Topic: Can hose clamps and softening rubber boots cure climbing RPMs?

[Jore]

Yesterday I tried syncing my carbs, and realized that I have a vacuum leak, which makes idle climb to around 3K.

I've spent most of the afternoon today reading about softening the rubber intake boots. So my question is:

If I soften the boots and use hose clamps for a tighter grip on the carbs, and also put some vaseline to try and make  tighter seal, will that help in stopping the leak?

It's probably easier to just buy new intake boots, but I'm cheap!

[bryanj]

Hose clips won't work as they are too wide and distort the rubber even more

[bjbuchanan]

If you are hard up or want to give it a shot to try to isolate the issues try some permatex ultra black. I thin swipe is all that is necessary on the surfaces the boots get *slid* on to. If you put the swipe on the boot itself it will just squish out in to the intake tract and be largely wasted.

The true cure is fresh, not beaten up clamps and soft boots but sometimes you gotta make magic happen. Responsibly using the RTV won't impact anything else and won't gunk stuff up, just don't be hamfisted

[Jore]

Ok, I'll give it try with a thin swipe of rtv, and report back to see what happens.
Should I still try softening the boots?

[tool14]

try soaking them in wintergreen oil .

[bjbuchanan]

The wintergreen works effectively for the carb manifolds, the airbox rubbers not so much. They just don't have that same lasting impact. See if you can soften them first it would be better than the RTV. That is like a last resort if you can't get the boots

[mono]

Can hose clamps and softening rubber boots cure climbing RPMs?

I tried clamping my wrist but only by cutting the throttle cable did it for me. As for the rubber boots, the sheep couldn't climb away.

*facepalm*

[Duanob]

Have you chacked your o-rings between the intakes and the head? You say you have a vacuum leak I would look there first.

[bjbuchanan]

Have you chacked your o-rings between the intakes and the head? You say you have a vacuum leak I would look there first.

Good point, forgot the small bikes have those O-rings

[Jore]

I changed the O-rings that same day I tried to synch the bike.

Currently I'm trying to find wintergreen oil in this part of the world.

[bjbuchanan]

Try a regular old pharmacy/drug store that is where we find it stateside

[Jore]

There's 2 or 3 old time drug stores scattered around town, I'll try those.

[Jore]

The 400's at least mine does have O-rings.

[OldSchool_IsCool]

Before you get too wound up on the leaky boot theory, take some carb cleaner, start the bike and spray each boot separately. If the engine speeds up when sprayed, your leak is confirmed and located.  If you get no engine response, time to think on another theory.

[Jore]

What other theories could I consider?

[phil71]

bad sync.

[Rookster]

There are a bunch of things that can cause the high idle.  Vacuum leak is one.  Sticky slides, one or more slides too high, no push cable, bad sync, float levels too high, sticking or worn cables, poorly routed cables.  Any or all of these things can cause the high idle.  The SOHC4s have a tendency to do this.  The Keihins are almost too adjustable.

Scott

[Jore]

Now that you mention it, the bike doesn't have a push cable, and how knows how old the pull cable is. The floats are set at 22 mm, the slides all move freely and are about the same hight, when I did the bench sync I set them to about 1/16th for the opening. So I still have some points to check.

But still I think it's a vacuum leak, and a considerable one because the bike only starts with the choke on and will continue running with the choke halfway opened after that it just stalls.

One  question, the sync gages I can borrow are in PSI, does anyone know how many PSI should the bike pull?

[phil71]

You don't want to pay attention to those numbers, you just want them all the same, using #2 as the benchmark.

[Jore]

At least I had that correctly all of my carbs where giving the same reading after some minor adjstments.

[phil71]

you keep saying vacuum leak, but you haven't said that you found it definitively . WD 40/ carb cleaner/ propane.. one of those will determine for sure, if not, it could even be a sticky timing advancer holding the rpms up.

[Jore]

How can I check the timming advancers? I one thread I read that the springs start sagging over time and you can basically shorten them a few coils to aid in that.

[phil71]

mark and remove your points plate, and the advancer mechanism is there. Sometimes the pivot is frozen from rust, and yes, the springs do stretch out. It should move very freely when you push and pull the weights. If it doesn't, spray it up with some liquid wrench and use some pliers wrapped in a rag to work it back and forth till it pivots with ease.

[Jore]

Thanks I'll give that a go.

[Jore]

I took the carbs off, turns out the intake boots are rock solid (that´s not new), but one has the rubber separated from the metal flange (so that's new). I'll have to look around for something to fix it, or either order a set from the states, but I don't really have the funds to do that now.

In the mean time, I'm also going to check the advance springs and change the regulator and rectifier.