Carb Rebuild Challanges, Expert Advise Needed

[Guest]

Pulled the VM carbs from my recently acquired '79 1000E-

I had noticed the throttle liked to stick in the wide open position, and opening the carbs I found out why - somehow, the bottoms of the slides have nicks and scoring which slightly which hung up in the slide tube when they were fully open.



(sorry for the crappy phone pics)

I couldn't even get the slides out without working the nicks down with some emory cloth. Now they're out, and I can easily smooth out the high marks on the outside of the slides so that they move freely.

My question is, are these nicks going to alter the airflow or change the carbs performance? What do I need to look out for?

Here's a front view, from this perspective the nicks and scoring don't seem to have altered the bottom profile at the very outside surface.



Okay, that was question one.

Question two, what to do about a broken choke tube?



Not sure what the PO was doing to cause this sort of damage, or why it was put back together in this state...

I'm thinking these tubes are brass and probably pressure fit.

Anyone have an effective way to remove/replace them? Are parts available ? -from where?

I'm wondering if I can extract, braze or solder the two pieces, redrill the holes that it broke across, and replace it. Of course, I'm not sure I can remove the stub without destroying it, and a repair won't be perfect and will most certainly alter the fuel throughput to some degree.

Long post - if you made it through it thanks. And thanks in advance for your replies.

[SqDancerLynn1]

The only way to get the choke tube is to make one or get one out of another carb. It is a press fit

[smagnusen]

I got the remainder of the choke tube out without further damaging it. For those who may find themselves in this predicament, here's how I effectively removed it:

I did a quick search and found that the coefficient of expansion of brass and copper was lower than that of aluminum. Assuming this was a pressure fit, heating the area will expand the aluminum more than the tube inside it, easing its removal.

I threw finishing nail in my drill press and tapered it slightly with a file and emory cloth until it fit into the choke tube stub to protect it from crushing during extraction.

I heated the area with a propane torch, inserted the tapered nail into the choke tube stub and twisted it out with a needle nose. It came right out. Here's a crappy pic.



Instead trying to find a replacement or fabricate a new one [I would never get the jet size correct], I'm going to connect the two pieces with a small brass sleeve and solder it in place.

[tkent02]

Sounds like you got the hard part. As far as the nicks in the slide, the get there from prying the slide up after it sits a few years and gets stuck, one of my old bikes was like that. Smooth it out so it doesn't stick anymore, if there are any differences in airflow it will be taken care of when you vacuum synch the carbs.
My bike ran fine that way.

[hampshirehog]

In answer to how much the wear on slides will affect your bike, you won't know until you're up and running. You might need new slides or carbs or they might be fine. I've run loads of bikes with pretty worn out slides and they've been fine. There's only one way to find out...

Incidentally, the fact that your slides jammed is the reason why these bikes are fitted with a push-pull throttle.

Solder is the way to go on those tubes; the trick is to get the parts really clean and use a good flux as that brass gives the illusion of being impregnated with fuel after sitting in it all that time.

[Dogma]

Some of the better stocked hobby shops have small diameter brass tubing. You might find a replacement there.

[Nessism]

Stuck slides will typically fall right out if you heat the carb bodies first - breaks down the varnish gum.

Dogma's suggestion about trying a hobby store for brass tubing is a good one. Worth a try.

[rapidray]

Smagnusen! You are MY kind of guy!! I am impressed with your
"Get er done!" attitude!! Call me at 714-356-7845 if I can ever help you or you want to help ME! Ray.

[smagnusen]

Just a (poor) picture to show the repaired choke tube. The tube broke across four tiny holes on the upper end of the tube. Since I was going to sleeve this area I had to redrill the holes through the sleeve. I was suprised that my local hardware store had a drill bit that was the correct size (it looked more like a sewing needle). Since it was way too small to fit into any chuck I had, I broke of the end of a pencil, jammed the bit into the eraser, and chucked the pencil end. I had to hold the bit steady with my fingers as I drilled but it was easy and effective. Thanks guys!



You can see the repaired sleeve on the left. Now to paint them like Renobruce! -if I'm lucky...

[rcp]

Nice innovative solution!

I was suprised that my local hardware store had a drill bit that was the correct size (it looked more like a sewing needle). Since it was way too small to fit into any chuck I had, I broke of the end of a pencil, jammed the bit into the eraser, and chucked the pencil end. I had to hold the bit steady with my fingers as I drilled but it was easy and effective.

If you're ever again looking for a chuck for teeny drill bits - what you want is a pin vise. Modeller's hobby shops often have them. I've also found the small Jacobs-style chuck that came with my flex-shaft die grinder to be really nice for drilling small precision holes.

- Richard