Carb Expert Please


5 replies to this topic
  • Snow Drift

Posted May 29, 2014 - 04:53 AM

#1

So I rejetted and rebuilt the carb a few months ago and then did the valves and now the swingarm and linkage bearings. I hadn't done the last two air jets in the bell housing of the carb.

 

When putting in the main 110 air jet, I tightened too hard out of fear that it might rattle loose, get back fired out and then sucked into the cylinder. So I thought that I had now ripped the thread when putting them in this weekend but I'm not sure what has happened.

 

I took it out again and tried putting it back in again and it seemed to go in tight like I had slightly damaged the thread/cross threaded it. I took it out and got another same 110 main jet from my AIS removal kit and tried that. It went in okish but I did the same again, the screwdriver slipped when tightening and it damaged the brass top to the jet.

 

Looking down the hole the brass jet top slot where the screwdriver goes looks bent slightly and damaged/chipped. The area around it looks a little scratched where the screwdriver scratched the sides of the hole as it was turning and jumped off the top of the jet.

 

I was so upset as I've put so much effort into it only to mess it up on something so stupid. My question is what I should do. I don't know whether to risk taking the jet out, try and blow the carb passage out and then put the least of the two 110 air jets back in and hope the thread isn't wrecked.

 

Or should I leave it in as it is currently in and tight and not worry about any metal fragments or swarf that may or may not have entered the carb. I read somewhere on here that a small grain could be enough to gouge the cylinder, and I would be so upset if that happened.

 

Can someone give me a diagram or idea, or explanation of where these air jet passages go to and if I can blow that out from the other end without dismantling the whole carb again, as it was really a lot of effort to get it back together perfectly in my own mind.

 

Also is it possible that I've cut the thread of the whole deeper with the jet acting as a cutting tool into the alloy. It seems almost as if the air jet has gone in a little further, but as I said it seems tight so the thread doesn't seem ripped, or will taking it out possible now rip the thread?

 

 



  • Krannie McKranface

Posted May 29, 2014 - 04:57 AM

#2

If the hole in the center of the jet is not molested, it's fine

See how it runs and go from there.

Don't worry about any brass fragments that small; it is insignifigant

 

 

...and did you service the accelerator pump, hot start, and choke too?



  • bobpara

Posted May 29, 2014 - 06:11 AM

#3

I'd have to see it to be 100% sure but this is what I would do:

 

1) Get a new jet, brass is softer than aluminum and the threads on the jet may have taken the brunt of the stripping

2) Get some JB Wled and mix it up well, take a tooth pick and smear a tiny bit on the aluminum thread surface (JB Weld is fuel proof)

3) BE CAREFUL NOT TO GOB THE STUFF IN THERE AND PLUG UP THE JET

4) Thread the thing in there and for god sakes dont king-kong the thing in there....just sung will do

 

Lesson Learned: You rarely need to king kong bolts into place. If in doubt, use some BLUE locktite and tighten normally.

Tightening the skix out of bolts ends up badly about 25% of the time.....bad odds

I'd use blue loctite instead



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  • Snow Drift

Posted May 29, 2014 - 09:51 AM

#4

It is such a dilema in my mind because if I leave it, I'm going to be thinking that there is now fragments in the carb and it is going to damage my cylinder, piston or valves.

 

If I take it out and find that it damages the thread when coming out then I'm going to be looking at major expense of a new carb and the time and at that stage really upset.

 

I wouldn't really want to use J&B weld although I have used it on a quad bike engine. The centre of the jet is actually fine and not damaged so that shouldn't be a problem.

 

I find it so difficult with jets because they go in and then stop and then they don't really move any further. Usually bolts begin to tighten then you can feel when tight.

 

I did the whole carb, cleaned it, took it all apart, changed the jets and needle blew it out, put in an adjustable fuel screw. This is why I really don't want to let a problem sit.

 

I appreciate both of your replies I'm not sure how to convince myself one way or another though. I was thinking if I could trace the other end of the tunnel for the jet then I could blow it out from reverse of just check that passage?


Edited by Snow Drift, May 29, 2014 - 09:53 AM.


  • grayracer513

Posted May 29, 2014 - 11:05 AM

#5

JB weld is an extraordinarily bad idea here.

 

First, it's an air jet, they simply aren't as critical as fuel jets.  You cannot have "cut the threads deeper", because the jet bottoms against the base of the bore.  As long as it's in there reasonably squarely, it doesn't matter.

 

The stray pieces of metal you're worried about, which likely don't exist, would flow downstream in the pilot circuit and most probably get hung up in the passageways before even making it to the intake port, and if they were small enough to escape into the airstream, the engine would be quite capable of digesting them without damage.

 

As said, run it and see how it goes.

 

And leave the JB Weld on the shelf.



  • Snow Drift

Posted June 02, 2014 - 08:56 AM

#6

Thanks.


Edited by Snow Drift, June 03, 2014 - 04:55 AM.





 
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