Got 82 750T back together, won't start again!

[chef1366]

Make sure your throttle linkage isn't hanging up on an intake boot clamp screw. I know it sounds silly but I did it once. Have you tried backing off your idle adjuster?

[ron bayless]

The only time my bike ever overrevved up like you are describing was when the throttle cable was stuck into the wrong position,like it was wide open.Once I got it back into its proper holder and adjusted it a little i wound up having to use the idle screw to get it to idle faster.

[froldt]

Well, I checked, and as far as I can tell the throttle cable isn't stuck, and the idle screw is set just about right (2.5 turns).
It took a couple of tries (low battery still, gotta get a good charger) but she fired up and immediately revved up to about 6k. Turned off the choke and she idled down to around 3500. It's been too long without a ride, so away we went! Of course, when I stopped to check on the idle screw, I bumped the kill switch, so I got to push-start her. Good thing there was a bit of a hill!

She's still revving high, and the warmer she gets, the faster she revs. I pulled back into the shed and she was running around 6000 rpm. Surely there isn't that much air getting in the boots? I didn't try to adjust them any, yet.
So I hit the kill switch and turned off the key... She kept running for a second or so... Could that mean she's getting too much fuel?

[DimitriT]

When it revs higher as it warms up it means its lean. You need to richen up the idle circuit (by backing out the idle mixture screws) and close up the throttles (by turning in the idle throttle knob). Make small adjustments these two things until its stable.

When's the last time you did a vacume sync?

[froldt]

When it revs higher as it warms up it means its lean. You need to richen up the idle circuit (by backing out the idle mixture screws) and close up the throttles (by turning in the idle throttle knob). Make small adjustments these two things until its stable.

When's the last time you did a vacume sync?

Where are the idle mixture screws (on the carb, I know, but where exactly)?

I've never done a vacuum sync. I rebuilt the carbs a couple of months ago and just got her running a few days ago. I bench sync'd them. I figured that would be enough to get her running and fine-tune from there. Hmm... now I'll need to find someone with a vacuum sync set.

[DimitriT]

The idle mixture screws are recessed in the little towers which point up and sit just back of the engine side rubber intakes. On some bikes there is an aluminum plug which fits into the recess and seals off access to the screw. You can remove these plugs to get to them.

When you cleaned the carbs, did you remove the screws to clean out the passage and replace the o-ring which sits around the screw tip?

[chef1366]

You say you rebuilt the carbs. Did you dip them with the idle mixture screw in them and ate up the o-rings? Did you put the rubber cap over the pilot jet?

[froldt]

Sorry about waiting so long to reply. Just got back from vacation. It's so terribly annoying that I think I know now what to do to fix my bike, but being across the continent from her. Even worse, my cousin (whom I stayed with part of the time) never rides his bike. Well, he did "ride" it out to clean it, then back in the garage. My uncle came over to show me a "real bike." He loves giving my cousin a hard time about his Sportster.

The idle mixture screws are recessed in the little towers which point up and sit just back of the engine side rubber intakes. On some bikes there is an aluminum plug which fits into the recess and seals off access to the screw. You can remove these plugs to get to them.

When you cleaned the carbs, did you remove the screws to clean out the passage and replace the o-ring which sits around the screw tip?

I did remove the screws and replace the o-rings.

You say you rebuilt the carbs. Did you dip them with the idle mixture screw in them and ate up the o-rings? Did you put the rubber cap over the pilot jet?

I did replace the rubber cap over the pilot jet. I'm not sure, but I think that the rebuild kit came with a new one.

[froldt]

When it revs higher as it warms up it means its lean. You need to richen up the idle circuit (by backing out the idle mixture screws) and close up the throttles (by turning in the idle throttle knob). Make small adjustments these two things until its stable.

Apparently I didn't make small enough adjustments last night when I gave 'er a try. Is there a starting point for the idle mixture screws?

[DimitriT]

Apparently I didn't make small enough adjustments last night when I gave 'er a try. Is there a starting point for the idle mixture screws?

I usuall go with 2 or 3 turns out which is rich. That's just to start it up. Use choke and get it warmed up and idling. Turn off choke and adjust idle speed using the knob under the carbs.

Once its idling around 1100 RPM I turn each mixture screw in 1/4 turn and wait 3 seconds. If the idle doesn't drop, I go in another 1/4 turn. Eventually the idle with drop. At this point I turn it OUT 1/4 turn.

It's important you wait 3 seconds for the RPMs to catch up to the mixture setting.

Use a fan on the motor or it will get too hot and your settings won't be correct.

That's a good enough spot for me.

If you notice the revs increasing once the bike gets real hot, you may want to adjust the mixture (richen it) a touch by:

a. turning the mixture screws OUT 1/8 turn
b. turning the RPM knob OUT (counter clockwise) until the RPMs drop to 1100 again

It's normal for the RPMs to go from 1000 to 1200 depending on temperature.

[froldt]

Well, I went through and tried to adjust some things... and now she won't start. Actually, I adjusted the mixture screws, and after a couple of tries she started up.
However, the idle still wouldn't go below about 4k. Then, when I pushed, really really hard, on the throttle control on the carbs, it would dip down to about 2k. So... I messed with the linkage and some bolts to try and make it so that the throttle wasn't stuck open, and now she won't start.

A friend told me I need to make sure the jets aren't sticking. How do I go about doing that?

Also, whomever designed the airbox needs to be drawn and quartered, then tarred and feathered. Bah! I can't get that sucker on for anything.

[chef1366]

You need the airbox on to start it.

[froldt]

You need the airbox on to start it.

It's on, but the hoses (I guess that's what you'd call them)/boots aren't connected. I can get the #4 boot on, and that's it. Sometimes I can get #1 on most of the way...