CarbTune Adaptors

[Guest]

I'm finally ready to sync the carbs on my 81 1100e, and I have a new CarbTune Pro. I'm having a heckuva time trying to thread in those nylon adapters. My intake runners have a #4 bolt, so I'm using the 4 x 5 mm nylon adapters. The bolts measure 4.8 mm, the adapters measure 4.7 mm, and the threads seem to match up well. I'm using a short piece of the CarbTune hose as a tool to get the angle as sraight as possible and to apply finger pressure only. I've managed to get in the two for cylinders 1&4, and they seem to be threaded properly such that I can back them out with finger pressure, but it was anything but easy, and 2&3 still elude me. They just don't seem to want to go in without forcing and stripping. It's not supposed to be this difficult. I'm about to order the brass fittings, but the nylon ones are supposed to be easier. What's going on here?

 

[Nessism]

I made a set of adapters by taking an allen head screw, with threads that match the engines sync ports, and drilling a hole down the center. Then some pieces of copper tubing were JB Welded in the allen hex. Throw an O-ring on the threads and go to town. Much easier to thread into the engine than those cheap plastic adapters

 

[bwringer]

What do you mean by "#4 bolt"? They're metric, not USS inch sizes.

The threads are metric, 5mm. Sometimes the threads on the plastic adapters have some molding flash in them, so make sure they'll thread smoothly into a metric nut with a 5mm thread. The brass adapters do have cleaner threads and go in much easier.

The angle is VERY awkward -- I usually use the trick you mentioned with a piece of hose.

 

[Guest]

So I got excited when I found I actually had a 5 mm nut. It is a 5 mm bolt, but it takes a 4 mm wrench. I chased the nylon threads with a 5 mm nut, and still no go. Great idea by the way. I've now stripped two of them enough now so that I can't even thread them well into the outside cylinders. They just seem like they need too much pressure, and all they want to do is jam up, although that will probably work. And then, even trying to re-thread in one that I've had in before, it's anything but easy. It just seems like nylon is not the right tool for this job. I guess I'll order the brass.