High RPM issue

[ppv]

I think its very possible useing the bread ty thing .it happend to me you have to turn the idle screw in first then do bread ty then loosen idle screw thats what worked for me if you dont it leaves the butterflys open to much hope this helps after that adjust your idle screw

[AlanB]

Hi Guys,

Some members have posted about leaks between brand new boots and the head; Two types are available, one needs gaskets.

If the boots are not original Yamaha, they will need sealed to the head........ I would check for vac leaks there anyway!

AlanB

[BlkMage]

Originally posted by AlanB
Hi Guys,

Some members have posted about leaks between brand new boots and the head; Two types are available, one needs gaskets.

If the boots are not original Yamaha, they will need sealed to the head........ I would check for vac leaks there anyway!

AlanB

The new boots are Yamaha parts.

Oh, and while we're on that, how does one properly check for leaks?

[ratbyk]

One way to check for vacuum leaks is to get an oil can with some light oil in it. Start engine and lightly apply small amounts of oil to possible leak areas. If there is a vacuum leak the oil will be sucked away quite quickly.
Would suggest that you remove the fuel tank/reverse it so that it sits on the seat area so that you have a good view all around the carbs.

[ppv]

the big screw in back of the carbs

[BlkMage]

Originally posted by ppv
the big screw in back of the carbs

Wait...what?
I'm sorry, but I can't understand what you're saying. What about it?

[Ken Talbot]

The single big screw at the back is the idle speed adjustment screw. But you already knew that, eh?

[BlkMage]

Originally posted by Ken Talbot
The single big screw at the back is the idle speed adjustment screw. But you already knew that, eh?

That I did. In fact, when this first started, I thought it was because I hadn't adjusted that screw since my carb rebuild and new spark plugs. But alas, I can crank that all the way out so it doesn't even touch the throttle, no effect.

[oseaghdha]

Originally posted by BlkMage
While we wait, I have a report. I changed the line from the fuel valve (where the 4 fuel lines come in) to the number 2 carb boot engine side. It did ok for a minute or so, but then backfired HARD a couple of times and I killed it. My dad said before, just before it started reving, it would click a couple of times almost sounding like a backfire. Hope this info helps.

Intake backfire= vacuum leak.
Check the boots to the head. Spray carb cleaner at the joints at idle.
Someone, John(?), found Pinto(?) thermostat gaskets work at that joint.

[AlanB]

Hi BlkMage,

If the main idle adjuster does not make a difference, then something else is holding the throttles open.

If it comes and goes, then it is probably hanging on the throttle cable; Back off the adjuster at the handlebar to give more slack. If the problem alters as you turn the 'bars, the cable needs re-routed.

it is possible to get either the clips on the boots, or the vac hose to the advance unit to interfere with the throttle linkage.
...........Don't ask how I know!!

If the engine is revving up, it is getting air from somewhere.

Either the throttles are not closing, or there is another way past; or in other words, a vac leak.

AlanB

[BlkMage]

Alright, more progress. Looks like a wire in the pickups might have been grounding out. My dad's trying to fix it, but in the meantime, anyone know where I could get a new assembly? This one's kinda crap.

[BlkMage]

Originally posted by BlkMage
Alright, more progress. Looks like a wire in the pickups might have been grounding out. My dad's trying to fix it, but in the meantime, anyone know where I could get a new assembly? This one's kinda crap.

Nevermind, found one for $140, so we're going to rewire this one. Hopefully have it running tomorrow.

[ratbyk]

Sounds like it should be going Zooorm Zooorm pretty soon.
Hang on!

[BlkMage]

Originally posted by ratbyk
Sounds like it should be going Zooorm Zooorm pretty soon.
Hang on!

Maybe even today...just got back from rewiring, hopefully have it running in a couple of hours so I can show it to the guy that sold it to me (birthday party at his house). If not, at least tomorrow so I can bring it over for my new turn signal rewire job at another friend's house.

[BlkMage]

Things just got ugly...

Well, still having problems, my father seems to think he can fix it by adjusting the timing (even though I agree with the book that you CAN'T on an '81) and refuses to check for leaks on the boots.

Maybe it won't be running for a while...