. On the inside of the cyld widen the outer port edges on both and put a small radius, not top or bottom only the outside inner port edges. You could do it with a few files and some elbow grease. I ground my flyw fins down 3/8" on the side of my 8" bench grinder. If you can take the thing apart and put it back together you can mod it yourself.
I have seen alot of bikes and racing cars with tuned air intake tubes, my 1973 2002 BMW Tii has 24" long alum U tubes from the head intake port to a big alum center plenium, fuel injected with a 3" V stack air intake & throttle plate like Walbro carb. Just need to find the right length & shape.
 

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Discussion Starter · #10 ·
Epr,

Thanks for the help, you saved me some searching time.

Im going to have to try ur advise on the original parts, since ill have them out to test the new kit.

I'm glad to hear that about the intake , I kinda laughed at my self when I first set it up, but it ended up working pretty well, I'm going to clean it up abit more now.
 

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These engines are small they don't suck that much air. The carb faces backwards, and it has to work for air, while your tube catches air at 15-30+mph and it has to go down the carb. The reason the center of the carb is small, is it compresses the air which makes it faster which makes a vacuum which draws gas up the main jet tube into the carb.
I would try to start the tube big and reduce the size of the tube till it gets to the carb, which looks like a copy 15mm Walbro WYK pumper carb.
It has no venturi a 15mm hole thru the piston, gas is suck up the brass tube in the middle of its bore. So, starting with 1 1/2" to 2" pipe and reducing it down to a final size at the U tube and into the carb, or better yet a U pipe with 44mm ID onto the 44mm OD X 15mm ID V-stack, w/ choke plate behind.
 

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Discussion Starter · #12 ·
Right now the yellow bike has a velocity stack and choke hidden under that U shaped tube and it's all connected to an upgraded walbro carburetor , the carb ended being one of the best things I did for that bike.

I think once I finish the x-7 I'm going to get a bbk for the cag.

My x-7 parts are almost here... I'm very happy with how fast some of these companies ship.
 

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I like PayPal too cause it's easy, no name or address to fill out they take care of shipping it's fast and there fast.
 

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Discussion Starter · #14 ·
I think the last package will arrive today, I'll post some photos when it comes.

Should I lubricate the crank or bearings before rebuilding, or just let the oil gas mix do its job? I nevered fully pulled the bearings or cank out of the case.

Also I planned on using a little blue rtv on the crank case and head gaskets to create a better seal is this ok or just use the bare gasket?

I'm wondering why the image on the package shows what looks like to me is a 4 cyl head and gasket and then states not to be used on heads or areas in contact with gas...
 

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They use it on valve cover gaskets and water pump gaskets on a car where it's not so hot & oily. I tried Ultra High Temp Copper RTV 750 degrees on my intake stuff, not good around 2 stroke stuff.
A $9 tube of Yamabond is the Ticket, I have used almost everything I could find, Hondabond is good to so, find a dealer near You,lol. I have had a tube for 2 years. Becareful it drys really fast. Everything has to be Clean, I use acetone and a rag, you might want rubber gloves, Your better half can use it to take off their nail polish,lol. On my A2 Cag I pop the cylinder up still on the rod piston in the hole, cut the .025" paper gasket of the block and cyld bottom. Quickly spread a very thin layer on the case surface with my fore finger, pulled the cyd down,4 bolts finger tight, next day, tighten the head bolts, and prepare to get your arm ripped off or hand injured, better gets some more start rope at the nearest hardware store.
EDIT: I use Permatex Copper Head Gasket Spray on all copper or paper gaskets, and the bond w/ no gasket
 

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Discussion Starter · #16 ·
Thanks EPR.
Yeah I'll try to find some.I bet it won't be in time and I'll end up going bare gasket this time, I'm impatient sometimes.

Well parts are in!!!! Few companies just did and awesome job while others were a little mistake prone, all in all I got mostly what I ordered.

I when ahead and measured the claimed 52cc head and while it's the same mm bore as stock I do see where the ceiling has been widened (I assume this is where the company claims the extra cc's come from?

the new pistons looks much better quality than the stock one, The new heads have a more solid look( however I doubt it's any stronger). But the major difference is the new heads have a smaller dept than the stock head, which goes against what I thought the company was trying to do by increasing the cc, is this for a higher compression?

I guess I'll find out on the track..lol
at least I'll have new pistons for the stock heads and some 2 stroke polished head paper weights. Lol


 

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That Walbro manifold is for a Cag reed port engine not your piston port engine. You have the thin alum adaptor plate that fits the 15mm manifold. Looks like you got a real Walbro? These parts people throw this 49cc thing around all the time and it is confusing. Now you have me wondering if you can mod a Cag intake to bolt to a piston port head. You need an alum piston port intake manifold, bore it to 15.88mm or match the carb bore, and fill in part of the pulse slot for the 603 or 813.
 

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Discussion Starter · #19 ·
Haha good question.. Id like to know also.
Well you are correct, good eye, yeah I knew parts would be incorrect or wrong so I order back up options ;).

However I did need to work with one company a bit because of that manifold was incorrect and the two gears were 18 tooth lol not 14.

But out of the negotiations I have an exhaust on the way, all in all I'm happy.

The bike is together minus the sprocket and soon to be exhaust.
Also I had to take the new hp spring out its way too loose and the bike trys to take off.... I recommend stick with stock or just get a new clutch.

I haven't floored it yet. But **** this thing feels soooo powerful.

Pics to follow.


Thanks for your help EPR, it's been a blessing.
 
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