stuck pilot screw

[nashorn]

Has anyone got any advice on how to remove a stuck pilot screw. The darned thing is stuck fast, and the screwdriver slot is well rounded off. The carb is off the bike, the thread is soaking in wd 40, but I don't have much faith that this will do the job.

M600 year 2000

Thanks

[blue_toaster]

have you got a replacement screw?

[Sirc]

Short term solution is another pair of carbs unfortunately.. If you have anything left that you reckon you could turn with a screwdriver then carefully heating up the carb body can sometimes be enough to help free it off. A more severe measure involves cutting the top of the tubular housing off the carb body so you can get fresh access to the top of the screw which you can then cut a fresh slot in with a junior hacksaw blade (still might have to heat it up though).

[rac3r]

Release oil/spray worked well for me when I had a stuck exhaust stud

[blue_toaster]

it was the junior hacksaw, or maybe a screw extractor I was thinking of should a damn good soaking of WD40 not work. You do need good access to the screw though

[utopia]

Some say that wd40 isn't the best penetrating oil. I've heard plus-gas being recommended, and also that vinegar is good.
re. heating to loosen the thread, its partly the different expansion rates of the alloy body compared to the brass (?) screw that loosens things off. The other factor is that the body receives heat first, so expands first. So, since you've got the carb off the bike, why not try the effect of cooling too. You could put it in the fridge, perhaps overnight, and see if that had any effect. Also, if it was all stone cold before you applied any heat, the screw would be at its smallest while the body expanded, so you'd get the best shot at it loosening, perhaps....?
Its worth trying the heat cycling thing a few times.
The other thing that often helps is a sharp (but not excessive) blow with a hammer and punch on the end of the screw, to jar the threads. This may also have the side effect of slightly restoring the screwdriver slot.

[Sirc]

I tried the cooling trick, repeatedly but without success. The heat cycling can work of course, it's a bit 'how long is a piece of string' in't it? The only method that has the highest success rate/least damage is to drill right thru 2.5/3mm, cut a thread with a L/H thread and then use a caphead screw with corresponding thread. Trick these days is finding the last bit.
A good, late friend of mine once said 'there's no such thing as an 'easy-out' and I have found the same more or less. Used where there isn't much meat/wall thickness, and even worse if material is soft, they tend to expand the screw you are trying to rotate making the job even harder
In case you need to clean thread up, it's M6 x 05 mm pitch. Also, if you get stuck for replacements I just got a pair from Allens Performance Limited Bingham Notts - they are around £15 the pair posted. I can help with a part number/phone number if necessary.

[Nickj]

A few hot cold cycles might just break the gunge up, sometimes it works sometimes it doesn't. Gas mark 5+ and let it soak up the head for 15-20mins then get it down to handlable temperature then hit it with a pipe freezer spray. If there's ever been any glue or thread lock used then heat is the best one to clear it.
In general you do need to be a bit more agressive with the heat cold than you think, found that in my landie days, stubborn nut? Hit it with the gas axe to a nice cherry colour and allow it to cool to black then crank it off.
You might also like to try some screw grab, awesome stuff if there is enough slot of any kind on a screw or hex head.

[Sirc]

Nick -we're talking about pilot screws on the Mikuni carbs? Too much freezer spray immediately after any decent heat can literally have a 'shattering' effect from experience, best to hit it with a penetrating fluid instead. Totally agree re: heating exhaust studs but these are a walk in the park compared with nashorns problem.

[Saint aka ML]

Do no re Mikumi but on FCR my pilot screws have rubber seal so heating that up might just melt it and turn it in to glue.

[Sirc]

totally Lucaz, you can easily overdo it but as it's a last resort before carb body is probably scrapped it's worth the risk.

[gary tompkins]

common problem

Often not helped if the rubber blanking plugs have been lost or left out, and water and salt spray get in. Add to that galvanic corrosion due to brass/alluminium in contact and it's bound to end in tears.

[Kato]

Have in the past had to drill them and use an easy out, this is however not as easy as it sounds...

[nashorn]

Thanks for all your help,

Blue Toaster - no, I do not have a replacement, and I guess the stuck one will be U/S by the time it is out

Sirc, I could do with the info please,

Thanks again to all - I will persevere!

[jerry]

I had to get a machine shop to get the bugger out

WD40 is not penetrating oil !...............use PLUS GAS

[revver]

Had a seized pilot screw on mine. managed to get a second hand pair.

[nashorn]

Here is the happy ending!
I had to resort to brutal methods to remove the pilot screw. I sawed off the 'tube' around the pilot screw to get better access. I tried tapping it with a hammer and punch to encourage it to unscrew, I tried allsorts but to no avail. I ended up drilling through the screw with a cordless drill, starting off with a very small dia drill and gradually increasing the drill diameter until i was as close to the ali thread as possible. Using a sharp "V" needle file inserted in the drill hole I cut through the wall of the brass to weaken the remains of the screw. The brass is quite crumbly. I tapped the top of the thread with a scriber and pin hammer and winkled the remains of the screw out. There was some damage to the thread in the carb body, but I was able to clean this up with an M6 x 0.5 mm second tap (thanks for the tip Sirc).
The guys at NRP www.nrp-carbs.co.uk were unbelievable helpful. They had the spares I needed, AND suggested that I had further probs with the choke plungers (I could not use the choke when starting as the engine would completely flood). I took their advice, fitted the new choke plungers, new pilot screw, new float valves and gaskets. I reset the float height, set the pilot screws at 1.75 turns and put it all together
The bike is now excellent. Starts immediately, ticks over well, and runs very well. No misfire, no hesitation, smooth and lively and is now a joy to ride.
Thanks guys for all your help

[Pomp1]

had to remove one recently and as Slob can witness is a PITA. Had to drill through and use a special bolt removing tool as the normal twist and pull ones didn't work, plus a copious amount of heat.
Tool here..
http://www.grahamtool.com/images/products/detail/35580_professional_bolt_and_screw_extractor_no_5.j pg