How to repair broken carb
 

Hi all,

Despite being aware that the material that carburettors are made of is very brittle, I still managed to snap off a part of one of the pillars that the float pivot pin pushes through!

It snapped through the hole that the pivot pin locates in, the pin was already three quarters of the way through when disaster struck.

I was thinking of trying to stick it back together with liquid metal, has anyone done this or have a better idea?

Mark

If your on the raod then give it a go you don't have anything to loose if your at home then troll ebay and the breakers sites as it's just not worth the hassle matey.

ouch!
 

your in a world of hurt there mark...... Carbs are very delicate and made from a very strange mix of alloy. ( as you have found out)

Your BEST bet, is a secondhand Carby but failing that you could try to fix using JB weld or similar.

What Bike is it? can you post a pic of the Damage?

Martyn

Mark,
That post is going to be tricky to fix.
Is it thick enough to drill and pin the centre of the post to give the repair some strength. Or can you slide a short section of tube over the post and fill it with liquid metal. Model shops have a good selection of brass tube; they also have good petrol / fuel resistant glues.

I saw this product at the bike show it maybe an option.
Aluminium Welding
I am sure if you gave them a call they would be able to confirm if it is fixable and maybe put you in touch with someone who could do it for you.

Steve

Metal repair examples and materials
 

Mark,
Have a look through this thread and it might suggest another material or technique for this delicate repair:-

http://www.horizonsunlimited.com/hub...t=metal+repair

If you do get success it would make a good case/example in that thread!!

Good luck,

for future reference ...
 

When, in future you have carbs apart, clean all brass pins with some scotchbrite) or very fine wet n dry, and 'oh so gently' with a round needle file, just make sure the hole for the pin is clear.remove the merest hint of material.
before assembling with the float, push the pin through by Hand, it should be a firm push, not having to tap it or hammer it.
Remove pin, and reassemble, this way it should not ever stick again.
I know this is a bit 'stable door and the horse is gone' but it may help you in future or someone else.

Martyn

Many float pins are knurled on one end, and can only be pushed out one way if you don't want to break the post - notably Bings. Have a CLOSE look at the end of the pin before trying to remove - you should be able to spot the one that is dead round and the one that is a little "rough". Needless to say knock it out from the dead smooth and round end so the rough bit comes out first - and put it back in the same way, smooth end first. It should take almost no pressure to come out. Anything more than a very light tap and look again. A good idea is to hold it in your hand - less pressure on the carb than when it's on the bench.

But now that the horse is out :( you should be able to drill a very small hole across the post below the pin and safety wire it on. A dab of jbweld or similar if needed to hold it in place, but only if necessary - I suspect a good safety-wire job will be fine. The safety wire holding my windscreen together has been doing fine for 10 years! :)

Good luck!

Carbs regularly go on ebay for less than the price of a tube JB Weld !!

I wouldnt trust a chemical metal repair in a carb. One vibration too much and a bit comes unstuck and next minute its in your jet, breather or holding the float open..

Yep. Good stuff. Easier to use than brazing. About the same as silver-soldering. Dead cheap too.

if you can get it, this is PETROL resistant
 

J-B Weld Company - J-B STIK Product Information

it kneads up like putty, made by same people as JB weld, ive used JB weld and its fantastic stuff.

Martyn

I have a set of carbs of a 3AJ they will need a very good clean but the bodies are good you could use your jets, float, needles etc. These carbs got left out in the rain at an auto jumble so really do need a good clean
£20 plus postage if you want, I am in North London

Thanks for all the advice
 

All,

Thanks for your suggestions.

I probably should have said in my original post that I was at home in the UK, and the carb is off a friends SR500 (similat engine to XT500).

Grants idea of drilling a small hole and using safety wire is something I hadn't thought of and seems a good idea, but I will investigate the cost and availability of a second hand carb first.

As an aside, does oneone know how to de-restrict a power limited SR500, we have replaced the restricted inlet boot (between carb and cylinder head) and re-jetted the carb. Is there anything else?

Thanks

Mark

Don't forget to ensure when doing the carb repair (if you do it) that the float still moves freely, and can't move out of place, thus causing the valve to stick open or closed, causing overflow or fuel starvation respectively. Check the float height while you're at it (the manual should have the procedure and the setting, if u don't already know it).. all the fiddling around can easily change the setting.

Re de-restriction, check the float height too, and the idle speed adjustment.. if you've re-jetted it correctly, there *should* be very little else to do.