throttle tumb screw thing-um-bob

[Jon_P]

what or why is that tumb screw on the bottom of the throttle? i have always had my throttle snap back closed on every bike i had. i can see where on a longer trip it would be nice maybe. is that its purpose? so you dont have to hold the throttle?

[airhead]

In a word..........yes!!

It's designed to take a lot of the tension from the return spring on longer runs, and will seldom 'lock' it solid unless screwed really tight. It will very slowly let the throttle return to near idle if let go. Gives the hand a bit of a rest, and you can get enough time to lift it off the grip for a stretch/relieve without dropping momentum.

Bill......................;-)

[MrRiden]

What bill said and I also use it to keep the idle up a bit during first warm up while I get my helmet / jacket / gloves on.

[tagordon]

I am told its usefull when performing svc/maint adjustments that require off idle engine speeds.

I recently noticed this bolt missing. And that this is an outlet that the grease, from the throttle housing, escapes from. I cleaned out the remaining old grease & put moly grease inside. When reassembling I saw excess grease escaping from hole.
Due to have replacement bolt ( I hope the spring is included / as both have same part# ) arrive 8/15/07 as well as the screws for the vacuum holes on the carbs & new cover for brake MS.
Brake MS leaks when fluid above half full & bike off level. As in when parked & bars turned. Cover is bent / seal under it looks good. So trying cover first.

[Rob Valdez 79 R65]

I am 99% sure the spring is included.  It has a nylon tip that contacts the throttle.

[airhead]

I'll provide the other 1%.........it is part of it.

Bill..................;-)

[Bob_Roller]

Is the drilled hole filled with a short screw or plug from the factory, because I have never noticed it on the bottom of the housing. I guess I need to check this out over my weekend. If any one is interested in this, the part number is : 32721230874, about $9 US, you get 2 parts, the bolt and the spring. What does the plastic tip on the bolt actually contact , the throttle tube ?

[Rob Valdez 79 R65]

Yes, the throttle tube, or maybe near or on the gear teeth.

IIRC, they had a plastic plug.

For a while there (maybe it was the K bikes I am thinking of), you had to drill a hole and tap it.

[Bob_Roller]

It's amazing that after almost 27 years of ownership, you can actually find something on the bike, that you didn't even know existed. I just took a look , and it looks like a plug with serrated edges is filling the hole.

[tagordon]

It possibly fits into the slot on the throttle sleeve. Thats what I believe. If you look @ the throttle sleeve / grip there is a groove in the radius of it. The reason I had mine apart was to align the teeth on the grip with the teeth on the cable pull cam. Not sure if I am naming these parts correctly. Hope you know what I mean. Anyway I had a really long pull to come off idle & was looking to see what I might be able to do about it. Thats when I discovered the parts were not lined up correctly. I also discovered threaded hole & groove in radius of throttle grip.

[Rob Valdez 79 R65]

The top cap of the cam/chain-drive has a lip coming off the outside edge of the cap.  It is curved to fit into that slot.  
That is what holds the throttle sleeve in place.

It may also accommodate the set screw.  I don't know.

[airhead]

Rob is right about the groove being the tube retainer. The screw nylon tip actually bears on the rim of the tube near the cog. If you check, the nylon tip is actually spring loaded to stop you over tightening it (not the main outer spring, which is used to stop the screw loosening and falling out when not in use). Best to keep lube to a minimum around the area the screw tip runs as it means you have to have it much tighter than it needs to be.


Bill....................;-)