My first BBK install

speedy1125 Guest	My first BBK install Mar 26, 2011 19:41:03 GMT -5 Quote Select Post Deselect Post Link to Post Back to Top Post by speedy1125 on Mar 26, 2011 19:41:03 GMT -5 compression is probably too high with the stock head.

Fox Scoot Master! So. Cal Posts: 6,301	My first BBK install Mar 26, 2011 19:47:18 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by Fox on Mar 26, 2011 19:47:18 GMT -5 Yeah I guess I've officially joined the "tuners" ranks. I'll probably end up tearing it all apart again... I just wanna ride the damn thing.
	Last Edit: Mar 26, 2011 19:47:48 GMT -5 by Fox Dave

stepthrutuner Scootaholic! Scamp your way to sanity Posts: 4,402	My first BBK install Mar 26, 2011 22:29:17 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by stepthrutuner on Mar 26, 2011 22:29:17 GMT -5 You'll figure it out and be a better person for it. :rockon:
	<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><> A two stroke with a tuned pipe: A prime example of multi-multi-tasking. <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>

Fox
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My first BBK install Apr 7, 2011 12:14:31 GMT -5

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Post by Fox on Apr 7, 2011 12:14:31 GMT -5

It's a rainy day so I finally had some time to screw around with the engine and after trying different jets and even a stock carburetor on there with no good results I checked the cam alignment and it was off by one tooth. Not sure how that happened but after correcting it the damn thing has so much compression now that it won't turn over with the starter and it kicks back when I kick it. I guess speedy was right about the compression being too high with the stock head.

I want to install an extra base gasket but I thought I would ask you guys if that's the right way to go or should I get a different head? Scrappy sells what they call a "Big Bore Head". Anyone tried one before?

Thanks

Last Edit: Apr 7, 2011 12:30:10 GMT -5 by Fox

Dave

90GTVert Administrator Posts: 41,613 Location: Preston, MD	My first BBK install Apr 7, 2011 12:29:30 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by 90GTVert on Apr 7, 2011 12:29:30 GMT -5 The base gasket is the easy way as long as you don't end up with any leaks.
	Brent Life is better at high RPM.

Fox Scoot Master! So. Cal Posts: 6,301	My first BBK install Apr 7, 2011 12:30:54 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by Fox on Apr 7, 2011 12:30:54 GMT -5 I'll be sure to use plenty of RTV on it. Thanks Again!
	Dave

Fox
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My first BBK install Apr 7, 2011 19:56:38 GMT -5

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Post by Fox on Apr 7, 2011 19:56:38 GMT -5

So I get the whole thing back together and it won't start now unless I spin the engine with a drill. Obviously not enough compression now.

For sale: One blue JMStar 80cc

Just kidding. ;D I'll tear that P.O.S apart again and again til I get it right.

Dave

90GTVert Administrator Posts: 41,613 Location: Preston, MD	My first BBK install Apr 7, 2011 20:08:56 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by 90GTVert on Apr 7, 2011 20:08:56 GMT -5 Just 1 extra gasket and it won't start? I'd suspect something else is up.
	Brent Life is better at high RPM.

Fox
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My first BBK install Apr 7, 2011 22:35:27 GMT -5

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Post by Fox on Apr 7, 2011 22:35:27 GMT -5

Yeah. It's gotta be a carburetor issue. I put it back the way it was with one base gasket and now it starts but craps out at high RPM and spits gas out the back of the carb like it did before. I tried a stock carb on there and it helped a little but I gotta play with the jetting. I have a few loose jets but they all look the same size. They don't have any markings on them at all so I'm not sure what they are. I have a box of carbs with jets that might be marked but that'll have to wait til morning.

I'm really disappointed with this kit.

Dave

speedy1125
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My first BBK install Apr 8, 2011 1:42:09 GMT -5

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Post by speedy1125 on Apr 8, 2011 1:42:09 GMT -5

I worked on one a long time ago that was doing a similar thing, rev it up and it would spit back through the carb.
Took the valve cover off and the exhaust cam lobe was badly worn down. Have you verified your mechanical timing? A tooth off can cause the same thing.

Fox Scoot Master! So. Cal Posts: 6,301	My first BBK install Apr 8, 2011 8:40:06 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by Fox on Apr 8, 2011 8:40:06 GMT -5 Yeah the cam is lined up perfectly. It idles great. Nice and quiet without a miss.
	Dave

speedy1125
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My first BBK install Apr 8, 2011 17:37:10 GMT -5

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Post by speedy1125 on Apr 8, 2011 17:37:10 GMT -5

Still the stock head right? Compression on a stock 50cc is 10.5:1 which is kinda pushing it.

I still suspect compression is too high with the stock head and 50mm bore. The problem you had after installing another base gasket is a head-scratcher though.

Last Edit: Apr 8, 2011 17:38:06 GMT -5 by speedy1125

Fox Scoot Master! So. Cal Posts: 6,301	My first BBK install Apr 8, 2011 17:53:24 GMT -5 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by Fox on Apr 8, 2011 17:53:24 GMT -5 I'm done with this bore kit. I'm gonna put it back stock. If anyone wants the 50mm piston and cylinder w/pin and clips and the 20mm carb it'll be up in the for sale section in a while...
	Dave

dan72240z
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My first BBK install Apr 8, 2011 19:23:16 GMT -5

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Post by dan72240z on Apr 8, 2011 19:23:16 GMT -5

I think your main jet is to high. I used an 88. I have the same kit. Got it off ebay. I also got a better air filter to let it breath better. The weaights that come with the kit are 7g I think. They are slightly heaver than stock. this is becouse the power band is a little lower with the bbk. I installed every thing that came with the kit. Put 88 main jet and breather. First run got it to 48 mph and it got there fast. I think it would have gone faster but I will wait till is broke in to try that.

Fox
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My first BBK install Apr 8, 2011 20:29:28 GMT -5

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Post by Fox on Apr 8, 2011 20:29:28 GMT -5

Well I tried it with a 78, 88, 90 and a 95 and it won't run right with any of them.

I'm gonna try advancing and retarding the cam a tooth and see if that has any effect and if not then I'm done with it. I fear the effect will probably be a bent valve.