Carb Popping off then broke intake!?

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placidscene

New Member
Apr 1, 2012
318
3
0
Austin, TX
The last time I rode, I thought I was getting close to having all of my carb problems figured out, it wasn't 2 stroking as bad, and seemed to be going a little faster without bogging as much. Then my NT carb popped off. That was the problem I kept having with the CNS carb before I finally tightened it so much that the collar broke! Once it did it a second time, I though that was enough, so I took the intake off and drilled a hole though the carb collar and the intake and used a self tapping screw instead of the collar clamp to secure the carb to the intake. I put plenty of pooky on the intake, re-mounted it and waited till the next day to take it out again.
The next day I took it out, let it warm up and gave it the gas. I heard a POP again and though "there's no way that carb popped off again." I was right, it didn't. The intake manifold broke in TWO!???
The only thing I can figure that would give back pressure through the carb like that is that maybe the catalytic converter in the muffler is completely blocked.
I called SBP and spoke to them. They hadn't experienced that, and thought maybe I was right.
Anyone else ever experienced this? I am going to drill a hole through the cat and see if that corrects the problem, but first I have to get a new intake.
I will keep you posted.
 

2door

Moderator
Staff member
Sep 15, 2008
16,302
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Littleton, Colorado
If your intake manifold was the older cast aluminum type, it breaking is not that unusual. They would crack even without a hole drilled in them. When you order a replacement make sure it is a steel manifold, not cast aluminum.

There is a product that many of us use to seal the carburetor to the manifold. It's called SealAl and is formulated for use with gasoline. Many silicone based sealers are not and will soften and turn to goo after a period of exposure to gasoline. Read the labels of any product you plan to use first to check for compatibility.

Tom
 

placidscene

New Member
Apr 1, 2012
318
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Austin, TX
My intake broke where it connects to the motor, not where I drilled it. I will try to post pics later, but my bike is still at the house that I am moving from.

The Pooky I was referring too is called Super Black and is for automotive use. It is fine for gasoline exposure.

Any other thoughts, anyone?
 

placidscene

New Member
Apr 1, 2012
318
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Austin, TX
I finally got around to taking pics. If you look where the carb attaches, you can see the set screw I added. you can also see where it broke the intake.
 

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2door

Moderator
Staff member
Sep 15, 2008
16,302
175
63
Littleton, Colorado
As I said above, those cast aluminum manifolds are known for breaking. I doubt your set screw had anything to do with it. They just, break.

Excessive vibration coupled with the weight of the carburetor hanging out there is just more than the thin casting can take. Order a new steel manifold and make sure your engine mounts are solidly attached to the frame and you'll be good to go.
Tom
 

killercanuck

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Dec 17, 2009
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Wallaceburg ON
that sucks placi. But yea like Tom said, those intakes are known for breaking. It has nothing to do with the hole you drilled. They just do that sometimes and is well documented.

If you think your exhaust is clogged causing the carb pop-offs(which is likely after 100's of miles), I've had luck throwing them in a fire pit to burn the gunk out. Just take it out before it starts to melt eh. Oh, and have some barbecue paint handy. :p

Get a steel intake for a replacement. Maybe a fellow Texan can help you out on the cheap.

gl.
 

leaded50

New Member
Oct 29, 2011
179
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Norway
backpressure, by clogged exhaust, or wrong timing could also be the answer because it pops of. And when it cant.......something just gotta bend.....break!
 

placidscene

New Member
Apr 1, 2012
318
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Austin, TX
I don't have time this week, (I am really missing riding!), but I will try to fix exhaust. If that fails, I will try to figure out the timing.
I will post results when I get to it.
Thanks!
 

placidscene

New Member
Apr 1, 2012
318
3
0
Austin, TX
I was finally able to work on my bike again yesterday after the move.
I put the old long offset steel intake on until i can get a short steel intake, and I drilled several holes through the catalytic converter in the muffler.
The bike started right up!
I ran it around for an hour yesterday and an hour today with no engine issues. Only prob i had was the spring on my chain tensioner came off and I had to peddle back, retrieve it, and put it back on. THE CARB STAYED ON THE BIKE THE WHOLE TIME!

The bike still will not run wide open throttle unless I turn down the fuel at the pet cock.
I think that indicates that I have the needle set too rich, but if I lean it down, it bogs at lower RPMs. Any suggestions on that?
 

placidscene

New Member
Apr 1, 2012
318
3
0
Austin, TX
Yeah, your right, forgot.
I actually already put in a smaller jet.
Went from a stock to a .67 I think.
Maybe I need a couple sizes smaller yet.
Ill try that next. Thanks for the tip
 

tooljunkie

Member
Apr 4, 2012
663
5
16
Manitoba,Canada
another thing i noticed,was the motor mount spacer,stacked at the rear of the frame,i wonder if you might be better off with the double stack mount on the front of the engine?it might change the way the engine shakes to prevent this again?
just a thought,but if it seems to be working ,maybe leave it.
 

placidscene

New Member
Apr 1, 2012
318
3
0
Austin, TX
It is the only way I could get the engine to fit in this frame and be halfway level.
I think I am about to buy a cruiser and start my second build by taking this one apart. So I will still have to figure out the engine issues anyway.
 

placidscene

New Member
Apr 1, 2012
318
3
0
Austin, TX
OK! I fixed it!
I decided to stick with the current set up on my frame.

I finally got around to buying a long drill bit and drilling several holes all the way through the catalytic converter in the muffler. PROBLEM SOLVED!

I have not had any more issues with the carb coming off the bike. The cat must have been so clogged up that the exhaust was not able to escape properly!

Added benefit... Believe it or not, the bike is actually not as loud! It has a little bit throatier sound to it instead of a high pitched pop.