Sc46

[Diamond Geezer]

Hi guys

I have an sc 46 where the bolts screw into the carb to hold it on one of the threads have gone in the carb any ideas what I can do to fix it.

[Tony H]

Maybe tap slightly bigger thread and buy slightly bigger bolts.

[Diamond Geezer]

Hi Tony 

not much meat left to do that.

[Tony H]

Can't you buy a metal weld type of glue, that might do the trick, if you clean it of all oil first. 

[Keith Berriman]

If I remember correctly the screw size is M3 maybe try the screws used to fix switches and sockets at M3.5 if enough metal available

 

 

 

[Keith Berriman]

Alternative new carb 

[Kevin Fairgrieve]

I have an old ASP with the same issue.

I just put an M3 bolt all the way through with a locknut. Thus far it has run with no issue`s at all. 

 

It did need a little retune first off, but I expected that.

 

 

[Martin Harris - Moderator]

Room for a thread repair insert? A bit pricey for a one off job but very handy to have for odd repairs and reinforcing threads in aluminium that may be subject to wear...

[Robin Colbourne]

Diamond Geezer, Could you rotate the carburettor in the hole on the crankcase anti-clockwise enough to enable you to drill and tap new holes in the carb body for the securing screws?
You may need to reposition the thottle arm on the carb so it doesn't hit the propeller, and use a ball joint on the throttle arm as it won't be perpendicular to the throttle pushrod.

South Coast Hobbies have boxes of used engine parts on their stall at the shows.  If you sent them some photos of your carb next to a tape measure they might have one they could sell you?  South Coast Hobbies

Failing that I would keep an eye open on Ebay for a 'parts or not working' engine you can cannibalize for the carb.

[Robin Colbourne]

38 minutes ago, Kevin Fairgrieve said:

I have an old ASP with the same issue.

I just put an M3 bolt all the way through with a locknut. Thus far it has run with no issue`s at all. 

 

It did need a little retune first off, but I expected that.

 

 

What Kevin said is good advice.  A lot of these engines are optimised for RPMs far higher than most UK fliers can get away with for noise reasons, so a bit of loss of choke area isn't the end of the world.  You could alway waist the screw a bit where it crosses the carb bore, if you really thought it would make a difference.

[Andrew Calcutt]

Put a longer 3mm right through as said I have done this and it works.

[Nigel Dell]

Have just done a similar repair, leave the hole as is i.e. do not drill out, what’s left of the thread will key the repair, I used JB Weld, the slow drying original, fill the hole leaving it proud so you can sand back to size, leave for approximately 1 hour then I put it into the oven at 180 degrees and baked it for 30 minutes, I have also put it under an incandescent spot light for an hour if the oven is a no go with the same results, leave it for 24 hours to be sure it has gone off completely, file the outside flush, drill preferably in a pillar drill using a small drill to start gradually increasing in size, don’t be tempted to go to the size required first off, tap hole, then take down the inner face, I use a reamer carefully for this but you can leave it proud if you want to give a bit more meat for the screw, I do put a little oil on the repair before screwing together to stop any ‘grab’ when screwing in, just don’t over tighten, this repair has lasted many seasons. 

[kc]

One of the tricks that works for worn threads in soft metals is instead of the bolt  to use a stud ( or use a long bolt as a stud ) and a nut.   The stud is screwed in then the nut is used for tightening.   The principle is that you don't rotate the stud in the worn hole when tightening but just the nut on the stud ( steel onto steel ) this saves chewing the worn hole even more.

Usually works.

[Diamond Geezer]

Thanks guys for all your comments I sorted it retapped it to 3.5mm used a screw from a 15 amp choc block works a treat.