Carb disassembly problems

[jamestnewsonr65]

Hi there.
Whilst trying to dissasemble my carbs ready for vapour blasting I have run in to a few problems..... The first is a sheared screw on the butterfly assembly, rendering it well and truly stuck.



The second is that the screws on the top cap are well and truly seized. I've managed to get one of of each, but not both and now the screws are very near to destroying the head.

Kind of wish I had not started this job now. Any suggestions on how to remedy my problems would be great as I need to strip them before Saturday ready for cleaning.

[DerekM]

I used a screw extractor for the top cap, if there is enough material left i would suggest using one. If not, i would drill the screw material out of the top cap while trying not to damage the threads in the carb body.
patience, heat and PB blaster otherwise and worse case scenario, drill and replace.

[Bob_Roller]

You probably won't be able to remove the broken screw in the throttle shaft, it sounds like the first time I removed them on my '81 R65, even with filing the peened end down, the screw would not come out .

I drilled out the remaining screw and got a new throttle shaft, there is very little thread on the throttle shaft that the screw threads into .

On the carb top you may have to drill out the screw as well, you can drill off the screw head to get the top off, then decide on where to go from there, I would use caution in using an 'easy-out ', if the screw is seized in there you may break off the easy-out in the process and compound your problems .

[jamestnewsonr65]

Thanks for the speedy replies. I never thought of a new throttle shaft. Looks like they are £10 from moto-bins so not too bad.

Will try the screw remover method with caution and if all else fails then drill it out. What type of drill bits are needed for drilling screws, anything specific?

Once again thanks for the support when things go slightly off plan!

[Barry]

Any decent quality drill bit will do the job. They are usually marked HSS for high speed steel. The most important thing is that the drill is sharp, preferably a new one. The brass screw is softer and will be easier but actually brass in particular needs a very sharp drill. Several sizes will be needed to start small and work up but don't start so small that you break the drill bit. Rather than a hand held drill you really want to be doing this in a drill press for better control.

[montmil]

The buggered screws in the top cover can be drilled. Just stop before going into the aluminum cover. With the tension from over-tightening released, the screws may come out easily. There is the option of drilling stuck threaded shaft with a left-handed bit. In the past, this has worked for me.

For those having carb top screw issues here in 'murica, a 10-32 machine screw is a matching replacement. Find a nice dome-top, counter-sunk screw. Have both Bings on my "81 R65 so equipped.

[Luca]

If you can get a second set of hands to help you, you can also use impact on the dome screws.  With a sturdy block underneath the carb top ears whack a screwdriver into the screw head to shock the screw.

Better yet, if you've got a hand impact driver (the type you hit with a hammer) that will do the job nicely.  Just have to be careful not to put any bending forces on the dome ears or you will wreck them.  I picked up one of these tools for about $25 and it is the best way to remove stuck screws on Jap bike engine cases, auto brake disc locating screws, etc.

[montmil]

... if you've got a hand impact driver (the type you hit with a hammer) that will do the job nicely.

In 1965, there were but five motorcycles registered within Denton, Texas. My Triumph, a H-D XLR that was sorta kinda street legal, a BSA and two BMW R69S.

I easily scored a part-time job at the new and as yet un-opened Honda dealership that was in the "gittin' ready to" stage. I did a bit of everything in those early You Meet the Nicest People days. Working on the Hondas with their JIS crankcase screws tightened by Godzilla's off-spring made it mandatory to have your hammer and impact driver at the ready.

Forty-nine years later, I still have it -stashed somewhere in the back of one of the rollabouts. Clever tool. [smiley=thumbup.gif]

[Ed Miller]

For those having carb top screw issues here in 'murica, a 10-32 machine screw is a matching replacement. Find a nice dome-top, counter-sunk screw. Have both Bings on my "81 R65 so equipped.

Thanks for that timely bit, Monte.  I couldn't get one of mine out last weekend.  Mine are the stainless replacements somebody sells, with a little hex hole.  My hammer impact worked well on the originals (I wonder where I stashed those, now that I think about it) but I don't have a bit to fit the new screws.  I guess I didn't use enough anti-seize on the new screws.

[Barry]

I still have the original screws and take care not to over tighten them. As well as the threads I also make sure to put anti seize on the relatively large surface area of the countersink itself which I think is sometimes the cause of them sticking.  

[georgesgiralt]

Dunno what is the exact cause of 'them sticking but I was told that mixing aluminium alloy and steel (particularly stainless) is not a good idea....
I do move them from time to time in order to free them. And have changed them many times since I bought the bike 30 years ago...

[montmil]

...  Mine are the stainless replacements somebody sells...

Was at a DIY / Ace hardware store just today and spotted stainless 10-32 machine screws -for our Bings- with a cross-point, domed head. $0.44 each. Slather them with anti-seize and do as Georges says... break 'em loose every few months.

[jamestnewsonr65]

Ive ordered a screw extractor kit with drill bits and HSS bits also so hoping I can drill these out and get the shafts removed also. Seemed so easy when I thought about get them vapour blasted.

Will let you know how I get on.
Also I need to post some build pics in the restoration threads.

[donbmw]

When the butterfly screws were installed originally the thread end was staked  so they would not back out. Sometimes when the original screw are taken out they will to come out and the head strips off. The top screws I have used a hand held hammer impact  to get those loose. If you don't have one sometimes holding a screw driver real tight while twisting and hit it with a hammer will loosen the screws.

Don

[georgesgiralt]

To allow for the screwdriver to get grip, put some grinding paste on the head. It helps ...
As for the butterfly screws, you've to file the innards of the screw BEFORE unscrewing. In order to remove the slammed portion of the thread , otherwise it will ruin the whole lot...