My sons moped stripped the threads on the cast iron exhaust flange.Easy you might say,put in a helicoil, so we did and it shattered the flange.
What in your opinion can i do to fix it.
can it be built up with weld and drilled and tapped or can i do something else?
Ray

Hi Ray,

Without seeing a photo it's hard to be specific, but most repairs
are best made using Oxy/act or Carbon arc and Bronze rods.
Clean CI & build up with bronze, grind & re tap.

Hope this helps.

Paul G

I found some good stuff for you here >

http://www.twi.co.uk/j32k/protected/band_3/jk25.html

I knew this would be a bugger.
My brother is going to take it to work on monday and see if the guy who does there ally and stainless can sort it out.
Thanks Paul+Paul...

Ray,

Not wanting to be a misery - but is there a bike breaker in your town? A replacement may be quicker, better and cheaper.

Cast iron is renowned for the difficulty of repairs, if helecoils don't do the job. You can't really arc weld it - it will crack, distort, or something else nasty - brazing may not be tough enough, and so on.

It's great stuff when it's intact, but brittle and difficult to mend.

David

Ye, there are a couple round here but the bike is only 18 months old so not likely to be in there yet and a new barrel,rings, and gaskets is at least £120 unless i can get after market parts.
Ive had word from one of my sons mates that he knows someone who crashed his with no insurance and is looking to sell it for £50 so all is not lost yet.
Thanks anyway...

Are you sure it is cast iron? most are made from cast steel which can be mig'd quite successfully.

I couldn,t tell the difference but if you tell me what to look for i,ll check.

File a bit of it, if it stays dull and gives graphite like dust it is cast iron, if is files nice and shiney, and the cut is more granular it is cast steel.

Dull grey smooth.
Filings are mostly dark grey with a few shiny speckles.


Come to think of it it,s an all in one casting so shouldn,t it have to be steel to be able to run the piston in it?
Or is that a missconception?
[Edited on 26/3/04 by ray.h.]

[Edited on 27/3/04 by ray.h.]

Definately cast iron. SH*T.

I have welded many manifolds in the past and other cast items . The way to do it is to use nickel rods and preheat the casting to at least 200c in an oven, weld using the special rods and doing a short section at a time and then peening the weld with a small ballpein hammer as it cools for a few seconds, before welding a bit more. When fully welded replace in the oven and leave to cool.
Welding electrodes are avilable from boc or Eutectic .
Another option is spray welding but requires specialist equipment , may be worth ringing around a few machine shops before scrapping the barrel .
Paul.

quote:

---

Originally posted by snoopy
had this with transit van manifold found that the only way to stop it cracking and falling off after miging it up was to first get it glowing with burning gear and welding it whilst red hot but not sure if it will work on a moped barrel ?

---

Hi again,

The preheat temp for C I is 600c.
A workshop test for this is lay a piece of
match stick on the clean heated area and
it should char (go dark brown).
Weld using oxy/act (you need this to preheat anyway) and bronze rod.
With a simple shape, like a lug on a
manifold, you only need to locally preheat.
Do not confuse bronze welding with brazing, totally different.
Cool slowly, (e.g. wrap it up in a fire blanket).
Can be arc welded, Monel rod IMHO (copper / nickel) but you need to preheat
with O/A anyway.
If welded with soft iron (mild steel) the
carbon from the C I migrates to the S I
turning it to high carbon steel (brittle like
a drill or tap)

If you have a go, good luck.

Paul G

SUCCESS.



My brother stick welded it with what he called cast rods.
Looks good,just have to see if it will take a tap (fingers crossed)
Thanks for all your advice.
Ray...